Molecular genetics of tooth agenesis

Congenital missing of teeth, tooth agenesis or hypodontia, is one of the most common developmental anomalies in man. The common forms in which one or a few teeth are absent, may cause occlusal or cosmetic harm, while severe forms which are relatively rare always require clinical attention to support and maintain the dental function. Observation of tooth agenesis is also important for diagnosis of malformation syndromes. Some external factors may cause developmental defects and agenesis in dentition. However, the role of inheritance in the etiology of tooth agenesis is well established by twin and family studies. Studies on familial tooth agenesis as well as mouse null mutants have also identified several genetic factors. However, these explain syndromic or rare dominant forms of tooth agenesis, whereas the genes and defects responsible for the majority of cases of tooth agenesis, especially the common and less severe forms, are largely unknown. In this study it was shown, that a dominant nonsense mutation in PAX9 was responsible for severe tooth agenesis (oligodontia) in a Finnish family. In a study of tooth agenesis associated with Wolf-Hirschhorn syndrome, it was shown that severe tooth agenesis was present if the causative deletion in 4p spanned the MSX1 locus. It was concluded that severe tooth agenesis was caused by haploinsufficiency of these transcription factors. A summary of the phenotypes associated with known defects in MSX1 and PAX9 showed that, despite similarities, they were significantly different, suggesting that the genes, in addition to known interactions, also have independent roles during the development of human dentition. The original aim of this work was to identify gene defects that underlie the common incisor and premolar hypodontia. After excluding several candidate genes, a genome-wide search was conducted in seven Finnish families in which this phenotype was inherited in an autosomal dominant manner. A promising locus for second premolar agenesis was identified in chromosome 18 in one family and this finding was supported by results from other families. The results also implied the existence of other loci both for second premolar agenesis and for incisor agenesis. On the other hand the results did not lend support for comprehensive involvement of the most obvious candidate genes in the etiology of incisor and premolar hypodontia. Rather, they suggest remarkable genetic heterogeneity of tooth agenesis. The available evidence suggests that quantitative defects during tooth development predispose to a failure to overcome a developmental threshold and to agenesis. The results of the study increase the understanding of the etiology and heredity of tooth agenesis. Further studies may lead to identification of novel genes that affect the development of teeth.

Phylogeography and Adaptive Divergence of Three-spined Stickleback Populations

Genetic studies on phylogeography and adaptive divergence in Northern Hemisphere fish species such as three-spined stickleback (Gasterosteus aculeatus) provide an excellent opportunity to investigate genetic mechanisms underlying population differentiation. According to the theory, the process of population differentiation results from a complex interplay between random and deterministic processes as well historical factors. The main scope in this thesis was to study how historical factors like the Pleistocene ice ages have shaped the patterns molecular diversity in three-spined stickleback populations in Europe and how this information could be utilized in the conservation genetic context. Furthermore, identifying footprints of natural selection at the DNA level might be used in identifying genes involved in evolutionary change. Overall, the results from phylogeographic studies indicate that the three-spined stickleback has colonized the Atlantic basin relatively recently but constitutes three major evolutionary lineages in Europe. In addition, the colonization of freshwater appears to result from multiple and independent invasions by the marine conspecifics. Molecular data together with morphology suggest that the most divergent freshwater populations are located in the Balkan Peninsula and these populations deserve a special conservation genetic status without warranting further taxonomical classification. In order to investigate the adaptive divergence in Fennoscandian three-spined stickleback populations several approaches were used. First, sequence variability in the Eda-gene, coding for the number of lateral plates, was concordant with the previously observed global pattern. Full plated allele is in high frequencies among marine populations whereas low plated allele dominates in the freshwater populations. Second, a microsatellite based genome scan identified both indications of balancing and directional selection in the three-spined stickleback genome, i.e. loci with unusually similar or unusually different allele frequencies over populations. The directionally selected loci were mainly associated with the adaptation to freshwater. A follow up study conducting a more detailed analysis in a chromosome region containing a putatively selected gene locus identified a fairly large genomic region affected by natural selection. However, this region contained several gene predictions, all of which might be the actual target of natural selection. All in all, the phylogeographic and adaptive divergence studies indicate that most of the genetic divergence has occurred in the freshwater populations whereas the marine populations have remained relatively uniform.

Flight metabolic rate in the Glanville fritillary butterfly

Dispersal is a highly important life history trait. In fragmented landscapes the long-term persistence of populations depends on dispersal. Evolution of dispersal is affected by costs and benefits and these may differ between different landscapes. This results in differences in the strength and direction of natural selection on dispersal in fragmented landscapes. Dispersal has been shown to be a nonrandom process that is associated with traits such as flight ability in insects. This thesis examines genetic and physiological traits affecting dispersal in the Glanville fritillary butterfly (Melitaea cinxia). Flight metabolic rate is a repeatable trait representing flight ability. Unlike in many vertebrates, resting metabolic rate cannot be used as a surrogate of maximum metabolic rate as no strong correlation between the two was found in the Glanville fritillary. Resting and flight metabolic rate are affected by environmental variables, most notably temperature. However, only flight metabolic rate has a strong genetic component. Molecular variation in the much-studied candidate locus phosphoglucose isomerase (Pgi), which encodes the glycolytic enzyme PGI, has an effect on carbohydrate metabolism in flight. This effect is temperature dependent: in low to moderate temperatures individuals with the heterozygous genotype at the single nucleotide polymorphism (SNP) AA111 have higher flight metabolic rate than the common homozygous genotype. At high temperatures the situation is reversed. This finding suggests that variation in enzyme properties is indeed translated to organismal performance. High-resolution data on individual female Glanville fritillaries moving freely in the field were recorded using harmonic radar. There was a strong positive correlation between flight metabolic rate and dispersal rate. Flight metabolic rate explained one third of the observed variation in the one-hour movement distance. A fine-scaled analysis of mobility showed that mobility peaked at intermediate ambient temperatures but the two common Pgi genotypes differed in their reaction norms to temperature. As with flight metabolic rate, heterozygotes at SNP AA111 were the most active genotype in low to moderate temperatures. The results show that molecular variation is associated with variation in dispersal rate through the link of flight physiology under the influence of environmental conditions. The evolutionary pressures for dispersal differ between males and females. The effect of flight metabolic rate on dispersal was examined in both sexes in field and laboratory conditions. The relationship between flight metabolic rate and dispersal rate in the field and flight duration in the laboratory were found to differ between the two sexes. In females the relationship was positive, but in males the longest distances and flight durations were recorded for individuals with low flight metabolic rate. These findings may reflect male investment in mate locating. Instead of dispersing, males with high flight metabolic rate may establish territories and follow a perching strategy when locating females and hence move less on the landscape level. Males with low metabolic rate may be forced to disperse due to low competitive success or may show adaptations to an alternative strategy: patrolling. In the light of life history trade-offs and the rate of living theory having high metabolic rate may carry a cost in the form of shortened lifespan. Experiments relating flight metabolic rate to longevity showed a clear correlation in the opposite direction: high flight metabolic rate was associated with long lifespan. This suggests that individuals with high metabolic rate do not pay an extra physiological cost for their high flight capacity, rather there are positive correlations between different measures of fitness. These results highlight the importance of condition.

Nephrin-associated molecules in human glomerular diseases

The glomerular epithelial cells and their intercellular junctions, termed slit diaphragms, are essential components of the filtration barrier in the kidney glomerulus. Nephrin is a transmembrane adhesion protein of the slit diaphragm and a signalling molecule regulating podocyte physiology. In congenital nephrotic syndrome of the Finnish type, mutation of nephrin leads to disruption of the permeability barrier and leakage of plasma proteins into the urine. This doctoral thesis hypothesises that novel nephrin-associated molecules are involved in the function of the filtration barrier in health and disease. Bioinformatics tools were utilized to identify novel nephrin-like molecules in genomic databases, and their distribution in the kidney and other tissues was investigated. Filtrin, a novel nephrin homologue, is expressed in the glomerular podocytes and, according to immunoelectron microscopy, localizes at the slit diaphragm. Interestingly, the nephrin and filtrin genes, NPHS1 and KIRREL2, locate in a head-to-head orientation on chromosome 19q13.12. Another nephrin-like molecule, Nphs1as was cloned in mouse, however, no expression was detected in the kidney but instead in the brain and lymphoid tissue. Notably, Nphs1as is transcribed from the nephrin locus in an antisense orientation. The glomerular mRNA and protein levels of filtrin were measured in kidney biopsies of patients with proteinuric diseases, and marked reduction of filtrin mRNA levels was detected in the proteinuric samples as compared to controls. In addition, altered distribution of filtrin in injured glomeruli was observed, with the most prominent decrease of the expression in focal segmental glomerulosclerosis. The role of the slit diaphragm-associated genes for the development of diabetic nephropathy was investigated by analysing single nucleotide polymorphisms. The genes encoding filtrin, densin-180, NEPH1, podocin, and alpha-actinin-4 were analysed, and polymorphisms at the alpha-actinin-4 gene were associated with diabetic nephropathy in a gender-dependent manner. Filtrin is a novel podocyte-expressed protein with localization at the slit diaphragm, and the downregulation of filtrin seems to be characteristic for human proteinuric diseases. In the context of the crucial role of nephrin for the glomerular filter, filtrin appears to be a potential candidate molecule for proteinuria. Although not expressed in the kidney, the nephrin antisense Nphs1as may regulate the expression of nephrin in extrarenal tissues. The genetic association analysis suggested that the alpha-actinin-4 gene, encoding an actin-filament cross-linking protein of the podocytes, may contribute to susceptibility for diabetic nephropathy.

Molecular genetics of X-linked cone-rod dystrophy and Åland Island eye disease

Inherited retinal diseases are the most common cause of vision loss among the working population in Western countries. It is estimated that ~1 of the people worldwide suffer from vision loss due to inherited retinal diseases. The severity of these diseases varies from partial vision loss to total blindness, and at the moment no effective cure exists. To date, nearly 200 mapped loci, including 140 cloned genes for inherited retinal diseases have been identified. By a rough estimation 50% of the retinal dystrophy genes still await discovery. In this thesis we aimed to study the genetic background of two inherited retinal diseases, X-linked cone-rod dystrophy and Åland Island eye disease. X-linked cone-rod dystrophy (CORDX) is characterized by progressive loss of visual function in school age or early adulthood. Affected males show reduced visual acuity, photophobia, myopia, color vision defects, central scotomas, and variable changes in fundus. The disease is genetically heterogeneous and two disease loci, CORDX1 and CORDX2, were known prior to the present thesis work. CORDX1, located on Xp21.1-11.4, is caused by mutations in the RPGR gene. CORDX2 is located on Xq27-28 but the causative gene is still unknown. Åland Island eye disease (AIED), originally described in a family living in Åland Islands, is a congenital retinal disease characterized by decreased visual acuity, fundus hypopigmentation, nystagmus, astigmatism, red color vision defect, myopia, and defective night vision. AIED shares similarities with another retinal disease, congenital stationary night blindness (CSNB2). Mutations in the L-type calcium channel α1F-subunit gene, CACNA1F, are known to cause CSNB2, as well as AIED-like disease. The disease locus of the original AIED family maps to the same genetic interval as the CACNA1F gene, but efforts to reveal CACNA1F mutations in patients of the original AIED family have been unsuccessful. The specific aims of this study were to map the disease gene in a large Finnish family with X-linked cone-rod dystrophy and to identify the disease-causing genes in the patients of the Finnish cone-rod dystrophy family and the original AIED family. With the help of linkage and haplotype analyses, we could localize the disease gene of the Finnish cone-rod dystrophy family to the Xp11.4-Xq13.1 region, and thus establish a new genetic X-linked cone-rod dystrophy locus, CORDX3. Mutation analyses of candidate genes revealed three novel CACNA1F gene mutations: IVS28-1 GCGTC>TGG in CORDX3 patients, a 425 bp deletion, comprising exon 30 and flanking intronic regions in AIED patients, and IVS16+2T>C in an additional Finnish patient with a CSNB2-like phenotype. All three novel mutations altered splice sites of the CACNA1F gene, and resulted in defective pre-mRNA splicing suggesting altered or absent channel function as a disease mechanism. The analyses of CACNA1F mRNA also revealed novel alternative wt splice variants, which may enhance channel diversity or regulate the overall expression level of the channel. The results of our studies may be utilized in genetic counseling of the families, and they provide a basis for studies on the pathogenesis of these diseases. In the future, the knowledge of the genetic defects may be used in the identification of specific therapies for the patients.

Genetic analysis of chromosomal regions 2q33, 7q32 and 19q13 in multiple sclerosis susceptibility

Multiple sclerosis (MS) is an immune-mediated demyelinating disorder of the central nervous system (CNS) affecting 0.1-0.2% of Northern European descent population. MS is considered to be a multifactorial disease, both environment and genetics play a role in its pathogenesis. Despite several decades of intense research, the etiological and pathogenic mechanisms underlying MS remain still largely unknown and no curative treatment exists. The genetic architecture underlying MS is complex with multiple genes involved. The strongest and the best characterized predisposing genetic factors for MS are located, as in other immune-mediated diseases, in the major histocompatibility complex (MHC) on chromosome 6. In humans MHC is called human leukocyte antigen (HLA). Alleles of the HLA locus have been found to associate strongly with MS and remained for many years the only consistently replicable genetic associations. However, recently other genes located outside the MHC region have been proposed as strong candidates for susceptibility to MS in several studies. In this thesis a new genetic locus located on chromosome 7q32, interferon regulatory factor 5 (IRF5), was identified in the susceptibility to MS. In particular, we found that common variation of the gene was associated with the disease in three different populations, Spanish, Swedish and Finnish. We also suggested a possible functional role for one of the risk alleles with impact on the expression of the IRF5 locus. Previous studies have pointed out a possible role played by chromosome 2q33 in the susceptibility to MS and other autoimmune disorders. The work described here also investigated the involvement of this chromosomal region in MS predisposition. After the detection of genetic association with 2q33 (article-1), we extended our analysis through fine-scale single nucleotide polymorphism (SNP) mapping to define further the contribution of this genomic area to disease pathogenesis (article-4). We found a trend (p=0.04) for association to MS with an intronic SNP located in the inducible T-cell co-stimulator (ICOS) gene, an important player in the co-stimulatory pathway of the immune system. Expression analysis of ICOS revealed a novel, previously uncharacterized, alternatively spliced isoform, lacking the extracellular domain that is needed for ligand binding. The stability of the newly-identified transcript variant and its subcellular localization were analyzed. These studies indicated that the novel isoform is stable and shows different subcellular localization as compared to full-length ICOS. The novel isoform might have a regulatory function, but further studies are required to elucidate its function. Chromosome 19q13 has been previously suggested as one of the genomic areas involved in MS predisposition. In several populations, suggestive linkage signals between MS predisposition and 19q13 have been obtained. Here, we analysed the role of allelic variation in 19q13 by family based association analysis in 782 MS families collected from Finland. In this dataset, we were not able to detect any statistically significant associations, although several previously suggested markers were included to the analysis. Replication of the previous findings on the basis of linkage disequilibrium between marker allele and disease/risk allele appears notoriously difficult because of limitations such as allelic heterogeneity. Re-sequencing based approaches may be required for elucidating the role of chromosome 19q13 with MS. This thesis has resulted in the identification of a new MS susceptibility locus (IRF5) previously associated with other inflammatory or autoimmune disorders, such as SLE. IRF5 is one of the mediators of interferons biological function. In addition to providing new insight in the possible pathogenetic pathway of the disease, this finding suggests that there might be common mechanisms between different immune-mediated disorders. Furthermore the work presented here has uncovered a novel isoform of ICOS, which may play a role in regulatory mechanisms of ICOS, an important mediator of lymphocyte activation. Further work is required to uncover its functions and possible involvement of the ICOS locus in MS susceptibility.

Identification of genetic susceptibility loci for migraine

Migraine is the common cause of chronic episodic headache, affecting 12%-15% of the Caucasian population (41 million Europeans and some half a million Finns), and causes considerable loss of quality of life to its sufferers, as well as being linked to increased risk for a wide range of conditions, from depression to stroke. Migraine is the 19th most severe disease in terms of disability-adjusted life years, and 9th among women. It is characterized by attacks of headache accompanied by sensitivity to external stimuli lasting 4-72 hours, and in a third of cases by neurological aura symptoms, such as loss of vision, speech or muscle function. The underlying pathophysiology, including what triggers migraine attacks and why they occur in the first place, is largely unknown. The aim of this study was to identify genetic factors associated with the hereditary susceptibility to migraine, in order to gain a better understanding of migraine mechanisms. In this thesis, we report the results of genetic linkage and association analyses on a Finnish migraine patient collection as well as migraineurs from Australia, Denmark, Germany, Iceland and the Netherlands. Altogether we studied genetic information of nearly 7,000 migraine patients and over 50,000 population-matched controls. We also developed a new migraine analysis method called the trait component analysis, which is based on individual patient responses instead of the clinical diagnosis. Using this method, we detected a number of new genetic loci for migraine, including on chromosome 17p13 (HLOD 4.65) and 10q22-q23 (female-specific HLOD 7.68) with significant evidence of linkage, along with five other loci (2p12, 8q12, 4q28-q31, 18q12-q22, and Xp22) detected with suggestive evidence of linkage. The 10q22-q23 locus was the first genetic finding in migraine to show linkage to the same locus and markers in multiple populations, with consistent detection in six different scans. Traditionally, ion channels have been thought to play a role in migraine susceptibility, but we were able to exclude any significant role for common variants in a candidate gene study of 155 ion transport genes. This was followed up by the first genome-wide association study in migraine, conducted on 2,748 migraine patients and 10,747 matched controls followed by a replication in 3,209 patients and 40,062 controls. In this study, we found interesting results with genome-wide significance, providing targets for future genetic and functional studies. Overall, we found several promising genetic loci for migraine providing a promising base for future studies in migraine.

Identification of loci for migraine with aura

Common migraine, i.e. migraine with (MA) or without aura (MO), is a chronic neurological disorder affecting about 10% of the Caucasian population. In MA, migraine headache is preceded by visual, sensoric and/or dysphasic reversible aura symptoms. Twin and family studies have suggested a multifactorial mode of inheritance for common migraine, and a stronger genetic component for MA than for MO. Since there is no biological or genetic marker to identify common migraine, aura symptoms provide a distinctive character to identify those suspected of suffering from migraine. The aim of this study was to identify MA susceptibility loci in well-phenotyped migraine samples with familial predisposition using different gene mapping methods. Genes coding for endothelin1 and its receptors EDNRA and ENDRB are potential candidate genes for cortical spreading depression (CSD), which is considered to be the underlying mechanism of migraine aura. The role of these genes in MA was studied in 850 Finnish migraine cases and 890 control individuals. Rare homozygous EDNRA SNPs showed nominal association with MA and with the age of onset trait (20 years). This result was also detected in the pooled analysis on 648 German MA cases and 651 control individuals when the test was adjusted for gender and sample origin. Evaluation of SNP genotyping reactions with two different DNA polymerase enzymes ensured that the genotype quality was high, and thus the discovered associations are considered reliable. The role of the 19p13 region was studied in a linkage analysis of 72 Finnish MA families. This region contains two migraine-associated genes: CACNA1A, which is associated with a predisposition to a rare Mendelian form of MA, familial hemiplegic migraine (FHM), and the insulin receptor gene (INSR) that is associated with common migraine. No evidence of linkage between the 19p13 and MA was detected. A novel visual aura locus was mapped to chromosome 9q21-q22 with significant evidence of linkage using a genome-wide linkage approach in 36 Finnish MA families. Five additional, potential loci were also detected. The 9q21-q22 region has previously been linked to occipitotemporal lobe epilepsy and MA, both of which involve prominent visual symptoms. Our result further supports a shared background for these episodic disorders.

Timing of puberty : Genetic regulation

In the general population, the timing of puberty is normally distributed. This variation is determined by genetic and environmental factors, but the exact mechanisms underlying these influences remain elusive. The purpose of this study was to gain insight into genetic regulation of pubertal timing. Contributions of genetic versus environmental factors to the normal variation of pubertal timing were explored in twins. Familial occurrence and inheritance patterns of constitutional delay of growth and puberty, CDGP (a variant of normal pubertal timing), were studied in pedigrees of patients with this condition. To ultimately detect genes involved in the regulation of pubertal timing, genetic loci conferring susceptibility to CDGP were mapped by linkage analysis in the same family cohort. To subdivide the overall phenotypic variance of pubertal timing into genetic and environmental components, genetic modeling based on monozygous twins sharing 100% and dizygous twins sharing 50% of their genes was used in 2309 girls and 1828 boys from the FinnTwin 12-17 study. The timing of puberty was estimated from height growth, i.e. change in the relative height between the age when pubertal growth velocity peaks in the general population and adulthood. This reflects the percentage of adult height achieved at the average peak height velocity age, and thus, pubertal timing. Boys and girls diagnosed with CDGP were gathered through medical records from six pediatric clinics in Finland. First-degree relatives of the probands were invited to participate by letter; altogether, 286 families were recruited. When possible, families were extended to include also second-, third-, or fourth-degree relatives. The timing of puberty in all family members was primarily assessed from longitudinal growth data. Delayed puberty was defined by onset of pubertal growth spurt or peak height velocity taking place 1.5 (relaxed criterion) or 2 SD (strict criterion) beyond the mean. If growth data were unavailable, pubertal timing was based on interviews. In this case, CDGP criteria were set as having undergone pubertal development more than 2 (strict criterion) or 1.5 years (relaxed criterion) later than their peers, or menarche after 15 (strict criterion) or 14 years (relaxed criterion). Familial occurrence of strict CDGP was explored in families of 124 patients (95 males and 29 females) from two clinics in Southern Finland. In linkage analysis, we used relaxed CDGP criteria; 52 families with solely growth data-based CDGP diagnoses were selected from all clinics. Based on twin data, genetic factors explain 86% and 82% of the variance of pubertal timing in girls and boys, respectively. In families, 80% of male and 76% of female probands had affected first-degree relatives, in whom CDGP was 15 times more common than the expected (2.5%). In 74% (17 of 23) of the extended families with only one affected parent, familial patterns were consistent with autosomal dominant inheritance. By using 383 multiallelic markers and subsequently fine-mapping with 25 additional markers, significant linkage for CDGP was detected to the pericentromeric region of chromosome 2, to 2p13-2q13 (multipoint HLOD 4.44, α 0.41). The findings of the large twin study imply that the vast majority of the normal variation of pubertal timing is attributed to genetic effects. Moreover, the high frequency of dominant inheritance patterns and the large number of affected relatives of CDGP patients suggest that genetic factors also markedly contribute to constitutional delay of puberty. Detection of the locus 2p13-2q13 in the pericentromeric region of chromosome 2 associating with CDGP is one step towards unraveling the genes that determine pubertal timing.

Migraine Comorbidities : A Clinical and Molecular Genetic Study

Migraine is a highly prevalent disease, and despite several important breakthroughs there are still a many questions unanswered in the clinical, genetic and pathophysiological aspects of migraine research. Migraine has been linked to several other diseases such as epilepsy and stroke, but there are still unsolved issues concerning the true nature of these associations. Three genes predisposing to hemiplegic migraine and several loci associated to migraine have been identified, but so far no genes responsible for common forms of migraine have been recognized. Triptans have provided an important step in migraine treatment, but their usefulness in rare forms of migraine have been controversial. The Finnish Migraine Gene Project (FMGP) includes more than 1600 families and 7500 individuals. We evaluated comorbidity from 1000 consecutive subjects in the FMGP. To search for novel loci, we performed a genome-wide linkage scan in 36 families with high prevalences of migraine with visual aura. We collected 76 subjects from the FMGP who suffer from hemiplegic migraine and have used triptans. Finally, to study possible links between stroke and migraine we evaluated the prevalence of migraine in subjects with cervical artery dissection (CAD) and healthy controls. Migraine was associated with increased prevalence of allergy, hypotension and psychiatric diseases. Additionally, men suffering from migraine with aura had increased prevalence of epilepsy and stroke. Further evidence of association between migraine and epilepsy was found in our linkage study. The parametric two-point linkage analysis showed significant evidence of linkage between migraine aura and a locus on 9q21-q22. Interestingly, the same locus has been associated with occipitotemporal epilepsy. CAD seems to be a migraine risk factor, and therefore a link between stroke and migraine. Notably, CAD seems to alleviate migraine activity further indicating the association between these two conditions. Despite the contraindications of triptans, it seems that they are safe and effective in the abortive treatment of hemiplegic migraine.

Molecular Genetics of Age-related Macular Degeneration

Age-related macular degeneration (AMD; OMIM # 603075) is an eye disease of the elderly, signs of which appear after the age of 50. In the Western world it is a leading cause of permanent visual loss with a prevalence of 8.5% in persons under 54 years of age and of 37% in persons over 75 years of age. Early forms of AMD may be asymptomatic, but in the late forms usually a central scotoma in the visual field follows severely complicating daily tasks. Smoking, age, and genetic predisposition are known risk factors for AMD. Until recently no true susceptibility genes had been identified though the composition of drusen deposits, the hallmarks of AMD, has suggested that the complement system might play a role in the pathogenesis of AMD. When four groups reported in March 2005, that, on chromosome 1q32, a Y402H variant in the complement factor H (CFH) gene confers risk for AMD in independent Caucasian samples, a new period in the field of genetic research of AMD started. CFH is a key regulator of the complement system. Thus, it is logical to speculate, that it plays a role in the pathogenesis of AMD. We performed a case-control association study to analyse whether the CFH Y402H variant contain a risk for AMD in the Finnish population. Although the population of Finland represents a genetic isolate, the CFH Y402H polymorphism was associated with AMD also in our patient sample with similar risk allele frequencies as in the other Caucasian populations. We further evaluated the effects of this variant, but no association between lesion subtype (predominantly classic, minimally classic or occult lesion) or lesion size of neovascular AMD and the CFH Y402H variant was detected. Neither did the variant have an effect on the photodynamic therapy (PDT) outcome. The patients that respond to PDT carried the risk genotype as frequently as those who did not respond, and no difference was found in the number of PDT sessions needed in patients with or without the risk genotypes of CFH Y402H. Functional analyses, however, showed that the binding of C-reactive protein (CRP) to CFH was significantly reduced in patients with the risk genotype of Y402H. In the past two years, the LOC387715/ high-temperature requirement factor A1 (HTRA1) locus on 10q26 has also been repeatedly associated with AMD in several populations. The recent discovery of the LOC387715 protein on the mitochondrial outer membrane suggests that the LOC387715 gene, not HTRA1, is the true predisposing gene in this region, although its biological function is still unknown. In our Finnish patient material, patients with AMD carried the A69S risk genotype of LOC387715 more frequently than the controls. Also, for the first time, an interaction between the CFH Y402H and the LOC387715 A69S variants was found. The most recently detected susceptibilty gene of AMD, the complement component 3 (C3) gene, encodes the central component of the complement system, C3. In our Finnish sample, an additive gene effect for the C3 locus was detected, though weaker than the effects for the two main loci, CFH and LOC387715. Instead, the hemicentin-1 or the elongation of very long chain fatty acids-like 4 genes that have also been suggested as candidate genes for AMD did not carry a risk for AMD in the Finnish population. This was the first series of molecular genetic study of AMD in Finland. We showed that two common risk variants, CFH Y402H and LOC387715 A69S, represent a high risk of AMD also in the isolated Finnish population, and furthermore, that they had a statistical interaction. It was demonstrated that the CFH Y402H risk genotype affects the binding of CFH to CRP thus suggesting that complement indeed plays an important role in the pathogenesis of AMD.

Work Stress in the Nursing Profession : An Evaluation of Organizational Causal Attribution

The goal of this study was to examine the role of organizational causal attribution in understanding the relation of work stressors (work-role overload, excessive role responsibility, and unpleasant physical environment) and personal resources (social support and cognitive coping) to such organizational-attitudinal outcomes as work engagement, turnover intention, and organizational identification. In some analyses, cognitive coping was also treated as an organizational outcome. Causal attribution was conceptualized in terms of four dimensions: internality-externality, attributing the cause of one’s successes and failures to oneself, as opposed to external factors, stability (thinking that the cause of one’s successes and failures is stable over time), globality (perceiving the cause to be operative on many areas of one’s life), and controllability (believing that one can control the causes of one’s successes and failures). Several hypotheses were derived from Karasek’s (1989) Job Demands–Control (JD-C) model and from the Job Demands–Resources (JD-R) model (Demerouti, Bakker, Nachreiner & Schaufeli, 2001). Based on the JD-C model, a number of moderation effects were predicted, stating that the strength of the association of work stressors with the outcome variables (e.g. turnover intentions) varies as a function of the causal attribution; for example, unpleasant work environment is more strongly associated with turnover intention among those with an external locus of causality than among those with an internal locuse of causality. From the JD-R model, a number of hypotheses on the mediation model were derived. They were based on two processes posited by the model: an energy-draining process in which work stressors along with a mediating effect of causal attribution for failures deplete the nurses’ energy, leading to turnover intention, and a motivational process in which personal resources along with a mediating effect of causal attribution for successes foster the nurses’ engagement in their work, leading to higher organizational identification and to decreased intention to leave the nursing job. For instance, it was expected that the relationship between work stressors and turnover intention could be explained (mediated) by a tendency to attribute one’s work failures to stable causes. The data were collected from among Finnish hospital nurses using e-questionnaires. Overall 934 nurses responded the questionnaires. Work stressors and personal resources were measured by five scales derived from the Occupational Stress Inventory-Revised (Osipow, 1998). Causal attribution was measured using the Occupational Attributional Style Questionnaire (Furnham, 2004). Work engagement was assessed through the Utrecht Work Engagement Scale (Schaufeli & al., 2002), turnover intention by the Van Veldhoven & Meijman (1994) scale, and organizational identification by the Mael & Ashforth (1992) measure. The results provided support for the function of causal attribution in the overall work stress process. Findings related to the moderation model can be divided into three main findings. First, external locus of causality along with job level moderated the relationship between work overload and cognitive coping. Hence, this interaction was evidenced only among nurses in non-supervisory positions. Second, external locus of causality and job level together moderated the relationship between physical environment and turnover intention. An opposite pattern of interaction was found for this interaction: among nurses, externality exacerbated the effect of perceived unpleasantness of the physical environment on turnover intention, whereas among supervisors internality produced the same effect. Third, job level also disclosed a moderation effect for controllability attribution over the relationship between physical environment and cognitive coping. Findings related to the mediation model for the energetic process indicated that the partial model in which work stressors have also a direct effect on turnover intention fitted the data better. In the mediation model for the motivational process, an intermediate mediation effect in which the effects of personal resources on turnover intention went through two mediators (e.g., causal dimensions and organizational identification) fitted the data better. All dimensions of causal attribution appeared to follow a somewhat unique pattern of mediation effect not only for energetic but also for motivational processes. Overall findings on mediation models partly supported the two simultaneous underlying processes proposed by the JD-R model. While in the energetic process the dimension of externality mediated the relationship between stressors and turnover partially, all the dimensions of causal attribution appeared to entail significant mediator effects in the motivational process. The general findings supported the moderation effect and the mediation effect of causal attribution in the work stress process. The study contributes to several research traditions, including the interaction approach, the JD-C, and the JD-R models. However, many potential functions of organizational causal attribution are yet to be evaluated by relevant academic and organizational research. Keywords: organizational causal attribution, optimistic / pessimistic attributional style, work stressors, organisational stress process, stressors in nursing profession, hospital nursing, JD-R model, personal resources, turnover intention, work engagement, organizational identification.

Genetic Mechanisms Underlying Autism Spectrum Disorders

Autism is a childhood-onset developmental disorder characterized by deficits in reciprocal social interaction, verbal and non-verbal communication, and dependence on routines and rituals. It belongs to a spectrum of disorders (autism spectrum disorders, ASDs) which share core symptoms but show considerable variation in severity. The whole spectrum affects 0.6-0.7% of children worldwide, inducing a substantial public health burden and causing suffering to the affected families. Despite having a very high heritability, ASDs have shown exceptional genetic heterogeneity, which has complicated the identification of risk variants and left the etiology largely unknown. However, recent studies suggest that rare, family-specific factors contribute significantly to the genetic basis of ASDs. In this study, we investigated the role of DISC1 (Disrupted-in-schizophrenia-1) in ASDs, and identified association with markers and haplotypes previously associated with psychiatric phenotypes. We identified four polymorphic micro-RNA target sites in the 3 UTR of DISC1, and showed that hsa-miR-559 regulates DISC1 expression in vitro in an allele-specific manner. We also analyzed an extended autism pedigree with genealogical roots in Central Finland reaching back to the 17th century. To take advantage of the beneficial characteristics of population isolates to gene mapping and reduced genetic heterogeneity observed in distantly related individuals, we performed a microsatellite-based genome-wide screen for linkage and linkage disequilibrium in this pedigree. We identified a putative autism susceptibility locus on chromosome 19p13.3 and obtained further support for previously reported loci at 1q23 and 15q11-q13. To follow-up these findings, we extended our study sample from the same sub-isolate and initiated a genome-wide analysis of homozygosity and allelic sharing using high-density SNP markers. We identified a small number of haplotypes shared by different subsets of the genealogically connected cases, along with convergent biological pathways from SNP and gene expression data, which highlighted axon guidance molecules in the pathogenesis of ASDs. In conclusion, the results obtained in this thesis show that multiple distinct genetic variants are responsible for the ASD phenotype even within single pedigrees from an isolated population. We suggest that targeted resequencing of the shared haplotypes, linkage regions, and other susceptibility loci is essential to identify the causal variants. We also report a possible micro-RNA mediated regulatory mechanism, which might partially explain the wide-range neurobiological effects of the DISC1 gene.

Identification of genetic susceptibility loci for migraine

Migraine is the common cause of chronic episodic headache, affecting 12%-15% of the Caucasian population (41 million Europeans and some half a million Finns), and causes considerable loss of quality of life to its sufferers, as well as being linked to increased risk for a wide range of conditions, from depression to stroke. Migraine is the 19th most severe disease in terms of disability-adjusted life years, and 9th among women. It is characterized by attacks of headache accompanied by sensitivity to external stimuli lasting 4-72 hours, and in a third of cases by neurological aura symptoms, such as loss of vision, speech or muscle function. The underlying pathophysiology, including what triggers migraine attacks and why they occur in the first place, is largely unknown. The aim of this study was to identify genetic factors associated with the hereditary susceptibility to migraine, in order to gain a better understanding of migraine mechanisms. In this thesis, we report the results of genetic linkage and association analyses on a Finnish migraine patient collection as well as migraineurs from Australia, Denmark, Germany, Iceland and the Netherlands. Altogether we studied genetic information of nearly 7,000 migraine patients and over 50,000 population-matched controls. We also developed a new migraine analysis method called the trait component analysis, which is based on individual patient responses instead of the clinical diagnosis. Using this method, we detected a number of new genetic loci for migraine, including on chromosome 17p13 (HLOD 4.65) and 10q22-q23 (female-specific HLOD 7.68) with significant evidence of linkage, along with five other loci (2p12, 8q12, 4q28-q31, 18q12-q22, and Xp22) detected with suggestive evidence of linkage. The 10q22-q23 locus was the first genetic finding in migraine to show linkage to the same locus and markers in multiple populations, with consistent detection in six different scans. Traditionally, ion channels have been thought to play a role in migraine susceptibility, but we were able to exclude any significant role for common variants in a candidate gene study of 155 ion transport genes. This was followed up by the first genome-wide association study in migraine, conducted on 2,748 migraine patients and 10,747 matched controls followed by a replication in 3,209 patients and 40,062 controls. In this study, we found interesting results with genome-wide significance, providing targets for future genetic and functional studies. Overall, we found several promising genetic loci for migraine providing a promising base for future studies in migraine.

Rethinking Service Companies’ Business Logic: Do We Need a Customer-Dominant Logic as a Guideline?

Purpose –This paper explores and expands the roles of customers and companies in creating value by introducing a new a customer-based approach to service. The customer’s logic is examined as being the foundation of a customer-based marketing and business logic. Design/methodology/approach – The authors argue that both goods-dominant logics and service-dominant logics are provider-dominant. Contrasting the customer-dominant logic with provider-dominant logics, the paper examines the creation of service value from the perspectives of value-in-use, the customer’s own context, and the customer’s experience of service. Findings –Moving from a provider-dominant logic to a customer-dominant logic uncovered five major challenges to service marketers: Company involvement, company control in co-creation, visibility of value creation, locus of customer experience, and character of customer experience. Research limitations/implications – The paper is exploratory. It presents and discusses a conceptual model and suggests implications for research and practice. Practical implications –Awareness of the mechanisms of customer logic will provide businesses with new perspectives on the role of the company in their customer’s lives. We propose that understanding the customer’s logic should represent the starting-point for the marketer’s business logic. Originality/value – The paper increases the understanding of how the customer’s logic underpins the customer-dominant business logic. By exploring consequences of applying a customer-dominant logic, we suggest further directions for theoretical and empirical research.