Mycobacterium leprae downregulates the expression of PHEX in Schwann cells and osteoblasts

Neuropathy and bone deformities, lifelong sequelae of leprosy that persist after treatment, result in significant impairment to patients and compromise their social rehabilitation. Phosphate-regulating gene with homologies to endopeptidase on the X chromosome (PHEX) is a Zn-metalloendopeptidase, which is abundantly expressed in osteoblasts and many other cell types, such as Schwann cells, and has been implicated in phosphate metabolism and X-linked rickets. Here, we demonstrate that Mycobacterium leprae stimulation downregulates PHEX transcription and protein expression in a human schwannoma cell line (ST88-14) and human osteoblast lineage. Modulation of PHEX expression was observed to a lesser extent in cells stimulated with other species of mycobacteria, but was not observed in cultures treated with latex beads or with the facultative intracellular bacterium Salmonella typhimurium. Direct downregulation of PHEX by M. leprae could be involved in the bone resorption observed in leprosy patients. This is the first report to describe PHEX modulation by an infectious agent.

Mutational spectrum of the SPG4 (SPAST) and SPG3A (ATL1) genes in Spanish patients with hereditary spastic paraplegia.

BACKGROUND Hereditary Spastic Paraplegias (HSP) are characterized by progressive spasticity and weakness of the lower limbs. At least 45 loci have been identified in families with autosomal dominant (AD), autosomal recessive (AR), or X-linked hereditary patterns. Mutations in the SPAST (SPG4) and ATL1 (SPG3A) genes would account for about 50% of the ADHSP cases. METHODS We defined the SPAST and ATL1 mutational spectrum in a total of 370 unrelated HSP index cases from Spain (83% with a pure phenotype). RESULTS We found 50 SPAST mutations (including two large deletions) in 54 patients and 7 ATL1 mutations in 11 patients. A total of 33 of the SPAST and 3 of the ATL1 were new mutations. A total of 141 (31%) were familial cases, and we found a higher frequency of mutation carriers among these compared to apparently sporadic cases (38% vs. 5%). Five of the SPAST mutations were predicted to affect the pre-mRNA splicing, and in 4 of them we demonstrated this effect at the cDNA level. In addition to large deletions, splicing, frameshifting, and missense mutations, we also found a nucleotide change in the stop codon that would result in a larger ORF. CONCLUSIONS In a large cohort of Spanish patients with spastic paraplegia, SPAST and ATL1 mutations were found in 15% of the cases. These mutations were more frequent in familial cases (compared to sporadic), and were associated with heterogeneous clinical manifestations.

Cross-sectional observational study of 208 patients with non-classical urea cycle disorders.

Urea cycle disorders (UCDs) are inherited disorders of ammonia detoxification often regarded as mainly of relevance to pediatricians. Based on an increasing number of case studies it has become obvious that a significant number of UCD patients are affected by their disease in a non-classical way: presenting outside the newborn period, following a mild course, presenting with unusual clinical features, or asymptomatic patients with only biochemical signs of a UCD. These patients are surviving into adolescence and adulthood, rendering this group of diseases clinically relevant to adult physicians as well as pediatricians. In preparation for an international workshop we collected data on all patients with non-classical UCDs treated by the participants in 20 European metabolic centres. Information was collected on a cohort of 208 patients 50% of which were ≥ 16 years old. The largest subgroup (121 patients) had X-linked ornithine transcarbamylase deficiency (OTCD) of whom 83 were female and 29% of these were asymptomatic. In index patients, there was a mean delay from first symptoms to diagnosis of 1.6 years. Cognitive impairment was present in 36% of all patients including female OTCD patients (in 31%) and those 41 patients identified presymptomatically following positive newborn screening (in 12%). In conclusion, UCD patients with non-classical clinical presentations require the interest and care of adult physicians and have a high risk of neurological complications. To improve the outcome of UCDs, a greater awareness by health professionals of the importance of hyperammonemia and UCDs, and ultimately avoidance of the still long delay to correctly diagnose the patients, is crucial.

Complex genetics in idiopathic hypogonadotropic hypogonadism.

Idiopathic hypogonadotropic hypogonadism (IHH) is an important human disease model. Investigations of the genetics of IHH have facilitated insights into critical pathways regulating sexual maturation and fertility. IHH has been traditionally considered a monogenic disorder. This model holds that a single gene defect is responsible for the disease in each patient. In the case of IHH, 30% of cases are explained by mutations in one of eleven genes. In recent years, several lines of evidence have challenged the monogenic paradigm in IHH. First, disease-associated mutations display striking incomplete penetrance and variable expressivity within and across IHH families. Second, each locus is responsible for only a small percentage of cases. Third, more than one disease-associated mutation seems to be segregating in some families with IHH, and their combined or separate presence in individuals accounts for the variability in disease severity. Finally, IHH is not strictly a congenital and life-long disorder; occasionally it manifests itself during adulthood (adult-onset IHH); in other cases, the disease is not permanent, as evidenced by normal activity of the hypothalamic-pituitary-gonadal axis after discontinuation of treatment in adulthood (IHH reversal). Together, these observations suggest that IHH is not strictly a monogenic mendelian disease, as previously thought. Rather, it is emerging as a digenic, and potentially oligogenic disease, in which hormonal and/or environmental factors may critically influence genetic predisposition and clinical course. Future investigations of IHH should characterize the extent of the involvement of multiple genes in disease pathogenesis, and elucidate the contributions of epigenetic factors.

La maladie de Fabry chez l'adulte: aspects cliniques et progrès thérapeutiques [Fabry disease in adulthood: clinical aspects and therapeutic progress].

INTRODUCTION: Fabry disease is an X-linked recessive abnormality of glycosphingolipid metabolism that is due to deficiency of the lysosomal enzyme alpha-galactosidase A. CURRENT KNOWLEDGE AND KEY POINTS: A majority of hemizygous men develop severe multisystemic disease (classic form), dominated by renal failure, progressive neurological and cardiac involvement. Nevertheless, some affected men retain sufficient enzyme activity and long remain asymptomatic (atypical form); their main manifestation is hypertrophic cardiomyopathy. Female heterozygous carriers are usually asymptomatic; 15% of them, however, have severe involvement of one or several organs. Laboratory, histologic and molecular diagnosis identifies 100% of hemizygous and over 80% of heterozygous subjects. FUTURE PROSPECTS AND PROJECTS: With developments in molecular genetics, it is now possible to produce the human recombinant enzyme alpha-galactosidase A. Two recent studies had proven that this therapeutic approach was able to be clinically and histologically effective in men. In addition, the results of a trial of gene therapy in a Fabry gene knocked-out mouse appear promising.

Ever-young sex chromosomes in European tree frogs.

Non-recombining sex chromosomes are expected to undergo evolutionary decay, ending up genetically degenerated, as has happened in birds and mammals. Why are then sex chromosomes so often homomorphic in cold-blooded vertebrates? One possible explanation is a high rate of turnover events, replacing master sex-determining genes by new ones on other chromosomes. An alternative is that X-Y similarity is maintained by occasional recombination events, occurring in sex-reversed XY females. Based on mitochondrial and nuclear gene sequences, we estimated the divergence times between European tree frogs (Hyla arborea, H. intermedia, and H. molleri) to the upper Miocene, about 5.4-7.1 million years ago. Sibship analyses of microsatellite polymorphisms revealed that all three species have the same pair of sex chromosomes, with complete absence of X-Y recombination in males. Despite this, sequences of sex-linked loci show no divergence between the X and Y chromosomes. In the phylogeny, the X and Y alleles cluster according to species, not in groups of gametologs. We conclude that sex-chromosome homomorphy in these tree frogs does not result from a recent turnover but is maintained over evolutionary timescales by occasional X-Y recombination. Seemingly young sex chromosomes may thus carry old-established sex-determining genes, a result at odds with the view that sex chromosomes necessarily decay until they are replaced. This raises intriguing perspectives regarding the evolutionary dynamics of sexually antagonistic genes and the mechanisms that control X-Y recombination.

Maladie de Fabry: du diagnostic a l'enzymotherapie substitutive. [Fabry disease: diagnostic due of substitutive enzyme-therapy]

Fabry disease is a X-linked sphingolipid storage disorder resulting from the defective activity of the lysosomal enzyme, alpha-galactosidase A. Hemizygotes develop severe multisystemic disease, dominated by renal failure and progressive neurological and cardiac involvement, causing premature death. Thirty percent of heterozygotes have severe involvement of one or several organs. With developments in molecular biology, it is now possible to produce the human recombinant enzyme alpha-galactosidase A. More than 20 patients are now treated in Switzerland.

Pharmacological stimulation of edar signaling in the adult enhances sebaceous gland size and function.

Impaired ectodysplasin A (EDA) receptor (EDAR) signaling affects ectodermally derived structures including teeth, hair follicles, and cutaneous glands. The X-linked hypohidrotic ectodermal dysplasia (XLHED), resulting from EDA deficiency, can be rescued with lifelong benefits in animal models by stimulation of ectodermal appendage development with EDAR agonists. Treatments initiated later in the developmental period restore progressively fewer of the affected structures. It is unknown whether EDAR stimulation in adults with XLHED might have beneficial effects. In adult Eda mutant mice treated for several weeks with agonist anti-EDAR antibodies, we find that sebaceous gland size and function can be restored to wild-type levels. This effect is maintained upon chronic treatment but reverses slowly upon cessation of treatment. Sebaceous glands in all skin regions respond to treatment, although to varying degrees, and this is accompanied in both Eda mutant and wild-type mice by sebum secretion to levels higher than those observed in untreated controls. Edar is expressed at the periphery of the glands, suggesting a direct homeostatic effect of Edar stimulation on the sebaceous gland. Sebaceous gland size and sebum production may serve as biomarkers for EDAR stimulation, and EDAR agonists may improve skin dryness and eczema frequently observed in XLHED.

Systematic molecular and cytogenetic screening of 100 patients with marfanoid syndromes and intellectual disability.

The association of marfanoid habitus (MH) and intellectual disability (ID) has been reported in the literature, with overlapping presentations and genetic heterogeneity. A hundred patients (71 males and 29 females) with a MH and ID were recruited. Custom-designed 244K array-CGH (Agilent®; Agilent Technologies Inc., Santa Clara, CA) and MED12, ZDHHC9, UPF3B, FBN1, TGFBR1 and TGFBR2 sequencing analyses were performed. Eighty patients could be classified as isolated MH and ID: 12 chromosomal imbalances, 1 FBN1 mutation and 1 possibly pathogenic MED12 mutation were found (17%). Twenty patients could be classified as ID with other extra-skeletal features of the Marfan syndrome (MFS) spectrum: 4 pathogenic FBN1 mutations and 4 chromosomal imbalances were found (2 patients with both FBN1 mutation and chromosomal rearrangement) (29%). These results suggest either that there are more loci with genes yet to be discovered or that MH can also be a relatively non-specific feature of patients with ID. The search for aortic complications is mandatory even if MH is associated with ID since FBN1 mutations or rearrangements were found in some patients. The excess of males is in favour of the involvement of other X-linked genes. Although it was impossible to make a diagnosis in 80% of patients, these results will improve genetic counselling in families.

Generation and characterization of function-blocking anti-ectodysplasin A (EDA) monoclonal antibodies that induce ectodermal dysplasia.

Development of ectodermal appendages, such as hair, teeth, sweat glands, sebaceous glands, and mammary glands, requires the action of the TNF family ligand ectodysplasin A (EDA). Mutations of the X-linked EDA gene cause reduction or absence of many ectodermal appendages and have been identified as a cause of ectodermal dysplasia in humans, mice, dogs, and cattle. We have generated blocking antibodies, raised in Eda-deficient mice, against the conserved, receptor-binding domain of EDA. These antibodies recognize epitopes overlapping the receptor-binding site and prevent EDA from binding and activating EDAR at close to stoichiometric ratios in in vitro binding and activity assays. The antibodies block EDA1 and EDA2 of both mammalian and avian origin and, in vivo, suppress the ability of recombinant Fc-EDA1 to rescue ectodermal dysplasia in Eda-deficient Tabby mice. Moreover, administration of EDA blocking antibodies to pregnant wild type mice induced in developing wild type fetuses a marked and permanent ectodermal dysplasia. These function-blocking anti-EDA antibodies with wide cross-species reactivity will enable study of the developmental and postdevelopmental roles of EDA in a variety of organisms and open the route to therapeutic intervention in conditions in which EDA may be implicated.

Genome organization and gene expression shape the transposable element distribution in the Drosophila melanogaster euchromatin.

The distribution of transposable elements (TEs) in a genome reflects a balance between insertion rate and selection against new insertions. Understanding the distribution of TEs therefore provides insights into the forces shaping the organization of genomes. Past research has shown that TEs tend to accumulate in genomic regions with low gene density and low recombination rate. However, little is known about the factors modulating insertion rates across the genome and their evolutionary significance. One candidate factor is gene expression, which has been suggested to increase local insertion rate by rendering DNA more accessible. We test this hypothesis by comparing the TE density around germline- and soma-expressed genes in the euchromatin of Drosophila melanogaster. Because only insertions that occur in the germline are transmitted to the next generation, we predicted a higher density of TEs around germline-expressed genes than soma-expressed genes. We show that the rate of TE insertions is greater near germline- than soma-expressed genes. However, this effect is partly offset by stronger selection for genome compactness (against excess noncoding DNA) on germline-expressed genes. We also demonstrate that the local genome organization in clusters of coexpressed genes plays a fundamental role in the genomic distribution of TEs. Our analysis shows that-in addition to recombination rate-the distribution of TEs is shaped by the interaction of gene expression and genome organization. The important role of selection for compactness sheds a new light on the role of TEs in genome evolution. Instead of making genomes grow passively, TEs are controlled by the forces shaping genome compactness, most likely linked to the efficiency of gene expression or its complexity and possibly their interaction with mechanisms of TE silencing.

Phacomatoses et tumeurs génétiquement déterminées: la transition enfant-adulte [Phacomatosis and genetically determined tumors: the transition from childhood to adulthood]

Les phacomatoses regroupent des maladies du développement du neurectoderme, engendrant des manifestations cutanées ou du système nerveux central. Les symptômes de ces maladies peuvent affecter les individus atteints à différents moments de leur vie. Il s'agit de maladies, héréditaires ou congénitales, qui sont transmises de façon variable. Effectivement, certaines, telles que la neurofibromatose, la sclérose tubéreuse ou la maladie de von Hippel-Lindau sont autosomiques dominantes, alors que d'autres, telles que la maladie de Sturge-Weber sont sporadiques. Des transmissions autosomiques récessives liées à X ou des formes mosaïques existent également. Une revue de la littérature, comprenant les cinq phacomatoses les plus fréquemment vues par un neurochirurgien (neurofibromatose de type I et II, sclérose tubéreuse de Bourneville, maladie de Sturge-Weber-Krabbe, maladie de von Hippel-Lindau) a été effectuée en se centrant sur le diagnostic, la variabilité de la symptomatologie selon l'âge du patient et son traitement. Les cas de patients adultes et pédiatriques vus aux consultations de neurologie et neurochirurgie de l'hôpital de Lille (France) et Lausanne (Suisse), de 1961 à nos jours, ont été revus pour illustrer les différentes pathologies rencontrées, selon l'âge des patients atteints. Le phénotype de ces maladies se modifie avec l'âge, car les gènes incriminés sont des gènes impliqués dans la différentiation tissulaire et sont activés à des âges différents suivant les tissus. Le rôle du neurochirurgien sera variable selon l'âge et le syndrome du patient. Il importe de connaître les variations du phénotype de ces maladies avec l'âge ainsi que les conséquences à long terme des traitements pour proposer au patient un suivi neurochirurgical personnalisé. Phacomatoses, or neurocutaneous disorders, are a group of congenital and hereditary diseases characterized by developmental lesions of the neuroectoderm, leading to pathologies affecting the skin and the central nervous system. There is a wide range of pathologies affecting individuals at different moments of life. The genetics is variable: while neurofibromatosis 1 and 2, tuberous sclerosis and von Hippel-Lindau disease are all inherited as autosomal dominant traits, Sturge-Weber syndrome is sporadic. Other neurocutaneous disorders can be inherited as autosomal recessive traits (i.e., ataxia-telangiectasia), X-linked (i.e., incontinentia pigmenti) or explained by mosaicism (i.e., hypomelanosis of Ito, McCune-Albright syndrome). In this review, we discuss the major types of neurocutaneous disorders most frequently encountered by the neurosurgeon and followed beyond childhood. They include neurofibromatosis types 1 and 2, tuberous sclerosis, Sturge-Weber syndrome and von Hippel-Lindau disease. In each case, a review of the literature, including diagnosis, genetics and treatment will be presented. The lifespan of the disease with the implications for neurosurgeons will be emphasized. A review of cases, including both pediatric and adult patients, seen in neurosurgical practices in the Lille, France and Lausanne, Switzerland hospitals between 1961 and 2007 is presented to illustrate the pathologies seen in different age-groups. Because the genes mutated in most phacomatoses are involved in development and are activated following a timed schedule, the phenotype of these diseases evolves with age. The implication of the neurosurgeon varies depending on the patient's age and pathology. While neurosurgeons tend to see pediatric patients affected with neurofibromatosis type 1, tuberous sclerosis and Sturge-Weber syndrome, there will be a majority of adult patients with von Hippel-Lindau disease or neurofibromatosis type 2

Pharmacological inhibition of fibroblast growth factor (FGF) receptor signaling ameliorates FGF23-mediated hypophosphatemic rickets.

Fibroblast growth factor 23 (FGF23) is a circulating factor secreted by osteocytes that is essential for phosphate homeostasis. In kidney proximal tubular cells FGF23 inhibits phosphate reabsorption and leads to decreased synthesis and enhanced catabolism of 1,25-dihydroxyvitamin D3 (1,25[OH]2 D3 ). Excess levels of FGF23 cause renal phosphate wasting and suppression of circulating 1,25(OH)2 D3 levels and are associated with several hereditary hypophosphatemic disorders with skeletal abnormalities, including X-linked hypophosphatemic rickets (XLH) and autosomal recessive hypophosphatemic rickets (ARHR). Currently, therapeutic approaches to these diseases are limited to treatment with activated vitamin D analogues and phosphate supplementation, often merely resulting in partial correction of the skeletal aberrations. In this study, we evaluate the use of FGFR inhibitors for the treatment of FGF23-mediated hypophosphatemic disorders using NVP-BGJ398, a novel selective, pan-specific FGFR inhibitor currently in Phase I clinical trials for cancer therapy. In two different hypophosphatemic mouse models, Hyp and Dmp1-null mice, resembling the human diseases XLH and ARHR, we find that pharmacological inhibition of FGFRs efficiently abrogates aberrant FGF23 signaling and normalizes the hypophosphatemic and hypocalcemic conditions of these mice. Correspondingly, long-term FGFR inhibition in Hyp mice leads to enhanced bone growth, increased mineralization, and reorganization of the disturbed growth plate structure. We therefore propose NVP-BGJ398 treatment as a novel approach for the therapy of FGF23-mediated hypophosphatemic diseases.

Theileria parva-transformed T cells show enhanced resistance to Fas/Fas ligand-induced apoptosis.

Lymphocyte homeostasis is regulated by mechanisms that control lymphocyte proliferation and apoptosis. Activation-induced cell death is mediated by the expression of death ligands and receptors, which, when triggered, activate an apoptotic cascade. Bovine T cells transformed by the intracellular parasite Theileria parva proliferate in an uncontrolled manner and undergo clonal expansion. They constitutively express the death receptor Fas and its ligand, FasL but do not undergo apoptosis. Upon elimination of the parasite from the host cell by treatment with a theilericidal drug, cells become increasingly sensitive to Fas/FasL-induced apoptosis. In normal T cells, the sensitivity to death receptor killing is regulated by specific inhibitor proteins. We found that anti-apoptotic proteins such as cellular (c)-FLIP, which functions as a catalytically inactive form of caspase-8, and X-chromosome-linked inhibitor of apoptosis protein (IAP) as well as c-IAP, which can block downstream executioner caspases, are constitutively expressed in T. parva-transformed T cells. Expression of these proteins is rapidly down-regulated upon parasite elimination. Antiapoptotic proteins of the Bcl-2 family such as Bcl-2 and Bcl-x(L) are also expressed but, in contrast to c-FLIP, c-IAP, and X-chromosome-linked IAP, do not appear to be tightly regulated by the presence of the parasite. Finally, we show that, in contrast to the situation in tumor cells, the phosphoinositide 3-kinase/Akt pathway is not essential for c-FLIP expression. Our findings indicate that by inducing the expression of antiapoptotic proteins, T. parva allows the host cell to escape destruction by homeostatic mechanisms that would normally be activated to limit the continuous expansion of a T cell population.

The murine interleukin-2 receptor gamma chain gene: organization, chromosomal localization and expression in the adult thymus.

Defects in the interleukin-2 receptor gamma (IL-2R gamma) chain in the man result in an X-linked severe combined immunodeficiency, SCIDX1, characterized by an absence of T-cell differentiation. This phenotype may result from pertubations in IL-2, IL-4-, IL-7- or IL-15-mediated signaling, as the IL-2R gamma chain forms an integral component of these receptor systems. We have isolated and characterized cDNA and genomic clones for the murine IL-2R gamma. The gene (Il2rg) is well conserved between mouse and man with respect to overall structure and size, and contains regions of high conservation in the promoter region as well. Il2rg maps to mouse X chromosome region 40, in a region of synteny with human Xq12-13.1. We have also explored the expression of the IL-2R gamma during thymocyte development. IL-2R gamma transcripts are detected in the earliest thymocyte precursor cells and persist throughout intrathymic development into the mature peripheral compartment. Genomic clones for the murine IL-2R gamma will allow for further studies on the regulation and function of this gene in vivo.