Adaptive evolution of four microcephaly genes and the evolution of brain size in anthropoid primates

The anatomical basis and adaptive function of the expansion in primate brain size have long been studied; however, we are only beginning to understand the genetic basis of these evolutionary changes. Genes linked to human primary microcephaly have received much attention as they have accelerated evolutionary rates along lineages leading to humans. However, these studies focus narrowly on apes, and the link between microcephaly gene evolution and brain evolution is disputed. We analyzed the molecular evolution of four genes associated with microcephaly (ASPM, CDK5RAP2, CENPJ, MCPH1) across 21 species representing all major clades of anthropoid primates. Contrary to prevailing assumptions, positive selection was not limited to or intensified along the lineage leading to humans. In fact we show that all four loci were subject to positive selection across the anthropoid primate phylogeny. We developed clearly defined hypotheses to explicitly test if selection on these loci was associated with the evolution of brain size. We found positive relationships between both CDK5RAP2 and ASPM and neonatal brain mass and somewhat weaker relationships between these genes and adult brain size. In contrast, there is no evidence linking CENPJ and MCPH1 to brain size evolution. The stronger association of ASPM and CDK5RAP2 evolution with neonatal brain size than with adult brain size is consistent with these loci having a direct effect on prenatal neuronal proliferation. These results suggest that primate brain size may have at least a partially conserved genetic basis. Our results contradict a previous study that linked adaptive evolution of ASPM to changes in relative cortex size; however, our analysis indicates that this conclusion is not robust. Our finding that the coding regions of two widely expressed loci has experienced pervasive positive selection in relation to a complex, quantitative developmental phenotype provides a notable counterexample to the commonly asserted hypothesis that cisregulatory regions play a dominant role in phenotypic evolution. Key words: ASPM, MCPH1, CDK5RAP2, CENPJ, brain, neurogenesis, primates.

Mandibulofacial Syndrome With Growth and Mental Retardation, Microcephaly, Ear Anomalies With Skin Tags, and Cleft Palate in a Mother and Her Son: Autosomal Dominant or X-Linked Syndrome?

We report on a Brazilian mother and her son affected with mandibulofacial dysostosis, growth and mental retardation, microcephaly, first branchial arch anomalies, and cleft palate. To date only three males and one female, all sporadic cases, with a similar condition have been reported. This article describes the first familial case with this rare condition indicating autosomal dominant or X-linked inheritance. (C) 2009 Wiley-Liss, Inc.

Haploinsufficiency of a Spliceosomal GTPase Encoded by EFTUD2 Causes Mandibulofacial Dysostosis with Microcephaly

Mandibulofacial dysostosis with microcephaly (MFDM) is a rare sporadic syndrome comprising craniofacial malformations, microcephaly, developmental delay, and a recognizable dysmorphic appearance. Major sequelae, including choanal atresia, sensorineural hearing loss, and cleft palate, each occur in a significant proportion of affected individuals. We present detailed clinical findings in 12 unrelated individuals with MFDM; these 12 individuals compose the largest reported cohort to date. To define the etiology of MFDM, we employed whole-exome sequencing of four unrelated affected individuals and identified heterozygous mutations or deletions of EFTUD2 in all four. Validation studies of eight additional individuals with MFDM demonstrated causative EFTUD2 mutations in all affected individuals tested. A range of EPTUD2-mutation types, including null alleles and frameshifts, is seen in MFDM, consistent with haploinsufficiency; segregation is de novo in all cases assessed to date. U5-116kD, the protein encoded by EFTUD2, is a highly conserved spliceosomal GTPase with a central regulatory role in catalytic splicing and post-splicing-complex disassembly. MFDM is the fast multiple-malformation syndrome attributed to a defect of the major spliceosome. Our findings significantly extend the range of reported spliceosomal phenotypes in humans and pave the way for further investigation in related conditions such as Treacher Collins syndrome.

Mutations in SLC1A4, encoding the brain serine transporter, are associated with developmental delay, microcephaly and hypomyelination

BACKGROUND L-serine plays an essential role in neuronal development and function. Although a non-essential amino acid, L-serine must be synthesised within the brain because of its poor permeability by the blood-brain barrier. Within the brain, its synthesis is confined to astrocytes, and its shuttle to neuronal cells is performed by a dedicated neutral amino acid transporter, ASCT1. METHODS AND RESULTS Using exome analysis we identified the recessive mutations, p.E256K, p.L315fs, and p.R457W, in SLC1A4, the gene encoding ASCT1, in patients with developmental delay, microcephaly and hypomyelination; seizure disorder was variably present. When expressed in a heterologous system, the mutations did not affect the protein level at the plasma membrane but abolished or markedly reduced L-serine transport for p.R457W and p.E256K mutations, respectively. Interestingly, p.E256K mutation displayed a lower L-serine and alanine affinity but the same substrate selectivity as wild-type ASCT1. CONCLUSIONS The clinical phenotype of ASCT1 deficiency is reminiscent of defects in L-serine biosynthesis. The data underscore that ASCT1 is essential in brain serine transport. The SLC1A4 p.E256K mutation has a carrier frequency of 0.7% in the Ashkenazi-Jewish population and should be added to the carrier screening panel in this community.

A novel mutation in BCS1L associated with deafness, tubulopathy, growth retardation and microcephaly

We report a novel homozygous missense mutation in the ubiquinol-cytochrome c reductase synthesis-like (BCS1L) gene in two consanguineous Turkish families associated with deafness, Fanconi syndrome (tubulopathy), microcephaly, mental and growth retardation. All three patients presented with transitory metabolic acidosis in the neonatal period and development of persistent renal de Toni-Debré-Fanconi-type tubulopathy, with subsequent rachitis, short stature, microcephaly, sensorineural hearing impairment, mild mental retardation and liver dysfunction. The novel missense mutation c.142A>G (p.M48V) in BCS1L is located at a highly conserved region associated with sorting to the mitochondria. Biochemical analysis revealed an isolated complex III deficiency in skeletal muscle not detected in fibroblasts. Native polyacrylamide gel electrophoresis (PAGE) revealed normal super complex formation, but a shift in mobility of complex III most likely caused by the absence of the BCS1L-mediated insertion of Rieske Fe/S protein into complex III. These findings expand the phenotypic spectrum of BCS1L mutations, highlight the importance of biochemical analysis of different primary affected tissue and underline that neonatal lactic acidosis with multi-organ involvement may resolve after the newborn period with a relatively spared neurological outcome and survival into adulthood. CONCLUSION Mutation screening for BCS1L should be considered in the differential diagnosis of severe (proximal) tubulopathy in the newborn period. What is Known: • Mutations in BCS1L cause mitochondrial complex III deficiencies. • Phenotypic presentations of defective BCS1L range from Bjornstad to neonatal GRACILE syndrome. What is New: • Description of a novel homozygous mutation in BCS1L with transient neonatal acidosis and persistent de Toni-Debré-Fanconi-type tubulopathy. • The long survival of patients with phenotypic presentation of severe complex III deficiency is uncommon.

Changes in miRNA Expression in a Model of Microcephaly

miRNAs function to regulate gene expression through post-transcriptional mechanisms to potentially regulate multiple aspects of physiology and development. Whole transcriptome analysis has been conducted on the citron kinase mutant rat, a mutant that shows decreases in brain growth and development. The resulting differences in RNA between mutant and wild-type controls can be used to identify genetic pathways that may be regulated differentially in normal compared to abnormal neurogenesis. The goal of this thesis was to verify, with quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), changes in miRNA expression in Cit-k mutants and wild types. In addition to confirming miRNA expression changes, bio-informatics software TargetScan 5.1 was used to identify potential mRNA targets of the differentially expressed miRNAs. The miRNAs that were confirmed to change include: rno-miR-466c, mmu-miR-493, mmu-miR-297a, hsa-miR-765, and hsa-miR-1270. The TargetScan analysis revealed 347 potential targets which have known roles in development. A subset of these potential targets include genes involved in the Wnt signaling pathway which is known to be an important regulator of stem cell development.

Ocular manifestations of microcephaly with or without chorioretinopathy, lymphedema or intellectual disability (MCLID) syndrome associated with mutations in KIF11

Purpose Microcephaly with or without chorioretinopathy, lymphedema or intellectual disability (MCLID) is an autosomal dominant condition. Mutations in KIF11 have been found to be causative in approximately 75% of cases. This study describes the ocular phenotype in patients with confirmed KIF11 mutations. Methods Standard ophthalmic examination and investigation including visual acuity, refraction and fundus examination was carried out in all patients. Fundus autofluorescence imaging (FAF) was performed in three patients, and four patients underwent spectral domain optical coherence tomography (OCT). Flash electroretinography (ERG) was performed in seven patients, and five underwent additional pattern electroretinography (PERG). Results The patients ranged in age from 2 to 10 years. Most presented with visual acuity loss. Fundus examination revealed lacunae of chorioretinal atrophy. Pigmentary macular changes and optic disc pallor were present in three of seven patients. Fundus autofluorescence demonstrated hypoautofluorescence at the macula in two of three patients. The lacunae of chorioretinal atrophy were hypoautofluorescent. The OCT showed atrophic maculae in three of four patients. Follow-up in one patient showed no deterioration of the vision over a 9-year period. The lesions appear not to be progressive on the follow-up imaging. Electrophysiology showed generalized rod and cone dysfunction and severe macular dysfunction. Inner retinal dysfunction was evident in three of seven patients. Conclusions Patients with KIF11 mutations show a specific ocular phenotype with variable expressivity and intrafamilial variability. Macular atrophy and dysfunction have not been consistently documented before. The fundus lesions appear non-progressive. The findings assist in providing an accurate diagnosis and thus improving the management and follow-up of patients with this syndrome.

Semiologia neurológica numa população de escolares da primeira série do ensino fundamental

We evaluated children in the first grade of a elementary school using neurological examination. With no previous knowledgement of their educational performance, were invited all children attending five classes of the first grade of an elementary public school chosen randomly, in Itatiba / Sao Paulo / Brazil, whose parents assigned a Commitment Term for participation in this research. Children who missed three evaluations in different days or whose parents did not assigned the Commitment Term were excluded. The Traditional Neurological Examination (ENT) (Lefevre, 1972) was applied. It was considered for normal the measurement of the skull circumference, proposed by Diament & Rodrigues (1976), and the application of all ENT items. The data were stored in a database of the Epi6 Program (Epidemiologic Information), and analyzed by percentage calculation and by the c2 test. The significance level was 0.05. Children evaluated were 124. The ENT results were normal in 87 (70.16%) and altered in 37 (29.83%). Among the alterations, there were observed: light tremor, light muscular hypotonia, speech acquisition delay, macrocephaly, microcephaly, hyperactivity, cranial nerve syndrome, central facial paralysis. One child presented corticospinal tract impairment syndrome of the distal lower extremities.

Rett Syndrome With and Without Detected MECP2 Mutations: an Attempt to Redefine Phenotypes

Background: The diagnosis of Rett syndrome (RTT) is based on a set of clinical criteria, irrespective of mutation status. The aims of this study were (1) to define the clinical differences existing between patients with Rett syndrome with (Group I) and without a MECP2 mutation (Group II), and (2) to characterize the phenotypes associated with the more common MECP2 mutations. Patients and Methods: We analyzed 87 patients fulfilling the clinical criteria for RTT. All were observed and videotaped by the same paediatric neurologist. Seven common mutations were considered separately, and associated clinical features analysed. Results: Comparing Group I and II, we found differences concerning psychomotor development prior to onset, acquisition of propositive manipulation and language, and evolving autistic traits. Based on age at observation, we found differences in eye pointing, microcephaly, growth, number of stereotypies, rigidity, ataxia and ataxic-rigid gait, and severity score. Patients with truncating differed from those with missense mutations regarding acquisition of propositive words and independent gait, before the beginning of the disease, and microcephaly, growth, foot length, dystonia, rigidity and severity score, at the time of observation. Patients with the R168X mutation had a more severe phenotype, whereas those with R133C showed a less severe one. Patients with R294X had a hyperactive behaviour, and those with T158M seemed to be particularly ataxic and rigid. Conclusion: A clear regressive period (with loss of prehension and language, deceleration of growth) and the presence of more than three different stereotypies, rigidity and ataxic-rigid gait seemed to be very helpful in differentiating Group I from Group II.

Non-Progressive Leukoencephalopathy with Bilateral Temporal Cysts

We report two cases of a peculiar leukoencephalopathy with temporal cysts. Both patients have a non-progressive neurological disorder with mental retardation, microcephaly and sensorineural deafness although clinical differences between them may reflect a different aetiology. The metabolic disorders with white matter involvement and the recently described leukoencephalopathies (Van Der Knaap disease, 'vanishing white matter disease') were excluded based on clinical, biologic and imaging findings. Cytomegalovirus infection is a likely possibility in the first case although the magnetic resonance imaging picture is only partially similar to previously reported cases. Our patients are strikingly similar to the patients reported by Deonna et al. and Olivier et al. We discuss the clinical and imaging findings in our patients and the differential diagnosis considering the known disorders of the white matter in childhood.

Mutations in the MECP2 Gene Are Not a Major Cause of Rett Syndrome-Like or Related Neurodevelopmental Phenotype in Male Patients

Rett syndrome is a genetic neurodevelopmental disorder that affects mainly girls, but mutations in the causative MECP2 gene have also been identified in boys with classic Rett syndrome and Rett syndrome-like phenotypes. We have studied a group of 28 boys with a neurodevelopmental disorder, 13 of which with a Rett syndrome-like phenotype; the patients had diverse clinical presentations that included perturbations of the autistic spectrum, microcephaly, mental retardation, manual stereotypies, and epilepsy. We analyzed the complete coding region of the MECP2 gene, including the detection of large rearrangements, and we did not detect any pathogenic mutations in the MECP2 gene in these patients, in whom the genetic basis of disease remained unidentified. Thus, additional genes should be screened in this group of patients.

The effect of homozygous deletion of the BBOX1 and Fibin genes on carnitine level and acyl carnitine profile.

BACKGROUND: Carnitine is a key molecule in energy metabolism that helps transport activated fatty acids into the mitochondria. Its homeostasis is achieved through oral intake, renal reabsorption and de novo biosynthesis. Unlike dietary intake and renal reabsorption, the importance of de novo biosynthesis pathway in carnitine homeostasis remains unclear, due to lack of animal models and description of a single patient defective in this pathway. CASE PRESENTATION: We identified by array comparative genomic hybridization a 42 months-old girl homozygote for a 221 Kb interstitial deletions at 11p14.2, that overlaps the genes encoding Fibin and butyrobetaine-gamma 2-oxoglutarate dioxygenase 1 (BBOX1), an enzyme essential for the biosynthesis of carnitine de novo. She presented microcephaly, speech delay, growth retardation and minor facial anomalies. The levels of almost all evaluated metabolites were normal. Her serum level of free carnitine was at the lower limit of the reference range, while her acylcarnitine to free carnitine ratio was normal. CONCLUSIONS: We present an individual with a completely defective carnitine de novo biosynthesis. This condition results in mildly decreased free carnitine level, but not in clinical manifestations characteristic of carnitine deficiency disorders, suggesting that dietary carnitine intake and renal reabsorption are sufficient to carnitine homeostasis. Our results also demonstrate that haploinsufficiency of BBOX1 and/or Fibin is not associated with Primrose syndrome as previously suggested.

Recurrent mutations in the CDKL5 gene: Genotype-phenotype relationships.

Mutations in the cyclin-dependent kinase-like 5 gene (CDKL5) have been described in epileptic encephalopathies in females with infantile spasms with features that overlap with Rett syndrome. With more than 80 reported patients, the phenotype of CDKL5-related encephalopathy is well-defined. The main features consist of seizures starting before 6 months of age, severe intellectual disability with absent speech and hand stereotypies and deceleration of head growth, which resembles Rett syndrome. However, some clinical discrepancies suggested the influence of genetics and/or environmental factors. No genotype-phenotype correlation has been defined and thus there is a need to examine individual mutations. In this study, we analyzed eight recurrent CDKL5 mutations to test whether the clinical phenotype of patients with the same mutation is similar and whether patients with specific CDKL5 mutations have a milder phenotype than those with other CDKL5 mutations. Patients bearing missense mutations in the ATP binding site such as the p.Ala40Val mutation typically walked unaided, had normocephaly, better hand use ability, and less frequent refractory epilepsy when compared to girls with other CDKL5 mutations. In contrast, patients with mutations in the kinase domain (such as p.Arg59X, p.Arg134X, p.Arg178Trp/Pro/Gln, or c.145 + 2T > C) and frameshift mutations in the C-terminal region (such as c.2635_2636delCT) had a more severe phenotype with infantile spasms, refractory epileptic encephalopathy, absolute microcephaly, and inability to walk. It is important for clinicians to have this information when such patients are diagnosed. © 2012 Wiley Periodicals, Inc.

Zika virus damages the human placental barrier and presents marked fetal neurotropism

An unusually high incidence of microcephaly in newborns has recently been observed in Brazil. There is a temporal association between the increase in cases of microcephaly and the Zika virus (ZIKV) epidemic. Viral RNA has been detected in amniotic fluid samples, placental tissues and newborn and fetal brain tissues. However, much remains to be determined concerning the association between ZIKV infection and fetal malformations. In this study, we provide evidence of the transplacental transmission of ZIKV through the detection of viral proteins and viral RNA in placental tissue samples from expectant mothers infected at different stages of gestation. We observed chronic placentitis (TORCH type) with viral protein detection by immunohistochemistry in Hofbauer cells and some histiocytes in the intervillous spaces. We also demonstrated the neurotropism of the virus via the detection of viral proteins in glial cells and in some endothelial cells and the observation of scattered foci of microcalcifications in the brain tissues. Lesions were mainly located in the white matter. ZIKV RNA was also detected in these tissues by real-time-polymerase chain reaction. We believe that these findings will contribute to the body of knowledge of the mechanisms of ZIKV transmission, interactions between the virus and host cells and viral tropism.