Genome wide analysis in a family with sensorineural hearing loss,autism and mental retardation

Hearing loss is a common congenital anomaly with an incidence of 1 in 1000 live births. It has been described together with several other clinical features as fortuitous association or commune genetic syndrome. In this study, we investigated a consanguineous Tunisian family with moderate to profound congenital hearing loss, mental retardation and autistic behaviors. We performed a genome wide microarray analysis study using approximately 300,000 SNPs in a common set of 7 invidious of this family. We identified regions of suggestive linkage with hearing loss on chromosomes 6p12 and 7q34. In addition, we identified a deletion on chromosome 8p in the two autistic individuals. This report presents an illustration of how consanguinity could increase familial clustering of multiple hereditary diseases within the same family. The application of next generation sequencing for this family seems to be a good strategy for further analysis leading to the identification of candidate genes.     

Marden-Walker syndrome: case report, nosologic discussion and aspects of counseling

The Marden-Walker syndrome is characterized by a mask-like face with blepharophimosis, micrognathia, cleft or high-arched palate, low-set ears, congenital joint contractures, decreased muscular mass, failure to thrive and psychomotor retardation. We report a boy with a phenotype mostly resembling the condition named Marden-Walker syndrome, with many of the criteria proposed for diagnosing this particular phenotype. In addition he had hypoplastic corpus callosum, cerebellar vermis hypoplasia, enlarged cisterna magna and vertebral abnormalities. During pregnancy there were reduced fetal movements. In the present patient the fetal hypokinesia sequence, due to central nervous system malformation, is most compatible with the diagnosis of Marden-Walker syndrome. The etiology is probably heterogeneous, but the possibility of autosomal recessive inheritance should be considered in genetic counseling.     

De Novo Mutations in NALCN Cause a Syndrome Characterized by Congenital Contractures of the Limbs and Face,Hypotonia, and Developmental Delay

Freeman-Sheldon syndrome, or distal arthrogryposis type 2A (DA2A), is an autosomal-dominant condition caused by mutations in MYH3 and characterized by multiple congenital contractures of the face and limbs and normal cognitive development. We identified a subset of five individuals who had been putatively diagnosed with “DA2A with severe neurological abnormalities” and for whom congenital contractures of the limbs and face, hypotonia, and global developmental delay had resulted in early death in three cases; this is a unique condition that we now refer to as CLIFAHDD syndrome. Exome sequencing identified missense mutations in the sodium leak channel, non-selective (NALCN) in four families affected by CLIFAHDD syndrome. We used molecular-inversion probes to screen for NALCN in a cohort of 202 distal arthrogryposis (DA)-affected individuals as well as concurrent exome sequencing of six other DA-affected individuals, thus revealing NALCN mutations in ten additional families with “atypical” forms of DA. All 14 mutations were missense variants predicted to alter amino acid residues in or near the S5 and S6 pore-forming segments of NALCN, highlighting the functional importance of these segments. In vitro functional studies demonstrated that NALCN alterations nearly abolished the expression of wild-type NALCN, suggesting that alterations that cause CLIFAHDD syndrome have a dominant-negative effect. In contrast, homozygosity for mutations in other regions of NALCN has been reported in three families affected by an autosomal-recessive condition characterized mainly by hypotonia and severe intellectual disability. Accordingly, mutations in NALCN can cause either a recessive or dominant condition characterized by varied though overlapping phenotypic features, perhaps based on the type of mutation and affected protein domain(s).     

Mutation analysis of CHRNA1, CHRNB1, CHRND, and RAPSN genes in multiple pterygium syndrome/fetal akinesia patients

Multiple pterygium syndromes (MPS) comprise a group of multiple congenital anomaly disorders characterized by webbing (pterygia) of the neck, elbows, and/or knees and joint contractures (arthrogryposis). MPS are phenotypically and genetically heterogeneous but are traditionally divided into prenatally lethal and nonlethal (Escobar) types. Previously, we and others reported that recessive mutations in the embryonal acetylcholine receptor g subunit (CHRNG) can cause both lethal and nonlethal MPS, thus demonstrating that pterygia resulted from fetal akinesia. We hypothesized that mutations in acetylcholine receptor-related genes might also result in a MPS/fetal akinesia phenotype and so we analyzed 15 cases of lethal MPS/fetal akinesia without CHRNG mutations for mutations in the CHRNA1, CHRNB1, CHRND, and rapsyn (RAPSN) genes. No CHRNA1, CHRNB1, or CHRND mutations were detected, but a homozygous RAPSN frameshift mutation, c.1177-1178delAA, was identified in a family with three children affected with lethal fetal akinesia sequence. Previously, RAPSN mutations have been reported in congenital myasthenia. Functional studies were consistent with the hypothesis that whereas incomplete loss of rapsyn function may cause congenital myasthenia, more severe loss of function can result in a lethal fetal akinesia phenotype.     

Localisation of merosin-positive congenital muscular dystrophy to chromosome 4p16.3

The congenital muscular dystrophies (CMD) are a heterogeneous group of autosomal recessive disorders, which present within the first 6 months of life with hypotonia, muscle weakness and contractures, associated with dystrophic changes on skeletal muscle biopsy. We have previously reported a large consanguineous family segregating merosin-positive congenital muscular dystrophy, in which involvement of known CMD loci was excluded. A genome-wide linkage search of the family conducted using microsatellite markers spaced at 10-Mb intervals failed to identify a disease locus. A second scan using a high-density SNP array, however, permitted a novel CMD locus on 4p16.3 to be identified (multipoint LOD score 3.4). Four additional consanguineous CMD families with a similar phenotype were evaluated for linkage to a 4.14-Mb interval on 4p16.3; however, none showed any evidence of linkage to the region. Our findings further illustrate the utility of highly informative SNP arrays compared with standard panels of microsatellite markers for the mapping of recessive disease loci.     

Atrichia, abnormal EEG, epilepsy and mental retardation in two sisters.

Two daughters of a nonconsanguineous couple are described. Both present mental retardation, epileptic seizures, congenital atrichia, histologically anomalous skin and abnormal EEG pattern. From a discussion of the literature on atrichia, the forms without involvement of teeth, nails and hidrosis, among which recessive inheritance prevails, are distinguished from each other. None of them coincide with the syndrome described here.     

Genetic counseling of a couple presenting respectively terminal transverse defects and congenital arthrogryposis.

A 29-year-old woman consulted together with her husband for a problem of congenital joint contractures. Clinical findings in the woman were characteristic of "amyoplasia congenita". In view of the severe distal limb involvement, the possibility of a distal arthrogryposis was also considered. Unexpectedly, the husband presented terminal transverse defects, mainly of the feet, suggestive of Adams-Oliver syndrome, an autosomal dominant condition with variable expression. This discovery significantly altered the counseling given to the couple, i.e. they had to be given a high recurrence risk for congenital limb malformations in their offspring and rigorous echographic monitoring of future pregnancies was advised.     

A variant of Freeman-Sheldon syndrome maps to 11p15.5-pter.

Distal arthrogryposis type 1 (DA1) and Freeman-Sheldon syndrome (FSS) are the two most common known causes of inherited multiple congenital contractures. We recently have characterized a new disorder (DA2B) with a phenotype intermediate between DA1 and FSS. We report the mapping of a gene that causes DA2B to chromosome 11p15.5-pter. Linkage analysis in a single kindred generated a positive LOD score of 5.31 at theta = 0 with the marker D11S922, and recombinants localize the gene to an approximately 3.5-6.5-cM region between the marker TH and the telomere. Analysis of additional families improves the LOD score to 6.45 at theta = 0 and suggests linkage homogeneity for DA2B.     

The effects of temperature, local anaesthetics, pH, divalent cations, and group-specific reagents on repriming and repolarization-induced contractures in frog skeletal muscle.

Contractures appear during repolarization of frog toe muscles in media containing perchlorate in place of chloride. These contractures were suppressed or delayed by certain procedures which retard the repriming of K contractures, i.e., by sufficient reduction in temperature or by alkaline pH in solutions lacking divalent cations. They also were greatly reduced without interference with repriming after treatment with a reagent which selectively modifies free amino groups. In the presence of appropriate concentrations of procaine, repriming was markedly impaired with only a small reduction in the amplitude of repolarization-induced contractures. Small contractures were produced during repolarization in chloride solutions in the presence of 10 mM procaine at pH 8.0. None of these procedures affected the changes produced by perchlorate solutions in the potential dependence and the time course of K contractures. The results support the view that activation and inactivation of contraction following depolarization are separate potential dependent processes. Tension appears to develop during repolarization when the reversal of inactivation occurs before the reversal of activation is completed, both steps being necessary to recover the reprimed resting state.     

Autosomal recessive sensorineural-conductive deafness,mental retardation,and pinna anomalies

Summary Three siblings, a boy and two girls aged 11, 9, and 4 years, were found to have a congenital disorder characterized by malformed, low-set ears and sensorineural-conductive hearing loss. Variable expressivity was evident, since the boy had both types I and III of microtia and his two sisters had only type I. The normal parents were third cousins. The analysis of these findings permits the identification of a distinct nosologic entity due to the homozygocity of an autosomal recessive mutation.     

Congenital heart defect and mental retardation in a patient with a 13q33.1-34 deletion

13q deletion syndrome is a rare genetic disorder caused by deletions of the long arm of chromosome 13. Patients with 13q deletion display a variety of phenotypic features. We describe a one-year-old female patient with congenital heart defects (CHD), facial anomalies, development and mental retardation. We identified a 12.75Mb deletion in chromosome region 13q33.1-34 with high resolution SNP Array (Human660W-Quad, Illumina, USA). This chromosome region contains about 55 genes, including EFNB2, ERCC5, VGCNL1, F7, and F10. Comparing our findings with previously reported 13q deletion patients with congenital heart defects, we propose that the 13q33.1-34 deletion region might contain key gene(s) associated with cardiac development. Our study also identified a subclinical deficiency of Factors VII and X in our patient with Group 3 of 13q deletion syndrome.     

A comparison of the effects of cationic, anionic, and neutral amphipathic agents on the contractile behaviour of frog skeletal muscle. I. Twitches and potential threshold for contraction

Cationic, anionic, and neutral amphipathic agents displayed striking differences as well as similarities in their effects on the contractile function of frog skeletal muscle. Slowed repolarization during the action potential appeared to account for twitch potentiation by low concentrations of alkyl trimethylammonium and by small n-alkanols (propanol, butanol). Small n-alkanols also caused a decrease in the potential threshold for K contractures and slower relaxation of submaximum K contractures as well as enhancement of chloride withdrawal and caffeine contractures, but these effects were not observed with larger alkanols. For the ionic amphipathic agents, the direction of the changes in the relation between Ko and K-contracture tension could be accounted for on the basis of the expected changes in surface charge, but the effects of these two types of agents on the rate of relaxation of submaximum K contractures were disproportionate and with the cationic series were opposite in direction to those produced by inorganic divalent cations. The reductions in the amplitude of chloride-withdrawal contractures by cationic as well as anionic amphipaths indicated that both types of agents can impair excitation-contraction coupling. Similar depressant effects on caffeine contractures demonstrate that these responses also can be influenced by events restricted to the external lamina of the sarcolemma. It is concluded that opposite effects can be produced by similar perturbations in different regions of the sarcolemma and that electrostatic as well as hydrophobic interactions can make an important contribution to the effects of amphipathic agents on twitches and contractures in skeletal muscle.     

16q subtelomeric deletion in proband with congenital malformations and mental retardation

We present a female child with mild mental retardation and congenital malformations. After fluorescence in situ hybridization (FISH) we found only abnormal karyotype in all cells. We used rapid FISH and original DNA probes--PAC62.10.1 and PAC20.19.N, specific for segments of chromosome 16q24. Karyotype of proband 46,XX.ish del(16)(q24.2:) (PAC20.19.N,PAC62.10.1-). Parent karyotypes are normal. This case may suggest the presence of clinical picture 16q- with defined clinical polymorphism at small telomeric loss, and also its necessary of the use of molecular-cytogenetic techniques in genetic departments.     

Case of unbalanced translocation (18, 22) in a child with congenital mental retardation

A cytogenetical examination of a boy aged 4 with congenital mental deficiency and multiple anomalies of its phenotype has revealed unbalanced translocation (18, 22) (18 qter----cen----22 qter).     

Congenital contractures,short stature,abnormal face,microcephaly, scoliosis,hip dislocation,and severe psychomotor retardation in two unrelated girls. a new MCA/MR syndrome?

Severe mental retardation, congenital contractures, short stature, microcephaly, ptosis, myopia, beaked nose, abnormal teeth, hip dislocation, and severe scoliosis, are described in a 16-year-old and an unrelated 24-year-old females. Results of all laboratory investigations were normal. Review of the literature, of the London Dysmorphology Data Base and POSSUM did not yield to any diagnosis. Whether these patients present a new MCA/MR syndrome is discussed.     

Lathosterolosis,a novel multiple-malformation/mental retardation syndrome due to deficiency of 3beta-hydroxysteroid-delta5-desaturase

We report the clinical, biochemical, and molecular characterization of a patient with a novel defect of cholesterol biosynthesis. This patient presented with a complex phenotype, including multiple congenital anomalies, mental retardation, and liver disease. In the patient's plasma and cells, we found increased levels of lathosterol. The biosynthesis of cholesterol in the patient's fibroblasts was defective, showing a block in the conversion of lathosterol into 7-dehydrocholesterol. The activity of 3beta-hydroxysteroid-Delta(5)-desaturase (SC5D), the enzyme involved in this reaction, was deficient in the patient's fibroblasts. Sequence analysis of the SC5D gene in the patient's DNA, showing the presence of two missense mutations (R29Q and G211D), confirmed that the patient is affected by a novel defect of cholesterol biosynthesis.     

Mutations in a novel gene, NHS, cause the pleiotropic effects of Nance-Horan syndrome, including severe congenital cataract, dental anomalies, and mental retardation

Nance-Horan syndrome (NHS) is an X-linked disorder characterized by congenital cataracts, dental anomalies, dysmorphic features, and, in some cases, mental retardation. NHS has been mapped to a 1.3-Mb interval on Xp22.13. We have confirmed the same localization in the original, extended Australian family with NHS and have identified protein-truncating mutations in a novel gene, which we have called "NHS," in five families. The NHS gene encompasses approximately 650 kb of genomic DNA, coding for a 1,630-amino acid putative nuclear protein. NHS orthologs were found in other vertebrates, but no sequence similarity to known genes was identified. The murine developmental expression profile of the NHS gene was studied using in situ hybridization and a mouse line containing a lacZ reporter-gene insertion in the Nhs locus. We found a complex pattern of temporally and spatially regulated expression, which, together with the pleiotropic features of NHS, suggests that this gene has key functions in the regulation of eye, tooth, brain, and craniofacial development.     

Mutations in KLHL40 Are a Frequent Cause of Severe Autosomal-Recessive Nemaline Myopathy

Nemaline myopathy (NEM) is a common congenital myopathy. At the very severe end of the NEM clinical spectrum are genetically unresolved cases of autosomal-recessive fetal akinesia sequence. We studied a multinational cohort of 143 severe-NEM-affected families lacking genetic diagnosis. We performed whole-exome sequencing of six families and targeted gene sequencing of additional families. We identified 19 mutations in KLHL40 (kelch-like family member 40) in 28 apparently unrelated NEM kindreds of various ethnicities. Accounting for up to 28% of the tested individuals in the Japanese cohort, KLHL40 mutations were found to be the most common cause of this severe form of NEM. Clinical features of affected individuals were severe and distinctive and included fetal akinesia or hypokinesia and contractures, fractures, respiratory failure, and swallowing difficulties at birth. Molecular modeling suggested that the missense substitutions would destabilize the protein. Protein studies showed that KLHL40 is a striated-muscle-specific protein that is absent in KLHL40-associated NEM skeletal muscle. In zebrafish, klhl40a and klhl40b expression is largely confined to the myotome and skeletal muscle, and knockdown of these isoforms results in disruption of muscle structure and loss of movement. We identified KLHL40 mutations as a frequent cause of severe autosomal-recessive NEM and showed that it plays a key role in muscle development and function. Screening of KLHL40 should be a priority in individuals who are affected by autosomal-recessive NEM and who present with prenatal symptoms and/or contractures and in all Japanese individuals with severe NEM.     

X-linked mental retardation and epigenetics

The search for the genetic defects in constitutional diseases has so far been restricted to direct methods for the identification of genetic mutations in the patients' genome. Traditional methods such as karyotyping, FISH, mutation screening, positional cloning and CGH, have been complemented with newer methods including array-CGH and PCR-based approaches (MLPA, qPCR). These methods have revealed a high number of genetic or genomic aberrations that result in an altered expression or reduced functional activity of key proteins. For a significant percentage of patients with congenital disease however, the underlying cause has not been resolved strongly suggesting that yet other mechanisms could play important roles in their etiology. Alterations of the 'native' epigenetic imprint might constitute such a novel mechanism. Epigenetics, heritable changes that do not rely on the nucleotide sequence, has already been shown to play a determining role in embryonic development, X-inactivation, and cell differentiation in mammals. Recent progress in the development of techniques to study these processes on full genome scale has stimulated researchers to investigate the role of epigenetic modifications in cancer as well as in constitutional diseases. We will focus on mental impairment because of the growing evidence for the contribution of epigenetics in memory formation and cognition. Disturbance of the epigenetic profile due to direct alterations at genomic regions, or failure of the epigenetic machinery due to genetic mutations in one of its components, has been demonstrated in cognitive derangements in a number of neurological disorders now. It is therefore tempting to speculate that the cognitive deficit in a significant percentage of patients with unexplained mental retardation results from epigenetic modifications.     

Growth retardation, distinct oriental-like facies, glaucoma, brachydactyly, ventricular septal defect and speech disorder. An unknown entity.

A caucasian boy with distinct oriental-like facies, short stature, brachydactyly, congenital ventricular septal defect, glaucoma, and speech disorder is reported. Routine laboratory tests, karyotype, and hormonal profile (IGF 1, growth hormone during provocative testing, thyroid hormones, prolactin, gonadotrophins) were normal. Radiologic skeletal survey did not disclose any abnormality. Both parents were apparently normal, but short in stature.