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MYO15A is located at the DFNB3 locus on chromosome 17p11.2, and encodes myosin-XV, an unconventional myosin critical for the formation of stereocilia in hair cells of cochlea. Recessive mutations in this gene lead to profound autosomal recessive nonsyndromic hearing loss (ARNSHL) in humans and the shaker2 (sh2) phenotype in mice. Here, we performed a study on 140 Iranian families in order to determine mutations causing ARNSHL. The families, who were negative for mutations in GJB2, were subjected to linkage analysis. Eight of these families showed linkage to the DFNB3 locus, suggesting a MYO15A mutation frequency of 5.71% in our cohort of Iranian population. Subsequent sequencing of the MYO15A gene led to identification of 7 previously unreported mutations, including 4 missense mutations, 1 nonsense mutation, and 2 deletions in different regions of the myosin-XV protein.

Objective Hereditary hearing impairment is a genetically heterogeneous disorder. In spite of this, mutations in the GJB2 gene, encoding connexin 26 (Cx26), are a major cause of nonsyndromic recessive hearing loss in many countries and are largely dependent on ethnic groups. The purpose of our study was to characterize the type and prevalence of GJB2 mutations among Azeri population of Iran. Methods Fifty families presenting autosomal recessive nonsyndromic hearing loss from Ardabil province of Iran were studied for mutations in GJB2 gene. All DNA samples were screened for c.35delG mutation by ARMS PCR. Samples from patients who were normal for c.35delG were analyzed for the other variations in GJB2 by direct sequencing. In the absence of mutation detection, GJB6 was screened for the del(GJB6-D13S1830) and del(GJB6-D13S1854). Result Thirteen families demonstrated alteration in the Cx26 (26%). The 35delG mutation was the most common one, accounting for 69.2% (9 out of 13 families). All the detected families were homozygous for this mutation. Two families were homozygous for delE120 and 299–300delAT mutations. We also identified a novel mutation: c.463–464 delTA in 2 families resulting in a frame shift mutation. Conclusion Our results suggest that c.35delG mutation in the GJB2 gene is the most important cause of GJB2 related deafness in Iranian Azeri population.

Objective Hereditary hearing loss is the most common neurosensory disorder in humans. Half of the cases have genetic etiology with extraordinary genetic heterogeneity. Mutations in one gene, GJB2, are the most common cause for autosomal recessive non-syndromic hearing loss (ARNSHL) in many different populations. GJB2 encodes a gap junction channel protein (connexin 26), and is located on DFNB1 locus on chromosome 13q12.11 which also involve another connexin gene, GJB6. Mutation screening of GJB2 revealed that a high number of patients with deaf phenotype have heterozygous genotype and carry only one mutant allele. As the first comprehensive study in Iran, we have targeted GJB2-related Iranian heterozygotes, looking for second mutant allele which leads to hearing impairment. They bear first mutation in their coding exon of GJB2. Method Using PCR-based direct sequencing, we assessed 103 patients with ARNSHL for variants in non-coding exon and promoter region of this gene, for the first time in Iran. Result We have identified the second mutant allele in splice site of exon-1 of GJB2 which is known as IVS1 + 1G > A in 17 probands. We found no mutation in promoter region of GJB2. Conclusion Our findings reveal that IVS1 + 1G > A mutation in noncoding exon of GJB2 is the most common mutation after 35delG within multi ethnical Iranian heterozygote samples. It emphasizes to approach exon1 of GJB2 in case of ARNSHL genetic diagnosis.

Mutations in GJB2, encoding connexin 26 (Cx26), cause both autosomal dominant and autosomal recessive nonsyndromic hearing loss at the DFNA3 and DFNB1 loci, respectively. Most of the over 100 described GJB2 mutations cause autosomal recessive nonsyndromic hearing loss. Only a minority has been associated with autosomal dominant hearing loss. In this study, we present two families with autosomal dominant nonsyndromic hearing loss caused by a novel mutation in GJB2 (p.Asp46Asn). Both families were ascertained from the same village in northern Iran consistent with a founder effect. This finding implicates the D46N missense mutation in Cx26 as a common cause of deafness in this part of Iran mandating mutation screening of GJB2 for D46N in all persons with hearing loss who originate from this geographic region.

By using homozygosity mapping in a consanguineous Pakistani family, we detected linkage of nonsyndromic hearing loss to a 7.6 Mb region on chromosome 3q13.31-q21.1 within the previously reported DFNB42 locus. Subsequent candidate gene sequencing identified a homozygous nonsense mutation (c.1135G>T [p.Glu379X]) in ILDR1 as the cause of hearing impairment. By analyzing additional consanguineous families with homozygosity at this locus, we detected ILDR1 mutations in the affected individuals of 10 more families from Pakistan and Iran. The identified ILDR1 variants include missense, nonsense, frameshift, and splice-site mutations as well as a start codon mutation in the family that originally defined the DFNB42 locus. ILDR1 encodes the evolutionarily conserved immunoglobulin-like domain containing receptor 1, a putative transmembrane receptor of unknown function. In situ hybridization detected expression of Ildr1, the murine ortholog, early in development in the vestibule and in hair cells and supporting cells of the cochlea. Expression in hair cell- and supporting cell-containing neurosensory organs is conserved in the zebrafish, in which the ildr1 ortholog is prominently expressed in the developing ear and neuromasts of the lateral line. These data identify loss-of-function mutations of ILDR1, a gene with a conserved expression pattern pointing to a conserved function in hearing in vertebrates, as underlying nonsyndromic prelingual sensorineural hearing impairment.

The genetic variants leading to impairment of intellectual performance are highly diverse and are still poorly understood. ST3GAL3 encodes the Golgi enzyme β-galactoside-α2,3-sialyltransferase-III that in humans predominantly forms the sialyl Lewis a epitope on proteins. ST3GAL3 resides on chromosome 1 within the MRT4 locus previously identified to associate with nonsyndromic autosomal recessive intellectual disability. We searched for the disease-causing mutations in the MRT4 family and a second independent consanguineous Iranian family by using a combination of chromosome sorting and next-generation sequencing. Two different missense changes in ST3GAL3 cosegregate with the disease but were absent in more than 1000 control chromosomes. In cellular and biochemical test systems, these mutations were shown to cause ER retention of the Golgi enzyme and drastically impair ST3Gal-III functionality. Our data provide conclusive evidence that glycotopes formed by ST3Gal-III are prerequisite for attaining and/or maintaining higher cognitive functions.

Introduction Mental retardation (MR) has heterogeneous aetiology mostly with genetic causes. Chromosomal aberrations are one of the most common causes of MR. Reports on chromosome abnormality rate among consanguineous families are sparse. In order to identify the chromosome abnormality rate in idiopathic mental retardation from consanguineous marriages, a total of 322 Iranian families with positive family history for MR were investigated in the Genetics Research Center. Material and methods In the majority of families (92%) at least two sibs were affected with MR and none had specific chromosomal syndromes such as Down syndrome. Standard cytogenetic techniques using high resolution GTG banding were carried out on all the patients. Results The overall chromosome abnormality rate contributing to mental retardation was 1.24% (4 cases), which comprised 46,XY,der(18)t(4;18)(q31.1;q23)mat; 45,XY,-21,-22,+der(22)t(21;22)(q21.1;q13.33)mat; 46,XY,rec(2)dup(2p)inv(2)(p25.1q37.3)pat, and 46,XY,der(11)t(10;11)(q25.2;q25)pat. Conclusions Although the most likely genetic cause of mental retardation in patients with consanguineous parents is autosomal recessive, the fact that 1.24% of our patients had chromosomal abnormalities emphasizes the importance of cytogenetic investigation as the first laboratory genetic tests for all MR patients. To our knowledge, this is the first report on the rate of chromosome abnormality among patients with idiopathic mental retardation from consanguineous marriages.

Brachyphalangy, polydactyly and tibial aplasia/hypoplasia syndrome (OMIM 609945) is a rare congenital disorder. Only seven patients have been reported to date, and the etiology of this syndrome is unknown. Autosomal dominant inheritance with variable expression has been suggested based on the presence of minor features in some parents and the fact that neither parental consanguinity nor pairs of affected siblings were observed. We report on the first patient with this syndrome who was born to consanguineous parents. Neither the mother nor the father, who were first cousins, had clinical features suggestive of a manifestation of brachyphalangy, polydactyly and tibial aplasia/hypoplasia syndrome. The patient had no siblings, and the family history was unremarkable. Clinical problems included brachydactyly of hands and feet, splaying of fingers and toes, preaxial polydactyly of feet, bilateral tibial aplasia, shortened radius and ulna, and characteristic facial dysmorphic signs. The detailed description of this patient adds to our knowledge of the clinical manifestations of brachyphalangy, polydactyly and tibial aplasia/hypoplasia syndrome and will eventually also contribute to the elucidation of the underlying gene defects.

Hearing loss is the most common form of sensory impairment in humans and is frequently progressive in nature. Here we link a previously uncharacterized gene to hearing impairment in mice and humans. We show that hearing loss in the ethylnitrosourea (ENU)-induced samba mouse line is caused by a mutation in Loxhd1. LOXHD1 consists entirely of PLAT (polycystin/lipoxygenase/alpha-toxin) domains and is expressed along the membrane of mature hair cell stereocilia. Stereociliary development is unaffected in samba mice, but hair cell function is perturbed and hair cells eventually degenerate. Based on the studies in mice, we screened DNA from human families segregating deafness and identified a mutation in LOXHD1, which causes DFNB77, a progressive form of autosomal-recessive nonsyndromic hearing loss (ARNSHL). LOXHD1, MYO3a, and PJVK are the only human genes to date linked to progressive ARNSHL. These three genes are required for hair cell function, suggesting that age-dependent hair cell failure is a common mechanism for progressive ARNSHL.

To the Editor: Hearing impairment is the most common genetic sensory defect in humans worldwide. It is estimated that profound hearing loss occurs in 4 out of every 10,000 children [Morton 1991]. Seventy percent of hereditary SNHL is nonsyndromic (DFN) and in at least 80% of these cases the inheritance is autosomal recessive (DFNB) [Smith et al., 2005]. Genetic studies have shown that mutations in 67 loci and 25 genes are associated with DFNB [Van Camp and Smith, 2008]. Further understanding of the molecular mechanisms associated with SNHL will assist in the development of therapeutics for hereditary hearing loss in the future. Mutations in the RDX gene that encodes the radixin protein have recently been shown to cause DFNB24 hearing loss in consanguineous Pakistani and Indian families [Khan et al., 2007]. In this study, we report a novel splice site mutation in the RDX gene in a consanguineous Iranian family with autosomal recessive non-syndromic hearing loss (ARNSHL). This mutation is only the fourth to be identified at the rare DFNB24 ARNSHL locus and the second that is predicted to lead to nonsense mediated decay or a truncated version of the radixin protein. A five-generation Iranian family with apparent congenital ARNSHL was studied (Fig.1). Family members in the fourth and fifth generations had severe-to-profound hearing loss suggesting autozygosity by descent (Fig.2). A complete physical examination and audiologic testing was completed on consenting family members and blood samples were obtained for DNA extraction. Liver function testing on affected individual V:2 showed total bilirubin (0.4 mg/dl), direct bilirubin (0.1 mg/dl), alanine transaminase (41 U/ml), aspartate transaminase (35 U/ml) and alkaline phosphatase (229 U/L), all normal. Human Research Institutional Review boards at the Welfare Science and Rehabilitation University and Iran University of Medical Sciences and the University of Iowa approved all procedures. Fig. 1 Pedigree of the Iranian family with ARNSHL. Open symbols = unaffected; filled symbols = ARNSHL. The genotypes and haplotypes for affected individuals and carriers are shown. Fig. 2 Audiograms from affected family members. All affected individuals displayed severe-to-profound bilateral ARNSHL. Genomic DNA from individuals III:1, IV:3, IV:4, IV:5, IV:6, IV:7, IV:8, V:1, V:2, V:3, and V:6 (Fig.1) was genotyped for 50,000 SNPs using Affymetrix (Santa Clara, CA, USA) 50K XBA GeneChips at the Translational Genomics Research Institute (Pheonix, Arizona). All genotypes were determined using the BRLMM genotyping algorithm [Di et al., 2005; Rabbee and Speed 2006]. Genotyping data were examined with PEDSTATS [Wigginton and Abecasis 2005] for Mendelian inheritance errors and MERLIN [Abecasis et al., 2002] for errors based on inferred double recombination events between tightly linked markers. Because the size of the pedigree was above the threshold for efficient implementation of the Lander-Green multipoint linkage mapping algorithm, a smaller subset of the pedigree was used which only considered the descendents of individuals III:1, III:2, III:3, III:4 (Fig.1). An autosomal, genome-wide parametric linkage analysis was carried out as the pedigree showed affected males and females. All linkage analyses were performed with MERLIN. The Lander-Green multipoint linkage mapping algorithm assumes linkage equilibrium. The markers were too close together to be in linkage equilibrium, so a smaller marker set was created using an in-house program (linkdatagen.pl;http://bioinf.wehi.edu.au/ software/). The binsize was set to 0.5 cM (i.e. the highest heterozygosity marker was chosen in each 0.5 cM interval) and 6140 autosomal markers were selected. Linkage analyses were carried out using the following parameters for the disease allele a, and normal allele A - Pr(a)=0.0001, Pr(disease|aa)=0.999, Pr(disease|AA or Aa)=0.001 - reflecting a highly penetrant, autosomal recessive disease model. The genetic map used was generated by Affymetrix using interpolation based on the empirical deCode, Marshfield and SNP Linkage (SLM1) genetic maps [Broman et al., 1998; Kong et al., 2002]. The physical map used was derived from the UCSC database using the NCBI Build 36.1 (March 2006; http://genome.ucsc.edu/cgi-bin/hgGateway). In the genome-wide analysis 38 Mendelian (.07% error rate) and 168 double recombinant errors were detected. A peak LOD score of 4.13 was achieved for a region on chromosome 11 (Fig.3) and there were no other regions where the LOD score exceeded 3. The critical region spanned approximately 3.6 cM between markers rs1789819 (109,185,632 bp) and rs10502160 (112,122,938 bp) (Fig.1). All four affected individuals included in the mapping were homozygous for a region between 108.814 cM and 112.368 cM on chromosome 11 (11q22.3-23.1). Fig. 3 Graphic showing the only significant LOD score achieved in the genome-wide analysis on chromosome 11. The dashed line indicates threshold (LOD score of 3). The dotted line at LOD score of 3.6 represents the Lander-Kruglyak threshold. The peak LOD score ... The critical region contained the known ARNSHL locus DFNB24. The RDX gene was amplified and sequenced using previously reported gene-specific primers [Khan et al., 2007]. A novel homozygous splice site mutation (c.698+1G>A) in intron 7 was found to segregate in affected family members (Fig.4). The +1G nucleotide of the 5’ donor splice site is invariant among all eukaryotes [Shapiro and Senapathy, 1987]. The c.698+1G>A mutation is predicted to result in read-through into intron 7 and a stop codon immediately following the amino acids encoded by exon 7. The last residue encoded by exon 7 would remain a lysine (K) due to the redundancy of the genetic code (AAG > AAA) and the next codon created would be a stop (TAA). This is predicted to result in a severely truncated protein lacking part of the FERM3 domain and the entire α- and c-terminal (CTD) domains (Fig.5), although the mutant mRNA may be subject to nonsense mediated decay and in this case no mutant protein would be produced. The c.698+1G>A mutation was not observed in 53 (106 chromosomes) Iranian and 133 (266 chromosomes) CEPH control individuals. Fig. 4 Sequence chromatograms showing the novel c.698+1G>A mutation in the RDX gene. Fig. 5 Domain structure of the RDX gene showing mutations known to cause DFNB24 hearing loss in humans. The novel splice site mutation described in this study (c.698+1G>A) is boxed. Radixin and ezrin are present in the hair cell stereocilia of the mouse inner ear [Kitajiri et al., 2004; Pataky et al., 2004]. While it is known that radixin functions as a linker between sub-cellular actin and the plasma membrane [Niggli and Rossy 2008], the exact role of this protein in the stereocilia of hair cells is unclear. Current knowledge of the role of these proteins in the inner ear comes from study of a radixin knockout mouse model. RDX −/− mice exhibit syndromic hearing impairment and hyperbilirubinemia [Kikuchi et al., 2002; Kitajiri et al., 2004]. The murine liver phenotype does not appear to model the human phenotype. One affected individual in the family reported here and another in a previously reported DFNB24 family have been shown to have normal liver function [Khan et al., 2007]. In conclusion, we have identified the first splice site mutation in the RDX gene and the first mutation known to cause DFNB24 hearing loss in the Iranian population. Our data also suggest that, in contrast to the murine model, liver dysfunction is not a component of the human phenotype. DFNB24 appears to be a rare form of ARSNHL as only four families have been reported. Further characterization of the molecular events triggered by this new mutation may increase our understanding of the function of radixin protein in the inner ear.

Cohen syndrome is characterised by mental retardation, postnatal microcephaly, facial dysmorphism, pigmentary retinopathy, myopia, and intermittent neutropenia. Mutations in COH1 (VPS13B) have been found in patients with Cohen syndrome from diverse ethnic origins. We have carried out mutation analysis in twelve novel patients with Cohen syndrome from nine families. In this series, we have identified 13 different mutations in COH1, twelve of these are novel including six frameshift mutations, four nonsense mutations, two splice site mutations, and a one-codon deletion. Since different transcripts of COH1 have been reported previously, we have analysed the expression patterns of COH1 splice variants. The transcript variant NM_152564 including exon 28b showed ubiquitous expression in all examined human tissues. In contrast, human brain and retina showed differential splicing of exon 28 (NM_017890). Moreover, analysis of mouse tissues revealed ubiquitous expression of Coh1 homologous to human NM_152564 in all examined tissues but no prevalent alternative splicing. (C) 2008 Wiley-Liss, Inc.

We describe a partial duplication of the chromosome 16 short arm [46,XY,dup(16)(p11.2p13.1)] in an Iranian girl with autism, neurodevelopmental delay, mental retardation, very poor memory, and dysmorphism including sparse hair, upslanting palpebral fissures, long philtrum, micrognathia, hypotonia, small feet and hands, syndactyly of the fingers, and hypoplastic thumbs. The patient now four years old, has a normal twin sister, and the parents are unrelated. The abnormal 16p was originally detected by banding cytogenetic techniques, and was characterized by multicolour banding fluorescence in situ hybridization (MCB). The MCB pattern on the derivative chromosome 16 indicated a direct duplication of the region 16p11.2 to 16p13.1.

We report on three siblings with a novel mental retardation (MR) syndrome who were born to distantly related Iranian parents. The clinical problems comprised severe MR, cataracts with onset in late adolescence, kyphosis, contractures of large joints, bulbous nose with broad nasal bridge, and thick lips. Two patients also had uni- or bilateral iris coloboma. Linkage analysis revealed a single 10.4 Mb interval of homozygosity with significant LOD score in the pericentromeric region of chromosome 4 flanked by SNPs rs728293 (4p12) and rs1105434 (4q12). This interval contains more than 40 genes, none of which has been implicated in MR so far. The identification of the causative gene defect for this syndrome will provide new insights into the development of the brain and the eye.

Recent studies have shown that autosomal recessive mental retardation (ARMR) is extremely heterogeneous, and there is reason to believe that the number of underlying gene defects goes into the thousands. To date, however, only four genes have been implicated in nonsyndromic ARMR (NS-ARMR): PRSS12 (neurotrypsin), CRBN (cereblon), CC2D1A, and GRIK2. As part of an ongoing systematic study aiming to identify ARMR genes, we investigated a large consanguineous family comprising seven patients with nonsyndromic ARMR in four sibships. Genome-wide SNP typing enabled us to map the relevant genetic defect to a 4.6 Mbp interval on chromosome 8. Haplotype analyses and copy-number studies led to the identification of a homozygous deletion partly removing TUSC3 (N33) in all patients. All obligate carriers of this family were heterozygous, but none of 192 unrelated healthy individuals from the same population carried this deletion. We excluded other disease-causing mutations in the coding regions of all genes within the linkage interval by sequencing; moreover, we verified the complete absence of a functional TUSC3 transcript in all patients through RT-PCR. TUSC3 is thought to encode a subunit of the endoplasmic reticulum-bound oligosaccharyltransferase complex that catalyzes a pivotal step in the protein N-glycosylation process. Our data suggest that in contrast to other genetic defects of glycosylation, inactivation of TUSC3 causes nonsyndromic MR, a conclusion that is supported by a separate report in this issue of AJHG. TUSC3 is only the fifth gene implicated in NS-ARMR and the first for which mutations have been reported in more than one family.

Adenosine kinase deficiency is a recently described defect affecting methionine metabolism with a severe clinical phenotype comprising mainly neurological and hepatic impairment and dysmorphism. Clinical data of 11 additional patients from eight families with adenosine kinase deficiency were gathered through a retrospective questionnaire. Two liver biopsies of one patient were systematically evaluated. The main clinical symptoms are mild to severe liver dysfunction with neonatal onset, muscular hypotonia, global developmental retardation and dysmorphism (especially frontal bossing). Hepatic involvement is not a constant finding. Most patients have epilepsy and recurrent hypoglycemia due to hyperinsulinism. Major biochemical findings are intermittent hypermethioninemia, increased S-adenosylmethionine and S-adenosylhomocysteine in plasma and increased adenosine in urine. S-adenosylmethionine and S-adenosylhomocysteine are the most reliable biochemical markers. The major histological finding was pronounced microvesicular hepatic steatosis. Therapeutic trials with a methionine restricted diet indicate a potential beneficial effect on biochemical and clinical parameters in four patients and hyperinsulinism was responsive to diazoxide in two patients. Adenosine kinase deficiency is a severe inborn error at the cross-road of methionine and adenosine metabolism that mainly causes dysmorphism, brain and liver symptoms, but also recurrent hypoglycemia. The clinical phenotype varies from an exclusively neurological to a multi-organ manifestation. Methionine-restricted diet should be considered as a therapeutic option.

We have investigated a consanguineous Iranian family with eight patients who suffer from mental retardation, disturbed equilibrium, walking disability, strabismus and short stature. By autozygosity mapping we identified one region with a significant LOD score on chromosome 9(p24.2-24.3). The interval contains the VLDLR gene, which codes for the very low-density lipoprotein receptor. This protein is part of the reelin signalling pathway, which is involved in neuroblast migration in the cerebral cortex and cerebellum. A homozygous deletion encompassing VLDLR has previously been found to cause a syndrome of cerebellar ataxia and mental retardation associated with cerebellar hypoplasia in the Hutterite population known as dysequilibrium syndrome (DES). The reported deletion however, contains an additional brain expressed gene of unknown function, whose involvement in the aetiology of the phenotype could so far not be excluded. We screened the coding region of VLDLR for mutations in our patients and found a homozygous c.1342C>T nucleotide substitution, which leads to a premature stop codon in exon 10. This is the first report of a mutation in patients with DES that affects VLDLR exclusively, confirming the central role of the very low-density lipoprotein receptor in the aetiology of this condition.

Nonsyndromic mental retardation is one of the most important unresolved problems in genetic health care. Autosomal forms are far more common than X-linked forms, but, in contrast to the latter, they are still largely unexplored. Here, we report a complex mutation in the ionotropic glutamate receptor 6 gene (GRIK2, also called "GLUR6") that cosegregates with moderate-to-severe nonsyndromic autosomal recessive mental retardation in a large, consanguineous Iranian family. The predicted gene product lacks the first ligand-binding domain, the adjacent transmembrane domain, and the putative pore loop, suggesting a complete loss of function of the GLU(K6) protein, which is supported by electrophysiological data. This finding provides the first proof that GLU(K6) is indispensable for higher brain functions in humans, and future studies of this and other ionotropic kainate receptors will shed more light on the pathophysiology of mental retardation.

Background: Congenital hearing loss due to different genetic and environmental causes affects 1 in 1000 newborns. Mutations in the GJB2 (Gap Junction Beta-2) gene encoding the gap junction protein connexin 26 have been established as the main cause of autosomal recessive non-syndromic hearing loss. Materials and methods: The aim of this study was to study the frequency of GJB2 Mutations in Lorestan non-syndromic deaf population by using ARMS/PCR, DHPLC and Direct sequencing. Results: 106 chromosomes from 53 patients were studied. Eighteen chromosome (17%) carried GJB2 mutations including: 35delG, 314del14, 512insAACG, -3170G>A, W24X, V95M, 510insCGAA. The last mutation is a novel GJB2 mutation and 35delG mutation was diagnosed in 10 chromosomes (9/4%), (4 patients were homozygote and 2 patients were heterozygote). Also polymorphism V153I were found in 3 families. ‏‏‏This frequency is significantly higher compared to the whole population of Iran. Conclusion: Unexpectedly, in this research just 17 percent of cases are covered. In this study 510 insCGAA mutation was seen. This is a new mutation which is not reported in other studied populations in the world. Hence, this research shows that – at least in our studied population- the effect of other genes that could cause non-syndromic hearing loss is possible and should be studied

Non-syndromic autosomal recessive Retinitis Pigmentosa (arRP) is a highly heterogeneous genetic visual disorder with a large number of causative genes. We aimed to determine the power of Whole Exome Sequencing (WES) in the identification of the genes responsible for non-syndromic arRP among Iranian patients.We used WES, followed by the Sanger sequencing to identify the underlying gene mutations causing non-syndromic arRP.Our study revealed disease-causing mutations in known arRP genes for 10 of the 13 families studied (76.9%). These mutations included two-frameshift insertion/deletion in CRB1 and ABCA4, one splicing mutation in PDE6B, four missense mutations in RP1, CRB1, PANK2 and IFT140, as well as three stop codon mutations in RDH12, PRCD, and C2orf71. Three remaining families harbored no mutation in previously known RP genes. Of the 10 diseases causing mutations identified among the investigated Iranian patients with non-syndromic arRP, eight variants had not been reported previously. We confirmed segregation of all 10 mutations with disease phenotypes in our studied population.This study supports the genetic heterogeneity of non-syndromic arRP in Iranian patients, and provides an opportunity to show the effectiveness of WES in the identification of pathogenic mutations among patients with non-syndromic arRP born to consanguineous parents.

Calpain3 is a calcium-dependent intracellular protease involved in an autosomal recessive form of muscular dystrophy known as limb-girdle muscular dystrophy type 2A. Many pathogenic mutations have been identified in calpain3, encoded by the CAPN3 gene, which leads to weakness of the pelvic and shoulder girdle muscles. In the present study, whole exome sequencing was performed on six unrelated Iranian families who presented with progressive muscle weakness, with a strong suspicion of Calpainopathies. Genetic analysis of CAPN3 gene revealed five causative variants which had not been reported in the Iranian population before including a novel 6 bp deletion (c.795_800delCATTGA) and four previously reported mutations (c.1939G > T, c.2243G > A, c.2257delGinsAA, and c.2380 + 2T > G). Our findings indicate that exome sequencing can be a very effective and affordable method to diagnose heterogeneous muscular dystrophies, especially in consanguineous populations such as Iran.

Intellectual Disability (ID) is one of the most common disabling impairments worldwide. Autosomal recessive ID (ARID), a genetically heterogeneous disorder, is more common in countries such as Iran where the rate of consanguineous marriages is high. Considering the social-economic burden of ARID in our country, it is crucial to find out whether couples who are cousins are carriers for disease causing mutations, in order to prevent the birth of an affected child.Using exome sequencing, we screened known ARID genes in a normal individual to identify possible mutations in heterozygous form.We identified four protein coding alleles which possibly affect protein function, in different ID genes: PMM2, RBM28, SLC19A3, and VPS13B.These findings can be used to prevent the birth of children with ARID by checking the other partner for possible disease causing variants.

The genetic basis of longevity is an important field of study because the majority of supercentenarian cases experience healthy aging and may only show age-related diseases in their last few years of life. It is clear that genetic factors play an important role in survival beyond 90 years of age, but the exact relationship of genetic variants to this phenomenon remains unknown.The aim of this project was to investigate different hypotheses that describe the relationship between genetic variants and human longevity in a living Iranian man by Whole Exome Sequencing.Initially, we conducted high quality DNA extraction on a peripheral blood sample. Then, whole exome sequencing was performed on the DNA and different bioinformatic software packages and databases were used to analyze the data. Tertiary analysis was performed on four genetic hypotheses for longevity.Analysis showed that among 27 metabolic variants which are related to longevity, 18 variants encompassed the exceptional longevity allele. In comparison with the NHGRI GWAS catalog, the case had 58 trait-associated variants of which 11 were homozygous for the risk allele. We also discovered 25 novel variants within candidate genes for aging and longevity and we detected seven longevity-associated variants in the sample.This study was performed on just one sample and so the results cannot be interpreted as a generalized principle for other elderly societies, but this is the first step towards investigation of the genetic basis of longevity in Iran and provides an insight for further studies in the field of longevity.

Intellectual disability (ID) is a neuro-developmental disorder which causes considerable socio-economic problems. Some ID individuals are also affected by ataxia, and the condition includes different mutations affecting several genes.We used whole exome sequencing (WES) in combination with homozygosity mapping (HM) to identify the genetic defects in five consanguineous families among our cohort study, with two affected children with ID and ataxia as major clinical symptoms.We identified three novel candidate genes, RIPPLY1, MRPL10, SNX14, and a new mutation in known gene SURF1. All are autosomal genes, except RIPPLY1, which is located on the X chromosome. Two are housekeeping genes, implicated in transcription and translation regulation and intracellular trafficking, and two encode mitochondrial proteins. The pathogenesis of these variants was evaluated by mutation classification, bioinformatic methods, review of medical and biological relevance, co-segregation studies in the particular family, and a normal population study.Linkage analysis and exome sequencing of a small number of affected family members is a powerful new technique which can be used to decrease the number of candidate genes in heterogenic disorders such as ID, and may even identify the responsible gene(s).

In a recent screening programme on hearing loss (HL), we examined 17 common autosomal recessive nonsyndromic hearing loss (ARNSHL) genes in every consanguineous Iranian family with ARNSHL that was referred to our centre. We first screened GJB2 mutations and then utilized a panel of three to four short tandem repeats to analyse rest of the loci. Once a homozygous by descent (HBD) pattern was observed for a given locus, direct sequencing was performed to identify the possible mutation. Families that did not show HBD pattern were screened through otologic sequence capture of pathogenic exons (OtoSCOPE) targeted sequencing panel (http://medicine.uiowa.edu/morl/otoscope/). Using this strategy, we identified two novel mutations in the immunoglobuline-like domain-containing receptor 1 gene (ILDR1, MIM 609739): a 2-bp deletion, c.1217-18delTC and a substitution, c.305T>A, in consanguineous Iranian deaf families. HL, which is the most common sensorineural impairment in humans, is caused by genetic defects in about half of all cases (Babanejad et al. 2012). In Iran, the frequency of HL is one in every 166 individuals and it ranks as the second most common disabling genetic impairment next to intellectual disability (Mahdieh et al. 2010; Babanejad et al. 2012). The ILDR1 gene in the DFNB42 locus (MIM 609646), which is located on chromosome 3q13.33, codes type-I transmembrane protein with a crucial role in epithelial barrier function in the ear (Borck et al. 2011; Higashi et al. 2013). Mutations in the ILDR1 gene are common in the Iranian deaf population and have been reported in five unrelated families (Borck et al. 2011; Babanejad et al. 2012; Diaz-Horta et al. 2012). Additionally, one deaf family from Saudi Arabia and nine from Pakistan were also identified with ILDR1 mutations (Aslam et al. 2005; Borck et al. 2011; Ramzan et al. 2014). In this study, we identified two other Iranian

Item does not contain fulltext AIMP1/p43 is a multifunctional non-catalytic component of the multisynthetase complex. The complex consists of nine catalytic and three non-catalytic proteins, which catalyze the ligation of amino acids to their cognate tRNA isoacceptors for use in protein translation. To date, two allelic variants in the AIMP1 gene have been reported as the underlying cause of autosomal recessive primary neurodegenerative disorder. Here, we present two consanguineous families from Pakistan and Iran, presenting with moderate to severe intellectual disability, global developmental delay, and speech impairment without neurodegeneration. By the combination of homozygosity mapping and next generation sequencing, we identified two homozygous missense variants, p.(Gly299Arg) and p.(Val176Gly), in the gene AIMP1 that co-segregated with the phenotype in the respective families. Molecular modeling of the variants revealed deleterious effects on the protein structure that are predicted to result in reduced AIMP1 function. Our findings indicate that the clinical spectrum for AIMP1 defects is broader than witnessed so far.

Knowledge of the genes responsible for intellectual disability, particularly autosomal recessive forms, is rapidly expanding. Increasing numbers of the gene show great heterogeneity and supports the hypothesis that human genome may contain over 2000 causative genes with a critical role in brain development.Since 2004, we have applied genome-wide SNP genotyping and next-generation sequencing in large consanguineous Iranian families with intellectual disability, to identify the genes harboring disease-causing mutations. The current study paved the way for identification of responsible genes in two unrelated Iranian families.We found two novel nonsense mutations, p.C77* and p.Q115*, in the calpain catalytic domain of CAPN10, which is a cysteine protease known to be involved in pathogenesis of noninsulin-dependent diabetes mellitus. Another different mutation in this gene (p.S138_R139ins5) has previously been reported in an Iranian family. All of these patients have common clinical features in spite of specific brain structural abnormalities on MRI.Different mutations in CAPN10 have already been found in three independent Iranian families. These results have strongly supported the possible role of CAPN10 in human brain development. Altogether, we proposed CAPN10 as a promising candidate gene for intellectual disability, which should be considered in diagnostic gene panels.

In the context of a comprehensive research project, investigating novel autosomal recessive intellectual disability (ARID) genes, linkage analysis based on autozygosity mapping helped identify an intellectual disability locus on Chr.12q24, in an Iranian family (LOD score = 3.7). Next-generation sequencing (NGS) following exon enrichment in this novel interval, detected a nonsense mutation (p.Q1010*) in the CLIP1 gene. CLIP1 encodes a member of microtubule (MT) plus-end tracking proteins, which specifically associates with the ends of growing MTs. These proteins regulate MT dynamic behavior and are important for MT-mediated transport over the length of axons and dendrites. As such, CLIP1 may have a role in neuronal development. We studied lymphoblastoid and skin fibroblast cell lines established from healthy and affected patients. RT-PCR and western blot analyses showed the absence of CLIP1 transcript and protein in lymphoblastoid cells derived from affected patients. Furthermore, immunofluorescence analyses showed MT plus-end staining only in fibroblasts containing the wild-type (and not the mutant) CLIP1 protein. Collectively, our data suggest that defects in CLIP1 may lead to ARID.

Autosomal recessive gene defects are arguably the most important, but least studied genetic causes of severe cognitive dysfunction. Homozygosity mapping in 78 consanguineous Iranian families with nonsyndromic autosomal recessive mental retardation (NS-ARMR) has enabled us to determine the chromosomal localization of at least 8 novel gene loci for this condition. Our data suggest that in the Iranian population NS-ARMR is very heterogeneous, and they argue against the existence of frequent gene defects that account for more than a few percent of the cases.

Hereditary hearing loss (HHL) is a very common disorder. When inherited in an autosomal recessive manner, it typically presents as an isolated finding. Interestingly and unexpectedly, in spite of extreme heterogeneity, mutations in one gene, GJB2, are the most common cause of congenital severe-to-profound deafness in many different populations. In this study, we assessed the contributions made by GJB2 mutations and chromosome 13 g.1777179_2085947del (the deletion more commonly known as del (GJB6-D13S1830) that includes a portion of GJB6 and is hereafter called Δ(GJB6-D13S1830)) to the autosomal recessive non-syndromic deafness (ARNSD) genetic load in Iran. Probands from 664 different nuclear families were investigated. GJB2-related deafness was found in 111 families (16.7%). The carrier frequency of the 35delG mutation showed a geographic variation that is supported by studies in neighboring countries. Δ(GJB6-D13S1830) was not found. Our prevalence data for GJB2-related deafness reveal a geographic pattern that mirrors the south-to-north European gradient and supports a founder effect in southeastern Europe. © 2005 Wiley-Liss, Inc.

Mutations in plectin, a widely expressed giant cytolinker protein can lead to different diseases mostly with signs of muscular dystrophy (MD) and skin blistering. The only report of plectin-related disease without skin involvement is limb-girdle muscular dystrophy type 2Q (LGMD2Q) phenotype, showing early-onset limb-girdle muscular dystrophy symptoms with progressive manner and no cranial muscle involvement. Here, we report a non-consanguineous Iranian family with two affected sisters showing progressive limb and ocular muscle weakness. Whole Exome Sequencing (WES) led to identification of a compound heterozygous mutations, p.Gln1022Ter (c.3064CT) and p.Gly3835Ser (c.11503GA), in PLEC gene. To the best of our knowledge, this would be the first report of a patient with LGMD and myasthenic symptoms without any skin involvement, caused by plectinopathy. This observation extends the phenotypic spectrum of PLEC related diseases and suggests a variable expression of the PLEC- related symptoms.

Author(s): Alber, Michael; Kalscheuer, Vera M; Marco, Elysa; Sherr, Elliott; Lesca, Gaetan; Till, Marianne; Gradek, Gyri; Wiesener, Antje; Korenke, Christoph; Mercier, Sandra; Becker, Felicitas; Yamamoto, Toshiyuki; Scherer, Stephen W; Marshall, Christian R; Walker, Susan; Dutta, Usha R; Dalal, Ashwin B; Suckow, Vanessa; Jamali, Payman; Kahrizi, Kimia; Najmabadi, Hossein; Minassian, Berge A | Abstract: ObjectiveWe aimed to generate a review and description of the phenotypic and genotypic spectra of ARHGEF9 mutations.MethodsPatients with mutations or chromosomal disruptions affecting ARHGEF9 were identified through our clinics and review of the literature. Detailed medical history and examination findings were obtained via a standardized questionnaire, or if this was not possible by reviewing the published phenotypic features.ResultsA total of 18 patients (including 5 females) were identified. Six had de novo, 5 had maternally inherited mutations, and 7 had chromosomal disruptions. All females had strongly skewed X-inactivation in favor of the abnormal X-chromosome. Symptoms presented in early childhood with delayed motor development alone or in combination with seizures. Intellectual disability was severe in most and moderate in patients with milder mutations. Males with severe intellectual disability had severe, often intractable, epilepsy and exhibited a particular facial dysmorphism. Patients with mutations in exon 9 affecting the protein's PH domain did not develop epilepsy.ConclusionsARHGEF9 encodes a crucial neuronal synaptic protein; loss of function of which results in severe intellectual disability, epilepsy, and a particular facial dysmorphism. Loss of only the protein's PH domain function is associated with the absence of epilepsy.

Next-generation sequencing has greatly ac- celerated the search for disease-causing defects, but even for experts the data analysis can be a major challenge. To facilitate the data processing in a clinical setting, we have developed a novel medical resequencing analysis pipeline (MERAP). MERAP assesses the quality of sequencing, and has optimized capacity for calling variants, including single-nucleotide variants, insertions and deletions, copy- number variation, and other structural variants. MERAP identifies polymorphic and known causal variants by fil- tering against public domain databases, and flags nonsyn- onymous and splice-site changes. MERAP uses a logistic model to estimate the causal likelihood of a given missense variant. MERAP considers the relevant information such as phenotype and interaction with known disease-causing genes. MERAP compares favorably with GATK, one of the widely used tools, because of its higher sensitivity for detecting indels, its easy installation, and its economical use of computational resources. Upon testing more than 1,200 individuals with mutations in known and novel dis- ease genes, MERAP proved highly reliable, as illustrated here for five families with disease-causing variants. We believe that the clinical implementation of MERAP will expedite the diagnostic process of many disease-causing defects. Hum Mutat 35:1427-1435, 2014. C � 2014 Wiley Periodicals, Inc.

NDST1 was recently proposed as a candidate gene for autosomal recessive intellectual disability in two families. It encodes a bifunctional GlcNAc N-deacetylase/N-sulfotransferase with important functions in heparan sulfate biosynthesis. In mice, Ndst1 is crucial for embryonic development and homozygous null mutations are perinatally lethal. We now report on two additional unrelated families with homozygous missense NDST1 mutations. All mutations described to date predict the substitution of conserved amino acids in the sulfotransferase domain, and mutation modeling predicts drastic alterations in the local protein conformation. Comparing the four families, we noticed significant overlap in the clinical features, including both demonstrated and apparent intellectual disability, muscular hypotonia, epilepsy, and postnatal growth deficiency. Furthermore, in Drosophila, knockdown of sulfateless, the NDST ortholog, impairs long-term memory, highlighting its function in cognition. Our data confirm NDST1 mutations as a cause of autosomal recessive intellectual disability with a distinctive phenotype, and support an important function of NDST1 in human development.

Mutations in the SLC26A4 gene at the DFNB4 locus are responsible for Pendred syndrome and non-syndromic hereditary hearing loss (DFNB4). This study included 80 nuclear families with two or more siblings segregating presumed autosomal recessive hearing loss. All deaf persons tested negative for mutations in GJB2 at the DFNB1 locus and were, therefore, screened for autozygosity by descent (ABD) using short tandem repeat polymorphisms (STRPs) that flanked SLC26A4. In 12 families, homozygosity for STRPs suggested possible ABD in this genomic region. Affected individuals in five families had a positive perchlorate discharge test. Sequence analysis of SLC26A4 identified ten mutations in eight families (T420I, 1197delT, G334V, R409H, T721M, R79X, S448L, L597S, 965insA and L445W), of which, four are novel (T420I, G334V, 965insA and R79X). These results imply that Pendred syndrome is the most prevalent form of syndromic hereditary hearing loss in Iran.

Background: Mental retardation/Developmental delay (MR/DD) is present in 1 - 3% of the general population (1, 2). MR is defined as a significant impairment of both cognitive (IQ < 70) and social adaptive functions, with onset before 18 years of age. Objectives: The purpose was to determine the results of subtelomeric screening by the Multiplex Ligation Dependent Probe Amplification (MLPA) Technique in 100 selected patients with idiopathic mental retardation (IMR) in Iran. Materials and Methods: A number of 100 patients with IMR, normal karyotypes and negative fragile-X and metabolic tests were screened for subtelomeric abnormalities using MLPA technique. Results: Nine of 100 patients showed subtelomeric abnormalities with at least one of the two MLPA kits. Deletion in a single region was found in 3 patients, and in two different subtelomeric regions in 1 patient. Duplication was only single and was present in 2 patients. Three patients were found to have both a deletion and duplication.MLPA testing in the parental samples of 7 patients which was accessible showed that 4 patients were de novo, 2 patients had inherited from a clinically normal mother, and one had inherited from a clinically normal father. Screening with the two MLPA kits (SALSA P036 and SALSA P070) proved abnormality in only five of the 9 patients. Conclusions: So, the prevalence rate of abnormal subtelomeres using MLPA technique in patients with idiopathic MR in our study was 5 - 9%, the higher limit referring to the positive results of one of the two MLPA kits, and the lower limit representing the results of positive double-checking with the two MLPA kits.

Succinic semialdehyde dehydrogenase (SSADH) deficiency is a disorder of the catabolism of the neurotransmitter gamma-aminobutyric acid (GABA) with a very variable clinical phenotype ranging from mild intellectual disability to severe neurological defects. We report here on a large Iranian family with four affected patients presenting with severe intellectual disability, developmental delay and generalized tonic–clonic seizures. Molecular genetic analysis revealed a missense mutation c.901A>G (p.K301E, RefSeq number NM_001080) in ALDH5A1 co-segregating with the disease in the family. The missense mutation affects an amino acid residue that is highly conserved across the animal kingdom. Protein modeling showed that p.K301E most likely leads to a loss of NAD+ binding and a predicted decrease in the free energy by 6.67 kcal/mol furthermore suggests a severe destabilization of the protein. In line with these in silico observations, no SSADH enzyme activity could be detected in patient lymphoblasts. © 2013 Wiley Periodicals, Inc.

Primary microcephaly (MCPH) is a genetic disorder in which affected individuals present with a head circumference 3 standard deviations (SDs) below the age- and sex-related mean and is accompanied by mental retardation without further associated malformations. Here we report a patient with sporadic MCPH from Northwest of Iran who was investigated for MCPH1 locus. Clinical examination and karyotype analyses were performed and microsatellite based mapping was done by using flanking and intragenic short tandem repeat (STR) markers for MCPH1 locus. For these markers the affected individual was homozygote and the parents were heterozygote. According to this pattern of allele sharing and also the cytogenetic findings, mutation screening of Microcephalin gene was performed and subsequent sequencing revealed a novel mutation in Microcephalin gene.

The following information was missing from the funding section: Austrian Science Fund ({"type":"entrez-protein","attrs":{"text":"P21667","term_id":"122622","term_text":"P21667"}}P21667-B09).

International audience; Congenital myasthenic syndromes (CMSs) are a heterogeneous group of genetic disorders affecting neuromuscular transmission. The agrin/muscle-specific kinase (MuSK) pathway is critical for proper development and maintenance of the neuromuscular junction (NMJ). We report here an Iranian patient in whom CMS was diagnosed since he presented with congenital and fluctuating bilateral symmetric ptosis, upward gaze palsy and slowly progressive muscle weakness leading to loss of ambulation. Genetic analysis of the patient revealed a homozygous missense mutation c.2503A.G in the coding sequence of MUSK leading to the p.Met835Val substitution. The mutation was inherited from the two parents who were heterozygous according to the notion of consanguinity. Immunocytochemical and electron microscopy studies of biopsied deltoid muscle showed dramatic changes in pre-and post-synaptic elements of the NMJs. These changes induced a process of denervation/reinnervation in native NMJs and the formation, by an adaptive mechanism, of newly formed and ectopic NMJs. Aberrant axonal outgrowth, decreased nerve terminal ramification and nodal axonal sprouting were also noted. In vivo electroporation of the mutated MuSK in a mouse model showed disorganized NMJs and aberrant axonal growth reproducing a phenotype similar to that observed in the patient's biopsy specimen. In vitro experiments showed that the mutation alters agrin-dependent acetylcholine receptor aggregation, causes a constitutive activation of MuSK and a decrease in its agrin-and Dok-7-dependent phosphorylation.

Myotonic dystrophy type 1 (DM-1) is a multi-system disorder affecting the muscles, brain, cardiovascular system, endocrine system, eyes and skin. Diagnosis is made by clinical, electrodiagnostic and genetic studies. This study aimed to determine the correlation between CTG expansion and distribution of muscle weakness and clinical and electrophysiological findings. Genetically confirmed DM-1 patients presenting to Shariati Hospital between 2005 and 2011 were included in this study. Clinical, electrodiagnostic and genetic testing was performed and the correlation between CTG expansion and distribution of muscle weakness and clinical and electromyographic findings was studied. Thirty-three genetically confirmed DM-1 patients were enrolled. Myotonia, bifacial weakness and distal upper limb weakness were seen in all patients. Diabetes mellitus was found in one patient (3%), cardiac disturbance in eight (24.2%), cataracts in eight (24.2%), hypogonadism in five (15.2%), frontal baldness in 13 (39.4%), temporalis wasting in 14 (42.4%), temporomandibular joint disorder in seven (21.2%) and mental retardation in eight (24.2%). The mean number of CTG repeats, measured by Southern blot, was 8780 (range 500-15,833). A negative correlation was found between CTG expansion and age of onset. Temporalis wasting and mental retardation were positively correlated with CTG expansion. No relationship was found between weakness distribution, electromyographic findings, other systemic features and CTG expansion. In this study of DM-1 in Iran, we found a correlation between CTG expansion and age of onset, temporalis wasting and mental disability. No correlation between CTG expansion and electrodiagnostic and other clinical findings were detected.

Mutations in the human aristaless-related homeobox (ARX) gene are amongst the major causes of developmental and neurological disorders. They are responsible for a wide spectrum of phenotypes, including nonsyndromic X-linked intellectual disability (NS-XLID), and syndromic (XLIDS) forms such as X-linked lissencephaly with abnormal genitalia (XLAG), Partington syndrome (PRTS), and X-linked infantile spasm syndrome (ISSX). The recurrent 24 bp duplication mutation, c.428_451dup(24 bp), is the most frequent ARX mutation, which accounts for ~40% of all cases reported to date.We have screened the entire coding sequences of the ARX gene in 65 Iranian families with intellectual disabilities in order to obtain the relative prevalence of ARX mutations. At first these families were screened for the most recurrent mutation, the c.428_451dup(24 bp). For samples with negative results, single strand conformation polymorphism (SSCP) analysis was performed.We identified one family with the c.428_451dup(24 bp) duplication. Three shifts (one shift in exon 5 and two shifts in exon 4) were also identified among the total families. According to the results of the sequencing analysis, two shifts were not associated with any mutation and the other one was a c.1347CT (p.G449G) substitution in exon 4.Hence, we suggest that molecular analysis of ARX mutations as a second cause of XLID should be considered as routine diagnostic procedure in any male who presents with either NS-XLID or XLIDS.

With a prevalence between 1 and 3%, hereditary forms of intellectual disability (ID) are among the most important problems in health care. Particularly, autosomal-recessive forms of the disorder have a very heterogeneous molecular basis, and genes with an increased number of disease-causing mutations are not common. Here, we report on three different mutations (two nonsense mutations, c.679C>T [p.Gln227( *)] and c.1114C>T [p.Gln372( *)], as well as one splicing mutation, g.6622224A>C [p.Ile179Argfs( *)192]) that cause a loss of the tRNA-methyltransferase-encoding NSUN2 main transcript in homozygotes. We identified the mutations by sequencing exons and exon-intron boundaries within the genomic region where the linkage intervals of three independent consanguineous families of Iranian and Kurdish origin overlapped with the previously described MRT5 locus. In order to gain further evidence concerning the effect of a loss of NSUN2 on memory and learning, we constructed a Drosophila model by deleting the NSUN2 ortholog, CG6133, and investigated the mutants by using molecular and behavioral approaches. When the Drosophila melanogaster NSUN2 ortholog was deleted, severe short-term-memory (STM) deficits were observed; STM could be rescued by re-expression of the wild-type protein in the nervous system. The humans homozygous for NSUN2 mutations showed an overlapping phenotype consisting of moderate to severe ID and facial dysmorphism (which includes a long face, characteristic eyebrows, a long nose, and a small chin), suggesting that mutations in this gene might even induce a syndromic form of ID. Moreover, our observations from the Drosophila model point toward an evolutionarily conserved role of RNA methylation in normal cognitive development.

Mutations in GJB2 are a major cause of autosomal recessive non-syndromic hearing loss (ARNSHL) in many populations. A single mutation of this gene (35delG) accounts for approximately 70% of GJB2 mutations that are associated with ARNSHL in Caucasians in many European countries and also in Iranian. In this study, we used PCR and restriction digestion to genotype five single nucleotide polymorphisms (SNPs) that define the genetic background of the 35delG mutation over an interval of 98Kbp that includes the coding and flanking regions of GJB2. Two microsatellite markers, D13S175 and D13S141, were also analyzed in patients and controls. These data suggest that the 35delG mutation originated in north and northwest of Iran.

The genetic basis of autosomal recessive mental retardation (ARMR) is extremely heterogeneous, and there is reason to suspect that the number of underlying gene defects may well go beyond 1,000. To date, however, only less than 10 genes have been implicated in non-specific/non-syndromic ARMR (NS-ARMR). As part of an ongoing systematic study aiming to identify further ARMR genes, we investigated a consanguineous family with three patients with NS-ARMR. By linkage analysis and subsequent mutation screening we identified a novel nonsense mutation (c.163C > T [p.Q55X]) in the second exon of the TUSC3 gene. This is the third MR causing defect in TUSC3 to be described and the second independent mutation in this gene in a cohort of more than 200 ARMR families from the Iranian population. This argues for a more prominent role of TUSC3 in the etiology of this genetically heterogeneous disorder as compared to most of the other so far identified ARMR genes. © 2011 Wiley-Liss, Inc.

As part of a large-scale, systematic effort to unravel the molecular causes of autosomal recessive mental retardation, we have previously described a novel syndrome consisting of mental retardation, coloboma, cataract and kyphosis (Kahrizi syndrome, OMIM 612713) and mapped the underlying gene to a 10.4-Mb interval near the centromere on chromosome 4. By combining array-based exon enrichment and next generation sequencing, we have now identified a homozygous frameshift mutation (c.203dupC; p.Phe69LeufsX2) in the gene for steroid 5α-reductase type 3 (SRD5A3) as the disease-causing change in this interval. Recent evidence indicates that this enzyme is required for the conversion of polyprenol to dolichol, a step that is essential for N-linked protein glycosylation. Independently, another group has recently observed SRD5A3 mutations in several families with a type 1 congenital disorder of glycosylation (CDG type Ix, OMIM 212067), mental retardation, cerebellar ataxia and eye disorders. Our results show that Kahrizi syndrome and this CDG Ix subtype are allelic disorders, and they illustrate the potential of next-generation sequencing strategies for the elucidation of single gene defects.

A clinically significant proportion of couples experience difficulty in conceiving a child. In about half of these cases male infertility is the cause and often genetic factors are involved. Despite advances in clinical diagnostics ∼50% of male infertility cases remain idiopathic. Based on this, further analysis of infertile males is required to identify new genetic factors involved in male infertility. This review focuses on cation channel of sperm (CATSPER)-related male infertility. It is based on PubMed literature searches using the keywords 'CATSPER', 'male infertility', 'male contraception', 'immunocontraception' and 'pharmacologic contraception' (publication dates from January 1979 to December 2009). Previously, contiguous gene deletions including the CATSPER2 gene implicated the sperm-specific CATSPER channel in syndromic male infertility (SMI). Recently, we identified insertion mutations of the CATSPER1 gene in families with recessively inherited nonsyndromic male infertility (NSMI). The CATSPER channel therefore represents a novel human male fertility factor. In this review we summarize the genetic and clinical data showing the role of CATSPER mutation in human forms of NSMI and SMI. In addition, we discuss clinical management and therapeutic options for these patients. Finally, we describe how the CATSPER channel could be used as a target for development of a male contraceptive.

Mutations in miRNA genes have been implicated in hearing loss in human families and mice. It is also possible that mutations in miRNA binding sites of inner ear targets alter gene expression levels and lead to hearing loss. To investigate these possibilities we screened predicted target genes of the miR-183 miRNA cluster known to be expressed in the inner ear sensory epithelium. In one Iranian family segregating autosomal recessive non-syndromic hearing loss (ARNSHL), we identified a homozygous variant in a predicted miR-96/182 binding site in the 3'UTR of the RDX (DFNB24) gene. However, in vitro functional studies showed that this site is not a functional target for miR-96/182. We extended our study to include the miR-183 genes themselves and 24 additional predicted target genes of the miRNA-183 cluster. Screening these miRNAs and target sequences in numerous families segregating either autosomal dominant non-syndromic deafness (ADNSHL) or ARNSHL did not identify any potential deafness-causing mutations. These results suggest that mutations disrupting gene regulation by the miR-183 cluster are not a common cause of human hearing loss.

Myosin VIIA mutations have been associated with non-syndromic hearing loss (DFNB2; DFNA11) and Usher syndrome type 1B (USH1B). We report clinical and genetic analyzes of a consanguineous Iranian family segregating autosomal recessive non-syndromic hearing loss (ARNSHL). The hearing impairment was mapped to the DFNB2 locus using Affymetrix 50K GeneChips; direct sequencing of the MYO7A gene was completed. The Iranian family (L-1419) was shown to segregate a novel homozygous missense mutation (c.1184G>A) that results in a p.R395H amino acid substitution in the motor domain of the myosin VIIA protein. Since one affected family member had significantly less severe hearing loss we used a candidate approach to search for a genetic modifier. This novel MYO7A mutation is the first reported to cause DFNB2 in the Iranian population and this DFNB2 family is the first to be associated with a potential modifier. The absence of vestibular and retinal defects, and less severe low frequency hearing loss, is consistent with the phenotype of a recently reported Pakistani DFNB2 family. Thus, we conclude this family has non-syndromic hearing loss (DFNB2) rather than Usher syndrome type 1B (USH1B), providing further evidence that these two diseases represent discrete disorders.