Two Iranian families with a novel mutation in GJB2 causing autosomal dominant nonsyndromic hearing loss

Mutations in GJB2 , encoding connexin 26 (Cx26), cause both autosomal dominant and autosomal recessive nonsyndromic hearing loss (ARNSHL) at the DFNA3 and DFNB1 loci, respectively. Most of the over 100 described GJB2 mutations cause ARNSHL. 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. © 2011 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83755/1/33209_ftp.pd

Genetic Causes of Putative Autosomal Recessive Intellectual Disability Cases in Hamedan Province

Objective: The aim of this study was to investigate the genetic causes of autosomal recessive intellectual disabilities (AR-ID) in Hamadan province of Iran. Materials & Methods: In this descriptive-analytical cross-sectional study, 25 families with more than one affected with putative autosomal recessive intellectual disability were chosen with collaboration of Welfare Organization of Hamadan province. Families were included a total of 60 patients (39 male and 21 female) whose intellectual disability had been confirmed by Raven IQ test. Each family was asked for clinical examination and getting consent form. Blood sample was collected from each family. One proband from each family was tested for CGG repeat expansion in FMR1 gene, chromosomal abnormalities and inborn errors of metabolism. We also performed homozygosity mapping based on STR markers for seven known MCPH loci in families with primary microcephaly and AR-ID. Results: Five families had full mutation of Fragile X syndrome. No chromosomal abnormalities were identified. Metabolic screening revealed one family with Medium Chain Acyl CoA Dehydrogenase deficiency. None of three families with primary microcephaly and AR-ID showed linkage to any of known seven MCPH loci. Conclusion: The main causes of ID in Hamadan province were Fragile X syndrome and Autosomal Recessive Primary Microcephaly with the frequencies of 20% and 12%, respectively

Comprehensive genotype-phenotype correlation in AP-4 deficiency syndrome; Adding data from a large cohort of Iranian patients

Mutations in adaptor protein complex-4 (AP-4) genes have first been identified in 2009, causing a phenotype termed as AP-4 deficiency syndrome. Since then several patients with overlapping phenotypes, comprised of intellectual disability (ID) and spastic tetraplegia have been reported. To delineate the genotype-phenotype correlation of the AP-4 deficiency syndrome, we add the data from 30 affected individuals from 12 out of 640 Iranian families with ID in whom we detected disease-causing variants in AP-4 complex subunits, using next-generation sequencing. Furthermore, by comparing genotype-phenotype findings of those affected individuals with previously reported patients, we further refine the genotype-phenotype correlation in this syndrome. The most frequent reported clinical findings in the 101 cases consist of ID and/or global developmental delay (97%), speech disorders (92.1%), inability to walk (90.1%), spasticity (77.2%), and microcephaly (75.2%). Spastic tetraplegia has been reported in 72.3% of the investigated patients. The major brain imaging findings are abnormal corpus callosum morphology (63.4%) followed by ventriculomegaly (44.5%). Our result might suggest the AP-4 deficiency syndrome as a major differential diagnostic for unknown hereditary neurodegenerative disorders

The influence of the BCL11A polymorphism on the phenotype of patients with beta thalassemia could be affected by the beta globin locus control region and/or the Xmn1-HBG2 genotypic background

To study the influence of the β globin locus control region (LCR) genotypic background on the phenotype modifying role of BCL11A polymorphisms, 100 cases of thalassemia, 48 homozygous for the A allele and 52 homozygous for the G allele at the 5′HS4-LCR palindromic polymorphic site were genotyped for two BCL11A single nucleotide polymorphisms (rs11886868 and rs766432) in the intronic region of this gene. The effect of these polymorphisms on HbF variation was also examined in 122 normal individuals. The 5′ HS4-LCR had the most significant role in determining the phenotype of these thalassemia patients. BCL11A polymorphisms showed a significant role in determining the phenotype of patients homozygous for the G allele at 5′HS4-LCR. However, the majority of patients homozygous for the A allele at 5′HS4-LCR, showed a severe phenotype, regardless of the BCL11A genotype. These results, without undermining the strength of BCL11A as a silencer of the γ globin gene, suggest that the LCR background, by governing the state of BCL11A binding to this region, plays a more significant role in determining the thalassemia phenotype than the level of BCL11A protein expression, that might be influenced by single nucleotide polymorphisms in intronic regions of the BCL11A gene. Functional studies to confirm the interactions between BCL11A and LCR could be useful in designing pharmacogenetic strategies for the treatment of beta thalassemia major

Next generation sequencing in a family with autosomal recessive Kahrizi syndrome (OMIM 612713) reveals a homozygous frameshift mutation in SRD5A3

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

Subcellular relocalization and nuclear redistribution of the RNA methyltransferases TRMT1 and TRMT1L upon neuronal activation

RNA modifications are dynamic chemical entities that expand the RNA lexicon and regulate RNA fate. The most abundant modification present in mRNAs, N6-methyladenosine (m6A), has been implicated in neurogenesis and memory formation. However, whether additional RNA modifications may be playing a role in neuronal functions and in response to environmental queues is largely unknown. Here we characterize the biochemical function and cellular dynamics of two human RNA methyltransferases previously associated with neurological dysfunction, TRMT1 and its homolog, TRMT1-like (TRMT1L). Using a combination of next-generation sequencing, LC-MS/MS, patient-derived cell lines and knockout mouse models, we confirm the previously reported dimethylguanosine (m2,2G) activity of TRMT1 in tRNAs, as well as reveal that TRMT1L, whose activity was unknown, is responsible for methylating a subset of cytosolic tRNAAla(AGC) isodecoders at position 26. Using a cellular in vitro model that mimics neuronal activation and long term potentiation, we find that both TRMT1 and TRMT1L change their subcellular localization upon neuronal activation. Specifically, we observe a major subcellular relocalization from mitochondria and other cytoplasmic domains (TRMT1) and nucleoli (TRMT1L) to different small punctate compartments in the nucleus, which are as yet uncharacterized. This phenomenon does not occur upon heat shock, suggesting that the relocalization of TRMT1 and TRMT1L is not a general reaction to stress, but rather a specific response to neuronal activation. Our results suggest that subcellular relocalization of RNA modification enzymes may play a role in neuronal plasticity and transmission of information, presumably by addressing new targets.NJ was supported by a UNSW International PhD fellowship. SC is supported by a fellowship from ”la Caixa'' Foundation (LCF/BQ/DI19/11730036). This work was supported by NHMRC funds (Project Grant APP1070631 to JSM), funds from the Australian Research Council (DP180103571 to EMN) and funds from the Garvan Young Investigator Award (to NS). This work was partly supported by the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) (PGC2018-098152-A-100 to EMN).The mass spectrometric analyses shown in Figure S3 were performed in the CRG/UPF Proteomics Unit which is part of the of Proteored, PRB3 and is supported by grant PT17/0019, of the PE I+D+i 2013-2016, funded by ISCIII and ERD