Digenic inheritance in autosomal recessive non-syndromic hearing loss cases carrying GJB2 heterozygote mutations: Assessment of GJB4, GJA1, and GJC3

Objective: Autosomal recessive non-syndromic hearing loss (ARNSHL) can be caused by many genes. However, mutations in the GJB2 gene, which encodes the gap-junction (GJ) protein connexin (Cx) 26, constitute a considerable proportion differing among population. Between 10 and 42 percent of patients with recessive GJB2 mutations carry only one mutant allele. Mutations in GJB4, GJA1, and GJC3 encoding Cx30.3, Cx43, and Cx29, respectively, can lead to HL Combination of different connexins in heteromeric and heterotypic GJ assemblies is possible. This study aims to determine whether variations in any of the genes GJB4, GJA1 or GJC3 can be the second mutant allele causing the disease in the digenic mode of inheritance in the studied GJB2 heterozygous cases. Methods: We examined 34 unrelated GJB2 heterozygous ARNSHL subjects from different geographic and ethnic areas in Iran, using polymerase chain reaction (PCR) followed by direct DNA sequencing to identify any sequence variations in these genes. Restriction fragment length polymorphism (RFLP) assays were performed on 400 normal hearing individuals. Results: Sequence analysis of GJB4 showed five heterozygous variations including cA51C>A, c.219C>T, c.507C>G, c.155_158delTCTG and c.542C>T, with only the latter variation not being detected in any of control samples. There were three heterozygous variations including c.758C>T, c.717G>A and c.3*dupA in GJA1 in four cases. We found no variations in GJC3 gene sequence. Conclusion: Our data suggest that GJB4 c.542C>T variant and less likely some variations of GJB4 and GJA1, but not possibly GJC3, can be assigned to ARNSHL in GJB2 heterozygous mutation carriers providing clues of the digenic pattern. (C) 2012 Elsevier Ireland Ltd. All rights reserved

The frequency of human leukocyte antigen-DRB1 alleles, using sequence-based genotyping in 68 parents-child trios study in Iranian subjects

Background: The human leukocyte antigen-DRB1 (HLA-DRB1) locus is one of the most polymorphic human loci and has a crucial role in the immune system. Assessing the allelic frequencies of HLA-DRB1 locus would be a fundamental factor in defining the origin of populations, relationships with other populations, disease association studies and the constitution of unrelated bone marrow donor registries. In the current study HLA-DRB1 alleles and their frequencies are determined in a family-based study by DNA sequencing-based typing high-resolution (2 field) level of typing. Materials and Methods: Genomic DNA from 3 members of 68 unrelated families (a total of 204 individuals) was extracted. Exon 2 of DRB1 gene was amplified and performed useing AssignTM SBT v4.7 sequence analysis software.Results: We had DRB1*11:04 with frequency of 0.0931, DRB1*03:01 with 0.0882, DRB1*11:01 with 0.0735, DRB1*13:01 with 0.071 and also alleles DRB1*08:03, DRB1*13:42, DRB1*14:04 and DRB1*14:07 with frequency of 0.0024.Conclusion: A total of 34 different alleles were found in the study subjects with DRB1*11:04, DRB1*03:01, DRB1*11:01 being the most frequent alleles respectively.  

Next generation sequencing identified novel truncating mutations in BBS9 causing Bardet Biedl syndrome in two Iranian consanguineous families: two novel pathogenic variants in BBS9 gene

Abstract Objectives Bardet-Biedl syndrome (BBS) is an autosomal recessive pleiotropic ciliopathy, which includes multi-organ clinical manifestations. The known genes involved in the development of the disease account for the causality in about 80% of the examined cases. Materials & Methods We investigated two Iranian unrelated clinically diagnosed BBS patients, using a targeted next-generation sequencing panel consisting of 18 known BBS genes. The detected variants were investigated in the pedigree and studied using in silico tools for their pathogenicity. Patients’ phenotypes were also assessed. Results Novel homozygous variants were detected in BBS9 gene in each patient, c.2014C>T, p.Gln672Ter and c.673_674insAA, p.Gln225GlnfsX10. The variants were segregated in the corresponding pedigree and were authenticated to obtain enough evidence to be categorized as pathogenic variants. Conclusion Patients with truncating mutations in the same gene seem to show similar phenotypic features. Detection of novel and family-specific mutations is typically expected in the genetic hereditary diseases inIran, which can finally lead to prevent the recurrence of the disease in the consanguineous marriages