Investigating GJB2 Mutation in 31 Individuals With Non-syndromic Hearing Loss

Background and Aim: Non-syndromic hearing loss is a genetically heterogeneous disorder. Mutation in the GJB2 gene is a major cause of non-syndromic hearing loss in numerous countries. This study aimed to evaluate GJB2 mutations in 31 individuals with non-syndromic hearing loss Methods & Materials: In this descriptive cross-sectional study, the required blood samples were collected from 31 individuals with non-syndromic hearing loss in Rasht and Bandar Anzali Cities, Gilan Province, Iran. After DNA isolation, the GJB2 gene was amplified by the PCR method and underwent sequencing. Ethical Considerations:This study was approved by the Ethics Committee of the Islamic Azad University, Mashhad Branch (Code: IR.IAU.MSHD.REC.1398.027). Results: In this study, 3 mutations were determined in 18 individuals with hearing loss. Accordingly, 35delG mutation had the highest frequency (48.38%) in individuals with hearing loss as homozygote (n=14) and heterozygote (n=2). A patient with heterozygosity in V153I mutation and a patient with compound heterozygosity in 35delG/G200R mutation was determined. Conclusion: It appears that 35delG mutation is a common mutation in the GJB2 gene in individuals with non-syndromic hearing loss in Guilan Province.

Genetic mutations in patients with nonsyndromic hearing impairment of minority and Han Chinese ethnicities in Qinghai, China

Objective Mutations in GJB2, SLC26A4, and mitochondrial (mt)DNA 12S rRNA genes are the main cause of nonsyndromic hearing impairment. The present study analyzed these mutations in ethnic minority and Han Chinese patients with nonsyndromic hearing impairment from Qinghai, China. Methods The SNPscan assay was used to analyze mutation spectra and frequencies in the two patient groups. Results GJB2 mutations were detected in 9.5% (20/210) of minority patients and 20.88% (48/230) of Han Chinese patients. The most common Han Chinese GJB2 variants were c.235delC and c.299_300delAT, whereas c.235delC and c.109G > A were the most prevalent in minority patients. SLC26A4 mutations were detected in 5.71% (12/210) of minority patients and 14.35% (33/230) of Han Chinese patients, and mtDNA 12S rRNA mutations were detected in 4.28% (9/210) of minority patients and 9.13% (21/230) of Han Chinese patients. Conclusions These data indicate that the mutation frequencies of three deafness-associated genes were significantly higher in Han Chinese patients than in minority patients. Moreover, the GJB2 mutation spectrum was shown to differ between these two patient groups.

Genetic Screening for 35delG Mutation in Egyptian Patients with Profound Sensorineural Hearing Loss Scheduled for Cochlear Implantation: A Population-Based Study

<b><i>Objectives:</i></b> The aim of this work was to assess the type and site of the 35delG gene mutation in patients presenting with profound SNHL and scheduled for cochlear implantation. The secondary objectives were to determine their geographical distribution throughout Egypt, screening of the parents for the mutation, and to correlate the type of mutation with clinical severity and outcomes after surgery. <b><i>Methods:</i></b> The study was carried out on 100 consecutive patients scheduled for cochlear implantation. Patients with syndromic hearing loss or noncongenital hearing loss (trauma, infections, and ototoxicity) were excluded. All patients were subjected to detailed history taking including geographic tagging for their origins in Egypt, imaging (CT and MRI cochlear implantation protocols), full audiological evaluation (PTA, ABR, and TEOAE), and genetic screening for GJB2 mutation using Invitrogen PCR mix and ApaI restriction enzyme (North America, CA, 10572-014). The parents of mutation-positive patients were also subjected to audiological and genetic analysis. All patients were subjected to postimplantation evaluation of hearing after 6 and 12 months. <b><i>Results:</i></b> There were 64 males and 36 females from 98 families. Ages ranged between 1.9 and 7 years (mean 3.72 years). They originated from all over Egypt but the majority came from the Giza and Cairo areas. The 35delG mutations were found in exon 2 in 31% of the cases and all were heterozygous. In the parents, 18 mothers and 13 fathers were positive but only 8 had mild to moderate SNHL. Hearing evaluation by pure tone and speech discrimination scores at 6 and 12 months showed that the 35delG children had a statistically better result compared to the children without this mutation. <b><i>Conclusion:</i></b> The prevalence of the 35delG mutation in nonsyndromic children in this sample was 31% which is different from previous studies in the Egyptian population but close to the values found in other populations in the Mediterranean basin.

Neurological Findings in Children without Congenital Microcephaly Exposed to Zika Virus in Utero: A Case Series Study

The Zika virus can induce a disruptive sequence in the fetal brain and is manifested mainly by microcephaly. Knowledge gaps still exist as to whether the virus can cause minor disorders that are perceived later on during the first years of life in children who are exposed but are asymptomatic at birth. In this case series, we describe the outcomes related to neurodevelopment through the neurological assessment of 26 non-microcephalic children who had intrauterine exposure to Zika virus. Children were submitted for neurological examinations and Bayley Scales-III (cognition, language, and motor performance). The majority (65.4%) obtained satisfactory performance in neurodevelopment. The most impaired domain was language, with 30.7% impairment. Severe neurological disorders occurred in five children (19.2%) and these were spastic hemiparesis, epilepsy associated with congenital macrocephaly (Zika and human immunodeficiency virus), two cases of autism (one exposed to Zika and Toxoplasma gondii) and progressive sensorineural hearing loss (GJB2 mutation). We concluded that non-microcephalic children with intrauterine exposure to Zika virus, in their majority, had achieved satisfactory performance in all neurodevelopmental domains. One third of the cases had some impairment, but the predominant group had mild alterations, with low occurrence of moderate to severe disorders, similar to other studies in Brazil.