A splice-site variant (c.3289-1G>T) in OTOF underlies profound hearing loss in a Pakistani kindred

Splice-altering variant of PJVK gene in a Mauritanian family with non-syndromic hearing impairment

PJVK gene was recently shown to create hypervulnerability to sound in humans and was the first human gene implicated in non-syndromic hearing impairment due to neural defect. Targeted next-generation sequencing of over 150 known deafness genes was performed in the proband. Sanger sequencing was used to validate the PJVK variant and confirm familial segregation of the disease. A minigene-based assay has been performed to assess the impact of the variant on splicing. We identified a novel c.550-6A > G acceptor splice-site variant in the PJVK gene in the homozygous state in a Mauritanian child with severe to profound congenital deafness. The substitution was located in intron 4. The effect of the variation was demonstrated by a minigene assay which showed that the variation, an insertion of an additional 5 bp, created a new splice site resulting in the appearance of a premature stop codon (p.Phe184Tyrfs*26) and likely a truncated protein. This result constitutes a new splice-site variant report in the PJVK gene leading to DFNB59 type associated with autosomal recessive non-syndromic hearing impairment (ARNSHI).

The natural history, clinical outcomes, and genotype-phenotype relationship of otoferlin-related hearing loss: a systematic, quantitative literature review

Congenital hearing loss affects one in 500 newborns. Sequence variations in OTOF, which encodes the calcium-binding protein otoferlin, are responsible for 1-8% of congenital, nonsyndromic hearing loss and are the leading cause of auditory neuropathy spectrum disorders. The natural history of otoferlin-related hearing loss, the relationship between OTOF genotype and hearing loss phenotype, and the outcomes of clinical practices in patients with this genetic disorder are incompletely understood because most analyses have reported on small numbers of cases with homogeneous OTOF genotypes. Here, we present the first systematic, quantitative literature review of otoferlin-related hearing loss, which analyzes patient-specific data from 422 individuals across 61 publications. While most patients display a typical phenotype of severe-to-profound hearing loss with prelingual onset, 10-15% of patients display atypical phenotypes, including mild-to-moderate, progressive, and temperature-sensitive hearing loss. Patients' phenotypic presentations appear to depend on their specific genotypes. For example, non-truncating variants located in and immediately downstream of the C2E calcium-binding domain are more likely to produce atypical phenotypes. Additionally, the prevalence of certain sequence variants and their associated phenotypes varies between populations due to evolutionary founder effects. Our analyses also suggest otoacoustic emissions are less common in older patients and those with two truncating OTOF variants. Critically, our review has implications for the application and limitations of clinical practices, including newborn hearing screenings, hearing aid trials, cochlear implants, and upcoming gene therapy clinical trials. We conclude by discussing the limitations of available research and recommendations for future studies on this genetic cause of hearing loss.

Association of R1939W and P1987R variants of Otoferlin (OTOF) gene with severe to profound nonsyndromic sensorineural hearing loss in Pakistani subjects

Objective

To find possible association of R1939W and P1987R variants of OTOF gene with severe to profound NSSHL in cochlear implant subjects.

Methods

It was a case control study, conducted from June 2021 to February 2022, comprising 50 cases of severe to profound NSSHL who had received cochlear implant from ENT Department, CMH Rawalpindi and 50 age-matched healthy controls from PEMH Rawalpindi. Blood samples were collected from all the subjects, followed by DNA extraction and allele-specific polymerase chain reaction, performed at Multi-disciplinary Laboratory of Department of Biochemistry and Molecular Biology, Army Medical College Rawalpindi. Statistical analysis was done using 'SPSS' and 'XLSTAT', followed by genetic analysis using 'SNPstat'.

Results

Mean age of the cases was 5.96 ± 4.62 years (N=50), comprising 58% males and 42% females. All had bilateral and prelingual HL. Parental consanguinity was 72%, whereas 62% cases had a positive family history of deafness. Alleles of R1939W and P1987R were not associated with NSSHL, as shown by their p values of 0.56 and 0.89 respectively. For R1939W ORs were 0.71 (dominant model) and 0.80 (overdominant model), indicating negative association with NSSHL. Regarding P1987R OR was 0.96 (log-additive model). Genotypes of both variants were not in HW Equilibrium (p <0.0001), whereas their alleles showed high LD (D'=0.92).

Conclusion

High percentage of parental consanguinity was observed among cochlear implant candidates. The OTOF variants R1939W and P1987R were found to have protective roles against NSSHL in study population.

Sef fimbria operon construction, expression, and function for direct rapid detection of Salmonella Enteritidis

Salmonella Enteritidis (SE) causes both horizontal and vertical transmission of diseases in poultry industry and is also one of the main causes of human food poisoning. Sequence analysis of the sef operon of poultry-derived Salmonella serotypes showed the presence of an entire sef operon in SE, whereas only sef pseudogenes were found in Salmonella Gallinarum and Salmonella Pullorum. Subsequently, the sef operon of SE was cloned into the pBR322 plasmid and expressed in a modified Escherichia coli strain SE5000. sef operon expression was demonstrated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, western blot, agglutination assay, and transmission electron microscopy. The results showed that SE5000+Sef, but not SE5000+pBR322, could specifically react with SE-positive chicken serum in an agglutination assay, which could be clearly visualized by the naked eye within less than 2 min. In contrast, SE5000+Sef could not be recognized in Salmonella Gallinarum- and Salmonella Pullorum-positive chicken sera. Next, taking advantage of the exclusive presence of an entire sef operon in SE, we set up an agglutination-based detection system to monitor the dynamics of Sef-targeted antibody from SE-infected chicks for 47 days. Using the proposed detection method, SE was readily detectable starting from 2 weeks post-infection. Finally, we compared the proposed SE5000+Sef-based detection system with commercially available agglutination antigen using the classical bacterial isolation and identification procedure as reference. The results showed that the SE5000+Sef system was more consistent with the results of bacterial isolation and identification with almost 100% accuracy. We established a simple, sensitive, and cheap agglutination method for rapid and specific detection of SE-infected chickens, which can facilitate epidemiological investigation and eradication of SE infections. KEY POINTS: • Only the Salmonella Enteritidis serotype expressed Sef fimbriae in chicken infected with SE. • A rapid, large-scale method of detection by the naked eye of detection of SE-infected chicken is presented.