MOLECULAR DIAGNOSIS OF A FAMILY WITH SYNDROMIC HEARING LOSS AND INTELLECTUAL DISABILITY USING WHOLE EXOME SEQUENCING IN KHYBERPAKHTUNKHWA, PAKISTAN

Abstract

Background:

Deafness or hearing loss is a condition in which a person is unable to learn to speak during their pre-or post-lingual years. Such patients either never speak or just occasionally produce meaningless sounds. Based on their causative agent, the severity varies from patient to patient and even from family to family. Primarily deafness is divided into two categories: syndromic and non-syndromic hearing loss. Along with other signs and symptoms, there are more than 400 conditions that result in hearing loss are referred to as syndromic hearing loss which are about 30% in different world populations. While 70% percent of prelingual hereditary HL is non syndromic (NSH).

Methodology:

In the present study, A family was recruited from the district Bannu, Khyber Pakhtunkhwa Province (KP), Pakistan, having medical problems including mental retardation and other physical disabilities. Molecular diagnosis of the family was performed using Whole Exome Sequencing to recognize the causal gene. First blood samples were collected from the targeted family in EDTA tubes and the samples were taken into the molecular lab at the Centre For Omic Sciences, Islamia College Peshawar. A standard phenol chloroform method was used to extract the DNA. Samples were quantified using Nano drop spectrophotometer and sample of one of the affected individuals was sent to 3billiom. Inc. for whole exome sequencing (WES). WES is NGS based method, which is the first line of molecular diagnostic tool for confirmation of the genome investigation.

Results:

The sequencing analysis results in a missense mutation in col11a2 at cDNA: NM_080680.3:

c.3031C>A located on exon 41 of chromosome 6p21.32. Furthermore, the variant was selected for segregation analysis by sanger sequencing for validation. But the Sanger validations was inclusive as some samples were failed due to insufficient DNA and the concern family did not corporate as they refused to give us more blood samples.

Conclusion:

In this study, we identified a missense heterozygous variant in a Pashtun family suffering from deafness and intellectual disabilities in the district of Banuu, Pakistan. A very critical role is being played by next-generation sequencing (NGS) in the diagnosis of rare genetic diseases that were previously difficult to identify. It was time-consuming, expensive, and difficult to conduct genetic testing in the past due to a lack of resources. Genetic testing should be done on regular bases as Khyber Pakhtunkhwa is the hub for rare genetical disorders due to high consanguinity rate.