GENETIC ANALYSIS OF FAMILIES HAVING AUTOSOMAL RECESSIVE INTELLECTUAL DISABILITY

Abstract

Background: Intellectual disability (ID) is a neuro-developmental defect that is manifested by development delay and learning disability. Such defects may be caused due to chromosomal disorders (trisomy 18 or Down syndrome) or single gene mutation. Its worldwide prevalence is estimated to be 1-3%. The genetic etiology of non-syndromic ID is poorly understood. To date, more than 100 loci have been reported to be associated with non-syndromic ID. The objective of this study was to identify the causative genes for three Materials & Methods: This cross-sectional study was conducted in the Institute of Basic Medical Sciences, Khyber Medical University, Peshawar, Pakistan from March 2014 to August 2015. The inclusion criteria set for the families was consanguineous relation and more than two patients per family (including cousins). All the patients were tested individually in friendly atmosphere using IQ test to scale the ID on the basis of performance. Thereafter, blood samples were taken by aseptic method and DNA was extracted for the purpose of doing genetic analysis. In genetic analysis, exome sequencing was performed to find the pathogenic variants. Subsequently. Sanger sequencing was also done to see the segregation of pathogenic variants. Results: Genetic analysis found mutation in AP4B1 in Family 1, in WDR62 in Family 2, while Family 3 was unremarkable. Conclusion: The study involved genetic analysis of three consanguineous families and found mutation in AP4B1 in Family 1, in WDR62 in Family 2, while Family 3 was unremarkable. The present research will help in devising molecular diagnostic technics for pre-marital and pre-conception testing.

Keywords

• intellectual disability
• dna
• genotype
• exomes
• exome sequencing
• gene clusters
• chromosome
• mutation
• chromosomal disorders
• molecular diagnostic technics.