Identification of Pathogenic Variants Causes Microcephaly In Sindh Families

Abstract

Introduction: The study was designed to identify the genetic mutation in families with autosomal recessive primary microcephaly (MCPH). Methodology: The present study was cross-sectional and conducted at the Department of Biochemistry, Quaid-e-Azam University, Islamabad in 2017. The two families (A and B) with MCPH phenotype randomly selected from Hyderabad and Tando Adam districts respectively. Informed written consent was taken, physical parameters were measured and blood samples were collected from both families. DNA was extracted from whole blood and PCR was performed. The ASPM gene located on chromosome 1 is known to play a vital role in mitotic spindle fiber regulation during neurogenesis, and also is the most probable causative agent of microcephaly. Therefore targeted Sanger sequencing method for the ASPM gene was selected for variant identification in both families. Results: The Sanger sequencing result showed the novel missense variant (c.5841T/C; p. K1862E) in 18 exon of ASPM gene in Family A and this variant predicted as damaging in mutation tester, and provean and also exhibited deleterious in Polyphen 2 and SIFT public database. Similarly in family B we found a previously reported protein pre termination variant (c.3978G/A; p.Trp1326*) (rs137852995) in exon 17 of ASPM gene. The later mutation was most predominant cause of microcephaly in KPK families. Conclusion: Therefore it is concluded that mutation in the ASPM gene is the most prominent genetic player of Microcephaly in Pakistani families. The current study aids in the genetic analysis of MCPH phenotype families in Pakistan alongwith the counseling of MCPH families.