Whole exome sequencing identifies a novel mutation in ASPM and ultra-rare mutation in CDK5RAP2 causing primary microcephaly in consanguineous Pakistani families

Authors

Ehtisham Ul Haq Makhdoom, Government College University, 38000, Faisalabad, Pakistan
Haseeb Anwar, Government College University, 38000, Faisalabad, Pakistan
Shahid Mahmood Baig, Aga Khan UniversityFollow
Ghulam Hussain, Government College University, Faisalabad, Pakistan

Document Type

Article

Department

Biological and Biomedical Sciences

Abstract

Background & objectives: Primary Microcephaly (MCPH) is a rare neurogenetic disease, manifesting congenitally reduced head circumference and non-progressive intellectual disability (ID). To date, twenty-eight genes with biallelic mutations have been reported for this disorder. The study aimed for molecular genetic characterization of Pakistani families segregating MCPH.
Methods: We studied two unrelated consanguineous families (family A and B) presenting >2 patients with diagnostic symptoms of MCPH, born to asymptomatic parents. We employed whole-exome sequencing (WES) of probands to find putative causal mutations. The candidate variants were further confirmed and analyzed for co-segregation by Sanger sequencing of all available members of each family. This study was conducted at Government College University, Faisalabad, Pakistan, and Cologne Center for Genomics (CCG), University of Cologne, Germany; during 2017-2020.
Results: We identified a novel homozygous variant c.10097_10098delGA, p.(Gly3366Glufs*19) in exon 26 of ASPM gene in family A which presents with moderate intellectual disability, speech impairment, visual abnormalities, seizures, and ptyalism. Family B was found to segregate nonsense, homozygous variant c.448C>T p.(Arg150*) in CDK5RAP2. The patients also exhibited mild to severe seizures without ptyalism that has not been previously reported in patients with mutations in the CDK5RAP2 gene.
Conclusion: We report a novel mutation in ASPM and ultra-rare mutation in the CDK5RAP2 gene, both causing primary microcephaly. The study expands the mutational spectrum of the ASPM gene to 212, and also adds to the clinical spectrum of CDK5RAP2 mutations. It also demonstrated the utility of WES in the investigation and genetic diagnosis of genetically heterogeneous disorders like MCPH. These findings would aid in diagnostic and preventive strategies including carrier screening, cascade testing, and genetic counselling.

Publication (Name of Journal)

Pakistan journal of medical sciences

Recommended Citation

Makhdoom, E. U., Anwar, H., Baig, S. M., Hussain, G. (2022). Whole exome sequencing identifies a novel mutation in ASPM and ultra-rare mutation in CDK5RAP2 causing primary microcephaly in consanguineous Pakistani families. Pakistan journal of medical sciences, 38(1), 84-89.
Available at: https://ecommons.aku.edu/pakistan_fhs_mc_bbs/960

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