Phenotypic Characterization of Intellectual Disability Caused by MBOAT7 Mutation in Two Consanguineous Pakistani Families

Abstract

A homozygous in-frame deletion (c. 758_778del; p. Glu253_Ala259del) in membrane-bound O-acyltransferase family member 7 (MBOAT7), also known as lysophosphatidylinositol acyltransferase (LPIAT1), was previously reported to be the genetic cause of intellectual disability (ID) in consanguineous families from Pakistan. Here, we identified two additional Pakistani consanguineous families with severe ID individuals sharing the same homozygous variant. Thus, we provide further evidence to support this MBOAT7 mutation as a potential founder variant. To understand the genotype-phenotype relationships of the in-frame deletion in the MBOAT7 gene, we located the variant in the fifth transmembrane domain of the protein and determined that it causes steric hindrance to the formation of an α-helix and hydrogen bond, possibly influencing its effectiveness as a functional transmembrane protein. Moreover, extensive neuropsychological observations, clinical interviews and genetic analysis were performed on 6 patients from the 2 families. We characterized the phenotype of the patients and noted the serious outcome of severe paraplegia. Thus, optimal management for symptom alleviation and appropriate screening in these patients are crucial.

Keywords: MBOAT7 gene; Pakistani consanguineous families; founder effect; in-frame deletion; intellectual disability.