Paternal uniparental disomy of chromosome 16 resulting in homozygosity of a GPT2 mutation causes intellectual and developmental disability

Recessive mutations in glutamate pyruvate transaminase 2 (GPT2) have recently been found to be associated with intellectual and developmental disability (IDD). In this study, we discovered a homozygous missense variant, NM_133443: [c.1172C > T, p. Pro391Leu], of GPT2 on chromosome 16 in a proband diagnosed with IDD through trio whole-exome sequencing (WES). The pathogenicity of the variant was further verified by bioinformatics analysis and functional studies in vitro. This autosomal recessive disease was caused by paternal uniparental disomy (UPD) which was further proven by single nucleotide polymorphism array (SNP array). In past literature, recessive diseases in chromosome 16 were usually due to maternal UPD where Mendel's law of inheritance was not applicable. However, in our case we found that paternal UPD can cause recessive diseases related to the GPT2 gene on chromosome 16. Our study provides an important line of evidence for the diagnosis of GPT2-related intellectual developmental disorders.