RT Journal Article SR Electronic T1 TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP 581 OP 586 DO 10.1136/jmedgenet-2014-102282 VO 51 IS 9 A1 David Gillis A1 Aiswarya Krishnamohan A1 Barak Yaacov A1 Avraham Shaag A1 Jane E Jackman A1 Orly Elpeleg YR 2014 UL http://jmg.bmj.com/content/51/9/581.abstract AB Background Trm10 is a tRNA m1G9 methyltransferase, which in yeast modifies 12 different tRNA species, yet is considered non-essential for viability under standard growth conditions. In humans, there are three Trm10 orthologs, one mitochondrial and two presumed cytoplasmic. A nonsense mutation in one of the cytoplasmic orthologs (TRMT10A) has recently been associated with microcephaly, intellectual disability, short stature and adolescent onset diabetes. Methods and results The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia. A homozygous Gly206Arg (G206R) mutation in the TRMT10A gene was identified using whole exome sequencing. The mutation segregated in the family and was absent from large control cohorts. Determination of the methylation activity of the expressed wild-type (WT) and variant TRMT10A enzymes with transcripts of 32P -tRNAGlyGCC as a substrate revealed a striking defect (<0.1% of WT activity) for the variant enzyme. The binding affinity of the G206R variant enzyme to tRNA, determined by fluorescence anisotropy, was similar to that of the WT enzyme. Conclusions The completely abolished m1G9 methyltransferase activity of the mutant enzyme is likely due to significant defects in its ability to bind the methyl donor S-adenosyl methionine. We propose that TRMT10A deficiency accounts for abnormalities in glucose homeostasis initially manifesting both ketotic and non-ketotic hypoglycaemic events with transition to diabetes in adolescence, perhaps as a consequence of accelerated β cell apoptosis. The seizure disorder and intellectual disability are probably secondary to mutant gene expression in neuronal tissue.