dUTPase (DUT) Is Mutated in a Novel Monogenic Syndrome With Diabetes and Bone Marrow Failure.

We describe a new syndrome characterized by early-onset diabetes associated with bone marrow failure, affecting mostly the erythrocytic lineage. Using whole-exome sequencing in a remotely consanguineous patient from a family with two affected siblings, we identified a single homozygous missense mutation (chr15.hg19:g.48,626,619A>G) located in the dUTPase (DUT) gene (National Center for Biotechnology Information Gene ID 1854), affecting both the mitochondrial (DUT-M p.Y142C) and the nuclear (DUT-N p.Y54C) isoforms. We found the same homozygous mutation in an unrelated consanguineous patient with diabetes and bone marrow aplasia from a family with two affected siblings, whereas none of the >60,000 subjects from the Exome Aggregation Consortium (ExAC) was homozygous for this mutation. This replicated observation probability was highly significant, thus confirming the role of this DUT mutation in this syndrome. DUT is a key enzyme for maintaining DNA integrity by preventing misincorporation of uracil into DNA, which results in DNA toxicity and cell death. We showed that DUT silencing in human and rat pancreatic ß-cells results in apoptosis via the intrinsic cell death pathway. Our findings support the importance of tight control of DNA metabolism for ß-cell integrity and warrant close metabolic monitoring of patients treated by drugs affecting dUTP balance.

A Missense Mutation in PPP1R15B Causes a Syndrome Including Diabetes, Short Stature, and Microcephaly.

Dysregulated endoplasmic reticulum stress and phosphorylation of eukaryotic translation initiation factor 2α (eIF2α) are associated with pancreatic ß-cell failure and diabetes. Here, we report the first homozygous mutation in the PPP1R15B gene (also known as constitutive repressor of eIF2α phosphorylation [CReP]) encoding the regulatory subunit of an eIF2α-specific phosphatase in two siblings affected by a novel syndrome of diabetes of youth with short stature, intellectual disability, and microcephaly. The R658C mutation in PPP1R15B affects a conserved amino acid within the domain important for protein phosphatase 1 (PP1) binding. The R658C mutation decreases PP1 binding and eIF2α dephosphorylation and results in ß-cell apoptosis. Our findings support the concept that dysregulated eIF2α phosphorylation, whether decreased by mutation of the kinase (EIF2AK3) in Wolcott-Rallison syndrome or increased by mutation of the phosphatase (PPP1R15B), is deleterious to ß-cells and other secretory tissues, resulting in diabetes associated with multisystem abnormalities.