@article {153, title = {Continued lessons from the INS gene: an intronic mutation causing diabetes through a novel mechanism.}, journal = {J Med Genet}, volume = {52}, year = {2015}, month = {2015 Sep}, pages = {612-6}, abstract = {

BACKGROUND: Diabetes in neonates usually has a monogenic aetiology; however, the cause remains unknown in 20-30\%. Heterozygous INS mutations represent one of the most common gene causes of neonatal diabetes mellitus.

METHODS: Clinical and functional characterisation of a novel homozygous intronic mutation (c.187+241G>A) in the insulin gene in a child identified through the Monogenic Diabetes Registry (http://monogenicdiabetes.uchicago.edu).

RESULTS: The proband had insulin-requiring diabetes from birth. Ultrasonography revealed a structurally normal pancreas and C-peptide was undetectable despite readily detectable amylin, suggesting the presence of dysfunctional β cells. Whole-exome sequencing revealed the novel mutation. In silico analysis predicted a mutant mRNA product resulting from preferential recognition of a newly created splice site. Wild-type and mutant human insulin gene constructs were derived and transiently expressed in INS-1 cells. We confirmed the predicted transcript and found an additional transcript created via an ectopic splice acceptor site.

CONCLUSIONS: Dominant INS mutations cause diabetes via a mutated translational product causing endoplasmic reticulum stress. We describe a novel mechanism of diabetes, without β cell death, due to creation of two unstable mutant transcripts predicted to undergo nonsense and non-stop-mediated decay, respectively. Our discovery may have broader implications for those with insulin deficiency later in life.

}, keywords = {Diabetes Mellitus, Humans, Infant, Insulin, Regular, Human, Introns, Mutation, Sequence Analysis, DNA}, issn = {1468-6244}, doi = {10.1136/jmedgenet-2015-103220}, author = {Carmody, David and Park, Soo-Young and Ye, Honggang and Perrone, Marie E and Alkorta-Aranburu, G and Highland, Heather M and Hanis, Craig L and Philipson, Louis H and Bell, Graeme I and Greeley, Siri Atma W} }