We report 10 heterozygous mutations in the human insulin gene in 16 probands with neonatal diabetes. A combination of linkage and a candidate gene approach in a family with four diabetic members led to the identification of the initial INS gene mutation. The mutations are inherited in an autosomal dominant manner in this and two other small families whereas the mutations in the other 13 patients are de novo. Diabetes presented in probands at a median age of 9 weeks, usually with diabetic ketoacidosis or marked hyperglycemia, was not associated with ␤ cell autoantibodies, and was treated from diagnosis with insulin. The mutations are in critical regions of the preproinsulin molecule, and we predict that they prevent normal folding and progression of proinsulin in the insulin secretory pathway. The abnormally folded proinsulin molecule may induce the unfolded protein response and undergo degradation in the endoplasmic reticulum, leading to severe endoplasmic reticulum stress and potentially ␤ cell death by apoptosis. This process has been described in both the Akita and Munich mouse models that have dominant-acting missense mutations in the Ins2 gene, leading to loss of ␤ cell function and mass. One of the human mutations we report here is identical to that in the Akita mouse. The identification of insulin mutations as a cause of neonatal diabetes will facilitate the diagnosis and possibly, in time, treatment of this disorder.endoplasmic reticulum stress ͉ insulin biosynthesis ͉ disulfide bonds ͉ unfolded protein response

Background/objective-Mutations in KCNJ11, ABCC8, or INS are the cause of permanent neonatal diabetes mellitus in about 50% of patients diagnosed with diabetes before 6 months of age and in a small fraction of those diagnosed between 6 and 12 months. The aim of this study was to identify the genetic cause of diabetes in 77 consecutive patients referred to the University of Chicago with diabetes diagnosed before 1 yr of age.

Background Recently, bi-allelic mutations in the transcription factor RFX6 were described as the cause of a rare condition characterized by neonatal diabetes with pancreatic and biliary hypoplasia and duodenal/jejunal atresia. Clinical Case A male infant developed severe hyperglycemia (446 mg/dL) within 24 hours of birth. Acute abdominal concerns by day five necessitated exploratory surgery that revealed duodenal atresia, gallbladder agenesis, annular pancreas and intestinal malrotation. He also exhibited chronic diarrhea and feeding intolerance, cholestatic jaundice, and subsequent liver failure. He died of sepsis at four months old while awaiting liver transplantation. The phenotype of neonatal diabetes with intestinal atresia and biliary agenesis clearly pointed to RFX6 as the causative gene; indeed, whole exome sequencing revealed a novel homozygous RFX6 mutation c.779A>C; p.Lys260Thr (K260T). This missense mutation also changes the consensus 5’ splice donor site before intron 7 and is thus predicted to cause disruption in splicing. Both parents, who were not known to be related, were heterozygous carriers. Conclusions Targeted genetic testing based on consideration of phenotypic features may reveal a cause among the many genes now associated with heterogeneous forms of monogenic neonatal diabetes. Our study demonstrates the feasibility of using modern sequencing technology to identify one such rare cause. Continued research is needed to determine the possible cost-effectiveness of this approach, especially when clear phenotypic clues are absent. Further study of patients with RFX6 mutations should clarify its role in pancreatic, intestinal and enteroendocrine cellular development and explain features such as the diarrhea exhibited in our case.

We studied the genetic and clinical features of diabetic subjects in a five-generation MichiganKentucky pedigree ascertained through a proband with pancreatic agenesis and homozygous for the IPF1 mutation Pro63fsx60. Diabetic and nondiabetic family members were genotyped and phenotyped. We also carried out genetic studies to determine the history of the IPF1 mutation in the Michigan-Kentucky family and a Virginia family with the same mutation. We identified 110 individuals. Thirty-four are currently being treated for diabetes and ten of these are Pro63fsX60 carriers (i.e. MODY4). Subjects with MODY as well as those with type 2 diabetes are characterized by obesity and hyperinsulinemia. Genetic studies suggest that the IPF1 mutation was inherited from an ancestor common to both the Michigan-Kentucky and Virginia families. MODY4 and type 2 diabetes in the Michigan-Kentucky pedigree are associated with obesity and hyperinsulinemia. Obesity and hyperinsulinemia have been observed occasionally in other subtypes of MODY suggesting that hyperinsulinemia may be a general phenomenon when obesity occurs in MODY subjects. Hypoinsulinemia in non-obese MODY subjects appears to be due to a functional defect in the beta cell. Genetic testing should be considered in multigenerational obese diabetic subjects, particularly when such families contain young diabetic members.

The amino acid sequence of rat ribosomal protein S16 was deduced from the sequence of nucleotides in a recombinant cDNA and confirmed from the NH&err&al amino acid sequence of the protein. S16 contains 145 ammo acids (the NHz-terminal methionine is removed after translation of the mRNA) and has a molecular mass of 16304. Hybridization of the cDNA to digests of nuclear DNA suggests that there. are 1 l-13 copies of the SI6 gene. The mRNA for the protein is about 700 nucleotides in length. Rat S16 is homologous to mouse S16 (there are 2 ammo acid changes and a residue is deleted) and r&iic;d to H~~acteri~ mor~mor~i ribosomal protein S3 and to ~s~heric~~ coli S9.Ribosomal protein Sl6; Ammo acid sequence; cDNA, (Rat)