Insulin resistance and exaggerated insulin sensitivity triggered by single-gene mutations in the insulin signaling pathway.

Whereas the genetic basis of insulin sensitivity is determined by variation in multiple genes, mutations of single genes can give rise to profound changes in such sensitivity. Mutations of the insulin receptor gene ()-which trigger type A insulin resistance, Rabson-Mendenhall, or Donohue syndromes-and those of the gene for the p85α regulatory subunit of phosphoinositide 3-kinase (), which give rise to SHORT syndrome, are the most common and second most common causes, respectively, of single-gene insulin resistance. Loss-of-function mutations of the genes for the protein kinase Akt2 () or for TBC1 domain family member 4 () have been identified in families with severe insulin resistance.

Regulation of mitosis-meiosis transition by the ubiquitin ligase β-TrCP in male germ cells.

The mitosis-meiosis transition is essential for spermatogenesis. Specific and timely downregulation of the transcription factor DMRT1, and consequent induction of expression, is required for this process in mammals, but the molecular mechanism has remained unclear. Here, we show that β-TrCP, the substrate recognition component of an E3 ubiquitin ligase complex, targets DMRT1 for degradation and thereby controls the mitosis-meiosis transition in mouse male germ cells.