Socs7 expression patterns, induction, and protein associations. (A) Socs7 mRNA expression was determined by Q PCR in 129S6 and C57BL mice fed a standard 10% fat diet ad libitum. Values are normalized relative to Hprt mRNA and plotted on a log scale. In addition to whole mouse tissues, collagenase-purified islets were also examined. Results are representative of 3 to 7 mice; error bars indicate ± SEM. *P < 0.05 between genotypes (1-tailed Student’s t test). 129S6 and C57BL/6 are indicated by light gray and dark gray bars, respectively. (B) A murine 129S6 multiple-tissue Northern blot was generated and probed with Socs7 full-length cDNA. Two bands were observed, the full-length transcript and a smaller, testis-specific (t.s.) isoform. The blot was stripped and reprobed with a Gapdh cDNA fragment as a loading control. Sk., skeletal. (C) Induction of Socs7 mRNA by insulin. Q-PCR for Socs7 in tissues isolated 1 hour after a physiological dose (0.75 U/kg) of insulin. Values are given as fold induction over level of Socs7 mRNA expression in untreated mice. Results from 4 treated (dark gray bars) and 4 untreated mice (light gray bars) are included. *P < 0.05 between stimulated and unstimulated mice of the same genotype (1-tailed Student’s t test). (D) Association of SOCS7 with insulin-signaling molecules. A full-length Socs7 cDNA was tagged with Xpress epitope and transfected into HEK293 cells with INSR or IRS1 as indicated. Immunoprecipitates of INSR or IRS1 and whole-cell lysates were blotted with an antibody recognizing SOCS7. Blots were stripped and reprobed with either antibodies against INSR or IRS1. WB, Western blot.