FIG. 1.

MCIP1 is overexpressed specifically in skeletal muscle of Myo-Cre/Flox-MCIP1 mice and inhibits calcineurin activity. (A) The Flox-MCIP1 transgene contains a CMV enhancer (CMV-Eh), a β-actin promoter (β-act-P), loxP sites, a CAT gene, a FLAG-tagged MCIP1, and a polyadenylation signal (pA). (B) Western blot demonstrating skeletal muscle-specific expression of the Flox-MCIP1 transgene in Myo-Cre/Flox-MCIP1 mice (Tg) compared to the wild type (WT). Each lane contains 20 μg protein and was probed with anti-MCIP1 antibodies. (C) Western blot analysis of calcineurin protein levels in the Tg animals compared to WT. Each lane contains 20 μg protein and was probed with anti-CnA antibodies. (D) Phosphatase assays of protein extracts from the gastrocnemius of WT and Tg mice. The calcium chelator EGTA was added to inhibit phosphatase activity of calcineurin. Okadaic acid (OA) was added to inhibit the phosphatases PP1 and PP2A. Phosphatase activity is defined as nanomoles of phosphate released per milligram of protein per minute. (E) Calcineurin activity in hind limbs of E17.5 WT and Tg embryos.