The cardiac expression of striated muscle LIM protein 1 (SLIM1) is restricted to the outflow tract of the developing heart.

LIM proteins perform critical roles in development and tissue differentiation. The skeletal muscle LIM protein 1 (SLIM1) comprises four and a half LIM domains. Northern blot analysis demonstrated high level expression of SLIM1 mRNA in adult human skeletal muscle with intermediate expression in adult heart and lower expression in other tissues. Western blot analysis using specific affinity-purified anti-SLIM1 antipeptide antibodies demonstrated a 32 kDa polypeptide in the aorta and atria of rabbit heart, but not in vena cava, interventricular septum or ventricular muscle. SLIM1 was also demonstrated in rabbit skeletal muscle. In situ hybridization of whole mouse embryos confirmed the cardiac expression of SLIM1 was restricted to the cardiac outflow tract from embryonic day 8.5-11. No expression was seen in atrial or ventricular muscle. SLIM1 mRNA was also demonstrated in the hindbrain, neural tube and somites. The localized expression of SLIM1 to the outflow tract of the embryonic heart implies an important role for the protein in the development of this region and possibly in congenital heart anomalies involving the separation and formation of the aortic and pulmonary trunks.