EMBRYONIC EXPRESSION SUGGESTS AN IMPORTANT ROLE FOR CRP2 SMLIM IN THEDEVELOPING CARDIOVASCULAR-SYSTEM/

Proteins of the LIM family are critical regulators of development and differentiation in various cell types. We have described the cloning o f cysteine-rich protein 2/smooth muscle LIM protein (CRP2/SmLIM), a LI M-only protein expressed in differentiated vascular smooth muscle cell s. As a first step toward understanding the potential functions of CRP 2/SmLIM, we analyzed its expression after gastrulation in developing m ice and compared the expression of CRP2/SmLIM with that of the other 2 members of the CRP subclass, CRP1 and CRP3/MLP, In situ hybridization in whole-mount and sectioned embryos showed that CRP2/StnLIM was expr essed in the sinus venosus and the 2 cardiac chambers at embryonic day 9. Vascular expression of CRP2/SmLIM was first seen at embryonic day 10, At subsequent time points, CRP2/SmLIM expression decreased in the heart but remained high in the vasculature, CRP1 was expressed both in vascular and nonvascular tissues containing smooth muscle cells, wher eas CRP3/MLP was expressed only in tissues containing striated muscle. These patterns of expression were maintained in the adult animal and suggest an important role for this gene family in the development of s mooth and striated muscle.