EXPRESSION OF A CYSTEINE-RICH PROTEIN (CRP) ENCODING GENE DURING EARLY DEVELOPMENT OF THE TROUT

Members of the cysteine-rich protein (CRP) define a subclass of LIM-on ly proteins implicated mainly in muscle differentiation. Until now. ve ry little is known concerning the expression of CRP encoding genes dur ing vertebrate development. We describe here the isolation of a trout (Oncorhynchus mykiss) gene encoding a cysteine-rich protein (TCRP) and the pattern of its mRNA accumulation during embryogenesis, focusing o n somitogenesis. TCRP encodes a putative protein with two LIM domains linked to a short glycine-rich region that displays 86%, 76%, 67% iden tity with chicken CRP2, CRP1 and MLP/CRP3 proteins, respectively. Whol e-mount in situ hybridisation showed that TCRP transcript is first det ected just before somitogenesis in the paraxial mesoderm, while it is absent in the axial structures. During somitogenesis, the expression o f TCRP was observed caudally in the elongating presomitic mesoderm and in the last formed somites. The labelling for TCRP was found to fade as the somites mature. At the end of the somitogenesis, TCRP transcrip ts accumulation was restricted to pronephros and branchial arches. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.