ISOLATION AND DEVELOPMENTAL EXPRESSION OF A RAT CDNA-ENCODING A CYSTEINE-RICH ZINC-FINGER PROTEIN

A number of cysteine-rich proteins have recently been isolated by homo logy screening, differential library screens, and association with oth er proteins. In this report, we describe the isolation of the rat cyst eine-rich protein from a rat brain library during a search for clones with homology to the delta-opioid receptor. One of the cDNAs isolated hybridized to a 1.8 kb mRNA abundantly expressed throughout the rat br ain as well as in rat fiver. In situ hybridization reveals a wide dist ribution in rat brain; in particular, abundant hybridization was detec ted in the hippocampus, cerebellum, habenula, reticular thalamic nucle us and interposed nucleus. Nucleotide sequence analysis of a 1403 bp c DNA clone indicated 77% identity with the cDNA for human cysteine-rich protein (hCRP), that translates into a 99% identity at the amino acid level. The predicted amino acid sequence suggests four zinc fingers, two of the C-4 class and two of the C2HC class. This structural motif is characteristic of members of the LIM domain protein family. The mRN A is serum-inducible in Balb/c 3T3 cells. Additional study suggests th at its expression is not induced by either NGF treatment of PC12h pheo chromocytoma cells, or inflammation-induced injury in the spinal cord at up to 60 min after injury. It does appear to be developmentally exp ressed in rat brain, consistent with a potential role in neuronal deve lopment. The rat CRP clone will be useful for studying the function of CRPs in rodent models.