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 homology screening, differential library screens, and association with other proteins. In this report, we describe the isolation of the rat cysteine-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 brain as well as in rat fiver. In situ hybridization reveals a wide distribution in rat brain; in particular, abundant hybridization was detected in the hippocampus, cerebellum, habenula, reticular thalamic nucleus and interposed nucleus. Nucleotide sequence analysis of a 1403 bp cDNA 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 mRNA is serum-inducible in Balb/c 3T3 cells. Additional study suggests that its expression is not induced by either NGF treatment of PC12h pheochromocytoma cells, or inflammation-induced injury in the spinal cord at up to 60 min after injury. It does appear to be developmentally expressed in rat brain, consistent with a potential role in neuronal development. The rat CRP clone will be useful for studying the function of CRPs in rodent models.