Structural characterization of the rat cysteine-rich intestinal protein gene and overexpression of this LIM-only protein in transgenic mice

Cysteine-rich intestinal protein (CRIP) has a double zinc-linger motif call ed the LIM domain, The most elementary member of the Group 2 LIM-only prote in family, GRIP was initially identified as a developmentally regulated int estinal gene, Subsequently, it was found to be highly expressed in immune c ells. The structural portion of the rat GRIP gene is comprised of five exon s extending over 1.8 kb, with the two zinc-finger motifs of the LIM domain being divided among the first three exons, In addition to transcriptional r egulatory elements previously identified in the promoter, consensus sequenc es for AP-1, AP-2 Sp-1, and a glucocorticoid response element are located w ithin the first intron, We have developed a line of transgenic mice that ov erexpress the rat GRIP gene with an expression profile that mirrors that of the endogenous gene. Driven by the homologous rat GRIP promoter, expressio n increased threefold to sevenfold in intestine, thymus, spleen, and lung o ver endogenous levels. The transgenic mice had only about 50% of the white blood cell count found in nontransgenic animals. Differential leukocyte cou nts showed transgenic animals had proportionately fewer lymphocytes and mor e monocytes, eosinophils, neutrophils, Flow cytometry data suggested that m ice overexpressing GRIP have more CD4(+)/CD8(+) thymic lymphocytes. These d ata suggest that GRIP plays a significant role in differentiation or matura tion of cells with rapid turnover such as those found in the intestine and immune system.