Identification of a novel Reg family gene, Reg III delta, and mapping of all three types of Reg family gene in a 75 kilobase mouse genomic region

Regenerating gene (Reg), first isolated from a regenerating islet cDNA libr ary, encodes a secretory protein with a growth stimulating effect on pancre atic beta cells that ameliorates the diabetes of 90% depancreatized rats an d non-obese diabetic mice. Rrg and Reg-related genes have been revealed to constitute a multigene family, the Reg family, which consists of three subt ypes (types I, II, III) based on the primary structures of the encoded prot eins of the genes. We have isolated three types of mouse Reg family gene (R eg I. Reg II, Reg IIIa, Reg III beta and Reg III gamma) [Unno et al. (1993) J. Biol. Chem. 268, 15 974-15 982; Narushima et al. (1997) Gene 185, 159-1 68]. In the present study, by Southern blot analysis of a mouse bacterial a rtificial chromosome clone containing the five Reg family genes in combinat ion with PCR cloning of every interspace fragment between adjacent genes, t he Reg family genes were mapped to a contiguous 75 kb region of the mouse g enome according to the following order: 5'-Reg III beta-Reg III alpha-Reg I I-Reg I-REg III gamma-3;. In the process of ordering the genes, we sequence d the 6.8 kb interspace fragment between Reg III beta and Reg III alpha and encountered a novel type III Reg gene, Reg III delta. This gene is divided into six exons spanning about 3 kb, and encodes a 175 amino acid protein w ith 40-52% identity with the other five mouse Reg (regenerating gene produc t) proteins. Reg III delta was expressed predominantly in exocrine pancreas , but not in normal islets, hyperplastic islets, intestine or colon, wherea s both Reg I and Reg II were expressed in hyperplastic islets and Reg III a lpha, Reg III beta and Reg III gamma were expressed strongly in the intesti nal tract. Possible roles of Reg III delta and the widespread occurrence of the Reg IIIb gene in mammalian genomes are discussed. (C) 2000 Elsevier Sc ience B.V. All rights reserved.