Albert B. Bianchi

Mouse chromosome 7

Center for Neuroscience, University of Tennessee, Memphis, 855 Monroe Avenue, Memphis, Tennessee 38163, USA Department of Carcinogenesis, University of Texas Science Park, Research Division, Smithville, Texas 78957, USA Department of Biochemistry and Cell Biology, SUNY at Stony Brook, Stony Brook, New York 11794-5215, USA Division of Genetics, Children’s Hospital of Philadelphia, 34th and Civic Center Boulevard, Philadelphia, Pennsylvania 19104, USA Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, Pennsylvania 19111, USA

A novel polymorphism near the mouse Int-2 locus

The mouse Int-2 gene, located within a proviral integration region in tumors induced by mouse mammary tumor virus (MMTV; Smith et al. 1988) encodes a 27 kDa protein which is structurally homologous to the basic fibroblastic growth factor family (Muller et al. 1990), and this product has been reported to have growth factor activity in transgenic mice in two epithelial tissues: mammary and prostate glands (Muller et al. 1990). As a result of our studies on mouse Chromosome (Chr) 7 related to the mouse skin carcinogenesis model in the outbred SENCAR mouse stock, we found a novel two-allele (A1 and A2) polymorphic marker upstream of the Int-2 gene (Bianchi et al. 1990, 1991). In order to study the allelic distribution among different inbred strains we used a polymerase chain reaction (PCR) strategy previously described (Bianchi et al. 1991). The A1 allele was found in SWR/J, SSIN, AKR/J, BALB/c, and C57BL/6J, whereas the A2 allele was present in the other strains studied (Fig. 1). In this report we also show that this polymorphism is the result of a B2-1ike repetitive sequence insertion in the A1 allele 1090 bp upstream of exon 3 in the Int-2 gene. We sequenced the DNA fragment encompassed by the BgllI and XbaI restriction sites, 960 bp upstream of exon 3 (Peters et al. 1989; Moore et al. 1986), and found that the A1 allele has a 204 bp insertion 129 bp upstream of the BgllI restriction site. A search throughout the GenBank and EMBL databases was carried out using a 30 bp sequence from the insert as input data. The result of this search showed B2 repetitive sequences. The alignment of the inserted fragment in A1 with mouse B2 repetitive se-