Alternative splicing, expression, and gene structure of the septin-like putative proto-oncogene Sint1

Sint1 (sept9), a murine gene of the septin family, was previously isolated as a putative proto-oncogene involved in T-cell lymphomagenesis. We now present its genomic structure and report on nine exons shared by all identified variants and at least four alternatively spliced 5' exons. Northern blot analyses using a Sint1 cDNA probe showed in almost all examined tissues two predominant transcripts of 3 and 4 kb. Exon-specific expression analyses assigned one of the 5' exons to the 4 kb transcript, while the other 5' exons seem to represent novel, tissue-specific, weakly expressed transcripts of different sizes, and none of them appear to hybridize to the major 3 kb transcript. Whole-mount in situ hybridization on post-implantation embryos revealed several areas strongly expressing Sint1, including neural crest cells, cephalic mesenchyme, and mesenchymal cells in the developing limb. A clustering of proviruses in four independent retrovirally induced tumors point to a region of about 3 kb around the most upstream exon as important for proviral deregulation of Sint1.