Splice variants of the mouse Tec gene are differentially expressed in vivo

Tec is a cytoplasmic protein tyrosine kinase that participates in the signa lling pathways of a broad range of cytokines. Up to five different Tec isof orms have been reported in the literature. We report here the genomic organ isation of the mouse Tec gene and the tissue expression pattern of the two predominant transcripts, TecIII and TecIV. The mouse Tec gene consists of 1 8 exons, spans more than 86 kb, and is 2.6 kb 5' to the gene for Txk, a Tec family member. Comparison of mouse and human Btk, human TXK, and mouse Tec genomic structures shows a high level of conservation of exon/intron bound aries. Compared with TecIV, the TecIII transcript has a 66-bp deletion in t he SH3 domain encoding region and is revealed here to arise by alternative splicing of exon 8. We show that both TecIII and TecIV are expressed as ear ly as embryonic day 10.5 in mouse development, as well as in adult and embr yonic organs. The ratio of TecIV to TecIII expression is markedly reduced i n adult liver and kidney tissues and d16 embryonic limb.