Assignment of the bovine TYK2 and PDE4A genes to bovine chromosome 7q15 by fluorescence in situ hybridization and radiation hybrid mapping.

The non-receptor tyrosine kinase TYK2 is a key component of the interferon signalling pathway. It can bind to the interferon ·/ß receptor where it mediates, together with another nonreceptor tyrosine kinase called JAK1, the phosphorylation of downstream targets. Other cytokine receptors that mediate their signals via TYK2 include the receptors for IL-6, IL-11, CNTF, LIF, and oncostatin M (Briscoe et al., 1996). Functional studies with Tyk2 deficient mice demonstrated that these mice are viable and show very specific changes in several cytokine responses. Surprisingly, interferon ·/ß signalling is only impaired but not completely abolished in these mice (Karaghiosoff et al., 2000, 2003). Naturally occurring mutations in the murine Tyk2 gene are associated with varying susceptibilities to infectious and autoimmune disease (Shaw et al., 2003). The human TYK2 gene consists of 25 exons spanning about 30 kb on chromosome 19p13.2 (Firmbach-Kraft et al., 1990; NCBI map viewer, human genome build 35.1). The murine Tyk2 gene also consists of 25 exons and is located on mouse chromosome 9A3 (NCBI map viewer, mouse genome build 32.1). Because of their important role for various immunological functions we started to characterize the non-receptor tyrosine kinase genes in livestock species. Following previous studies in pig (Kuiper et al., 2003; Leeb et al., 2004) we report here the assignment of the bovine TYK2 gene and the tightly linked PDE4A gene to BTA7q15 by FISH and RH mapping.