CHROMOSOMAL ASSIGNMENT OF 6 MUSCLE-SPECIFIC GENES IN CATTLE

Six genes expressed in skeletal or smooth muscle were assigned to bovi ne chromosomes using rodent, human or bovine cDNA probes. Myogenic det ermination factor (MYOD1) was 100% concordant with Bos taurus chromoso me (BTA) 15, and myogenin (MYOG) was 95% concordant with BTA 16. Smoot h muscle caldesmon (CALD1) and the skeletal muscle chloride channel ge ne (CLCN1) were 100% concordant with BTA 4. Myogenic factor 5 (MYF5) w as 90% concordant with BTA 5; this assignment was confirmed by fluores cence in situ hybridization of a bovine genomic MYF5 probe to BTA 5 ba nd 13 and the homologous band on river buffalo 4q. In some metaphases, specific hybridization signals were also observed on BTA 15 band 23, and the equivalent river buffalo homologue, with the MYF5 genomic prob e. Because MYOD1 and MYF5 share both nucleotide and functional homolog y and because MYOD1 was mapped in somatic cell hybrids to BTA 15, we s uggest that MYOD1 may be located at BTA 15 band 23. Herculin/myogenic factor 6 (MYF6) was assigned indirectly to BTA 5 by the hybridization of MYF5 and MYF6 probes to the same HindIII fragment in bovine genomic DNA. The assignment of MYF6 to BTA 5 is consistent with the tandem ar rangement of MYF5 and MYF6 in human, mouse and chicken, where these ti ghtly linked genes are separated by < 6.5 kb of DNA.