Physical mapping of two multi-gene families and comparative anchor loci in cattle and genetic linkage analysis on cattle chromosome 6

Abstract

The bovine genomic map has been expanded by both physical and genetic techniques. The physical asignment of the T-cell receptor(TCR)-CD3 family to three bovine syntenic groups was completed by using bovine x rodent somatic cell hybrids. TCR α (TCRA) and TCR δ (TCRD) were mapped to syntenic group U5, TCR β (TCRB) and TCR γ (TCRG) to U13, and CD3 δ (CD3D) and CD3 ε (CD3E) to U19 (chromosome 15). The adenine nucleotide translocator (ANT) gene family includes three functional sequences: ANT1, ANT2 and ANT3. Two of them, ANT2 and ANT3, were located on the X chromosome, and ANT1 was mapped to a new syntenic group, U25, using a panel of bovine x hamster and bovine x mouse hybrid somatic cells. Polymorphic studies were performed on three genes, either by analysis of restriction fragment length polymorphism (RFLP) or single-strand conformational polymorphism (SSCP). A syntenic analysis of human chromosome 11 (HSA11) homologs in bovine using bovine x rodent somatic cell hybrids defines several of the smallest conserved evolutionary unit segments (SCEUSs) among bovine, human and mouse. Acid phosphatase 2 (ACP2) and Thy^-1 cell surface antigen (THY1) were assigned to chromosome 15, while murine mammary tumor virus integration site oncogene homolog (INT2) and signal recognition particle receptor (SRPR) was assigned to U7. Comparative mapping of four homologous loci on HSA4, albumin (ALB), GABAa receptor α2 (GABRA2) and (β1 (GABRB1), and mineralocorticoid receptor (MLR) to bovine chromosomes further extended the known genomic conservation between HSA4 and bovine chromosomes 6 and 17. The ultimate goal of bovine genome mapping is to produce a linkage map consisting of genetic markers with interval spacing of no more than 20 centimogans (cM). A genetic map was established on chromosome 6 (syntenic group U15) involving the major bovine milk protein (casein) genes, ALB, GABRA2, kit oncogene (KIT), and complement component I (IF) by analysis of allelic segregation in a panel of reference families. The physical and genetic maps will be useful for further evolutionary study of the extant mammalian genomes and for the selective breeding of economically important traits in cattle.