Submitted to: Cytogenetics and Genome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 29, 2005
Publication Date: November 8, 2005
Citation: Connor, E.E., Ashwell, M.S., Schnabel, R., Williams, J.L. 2006. Comparative mapping of bovine chromosome 27 with human chromosome 8 near a dairy form QTL in cattle. Cytogenetics and Genome Research. 112:98-102.
Interpretive Summary: Body condition may contribute to a dairy cow's susceptibility to a wide variety of diseases and health problems, as well as reproductive disorders. The genetic correlation between body condition score and a type trait of dairy cattle called dairy form is very high. Previously, a region of bovine chromosome 27 was identified by our laboratory as potentially containing genes associated with the dairy form trait. Identification of genes contributing to variation in this trait could enhance our ability to modulate body condition and improve animal health through genetic selection. In the present study, eight genes and four genetic markers were mapped to the bovine genome and resulted in the identification of ADRB3 as a positional candidate gene contributing to the dairy form trait. This gene plays a role in fat metabolism and has been associated with metabolic diseases and fat deposition in sheep, mice and humans. Additional work currently is underway to determine whether variation in the bovine ADRB3 gene exists and to study the associations between ADRB3 and health and production traits such as dairy form, metabolic disease, and fat deposition in cattle.
In the absence of a complete and annotated bovine genome sequence, detailed human-bovine comparative maps are one of the most effective tools for identification of positional candidate genes contributing to quantitative trait loci (QTL) in cattle. In the present study, eight genes from human chromosome 8 were selected for mapping in cattle to improve breakpoint resolution and confirm gene order on the comparative map near the 40 cM region of the BTA27 linkage map. Previously, a QTL affecting dairy form was identified in this area of the chromosome. Our findings identified ADRB3 as a positional candidate gene contributing to the dairy form QTL based on its estimated position between 40 and 45 cM on the linkage map, its role in fat metabolism, and polymorphisms in the ADRB3 gene associated with obesity and metabolic disease in humans, as well as, carcass fat in sheep. Additional studies are underway to investigate the existence of polymorphisms in the bovine ADRB3 gene and their association with traits related to fat deposition in cattle.