A highly polymorphic bovine dinucleotide repeat D19S4 (IOBT 34) at chromosome 19q21

Radiation hybrid and genetic linkage mapping of two genes related to fat metabolism in cattle: fatty acid synthase (FASN) and glycerol-3-phosphate acyltransferase mitochondrial (GPAM)

Fatness traits, such as fat deposition, carcass composition, fat content, and the percentage of fat in milk, are economically relevant to cattle production. Fatty acid synthase (FASN) and glycerol-3-phosphate acyltransferase mitochondrial (GPAM) are two enzymes that play a central role in de novo lipogenesis. Both could be putative candidate genes for quantitative trait loci (QTL). Several clones containing the fatty acid synthase (FASN) and glycerol-3-phosphate acyltransferase mitochondrial (GPAM) genes were isolated after screening the INRA bovine bacterial artificial chromosome (BAC) library using PCR. Five microsatellite loci were derived from the BAC clones containing the genes of interest with heterozygosity values ranging from 27 to 78%, using DNA samples from the International Bovine Reference Panel (IBRP). The newly developed markers were genotyped on the IBRP animals and on a radiation hybrid panel to compare the obtained linkage and RH maps. Radiation hybrid maps were developed for chromosome BTA19 and BTA26 regions containing FASN and GPAM genes, respectively. The two genes and their associated microsatellite markers were located on the genetic or RH maps or on both. These microsatellite markers could be useful to study the QTL effect on fat synthesis in reference population.

Development of microsatellite markers and comparative mapping for bovine chromosome 19

Previous research has mapped an ovulation rate quantitative trait locus (QTL) to bovine chromosome 19. In an effort to enhance comparative mapping information and develop additional markers for refined QTL mapping, microsatellite markers were developed in a targeted approach. A bovine bacterial artificial chromosome (BAC) library was screened for loci with either known or predicted locations on bovine chromosome 19. An average of 6.4 positive BAC were identified per screened locus. A total of 10 microsatellite markers were developed for five targeted loci with heterozygosity of 7-83% in a sample of reference family parents. The newly developed markers were typed on reference families along with four previously mapped marker loci and used to create a linkage map. Comparison of locus order between human and cattle provides support for previously observed rearrangement. One of the mapped loci myotubularin related protein 4 (MTMR4) potentially extends the proximal boundary of a conserved linkage group.

An integrated radiation hybrid map of bovine chromosome 19 and ordered comparative mapping with human chromosome 17

We recently constructed a 5000-rad cattle whole-genome radiation hybrid panel with the primary objective of integrating linkage maps of microsatellites with evolutionarily conserved genes into one ordered map. This study utilized the panel to construct a radiation hybrid (RH) map of bovine chromosome 19 (BTA19). Twelve microsatellites from different cattle linkage maps, 15 coding genes, and 2 expressed sequence tags were placed on the BTA19 RH map, with 16 of the markers ordered with odds of at least 1000:1. When the BTA19 RH map was compared with human chromosome 17 cytogenetic and RH maps, rearrangements in linear order were revealed for homologous genes on these two chromosomes that are totally conserved at the level of synteny mapping. Radiation hybrids, which have to date been used almost exclusively in mapping the human genome, are a potentially powerful resource for constructing maps for other species and for ordered comparative mapping between species.

Cosmid-derived markers anchoring the bovine genetic map to the physical map

The mapping strategy for the bovine genome described in this paper uses large insert clones as a tool for physical mapping and as a source of highly polymorphic microsatellites for genetic typing, and was one objective of the BovMap Project funded by the European Union (UE). Eight-three cosmid and phage clones were characterized and used to physically anchor the linkage groups defining all the bovine autosomes and the X Chromosome (Chr). By combining physical and genetic mapping, clones described in this paper have led to the identification of the linkage groups corresponding to Chr 9, 12, 16, and 25. In addition, anchored loci from this study were used to orient the linkage groups corresponding to Chr 3, 7, 8, 9, 13, 16, 18, 19, and 28 as identified in previously published maps. Comparison of the estimated size of the physical and linkage maps suggests that the genetic length of the bovine genome may be around 4000 cM.