Mapping of 16 ESTs expressed in the bovine mammary gland during lactation

Abstract.

A bovine mammary gland cDNA-library was used to characterize and map genes expressed during lactation. Fifty cDNA clones selected by differential hybridization were sequenced from both ends, and sequences were examined for similarities with database sequences. For 34 of the transcripts, the sequences showed more than 80% similarity to previously characterized genes or expressed sequence tags (ESTs). Twenty cDNAs that could be of interest as candidate genes for milk production are selected for genetic or chromosomal mapping. Twenty-three out of the 39 designed primer pairs representing 16 cDNA clones amplified the expected fragments and were used for subsequent fluorescent single-strand conformation polymorphism analysis (F-SSCP) in the International Bovine Reference Panel families (IBRP). Ten polymorphic loci could be identified and used to genotype the IBRP animals, and nine of them were subsequently genetically mapped on nine chromosomes. In addition, eight loci from the 16 cDNA clones could be mapped by somatic cell hybrids, bringing the total number of mapped genes to 16, one of which was mapped genetically as well as physically. The mapped mammary gland ESTs are potentially useful for cloning economic trait loci by a positional candidate gene cloning approach.