Identification of genetic variants in differentially expressed sequences in cattle of different metabolic type – potential genetic markers of nutrient utilization

Abstract. Two cattle breeds serve as a model to identify genes and genetic variants, respectively, that are potentially associated with nutrient transformation: Holsteins bred for high milk production mainly, and Charolais bred for high body weight with outstanding muscular growth. The major differences between Charolais and Holstein regarding many general body parameters originate from differences in pathways and deposition of nutrients. In an initial experiment, expressed sequence tags (ESTs) differentially displayed between both cattle breeds were isolated by mRNA differential display in liver and intestine. Of the in total identified 277 ESTs, 79 showing the most prominent differences, were screened for single nucleotide polymorphisms (SNPs). Thirty four SNPs were detected in 30 ESTs In a direct sequencing approach based on the comparative sequencing of the corresponding amplicons generated by PCR from genomic DNA pools of 20 animals each of both cattle breeds,. Eighteen of these SNPs showed breed specific distribution of allelic variants. Occurrence of ESTs with a breed specific SNP distribution and localisation of the respective ESTs to chromosome regions known to be affecting carcass and growth traits in cattle suggest a trait association of the respective SNPs. The polymorphic nature of the SNP markers suggests that they will be useful for evaluating whether variation in these genomic regions influences nutrient pathways in cattle.