Whole-genome analysis for backfat thickness in a tropically adapted, composite cattle breed from Brazil.

Backfat thickness affects the preservation of the beef carcass after slaughter and confers organoleptic characteristics assessed by the consumer. One of the breeding goals for Canchim, a tropically adapted breed, is to comprehensively increase fat thickness. Our goals were to identify genomic regions associated with backfat in Canchim populations and validate the association of single nucleotide polymorphisms (SNPs) overlapping previously identified QTL regions known to affect fat deposition. Fifteen animals with lower and 15 animals with higher residues for backfat, according to a linear model using the SAS GLM procedure, were selected from a population of 1171 animals and genotyped using the BovineSNP50 BeadChip. Initial analysis revealed more than 100 SNPs that discriminated the tails of phenotypic distribution. One extended region of association included the centromeric region of chromosome (Chr) 14. Because this region overlapped with QTL from previous reports, we developed SNP assays to interrogate two linkage disequilibrium blocks, one in the centromeric region and another in the middle region of Chr 14 to confirm the association. The analysis validated the presence of specific haplotypes affecting fat thickness.

Discovery, profiling and identification of polymorphic mRNA target sites in cattle

Our laboratory is interested in post-translational modifications of histone proteins, with studies ranging from identification of novel modifications to functional characterization of these marks. Ultimately, we seek to provide a greater understanding of how histone modifications work together to form a ‘histone code’. This code is thought to regulate the recruitment of effector proteins that regulate the diverse functions associated with DNA, including gene transcription and DNA repair. Our recent studies show that RNA polymerase II recruits a variety of chromatinmodifying enzymes that contribute to the disruption, reassembly and maintenance of chromatin structure during the transcription elongation process. One enzyme we have focused on is Set2, which associates with the transcribing polymerase and methylates nucleosomal H3 on lysine 36. H3K36 methylation results in the recruitment of a histone deacetylase complex which functions to prevent inappropriate transcription initiation from occurring within the transcribed regions of genes. I will discuss our recent progress toward understanding how Set2 contributes to the organization and function of chromatin. In addition, I will highlight our progress on a proteomics project that is providing new insights into how “readers” of the histone code bind their cognate modifications using high-density histone peptide arrays.

Discovery, profiling and identification of polymorphic mRNA target sites in cattle

Our laboratory is interested in post-translational modifications of histone proteins, with studies ranging from identification of novel modifications to functional characterization of these marks. Ultimately, we seek to provide a greater understanding of how histone modifications work together to form a ‘histone code. This code is thought to regulate the recruitment of effector proteins that regulate the diverse functions associated with DNA, including gene transcription and DNA repair. Our recent studies show that RNA polymerase II recruits a variety of chromatinmodifying enzymes that contribute to the disruption, reassembly and maintenance of chromatin structure during the transcription elongation process. One enzyme we have focused on is Set2, which associates with the transcribing polymerase and methylates nucleosomal H3 on lysine 36. H3K36 methylation results in the recruitment of a histone deacetylase complex which functions to prevent inappropriate transcription initiation from occurring within the transcribed regions of genes. I will discuss our recent progress toward understanding how Set2 contributes to the organization and function of chromatin. In addition, I will highlight our progress on a proteomics project that is providing new insights into how “readers” of the histone code bind their cognate modifications using high-density histone peptide arrays.(AU)