Genomewide association study of lung lesions in cattle using sample pooling.

Bovine respiratory disease complex (BRDC) is the most expensive disease in beef cattle in the United States costing the industry at least US$1 billion annually. Bovine respiratory disease complex causes damage to lung tissue resulting in persistent lung lesions observable at slaughter. Severe lung lesions at harvest have been associated with decreased preharvest ADG and increased clinical BRDC in the feedlot. Our objective was to identify SNP that are associated with severe lung lesions observed at harvest in feedlot cattle. We conducted a genomewide association study (GWAS) using a case-control design for severe lung lesions in fed cattle at slaughter using the Illumina Bovine HD array (approximately 770,000 SNP) and sample pooling. Lung samples were collected from 11,520 young cattle, a portion of which had not been treated with antibiotics (participating in a "natural" marketing program), at a large, commercial beef processing plant in central Nebraska. Lung samples with lesions (cases) and healthy lungs (controls) were collected when both phenotypes were in close proximity on the viscera (offal) table. We constructed 60 case and 60 control pools with 96 animals per pool. Pools were constructed by sampling sequence to ensure that case and control pool pairs were matched by proximity on the processing line. The Bovine HD array (770,000 SNP) was run on all pools. Fourteen SNP on BTA 2, 3, 4, 9, 11, 14, 15, 22, 24, and 25 were significant at the genomewide experiment-wise error rate of 5% ( ≤ 1.49 × 10). Eighty-five SNP on 28 chromosomes achieved a false discovery rate of 5% ( ≤ 5.38 × 10). Significant SNP were near (±100 kb) genes involved in tissue repair and regeneration, tumor suppression, cell proliferation, apoptosis, control of organ size, and immunity. Based on 85 significantly associated SNP in or near a collection of genes with diverse function on 28 chromosomes, we conclude that the genomic footprint of lung lesions is complex. A complex genomic footprint (genes and regulatory elements that affect the trait) is consistent with what is known about the cause of the disease: complex interactions among multiple viral and bacterial pathogens along with several environmental factors including dust, commingling, transportation, and stress. Characterization of sequence variation near significant SNP will enable accurate and cost effective genome-enhanced genetic evaluations for BRDC resistance in AI bulls and seed stock populations.

Associations of genetic markers in cattle receiving differing implant protocols.

The potential interaction of growth-promoting implants and genetic markers previously reported to be associated with growth, carcass traits, and tenderness was evaluated. Two implant protocols were applied to subsets of steers (n = 383) and heifers (n = 65) that were also genotyped for 47 SNP reported to be associated with variation in growth, fat thickness, LM area, marbling, or tenderness. The "mild" protocol consisted of a single terminal implant [16 mg estradiol benzoate (EB), 80 mg trenbalone acetate (TBA) or 8 mg EB, 80 mg TBA given to steers and heifers, respectively]. The "aggressive" protocol consisted of both a growing implant (8 mg EB, 40 mg TBA) for the lightest half of the animals on the aggressive protocol and 2 successive implants (28 mg EB, 200 mg TBA) given to all animals assigned to the aggressive treatment. Implant protocol had measurable impact on BW and ADG (P < 0.05), with the aggressive protocol increasing these traits before the terminal implant (relative to the mild protocol), whereas the mild protocol increased ADG after the terminal implant so that the final BW and ADG over the experimental period were similar between protocols. Animals on the aggressive protocol had significantly increased (P < 0.05) LM area (1.9 cm(2)), slice shear force (1.4 kg), and intact desmin (0.05 units), but decreased (P < 0.05) marbling score (49 units) and adjusted fat thickness (0.1 cm), and yield grade (0.15 units). Among both treatments, 8 of 9 growth-related SNP were associated with BW or ADG, and 6 of 17 tenderness-related SNP were associated with slice shear force or intact desmin. Favorable growth alleles generally were associated with increased carcass yield traits but decreased tenderness. Similarly, favorable tenderness genotypes for some markers were associated with decreased BW and ADG. Some interactions of implant protocol and genotype were noted, with some growth SNP alleles increasing the effect of the aggressive protocol. In contrast, putative beneficial effects of favorable tenderness SNP alleles were mitigated by the effects of aggressive implant. These type of antagonisms of management variables and genotypes must be accounted for in marker assisted selection (MAS) programs, and our results suggest that MAS could be used to manage, but likely will not eliminate negative impact of implants on quality.

Ankyrin repeat and suppressor of cytokine signaling (SOCS) box-containing protein (ASB) 15 alters differentiation of mouse C2C12 myoblasts and phosphorylation of mitogen-activated protein kinase and Akt.

Ankyrin repeat and suppressor of cytokine signaling box-containing protein (ASB) 15 is a novel ASB gene family member predominantly expressed in skeletal muscle. We have previously reported that overexpression of ASB15 delays differentiation and alters protein turnover in mouse C(2)C(12) myoblasts. However, the extent of ASB15 regulation of differentiation and molecular pathways underlying this activity are unknown. The extracellular signal-regulated kinase (Erk) 1/2 and phosphatidylinositol-3 kinase-Akt (PI3K/Akt; Akt is also known as protein kinase B) signaling pathways have a role in skeletal muscle growth. Activation (phosphorylation) of the Erk1/2 signaling pathway promotes proliferation, whereas activation of the PI3K/Akt signaling pathway promotes myoblast differentiation. Accordingly, we tested the hypothesis that ASB15 controls myoblast differentiation through its regulation of these kinases. Stably transfected myoblasts overexpressing ASB15 (ASB15+) demonstrated decreased differentiation, whereas attenuation of ASB15 expression (ASB15-) increased differentiation. However, ASB15+ cells had less abundance of the phosphorylated mitogen-activated protein kinase (active) form, despite decreased differentiation relative to control myoblasts (ASB15Con). The mitogen-activated protein kinase kinase inhibitor, U0126, effectively decreased mitogen-activated protein kinase phosphorylation and stimulated differentiation in ASB15- and ASB15Con cells. However, inhibition of the Erk1/2 pathway was unable to overcome the inhibitory effect of overexpressing ASB15 on differentiation (ASB15+), suggesting that the Erk1/2 pathway is likely not the predominant mediator of ASB15 activity on differentiation. Expression of ASB15 also altered phosphorylation of the PI3K/Akt pathway, as ASB15+ and ASB15- cells had decreased and increased Akt phosphorylation, respectively. These data were consistent with observed differences in differentiation. Administration of IGF-I, a PI3K/Akt activator, in ASB15+ was able to partially override the previously observed phenotype of delayed differentiation, whereas administration of the PI3K/ Akt inhibitor, LY294002, decreased phosphorylation of Akt and differentiation of all cell lines similar to the untreated ASB15+ myoblasts. These results provide initial evidence that ASB15 has a role in early myoblast differentiation and that its effects may be mediated in part by the PI3K/Akt signal transduction pathway.