The objective of this study was to investigate the effects of bovine GH1, CAPN1 and CAST gene polymorphisms on carcass and meat traits in Nellore and Nellore x Bos taurus beef cattle. Three hundred animals were genotyped for GH1/MspI (TC/G in intron 3), CAPN316 (AF_252504.2:g.5709C>G) and CAST/RsaI (AY_008267.1:g282C>G) and phenotyped for rib eye area, backfat thickness, intramuscular fat, shear force (SF), and myofibrillar fragmentation index (MFI). No significant associations were observed between the GH1/MspI and CAST/RsaI polymorphisms and phenotypes, although the relation between the CAST/RsaI genotypes and meat tenderness evaluated by MFI approached significant. The fact that the CAPN316 polymorphism did not show adequate segregation in Nellore cattle confirms the difficulty of using this marker in breeding programs of different Bos indicus breeds. However, the positive results of the association analysis obtained for Nellore x B. taurus crosses contributed to the validation of previous findings.

This study was performed to compare CAPN1, CAPN2, CAST, TG, DGAT1 and LEP gene expressions and correlate them with meat quality traits in two genetic groups (Nellore and Canchim) in order to assess their expression profile and use their expression profile as genetic markers. We analyzed 30 young bulls (1 year old), 15 of each genetic group. Samples of the Longissimus dorsi muscle were collected for analysis of: total lipids (TL) and meat tenderness measured as Warner-Bratzler shear force (SF) and myofibrillar fragmentation (MFI) at day of slaughter and 7 days of aging. Gene expression profiles were obtained via RT-qPCR. TL and MFI showed differences between breeds, higher MFI in Canchim and higher TL in Nellore. Calpains showed no differential expression between groups, as did DGAT1, TG, and LEP. CAST was expressed more in the Nellore cattle. The only significant within-breed correlation (0.79) between gene expression and meat traits was found for DGAT1 and MFI in Canchim breed. Although the number of animals used in this study was small, the results indicate that the increased expression of CAST in Nellore may reflect tougher meat, but the lack of correlations with the meat traits indicates it is not a promising genetic marker.

Hox gene clusters encode a family of transcription factors that govern anterior-posterior axis patterning during embryogenesis in all bilaterian animals. The time and place of Hox gene expression are largely determined by the relative position of each gene within its cluster. Furthermore, Hox genes were shown to have their expression fine-tuned by regulatory microRNAs (miRNAs). However, the mechanisms of miRNA-mediated regulation of these transcription factors during fish early development remain largely unknown. Here we have profiled three highly expressed miR-10 family members of Nile tilapia at early embryonic development, determined their genomic organization as well as performed functional experiments for validation of target genes. Quantitative analysis during developmental stages showed miR-10 family expression negatively correlates with the expression of HoxA3a, HoxB3a and HoxD10a genes, as expected for bona fide miRNA-mRNA interactions. Moreover, luciferase assays demonstrated that HoxB3a and HoxD10a are targeted by miR-10b-5p. Overall, our data indicate that the miR-10 family directly regulates members of the Hox gene family during Nile tilapia embryogenesis.