PARENT SESSION
Preimplantation Embryo/Fetal Development

CANDIDATE GENES ASSOCIATED WITH ALTERED DEVELOPMENT OF SKELETAL MUSCLE IN BOVINE FETUSES FROM EMBRYOS PRODUCED IN VITRO.

Crosier, Adrienne¹, Farin, Peter², Rodriguez, Karina¹, Blondin, Patrick¹, Alexander, Joseph¹, Farin, Charlotte¹, ^{1 2}

ABSTRACT- Development of skeletal muscle in bovine fetuses resulting from the transfer of embryos produced in vitro is altered. The objective of this study was to identify candidate genes that may be associated with this altered development. Embryos were produced either in vivo, by superovulation of Holstein cows (MO), or in vitro. In vitro produced embryos were cultured in TCM-199 + 10% estrus cow serum (IVPS). Single Grade 1 blastocysts from each production system were transferred into recipients. On Day 222 of gestation, fetuses were recovered (n=5 each for MO and IVPS), weighed, and samples of semitendinosus muscle were snap frozen. Fetal body weights were 17.2 ± 0.4 kg for MO and 20.7 ± 0.4 kg for IVPS (P<0.01; lsmeans ± SEM). Semi-quantitative RT-PCR was used to determine skeletal muscle mRNA expression for GAPDH and the myogenic determining factors: myogenin, MyoD, Myf5, and myostatin. The percent luminance of PCR products was analyzed by GLM procedures using a model that included the main effects of treatment, reverse transcript reaction, sex, and appropriate interactions. Preliminary data analysis indicated no treatment effect on expression of mRNAs for GAPDH, myogenin, or MyoD. Expression of mRNA for Myf5 tended to be lower (P=0.076) in skeletal muscle of IVPS fetuses compared with MO fetuses (49 ± 3% and 97 ± 3%, respectively). There was a treatment by sex interaction (P=0.01) on the expression of myostatin mRNA. Male fetuses within the MO treatment had a higher level of expression for myostatin mRNA compared with females (72.0 ± 0.1% and 70.0 ± 0.1%, respectively). However, within the IVPS group, male fetuses had a lower level of expression for myostatin mRNA compared with females (65.5 ± 0.1% and 67.8 ± 0.1%; respectively). In conclusion, Myf5 and myostatin have been identified as potential candidate genes contributing to the altered development of skeletal muscle in fetuses from embryos produced in vitro. Supported by USDA 9602482 and NCSU-CVM

KEY WORDS: BOVINE, GENE EXPRESSION, SKELETAL MUSCLE, IN VITRO CULTURE