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Research Interests
Regulatory processes for growth and myogenesis; in mammalian and
non-mammalian models.
Research Summary
Primary and secondary myofibers are established prenatally in mammalian species, with little opportunity for post-natal muscle hyperplasia. Furthermore the total number of myofibers established prenatally in embryos and fetuses is dramatically influenced by competition for, as well as quality and quantity of, maternal nutrients. Scenarios of dramatic deficits in health and performance of offspring are frequently associated with limitations in maternal nutrient availability and this is often quite apparent in terms of its effects on fetal myogenesis. In multiparous species where several developing offspring are competing for limited resources the incidence of reduced birth weight and muscle fiber formation (runting) are quite common. Moreover, the long-lasting impact of adverse conditions during fetal development is well-known, as expressed in the "Barker Hypothesis" as it affects health, performance and disease susceptibility of these offspring (critical period) as well as their subsequent progeny (epigenetics). In a recent study in swine, we have established that marginal maternal nutrient restriction, results in altered epigenetic variance in surviving litters (Vinsky et al., 2007). Additionally, we have demonstrated that specific myogenic regulatory factors (mrf's) are altered in a detrimental manner in the developing embryos that are exposed to intrauterine crowding in early gestation (Tse et al., 2008). All mammals have a limited capacity for some muscle growth associated with increased cell recruitment (hyperplasia) under extreme conditions, such as severe myotrauma, and this process involves the specification and differentiation of 'satellite cells'. In addition to lower birth weight negatively impacting the lifelong performance of animals that deposit fewer mature muscle fibers prenatally, these runted offspring are further limited in their capacity for growth and repair of their skeletal muscle as dictated by a reduced number of mesenchymally derived satellite cells. It is poignant to note that the total satellite cell pool is also prenatally established and as such is altered by adverse in utero conditions. Therefore consequences of poor maternal nutrition can negatively influence the health and growth attributes of progeny that have been subject to formation and deposition of fewer intramuscular satellite cells. My research programs aim is to evaluate both the lasting genetic alterations associated with fetal exposure to sub-optimal uterine environments, as well as the critical periods where the in utero stressors impart the lasting deficits in fetal myogenesis.
Research Publications
2005-2009
Chapalamadugu, K.C., B.D. Robison, R.E. Drew, M.S. Powell, R.A. Hill, J.J. Amberg, K.J. Rodnick, R.W. Hardy, M.L. Hill, and G.K. Murdoch, Dietary carbohydrate level affects transcription factor expression that regulates skeletal muscle myogenesis in rainbow trout. Comp Biochem Physiol B Biochem Mol Biol, 2009.
F. Paradis, S. Novak, G.K. Murdoch, M. K. Dyck, W. T. Dixon and G. R. Foxcroft Temporal regulation of BMP2, BMP6, BMP15, GDF9, BMPR1A, BMPR1B, BMPR2 and TGFBR1 mRNA expression in the oocyte, granulosa and theca cells of developing preovulatory follicles in the pig (2009) Reproduction 138: p. 1–18.
K.A. Martins, G.K. Murdoch, Y. Shu, R. L. Harris, M. Gallo, W.T. Dixon, G. R. Foxcroft, T. Gordon, and C.T. Putman Satellite cell ablation attenuates short-term Fast-to-slow fibre type transformations in rat fast-twitch skeletal muscle. (2009) Pflugers Archive-European J. Physiology. 458: p. 325-335.
Allen, J.D., J.K. Ahola, M. Chahine, J.I. Szasz, C.W. Hunt, C.S. Schneider, G.K. Murdoch, and R.A. Hill, Effect of preslaughter feeding and ractopamine hydrochloride supplementation on growth performance, carcass characteristics, and end product quality in market dairy cows. J Anim Sci, 2009. 87(7): p.2400-8.
Ellis, J.L., E. Kebreab, N.E. Odongo, K. Beauchemin, S. McGinn, J.D. Nkrumah, S.S. Moore, R. Christopherson, G.K. Murdoch, B.W. McBride, E.K. Okine, and J. France, Modeling methane production from beef cattle using linear and nonlinear approaches. J Anim Sci, 2009. 87(4): p.1334-45.
Drew, R.E., K.J. Rodnick, M. Settles, J. Wacyk, E. Churchill, M.S. Powell, R.W. Hardy, G.K. Murdoch, R.A. Hill, and B.D. Robison, Effect of starvation on transcriptomes of brain and liver in adult female zebrafish (Danio rerio). Physiol Genomics, 2008. 35(3): p. 283-95.
Robison, B.D., R.E. Drew, G.K. Murdoch, M. Powell, K.J. Rodnick, M. Settles, D. Stone, E. Churchill,R.A. Hill, M.R. Papasani, S.S. Lewis, and R.W. Hardy. 2008. Sexual dimorphism in hepatic gene expression and the response to dietary carbohydrate manipulation in the zebrafish (Danio rerio). Comp Bioch Physiol Part D3:p. 141-154.
Sorensen, B.M., E. Chris Kazala, G.K. Murdoch, A.F. Keating, C. Cruz-Hernandez, J. Wegner, J.J. Kennelly, E.K. Okine, and R.J. Weselake, Effect of CLA and other C18 unsaturated fatty acids on DGAT in bovine milk fat biosynthetic systems. Lipids, 2008. 43(10): p. 903-12.
Tse, W.Y., S.C. Town, G.K. Murdoch, S. Novak, M.K. Dyck, C.T. Putman, G.R. Foxcroft, and W.T. Dixon, Uterine crowding in the sow affects litter sex ratio, placental development and embryonic myogenin expression in early gestation. Reprod Fertil Dev, 2008. 20(4): p. 497-504.