Master of Science, The Ohio State University, 2013, Animal Sciences

Myogenic satellite cells are heterogeneous multipotential stem cells required for muscle repair, maintenance, and growth. The membrane-associated heparan sulfate proteoglycans syndecan-4 and glypican-1 differentially regulate satellite cell proliferation, differentiation, fibroblast growth factor 2 (FGF2) signal transduction, and expression of myogenic regulatory factors. The objective of Specific Aims 1 and 2 was to determine the effect of age on satellite cell proliferation and differentiation using cells isolated from the pectoralis major muscle of 1 d, 7 wk and 16 wk old turkeys. Proliferation was significantly reduced in the 16 wk satellite cells, while differentiation was decreased in the 7 wk and the 16 wk cells beginning at 48 h of differentiation. Fibroblast growth factor 2 responsiveness was highest in the 1 d and 7 wk cells during proliferation; during differentiation there was an age-dependent response to FGF2. Syndecan-4 and glypican-1 expressing satellite cell populations decreased with age. These data demonstrate that declining syndecan-4 and glypican-1 satellite cell subpopulations which may be associated with age-related changes in satellite cell proliferation, differentiation, and FGF2 responsiveness. In specific aim 3, the effect of overexpressing syndecan-4 and glypican-1 was investigated. Syndecan-4 and glypican-1 overexpression did not have a significant effect on proliferation and differentiation in 1 d, 7 wk and 16 wk satellite cells. Overexpression of syndecan-4 and glypican-1 did not affect FGF2 responsiveness during proliferation. During differentiation, overexpression of syndecan-4 and glypican-1 increased differentiation at 48 h of differentiation in 1 d, 7 wk and 16 wk cells treated with FGF2 and decreased differentiation in 16 wk cells not treated with FGF2. Expression of myogenic regulatory factors MyoD, myogenin, and MRF4 were also affected by overexpression of syndecan-4 and glypican-1. These data demonstrate that syde (open full item for complete abstract)

Committee: Sandra Velleman (Advisor); Kristy Daniels (Committee Member); Ramesh Selvaraj (Committee Member) Subjects: Aging; Agriculture; Animal Sciences; Cellular Biology; Nutrition

Doctor of Philosophy, The Ohio State University, 2009, OSU Nutrition

The role of Delta-like protein 1 (DLK1) has been implicated in the muscle hypertrophy observed in DLK1 transgenic mice, callipyge sheep, mouse paternal uniparental disomy (pUPD) 12 and human pUPD14 syndromes. However, no study on DLK1 has been conducted in the avian species. The ultimate goal of this dissertation is to identify the role of chicken delta-like protein 1 (gDLK1) in skelelal muscle development, growth, and regeneration in poultry. The objectives of the first study were to clone and sequence a full length of chicken DLK1 cDNA, and to investigate the developmental regulation of gDLK1 during embryonic muscle development and postnatal muscle growth. The cloning and sequencing data revealed that gDLK1 contains a total of 1,161 base pairs, encoding 386 amino acids. The similarities of gDLK1 nucleotide and protein sequences were over 50% compared to mammalian species. In addition, chickens only express a full-length gDLK1 in various tissues at different ages without the alternative splicing variants. The expression of gDLK1 gene in pectoralis major muscle was significantly higher in embryonic stages rather than posthatching stages during muscle development (P < 0.05). The expression pattern of gDLK1 was very similar to the expression patterns of myogenin and Pax7 genes, suggesting a close association with myogenic activities. The objectives of the second study were to determine gDLK1 mRNA expression during primary muscle cell differentiation and during muscle regeneration after cold injury, as well as to compare gDLK1mRNA expression during skeletal muscle development in layers and broilers. In the chicken primary muscle cell culture, the peak expression of gDLK1 mRNA was highly associated with late stages of myogenesis after primary myoblast differentiation. During muscle regeneration, the induction of the gDLK1 gene consistently appeared at late stages of regenerative myogenesis. The expression data of gDLK1 associated with myogenic markers (Pax7, MyoD, and m (open full item for complete abstract)

Committee: Kichoon Lee PhD (Advisor); Earl Harrison PhD (Committee Member); Martha A. Belury PhD (Committee Member); Sandra G. Velleman PhD (Committee Member) Subjects: Biology

Doctor of Philosophy, Case Western Reserve University, 2009, Biochemistry

Ski is the most studied member of a family of proteins all sharing a conserved Dachshund homology domain. It has been implicated in oncogenic transformation, myogenic conversion of avian embryo fibroblasts and also many aspects of vertebrate development, especially myogenesis. Ski-/- mice exhibit severe defects in skeletal muscle and die at birth, yet little is know about either the underlying mechanisms or the role of Ski in adult muscle regeneration. In these studies, I used Ski knockout mice and C2C12 myoblast cultures to address these issues, respectively. Detailed analysis of Ski-/- embryos revealed dramatically reduced hypaxial muscles but less affected epaxial muscles. The reduced number of myogenic regulatory factor positive cells in Ski-/- mice suggested an insufficient myogenic cell pool to support muscle formation. However, both the dermomyotomal hypaxial progenitors and myotomal epaxial progenitors formed and committed to myogenic fate appropriately. The hypaxial muscle defect in Ski-/- mice was not caused by abnormal proliferation, terminal differentiation or apoptosis of the myogenic cells either, but due to impaired migration of embryonic hypaxial progenitors. Surprisingly, the normal distribution of fetal/postnatal myogenic progenitors in Ski-/- mice suggested different effects of Ski on the behaviors of embryonic and fetal/postnatal myogenic progenitors. In addition, although not affecting the terminal differentiation of embryonic myogenic cells, Ski was necessary for that of adult satellite-cell derived C2C12 myoblasts as evidenced by impaired myotube formation and reduced induction of genes essential for myogenic differentiation in the absence of Ski. This function was mainly mediated by Ski's ability to form a complex with Six1 and Eya3 and activate Myog transcription through a MEF3 site. It is important in the future to further study mechanisms underlying the contrasting effects of Ski on embryonic, fetal and adult muscle development, to investi (open full item for complete abstract)

Committee: David Samols PhD (Committee Chair); Ed Stavnezer PhD (Advisor); Clemencia Colmenares PhD (Committee Member); Nikki Harter PhD (Committee Member); Lynn Landmesser PhD (Committee Member) Subjects: Biomedical Research