Date of Completion

Spring 5-1-2017

Project Advisor(s)

David Goldhamer, Mary Bruno, Joseph Crivello

University Scholar Major

Molecular and Cell Biology


Developmental Biology | Genetics


MyoD and Myf5 are transcription factors that regulate myogenesis by promoting satellite cell transcription. The two genes are known to display functional redundancy. Both genes are considered myogenic determination genes and are expressed in satellite cells. The fate of myogenic precursors in the absence of both MyoD and Myf5 remains largely unknown. We aimed to begin attaining this knowledge as part of this project. We utilized a CreLoxP system to control the expression of MyoD in mice lacking Myf5. MyoD was knocked out at embryonic day (E) 11.5 during myogenesis. Limbs were collected from experimental mice following tamoxifen injection. Additionally, recombined MyoD-/-Myf5-/- myogenic progenitor cells were plated and grown individually in culture for 13 days. Immunofluorescence staining was performed on whole tissue samples and cell culture samples to analyze potential fate changes. No signal that may indicate a fate change was detected in the limbs of experimental mice collected 2 days following the excision of MyoD. Cell culture data demonstrated the presence of signal that may indicate a potential fate change. However, making concrete conclusions from this data proved difficult due to the lack of positive controls available. The second component of our project involved analyzing the function of MyoD in the regeneration of injured muscle. The CreLoxP system was utilized to excise MyoD from experimental mice containing a single allele of Myf5. Once again, MyoD was knocked out at E 11.5. Seven weeks following birth, mice limbs were injured and tissue samples were collected. Immunohistochemistry was utilized to analyze potential fate changes. Our data did not appear to demonstrate increase in signal that marks a fate switch, but is difficult to interpret with certainty without further studies.