Genetic Markers of Satellite Cells
Satellite cells express a number of distinctive genetic markers. Current thinking is that all satellite cells express PAX7 and PAX3 Moreover, both quiescent and activated human satellite cells can be identified by the membrane-bound neural cell adhesion molecule (N-CAM/CD56/Leu-19), a cell-surface glycoprotein. Myocyte nuclear factor (MNF), and c-met proto-oncogene (receptor for hepatocyte growth factor (HGF)) are less commonly used markers.
CD34 and Myf5 markers specifically define the majority of quiescent satellite cells. Activated satellite cells prove problematic to identify, especially as their markers change with the degree of activation; for example, greater activation results in the progressive loss of Pax7 expression as the they enter the proliferative stage. However, Pax7 is expressed prominently after satellite cell differentiation. Greater activation also results in increased expression of myogenic basic helix-loop-helix transcription factors MyoD, myogenin, and MRF4 - all responsible for the induction of myocyte-specific genes. HGF testing is also used to identify active satellite cells. Activated satellite cells also begin expressing muscle-specific filament proteins such as desmin as they differentiate.
The field of satellite cell biology suffers from the same technical difficulties as other stem cell fields. Studies rely almost exclusively on Flow cytometry and Fluorescence Activated Cell Sorting (FACS) analysis, which gives no information about cell lineage or behaviour. As such, the satellite cell niche is relatively ill-defined and it is likely that it consists of multiple sub-populations.
Read more about this topic: Myosatellite Cell
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