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Calcium sources used by post‐natal human myoblasts during initial differentiation
Author(s) -
Arnaudeau Serge,
Holzer Nicolas,
König Stéphane,
Bader Charles R.,
Bernheim Laurent
Publication year - 2006
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.20679
Subject(s) - cytoplasm , calcium , microbiology and biotechnology , receptor , myocyte , cellular differentiation , biology , immunostaining , chemistry , biochemistry , immunology , gene , immunohistochemistry , organic chemistry
Increases in cytoplasmic Ca 2+ are crucial for inducing the initial steps of myoblast differentiation that ultimately lead to fusion; yet the mechanisms that produce this elevated Ca 2+ have not been fully resolved. For example, it is still unclear whether the increase comes exclusively from membrane Ca 2+ influx or also from Ca 2+ release from internal stores. To address this, we investigated early differentiation of myoblast clones each derived from single post‐natal human satellite cells. Initial differentiation was assayed by immunostaining myonuclei for the transcription factor MEF2. When Ca 2+ influx was eliminated by using low external Ca 2+ media, we found that approximately half the clones could still differentiate. Of the clones that required influx of external Ca 2+ , most clones used T‐type Ca 2+ channels, but others used store‐operated channels as influx‐generating mechanisms. On the other hand, clones that differentiated in low external Ca 2+ relied on Ca 2+ release from internal stores through IP 3 receptors. Interestingly, by following clones over time, we observed that some switched their preferred Ca 2+ source: clones that initially used calcium release from internal stores to differentiate later required Ca 2+ influx and inversely. In conclusion, we show that human myoblasts can use three alternative mechanisms to increase cytoplasmic Ca 2+ at the onset of the differentiation process: influx through T‐types Ca 2+ channels, influx through store operated channels and release from internal stores through IP 3 receptors. In addition, we suggest that, probably because Ca 2+ elevation is essential during initial differentiation, myoblasts may be able to select between these alternate Ca 2+ pathways. J. Cell. Physiol. 208: 435–445, 2006. © 2006 Wiley‐Liss, Inc.