human muscle; myoblast differentiation; ionic channels; electrophysiology; myogenic transcription factors; calcium; SOCE; cameleon indicators
Uschakov Aaron, Grivel Jeremy, Cvetkovic-Lopes Vesna, Bayer Laurence, Bernheim Laurent, Jones Barbara E, Mühlethaler Michel, Serafin Mauro (2011), Sleep-deprivation regulates α-2 adrenergic responses of rat hypocretin/orexin neurons., in PloS one
, 6(2), 16672-16672.
Darbellay Basile, Arnaudeau Serge, Bader Charles R, Konig Stephane, Bernheim Laurent (2011), STIM1L is a new actin-binding splice variant involved in fast repetitive Ca2+ release., in The Journal of cell biology
, 194(2), 335-46.
Darbellay Basile, Arnaudeau Serge, Ceroni Dimitri, Bader Charles R, Konig Stephane, Bernheim Laurent (2010), Human muscle economy myoblast differentiation and excitation-contraction coupling use the same molecular partners, STIM1 and STIM2., in The Journal of biological chemistry
, 285(29), 22437-47.
Darbellay Basile, Arnaudeau Serge, König Stéphane, Jousset Hélène, Bader Charles, Demaurex Nicolas, Bernheim Laurent (2009), STIM1- and Orai1-dependent store-operated calcium entry regulates human myoblast differentiation., in The Journal of biological chemistry
, 284(8), 5370-80.
With the long-term goal of improving the survival of myoblasts injected for the treatment of muscle as well as non-muscle-related disorders, our group aims at unraveling the early steps of human myoblast differentiation that leads to myoblast fusion. Our previous work demonstrated that hyperpolarization of the membrane potential was one of the firsts events to occur. More recently, we discovered that a dephosphorylation at tyrosine 242 opens Kir2.1 inward rectifying K+ channels and thereby induces the hyperpolarization of myoblasts. The resulting increased driving force for Ca2+ caused by hyperpolarization promotes Ca2+ influx through Ca2+ channels. Another recent observation of our group is that several types of Ca2+ channels can provide the calcium signal required for differentiation, including store operated Ca2+ entry (SOCE) channels. Interestingly, we found that siRNAs-mediated silencing of the key players of SOCE channels reduced SOCE and impaired myoblast differentiation. On the contrary, overexpression of the key players of SOCE amplified SOCE and stimulated myoblast differentiation. Also, our electrophysiological and molecular biology data suggest that two Ca2+ signals are required to trigger human myoblast differentiation. These recent findings have lead us to review our working hypothesis for the early steps of myoblast differentiation and to propose the three following general objectives:1. Extend our understanding of the relationships between hyperpolarization, Ca2+ dependent pathways, and expression of MEF2 transcription factors. We plan to study the early steps of myoblast differentiation that control the expression of myogenin and MEF2 transcription factors and which are linked to ionic channel activity.2. Confirm that two Ca2+ signals are required to trigger human myoblast differentiation. We aim at identifying these two Ca2+ signals, and examine their correlation with CaMK and calcineurin activation. We shall follow cytoplasmic Ca2+ changes with various targeted dyes and examine whether these changes are primarily due to Ca2+ influxes through membrane channels or Ca2+ release from internal stores.3. Elucidate the pathways controlling the activation of K+ channels at the onset of myoblast differentiation. We intend to identify the kinases and phosphatases involved in the activation of Kir2.1 channels at the beginning of the differentiation process and evaluate their possible modulation by SOCE.These 3 projects should improve our understanding of human myoblasts differentiation. In addition, as all cells express and probably rely on ionic channels, our work on myoblasts might shed light on mechanisms involved in cellular differentiation in general.