L-type voltage-gated Ca2+ channel CaV1.2 regulates chondrogenesis during limb development

All cells, including nonexcitable cells, maintain a discrete transmembrane potential (V-mem), and have the capacity to modulate V-mem and respond to their own and neighbors' changes in V-mem. Spatiotemporal variations have been described in developing embryonic tissues and in some cases have been implicated in influencing developmental processes. Yet, how such changes in V-mem are converted into intracellular inputs that in turn regulate developmental gene expression and coordinate patterned tissue formation, has remained elusive. Here we document that the V-mem of limb mesenchyme switches from a hyperpolarized to depolarized state during early chondrocyte differentiation. This change in V-mem increases intracellular Ca2+ signaling through Ca2+ influx, via Ca(V)1.2, 1 of L-type voltage-gated Ca2+ channels (VGCCs). We find that Ca(V)1.2 activity is essential for chondrogenesis in the developing limbs. Pharmacological inhibition by an L-type VGCC specific blocker, or limb-specific deletion of Ca(V)1.2, down-regulates expression of genes essential for chondrocyte differentiation, including Sox9, Col2a1, and Agc1, and thus disturbs proper cartilage formation. The Ca2+-dependent transcription factor NFATc1, which is a known major transducer of intracellular Ca2+ signaling, partly rescues Sox9 expression. These data reveal instructive roles of Ca(V)1.2 in limb development, and more generally expand our understanding of how modulation of membrane potential is used as a mechanism of developmental regulation.