Calcium wave dynamics in the embryonic mouse gut mesenchyme: impact on smooth muscle differentiation

Intestinal smooth muscle differentiation is a complex physico-biological process involving several different pathways. Here, we investigate the properties of Ca²⁺ waves in the developing intestinal mesenchyme using GCamp6f expressing mouse embryos and investigate their relationship with smooth muscle differentiation. We find that Ca²⁺ waves are absent in the pre-differentiation mesenchyme and start propagating immediately following α-SMA expression. Ca²⁺ waves are abrogated by Ca_V1.2 and gap-junction blockers, but are independent of the Rho pathway. The myosine light-chain kinase inhibitor ML-7 strongly disorganized or abolished Ca²⁺ waves, showing that perturbation of the contractile machinery at the myosine level also affected the upstream Ca²⁺ handling chain. Inhibiting Ca²⁺ waves and contractility with Ca_V1.2 blockers did not perturb circular smooth muscle differentiation at early stages. At later stages, Ca_V1.2 blockers abolished intestinal elongation and differentiation of the longitudinal smooth muscle, leading instead to the emergence of KIT-expressing interstitial cells of Cajal at the gut periphery. Ca_V1.2 blockers also drove apoptosis of already differentiated, Ca_V1.2-expressing smooth muscle and enteric neural cells. We provide fundamental new data on Ca²⁺ waves in the developing murine gut and their relation to myogenesis in this organ.