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 Ca waves in the developing intestinal mesenchyme using GCamp6f expressing mouse embryos and investigate their relationship with smooth muscle differentiation. We find that Ca waves are absent in the pre-differentiation mesenchyme and start propagating immediately following α-SMA expression. Ca waves are abrogated by Ca1.2 and gap-junction blockers, but are independent of the Rho pathway. The myosine light-chain kinase inhibitor ML-7 strongly disorganized or abolished Ca waves, showing that perturbation of the contractile machinery at the myosine level also affected the upstream Ca handling chain. Inhibiting Ca waves and contractility with Ca1.2 blockers did not perturb circular smooth muscle differentiation at early stages. At later stages, Ca1.2 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. Ca1.2 blockers also drove apoptosis of already differentiated, Ca1.2-expressing smooth muscle and enteric neural cells. We provide fundamental new data on Ca waves in the developing murine gut and their relation to myogenesis in this organ.