During digit development, the correct balance of chondrogenic signals ensures the recruitment of undifferentiated cells into the cartilage lineage or the maintenance of cells at the undifferentiated stage. WNT/β catenin maintains the pool of progenitor cells, whereas TGFβ signalling promotes cartilage differentiation by inducing Sox9 expression. Moreover, WNT5A promotes the degradation of β catenin during mouse limb development. Although these mechanisms are well established, it is still unknown whether the signalling pathway downstream WNT5A is also involved in early chondrogenesis during digit formation. Thus, the aim of this study was to determine the role of WNT5A during the recruitment of progenitor cells during digit development. Our results showed that WNT5A activated calcium (Ca²⁺) release in the undifferentiated region during digit development. Further, the blockade of Ca²⁺ release or calcineurin (CaN) or nuclear factor of activated T-cells (NFAT) functions resulted in an inhibition of cartilage differentiation. Together, our results demonstrate that non canonical WNT5A-Ca²⁺-CaN-NFAT signalling plays a key role during embryonic digit development in vivo promoting the competence for chondrogenic signals and also acts as a permissive factor for chondrogenesis independently of cell death mechanisms.

在手指发育过程中，软骨形成信号的正确平衡可确保将未分化的细胞募集到软骨谱系中或将细胞维持在未分化的阶段。WNT /β连环蛋白可维持祖细胞库，而TGFβ信号传导则通过诱导Sox9表达来促进软骨分化。此外，WNT5A在小鼠肢体发育过程中促进β-连环蛋白的降解。尽管这些机制已经很好地建立，但是仍然未知WNT5A下游的信号通路是否也参与手指形成过程中的早期软骨形成。因此，本研究的目的是确定WNT5A在手指发育过程中募集祖细胞期间的作用。我们的结果表明，WNT5A活化钙（Ca ²⁺）在数字发育过程中在未分化的区域释放。此外，Ca ²⁺释放或钙调神经磷酸酶（CaN）或活化T细胞核因子（NFAT）功能的阻断导致软骨分化受到抑制。在一起，我们的结果表明，非典型的WNT5A-Ca ²⁺ -CaN-NFAT信号传导在体内胚胎数字发育过程中起着关键作用，从而促进了软骨形成信号的能力，并且还成为独立于细胞死亡机制的软骨形成的许可因子。