MARK2 and hydrops fetalis: Certainly previous work has demonstrated that PDGF-BB acts to promote survival of intestinal epithelial stem/progenitors by upregulating the serine/threonine kinase (AKT) activity.21 We failed to observe any apoptotic death within anagen HF mesenchyme (when DSCs are actively generating the CTS and contributing to the DP) in either Pdgfrα+/+ or Pdgfrα-deficient follicles.