Sonic Hedgehog (Shh) signaling plays key regulatory roles in embryonic development and postnatal homeostasis and repair. Modulation of the Shh pathway is known to cause malformations and malignancies associated with dysregulated tissue growth. However, our understanding of the molecular mechanisms by which Shh regulates cellular proliferation is incomplete. Here, using mouse embryonic fibroblasts, we demonstrate that the Forkhead box gene Foxd1 is transcriptionally regulated by canonical Shh signaling and required for downstream proliferative activity. We show that Foxd1 deletion abrogates the proliferative response to SHH ligand while FOXD1 overexpression alone is sufficient to induce cellular proliferation. The proliferative response to both SHH ligand and FOXD1 overexpression was blocked by pharmacologic inhibition of cyclin-dependent kinase signaling. Time-course experiments revealed that Shh pathway activation of Foxd1 is followed by downregulation of Cdkn1c, which encodes a cyclin-dependent kinase inhibitor. Consistent with a direct transcriptional regulation mechanism, we found that FOXD1 reduces reporter activity of a Fox enhancer sequence in the second intron of Cdkn1c. Supporting the applicability of these findings to specific biological contexts, we show that Shh regulation of Foxd1 and Cdkn1c is recapitulated in cranial neural crest cells and provide evidence that this mechanism is operational during upper lip morphogenesis. These results reveal a novel Shh-Foxd1-Cdkn1c regulatory circuit that drives the mitogenic action of Shh signaling and may have broad implications in development and disease.

Sonic Hedgehog（Shh）信号传导在胚胎发育以及产后体内稳态和修复中起着重要的调节作用。已知Shh途径的调节会引起与组织生长失调有关的畸形和恶性肿瘤。但是，我们对Shh调节细胞增殖的分子机制的理解还不完全。在这里，使用小鼠胚胎成纤维细胞，我们证明了叉头盒基因Foxd1受规范的Shh信号转录调控，并为下游的增殖活性所必需。我们显示Foxd1删除废除对SHH配体的增殖反应，而单独的FOXD1过表达足以诱导细胞增殖。对SHH配体和HSH的增殖反应。FOXD1过表达被细胞周期蛋白依赖性激酶信号传导的药理抑制所阻止。时程实验表明，Foxd1的Shh途径活化后，Cdkn1c的表达下调，而Cdkn1c编码细胞周期蛋白依赖性激酶抑制剂。与直接转录调控机制一致，我们发现FOXD1降低了Cdkn1c第二个内含子中Fox增强子序列的报道分子活性。支持这些发现对特定生物学背景的适用性，我们表明Fshd1和Cdkn1c的嘘调控在颅神经c细胞中被概括，并提供了该机制在上唇形态发生过程中起作用的证据。这些结果揭示了一种新型的Shh-Foxd1-Cdkn1c调节电路，该电路可驱动Shh信号的促有丝分裂作用，并可能对发育和疾病产生广泛的影响。