发育中的耳囊中SOX9和Wnt的拮抗活性确保SOX10对内淋巴发育的控制

文献信息

中文摘要

背景： 内耳的正常发育，包括内淋巴囊祖细胞的指定和分化，对听力和平衡至关重要。在导致躯干发育异常和耳聋的SOX9Y440X/+突变小鼠模型中，妊娠中期内淋巴系统发育受损与SOX10下调相关。其潜在的分子原因和意义尚不清楚。方法：在这里，我们在Sox9Y440X/+小鼠中发现，Sox10表达在明显分化之前，在E10.5耳囊的背内侧区域（通常发育为内淋巴管和囊）下调。E10.5耳囊的单细胞转录组分析显示Wnt通路基因表达增加，这与Sox10表达的区域特异性降低相关。通过在早期耳囊和更发育的内耳中表达稳定β-连环蛋白强制升高Wnt信号，抑制了Sox10表达。Wnt在源自人类多能干细胞的耳囊样类器官中对SOX10表达产生抑制作用。体外反式激活实验揭示了SOX9和Wnt信号对由保守增强子介导的Sox10反式激活的拮抗作用，这些增强子具有相邻/重叠的SOX9和TCF/LEF结合（Wnt效应子）基序。结果：我们提出一种保守的SOX9-Wnt拮抗作用，通过保守增强子调节SOX10以调控内淋巴细胞命运。结论：SOX9Y440X/+突变通过显性负效应和单倍剂量不足效应破坏这一调控回路，最终导致耳囊中祖细胞建立受损，而这些祖细胞对于听力和平衡的内淋巴系统发育至关重要。

英文摘要

Proper development of the inner ear, including specification and differentiation of progenitors for the endolymphatic sac, is crucial for hearing and balance. In a mouse model of the SOX9Y440X/+ mutation that causes campomelic dysplasia and deafness, impaired development of the endolymphatic system at mid-gestation was associated with SOX10 downregulation. The underlying molecular causes and significance are unclear. Here, we found in Sox9Y440X/+ mice, Sox10 expression was downregulated, prior to overt differentiation, in the dorsomedial aspect of the E10.5 otic vesicle that normally becomes the endolymphatic duct and sac. Single-cell transcriptomic profiling of E10.5 otic vesicles showed increased expression of Wnt pathway genes that was associated with the domain-specific decrease in Sox10 expression. Forced elevation of Wnt signaling by expression of stabilized β-catenin in the early otocyst and more developed inner ears, suppressed Sox10 expression. Wnt exerted an inhibitory effect on SOX10 expression in otocyst-like organoids derived from human pluripotent stem cells. In vitro transactivation assays reveal antagonistic action of SOX9 and Wnt signaling on Sox10 transactivation mediated by conserved enhancers with neighboring/overlapping SOX9- and TCF/LEF-binding (Wnt effectors) motifs. We propose a conserved SOX9-Wnt antagonism acting via conserved enhancers, regulates SOX10 to modulate endolymphatic cell fate. The SOX9Y440X/+ mutation disrupts this regulatory circuit through both dominant-negative and haploinsufficient effects culminating in impaired establishment of progenitors in the otocyst that are essential for the development of the endolymphatic system for hearing and balance.