Holzner Markus, Sonicki Tea, Hunn Hugo, Uliana Federico, Jiang Weijun, Gade Vamshidhar R, Weis Karsten, Wutz Anton, Di Minin Giulio
Institute of Molecular Health Sciences, Department of Biology, ETH Zurich, Zurich, Switzerland.
Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland.
Cell Death Differ. 2024 Dec 18. doi: 10.1038/s41418-024-01435-x.
The ER-resident proteins VMP1 and TMEM41B share a conserved DedA domain, which confers lipid scramblase activity. Loss of either gene results in embryonic lethality in mice and defects in autophagy and lipid droplet metabolism. To investigate their role in pluripotency and lineage specification, we generated Vmp1 and Tmem41b mutations in mouse embryonic stem cells (ESCs). We observed that ESCs carrying mutations in Vmp1 and Tmem41b show robust self-renewal and an unperturbed pluripotent expression profile but accumulate LC3-positive autophagosomes and lipid droplets consistent with defects in autophagy and lipid metabolism. ESCs carrying combined mutations in Vmp1 and Tmem41b can differentiate into a wide range of embryonic cell types. However, differentiation into primitive endoderm-like cells in culture is impaired, and the establishment of extra-embryonic endoderm stem (XEN) cells is delayed. Mechanistically, we show the deregulation of genes that are associated with WNT signaling. This is further confirmed by cell surface proteome profiling, which identified a significant reduction of the WNT-receptor FZD2 at the plasma membrane in Vmp1 and Tmem41b double mutant ESCs. Importantly, we show that transgenic expression of Fzd2 rescues XEN differentiation. Our findings identify the role of the lipid scramblases VMP1 and TMEM41B in WNT signaling during extra-embryonic endoderm development and characterize their distinct and overlapping functions.
内质网驻留蛋白VMP1和TMEM41B共享一个保守的DedA结构域，该结构域赋予脂质翻转酶活性。任一基因的缺失都会导致小鼠胚胎致死以及自噬和脂滴代谢缺陷。为了研究它们在多能性和谱系特化中的作用，我们在小鼠胚胎干细胞（ESC）中产生了Vmp1和Tmem41b突变。我们观察到，携带Vmp1和Tmem41b突变的ESC表现出强大的自我更新能力和不受干扰的多能性表达谱，但积累了LC3阳性自噬体和脂滴，这与自噬和脂质代谢缺陷一致。携带Vmp1和Tmem41b联合突变的ESC可以分化为多种胚胎细胞类型。然而，在培养中向原始内胚层样细胞的分化受损，并且胚外内胚层干细胞（XEN）的建立延迟。从机制上讲，我们展示了与WNT信号相关基因的失调。细胞表面蛋白质组分析进一步证实了这一点，该分析确定在Vmp1和Tmem41b双突变ESC的质膜上WNT受体FZD2显著减少。重要的是，我们表明Fzd2的转基因表达挽救了XEN分化。我们的研究结果确定了脂质翻转酶VMP1和TMEM41B在胚外内胚层发育过程中WNT信号传导中的作用，并表征了它们独特和重叠的功能。
