FBXL12-Mediated Degradation of ALDH3 is Essential for Trophoblast Differentiation During Placental Development

Abstract

How stem cells maintain their stemness or initiate exit from the stem cell state for differentiation remains largely unknown. Aldehyde dehydrogenase (ALDH) activity is a hallmark of stem cells-including embryonic, adult tissue, and cancer stem cells-and is essential for their maintenance. The mechanisms by which ALDH activity is regulated in stem cells have remained poorly understood, however. We now show that the ubiquitin-dependent degradation of ALDH3 mediated by FBXL12 (F box and leucine-rich repeat protein 12) is essential for execution of the differentiation program of trophoblast stem cells (TSCs). FBXL12 is present only in eutherian mammals, and its expression is largely restricted to the placenta during mouse embryogenesis. FBXL12 was found to interact specifically with members of the ALDH3 family and to mediate their polyubiquitylation. Most mice deficient in FBXL12 died during the embryonic or perinatal period probably as a result of abnormal development of the placenta, characterized by impaired formation of the junctional zone. ALDH3 accumulated in the FBXL12-deficient placenta, and forced expression of ALDH3 in wild-type TSCs phenocopied the differentiation defect of FBXL12-deficient TSCs. Conversely, inhibition of ALDH3 activity by gossypol rescued the phenotype of FBXL12 deficiency. Our results suggest that FBXL12 plays a key role in the downregulation of ALDH3 activity in TSCs and thereby initiates trophoblast differentiation during placental development. STEM CELLS 2015;33:3327-3340 SIGNIFICANCE STATEMENTAlthough aldehyde dehydrogenase (ALDH) activity has been known as a hallmark of stem cells, the mechanisms by which ALDH activity is regulated in stem cells have remained unclear. We show that the ubiquitin-dependent degradation of ALDH3 mediated by FBXL12 (F box and leucine-rich repeat protein 12) is essential for the differentiation of trophoblast stem cells (TSCs). FBXL12 interacts specifically with ALDH3 and to mediate its polyubiquitylation. Loss of FBXL12 results in unrestrained ALDH3 activity, resulting in a differentiation defect in TSCs and intrauterine growth retardation of mouse embryos. Our results thus indicate that FBXL12-mediated degradation of ALDH3 is essential for the differentiation from TSCs.

Blastocyst transfer in mice alters the placental transcriptome and growth

“…Alternatively, reduced differentiation of progenitor cells within the ectoplacental cone of transferred conceptuses might lead to fewer parietal-TGCs (Prl3d1 + cells) and/or spongtiotrophoblast cells (Prl2c2 + , Prl7a1 + , or Prl8a1 + cells) at E10.5 and thus reduced expression of these genes would result. In support of this hypothesis, Aldh3a1 and Il33, genes that regulate the differentiation and function of the progenitor cells within the ectoplacental cone (Nishiyama et al 2015, Wang et al 2017, were also downregulated in transferred placentas. To better understand the effects of blastocyst transfer on trophoblast differentiation, a histological examination and systematic assessment of trophoblast marker gene expression is required.…”

SCFFbxw7 ubiquitylates KLF7 for degradation in a manner dependent on GSK‐3‐mediated phosphorylation

“…F‐box proteins constitute a large family of >70 eukaryotic proteins (Jin et al, ), but the substrates of each F‐box protein have remained largely unknown. To identify substrates for a given F‐box protein, we previously developed a method termed differential proteomics‐based identification of ubiquitylation substrates (DiPIUS; Yumimoto, Matsumoto, Oyamada, Moroishi, & Nakayama, ), and we have applied this method to several systems (Nakajima et al, ; Nakayama, Yumimoto, Kawamura, & Nakayama, ; Nishiyama, Nita, Yumimoto, & Nakayama, ; Watanabe, Yumimoto, & Nakayama, ; Yamauchi, Nishiyama, Moroishi, Kawamura, & Nakayama, ; Yumimoto, Matsumoto, Onoyama, Imaizumi, & Nakayama, ).…”

“…Genes to Cells SUGIYAMA et Al. (Nakajima et al, 2015;Nakayama, Yumimoto, Kawamura, & Nakayama, 2018;Nishiyama, Nita, Yumimoto, & Nakayama, 2015;Watanabe, Yumimoto, & Nakayama, 2015;Yamauchi, Nishiyama, Moroishi, Kawamura, & Nakayama, 2017;Yumimoto, Matsumoto, Onoyama, Imaizumi, & Nakayama, 2013).…”

FBXL12 regulates T‐cell differentiation in a cell‐autonomous manner

“…Given that Fbxl12 À/À mice are smaller than littermate controls as a result of their intrauterine growth retardation (Nishiyama et al 2015), the differentiation block of T cells might have been expected to be a secondary effect of altered systemic conditions. We examined this possibility with two different experi- Figure 2 Ablation of FBXL12 impairs T-cell differentiation into CD4 and CD8 SP cells.…”