Project description:Proper regulation of extravillous trophoblast (EVT) cell invasion is critical for normal placental development and function. Growth differentiation factor 11 (GDF-11), a member of the transforming growth factor-β (TGF-β) superfamily, has been shown to promote EVT cell invasion, yet the underlying molecular mechanisms remain largely unclear. In this study, RNA sequencing identified angiopoietin-like 4 (ANGPTL4), a multifunctional secreted protein, as a novel downstream target of GDF-11. In vitro experiments demonstrated that GDF-11 significantly upregulated ANGPTL4 expression in both HTR-8/SVneo cells and primary human EVT cells. Mechanistically, we found that the type I TGF-β receptors ALK4 and ALK5 were essential for mediating the stimulatory effect of GDF-11 on ANGPTL4 expression. Further analysis revealed that SMAD3, but not SMAD2, was the key transcription factor involved in this process. Using both loss- and gain-of-function approaches, we demonstrated that ANGPTL4 was required for GDF-11-induced EVT cell invasion. Importantly, serum levels of GDF-11 were markedly reduced in patients with preeclampsia (PE), a pregnancy disorder associated with shallow trophoblast invasion and poor placentation. Together, our findings uncover a previously unrecognized GDF-11-ANGPTL4 signaling axis that regulates EVT cell invasion and provide new insight into the pathophysiology of PE.
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes