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Notch and Wnt signaling interplay on regulation of early embryo development

Publication . Batista, Mariana Raposo; Silva, Maria Elisabete Tomé Sousa; Costa, Luís Filipe Lopes da

Mammalian early embryo development requires action of a complex network of cell signaling pathways that coordinates cellular proliferation and differentiation events. Notch is a major regulator in embryonic and adult scenarios, also interplaying with other signaling pathways, such as Wnt. The objective of this work was to determine Notch signaling status in early embryo development and its influence on cellular differentiation and pluripotency maintenance, and on embryo competence to implant and develop to term. Additionally, the Notch/Wnt interplay was investigated in this scenario. Firstly, we analyzed individual embryo transcription of Notch components and their relation with transcription of pluripotency and differentiation gene markers (Sox2, Oct4, Klf4, Cdx2). Secondly, a pharmacological approach was used to induce Notch signaling (recombinant JAGGED1 and 2) and to inhibit Notch and/or Wnt signaling (DAPT and/or DKK1, respectively). Finally, embryos treated with DAPT and/or DKK1 were transferred to recipient females and implantation competency (at Day5 of gestation) and development to term (Day18) were evaluated. Results showed that transcription of Notch1-2, Jagged1-2 and Hes1 was highly prevalent and dynamic along stages of development. Transcription of Notch1, Notch2, Jagged2 and Hes1 correlated with each other and with that of Sox2, Oct4, Klf4 and Cdx2. In vitro embryo culture supplementation with JAGGED1 had no effect on embryo developmental kinetics, whereas supplementation with JAGGED2 abolished Jagged1 transcription, downregulated Cdx2 transcription and inhibited blastocyst hatching. Notch and Wnt had opposing effects on developmental kinetics, as Notch blockade retarded development and hatching, while Wnt blockade fastened it. We found evidences of Notch and Wnt interplay in early embryos as double blockade produced more severe phenotypes than expected by cumulative effects of single blockades. Notch and double blockade altered trophectoderm cell numbers and inner cell mass to trophectoderm ratio and all blockades altered transcription of Sox2, Oct4, Klf4 and Cdx2 throughout development. Implantation was unaffected by treatment, but Notch and double blockades affected the rate of Day18 developed fetuses. Notch blockade produced lighter and Wnt blockade heavier fetuses. Overall, results indicate that Notch is active in early embryo development where, together with Wnt, plays a significant role in controlling the pace of differentiation and proliferation of the blastocyst, ultimately affecting development to term.

2020-10-30Doctoral thesis

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