Transcriptome analysis of regeneration during Xenopus laevis experimental twinning

Abstract

Animal embryos have the remarkable property of self-organization. Over 125 years ago, Hans Driesch separated the two blastomeres of sea urchin embryos and obtained twins, in what was the foundation of experimental embryology. Since then, embryonic twinning has been obtained experimentally in many animals. In a recent study, we developed bisection methods that generate identical twins reliably from Xenopus blastula embryos. In the present study, we have investigated the transcriptome of regenerating half-embryos after sagittal and dorsal-ventral (D-V) bisections. Individual embryos were operated at midblastula (stage 8) with an eyelash hair and cultured until early gastrula (stage 10.5) or late gastrula (stage 12) and the transcriptome of both halves were analyzed by RNA-seq. Since many genes are activated by wound healing in Xenopus embryos, we resorted to stringent sequence analyses and identified genes up-regulated in identical twins but not in either dorsal or ventral fragments. At early gastrula, cell division-related transcripts such as histones were elevated, whereas at late gastrula, pluripotency genes (such as sox2) and germ layer determination genes (such as eomesodermin, ripply2 and activin receptor ACVRI) were identified. Among the down-regulated transcripts, sizzled, a regulator of Chordin stability, was prominent. These findings are consistent with a model in which cell division is required to heal damage, while maintaining pluripotency to allow formation of the organizer with a displacement of 90 0 from its original site. The extensive transcriptomic data presented here provides a valuable resource for data mining of gene expression during early vertebrate development.

Neural induction drives body axis formation during embryogenesis, but a neural induction-like process drives tumorigenesis in postnatal animals

“…An ectopic organizer induces formation of a conjoined twin containing neural tissues in a gastrula embryo. Vice versa, various studies showed that an embryo in the absence of organizer activity forms a “belly piece” only that contains no neural and dorsal structures ( Spemann, 1938 ; Gerhart, 2001 ; De Robertis, 2009 ; Sosa et al, 2019 ).…”

Protocol for culturing and imaging of ectodermal cells from Xenopus

“…Xenopus laevis animal cap cells are located in the animal (pigmented) pole of the blastula or early gastrula stage embryo ( Ariizumi et al., 2009 ). By microinjecting the embryo during the early cleavage stages one can overexpress or deplete gene products with great ease, making these cells a favorite system for researchers ( Asashima et al., 2009 ; Blum et al., 2015 ; Moriyama and De Robertis, 2018 ; Sosa et al., 2019 ). Only a few Xenopus permanent cell lines exist ( Smith and Tata, 1991 ) and animal cap cells provide a system closer to the in vivo situation.…”

Neural Induction: the General Principle for Embryogenesis and Tumorigenesis

“…Sagittal bisection of a blastula embryo generates two nearly normal embryos because both sides of the bisected embryos contain a half of the dorsal lip. If an embryo is bisected through the equatorial plane, the resulting dorsal half embryo develops into also an almost normal embryo because it contains the dorsal lip, whereas the ventral half without the dorsal lip forms a belly piece (De Robertis, 2009;Sosa et al, 2019).…”