The functional analysis of Type I postplasmic/PEM mRNAs in embryos of the ascidian Halocynthia roretzi
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Maternal factors, such as a muscle determinant macho-1 mRNA that is localized to the posterior-vegetal cortex (PVC) of fertilized ascidian eggs, are crucial for embryonic axis formation and cell fate specification. Maternal mRNAs that show an identical posterior localization pattern to that of macho-1 in eggs and embryos are called Type I postplasmic/PEM mRNAs. We investigated the functions of five of the nine Type I mRNAs so far known in Halocynthia roretzi: Hr-Wnt-5, Hr-GLUT, Hr-PEM3, Hr-PEN1, and Hr-PEN2. Suppression of their functions with specific antisense morpholino oligonucleotides (MOs) had effects on the formation of various tissues: Hr-Wnt-5 on notochord, muscle, and mesenchyme, although zygotic function of Hr-Wnt-5 is responsible for notochord formation; Hr-GLUT on notochord, mesenchyme, and endoderm; and Hr-PEN2 on muscle, mesenchyme, and endoderm. On the other hand, Hr-PEM3 and Hr-PEN1 MOs seemed to have no effect. We conclude that the functions of at least some localized maternal Type I postplasmic/PEM mRNAs are necessary for early embryonic patterning in ascidians.
KeywordsAscidian embryo Maternal RNA localization Type I postplasmic/PEM RNA Wnt Embryonic patterning
We thank the staff of the Asamushi Research Center for Marine Biology and the Otsuchi International Coastal Research Center for help in collecting live ascidian adults, and the staff of the Misaki Marine Biological Station and Seto Marine Biological Laboratory for help in maintaining them. We also thank Dr. Nori Satoh for providing HrBra cDNA, Dr. T. Nishikata for the Not-1, Mu-2, and Epi-2 monoclonal antibodies, Dr. Y. Sasakura for Hr-Wnt-5 cDNA, and Drs. T. Kawashima and Y. Kohara for MAGEST plasmids. This work was supported by Grants in Aid from MEXT (13044003) and JSPS (13480245 and 16107005) and by Toray Science and Technology Grant.
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