Patterning of brain precursors in ascidian embryos

• Published in: Development (Cambridge) Vol. 144; no. 2; pp. 258 - 264
• Main Authors: Esposito, Rosaria, Yasuo, Hitoyoshi, Sirour, Cathy, Palladino, Antonio, Spagnuolo, Antonietta, Hudson, Clare
• Format: Journal Article
• Language: English
• Published: England The Company of Biologists Ltd 15.01.2017; Company of Biologists
• Subjects: Animals; Animals, Genetically Modified; Body Patterning - physiology; Brain - embryology; Central nervous system; Ciona intestinalis - embryology; Development Biology; Ectoderm; Embryo, Nonmammalian; Embryonic Induction - physiology; Embryos; Gene expression; Life Sciences; Nervous system; Neural plate; Neural Plate - embryology; Neural stem cells; Neural Stem Cells - physiology; Notch protein; Pattern formation; Urochordata - embryology; Brain; Ascidian; Ciona; Neural patterning; Sensory vesicle
• ISSN: 0950-1991; 1477-9129
• DOI: 10.1242/dev.142307

In terms of their embryonic origins, the anterior and posterior parts of the ascidian central nervous system (CNS) are associated with distinct germ layers. The anterior part of the sensory vesicle, or brain, originates from ectoderm lineages following a neuro-epidermal binary fate decision. In contrast, a large part of the remaining posterior CNS is generated following neuro-mesodermal binary fate decisions. Here, we address the mechanisms that pattern the anterior brain precursors along the medial-lateral axis (future ventral-dorsal) at neural plate stages. Our functional studies show that Nodal signals are required for induction of lateral genes, including Delta-like, Snail, Msxb and Trp Delta-like/Notch signalling induces intermediate (Gsx) over medial (Meis) gene expression in intermediate cells, whereas the combinatorial action of Snail and Msxb prevents the expression of Gsx in lateral cells. We conclude that despite the distinct embryonic lineage origins within the larval CNS, the mechanisms that pattern neural precursors are remarkably similar.