title: Revised lineage of larval photoreceptor cells in Ciona reveals archetypal collaboration between neural tube and neural crest in sensory organ formation.
abstract: The Ciona intestinalis larva has two distinct photoreceptor organs, a conventional pigmented ocellus and a nonpigmented ocellus, that are asymmetrically situated in the brain. The ciliary photoreceptor cells of these ocelli resemble visual cells of the vertebrate retina. Precise elucidation of the lineage of the photoreceptor cells will be key to understanding the developmental mechanisms of these cells as well as the evolutionary relationships between the photoreceptor organs of ascidians and vertebrates. Photoreceptor cells of the pigmented ocellus have been thought to develop from anterior animal (a-lineage) blastomeres, whereas the developmental origin of the nonpigmented ocellus has not been determined. Here, we show that the photoreceptor cells of both ocelli develop from the right anterior vegetal hemisphere: those of the pigmented ocellus from the right A9.14 cell and those of the nonpigmented ocellus from the right A9.16 cell. The pigmented ocellus is formed by a combination of two lineages of cells with distinct embryonic origins: the photoreceptor cells originate from a medial portion of the A-lineage neural plate, while the pigment cell originates from the lateral edge of the a-lineage neural plate. In light of the recently proposed close evolutionary relationship between the ocellus pigment cell of ascidians and the cephalic neural crest of vertebrates, the ascidian ocellus may represent a prototypic contribution of the neural crest to a cranial sensory organ.
authors: Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan.
authors: Kouhei
authors: K
authors: Oonuma
authors: Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan.
authors: Moeko
authors: M
authors: Tanaka
authors: Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan; Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo, Japan.
authors: Koki
authors: K
authors: Nishitsuji
authors: Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo, Japan.
authors: Yumiko
authors: Y
authors: Kato
authors: Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan; Institute for Integrative Neurobiology, Graduate School of Natural Science, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan.
authors: Kotaro
authors: K
authors: Shimai
authors: Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan; Institute for Integrative Neurobiology, Graduate School of Natural Science, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan. Electronic address: tgk@center.konan-u.ac.jp.
authors: Takehiro G
authors: TG
authors: Kusakabe
mesh_terms: D000818:Animals; D002452:Cell Count; D019070:Cell Lineage; D002938:Ciona intestinalis / Q000166:cytology* / Q000378:metabolism; D007814:Larva / Q000166:cytology; D009432:Neural Crest / Q000166:cytology*; D054259:Neural Tube / Q000166:cytology*; D061848:Optical Imaging; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology* / Q000378:metabolism; D010858:Pigmentation; D055213:Retinal Pigment Epithelium / Q000166:cytology; D012679:Sense Organs / Q000166:cytology*
keywords: Ascidian; Cell lineage; Kaede; Ocellus; Photoreceptor cells