The Ascidian as a Model Organism in Developmental and Evolutionary Biology

Abstract

What Is an Ascidian?Ascidians, or sea squirts, are invertebrate chordates that belong to the earliest branch in the chordate phylum, the subphylum Urochordata or Tunicata (Figure 1A). Ascidian larvae possess a prototypical chordate body plan

A zinc finger transcription factor, ZicL, is a direct activator ofBrachyuryin the notochord specification ofCiona intestinalis

“…The formation of the ascidian notochord is an embryological process in which the molecular mechanisms operate from the beginning of fertilization until the terminal differentiation of specific structural gene function (for reviews, see Satoh, 2001;Satoh, 2003;Corbo et al, 2001). In ascidians, including Ciona intestinalis, C. savignyi and Halocynthia roretzi, the notochord comprises exactly 40 cells, and their lineage has been completely described (Conklin, 1905;Nishida, 1987).…”

Identification of candidate genes encoding the core components of the cell death machinery in the Ciona intestinalis genome

“…3 Larva of ascidians possesses the basic developmental and morphological features of vertebrates including a prominent notochord and a dorsal central nervous system. 4 Programmed cell death apparently takes place in these ascidians. 5,6 For example, the epidermal cells in the tail of ascidian tadpole larva rapidly undergo apoptosis during metamorphosis ( Figure 1).…”

Urochordates and the origin of natural killer cells: Identification of a CD94/NKR-P1-related receptor in blood cells ofBotryllus

“…In vertebrates, C-type lectin NK receptors are encoded by a number of related genes that all reside in one genomic region, the NK complex (23). Because the urochordate genome predates the expansion in gene number that occurred in vertebrates (24), it was of interest to determine whether BsCD94-1 was a single gene or member of a gene family. For that purpose we performed Southern blot analysis.…”