Research Projects
Because of vertebrate and invertebrate attributes (discussed here), Ciona is well suited for developmental studies. We are particularly interested in the notochord, which is the defining tissue of the Chordate phylum.
The notochord consists of a stiff rod of cells running the length of the embryo, and functions as a “scaffold” in the early embryo. The precise mechanisms that regulate and drive how these cells come together, a process known as convergence and extension, are under investigation. We have isolated a number of mutants that disrupt notochord development. One mutation,
aimless (aim), creates a apparent null in the essential PCP pathway gene prickle. The mutant
chongmague (chm) shows a more severe phenotype than aim, particularly in the notochord. As with aim/aim, notochord cells in chm/chm embryos undergo a degree of convergence to make a recognizable rod-structure in the tailbud embryo, although as development proceeds, the notochord cells become progressively dispersed through the tail and trunk. Most recently we have found that embryos that are homozygous for both the chm and aim mutations (chm/chm::aim/aim) differed greatly from that of either homozygous aim and chm embryos. These larvae had a complete failure of tail elongation, unlike the “short tailed” mutants chm and
aim, which still have a recognizable tail. Our immediate goal is to determine whether chm and aim are disrupting different aspects of a common mechanism of CE, or whether two independent mechanisms are at work. (This work was performed by M. Veeman, Nakatani, Y., Hendrickson, C., Ericson, V., Lin, C. Some of the work is published here
Development. 2008 Jan;135(1):33-41)
We have also isolated a number of mutants that disrupt the development and functioning of the Ciona nervous system, including spotless, immaculate, frimousse, vagabond, and bugeye. frimousse (frm) is a spontaneous C. intestinalis mutation that was initially identified as having an anterior truncation. We have found that the anterior neural plate of frm/frm embryos initially forms, but is not maintained (work performed by K. Deschet and E. Mulholland). immaculate (imm) and spotless (spt) are both albino mutants (J. Tresser and D. Jang). Finally, the bugeye mutant shows an open neural tube phenotype (M. Veeman).
In addition, we are looking at the marine environment and the genetic diversity of a wide range of Ascidian species that are found in the Santa Barbara waters. Nate Silva has been determining the level of polymorphism in highly diverse ascidians.