First published online June 22, 2006
Development 133, 1402e (2006)
© The Company of Biologists Limited
Germ-cell specification the ascidian way
The germ line is specified in many animal embryos by maternal RNAs and
proteins that are localized in a region of the egg called the germ plasm. The
equivalent region in ascidian embryos seems to be the postplasm at the
posterior pole but this region also contains somatic-cell determinants. On
p. 2683,
Shirae-Kurabayashi et al. propose that sea squirt postplasm regulates both
germ- and somatic-cell differentiation through an asymmetric cell division
that segregates the two types of determinants. Using CiVH, a
homologue of the Drosophila germline-specific gene vasa, and
other postplasm components as markers, the researchers show that the
postplasm-containing blastomeres, the B7.6 cells, divide asymmetrically to
form two distinct daughter cells: B8.11 and B8.12. The postplasmic components
mainly segregate into the B8.11 cells, which later associate with the gut
wall, but CiVH RNA and protein segregate into the B8.12 cells, which
are incorporated into the gonad. This redistribution of specific maternal
molecules into the B8.12 cells, the researchers suggest, drives germ-cell
specification in ascidians.
Related articles in Development:
- Dynamic redistribution of vasa homolog and exclusion of somatic cell determinants during germ cell specification in Ciona intestinalis
- Maki Shirae-Kurabayashi, Takahito Nishikata, Katsumi Takamura, Kimio J. Tanaka, Chiaki Nakamoto, and Akira Nakamura
Development 2006 133: 2683-2693.
[Abstract]
[Full Text]
