First published online March 22, 2007
Development 134, 805e (2007)
© The Company of Biologists Limited
Fishy mechanism for left-right asymmetry
During gastulation, Nodal signalling on the left side of the ventral node
establishes the left-right (LR) axis of the embryo, which controls the
position of the internal organs. In mouse embryos, polycystic kidney disease 2
(Pkd2), which encodes the Ca2+-activated channel
polycystin 2 (PC2), is thought to activate left-side-specific Nodal
transcription. Now, Schottenfeld and colleagues reveal that LR patterning in
zebrafish embryos also requires pkd2 but that here, pkd2
restricts expression of the nodal gene southpaw
(spaw) to the left half of the embryo (see
p. 1605). They show
that curly up (the zebrafish ortholog of Pkd2) mutants have
LR defects in organ positioning that resemble human heterotaxia. But, whereas
there is no activation of Nodal in the lateral plate mesoderm of
mouse Pkd-/- embryos, spaw is bilaterally
activated in curly up embryos, they report. Thus, although PC2 is
involved in LR patterning in both zebrafish and mouse embryos, its function in
this process might not be conserved, a result that calls into question the
so-called two-cilia hypothesis for LR axis formation.
Related articles in Development:
- Zebrafish curly up encodes a Pkd2 ortholog that restricts left-side-specific expression of southpaw
- Jodi Schottenfeld, Jessica Sullivan-Brown, and Rebecca D. Burdine
Development 2007 134: 1605-1615.
[Abstract]
[Full Text]
