First published online March 23, 2006
Development 133, 804e (2006)
© The Company of Biologists Limited
Making tracks to axis determination
An early event in the development of multicellular organisms is the
establishment of the anteroposterior (AP) and dorsoventral (DV) axes. In
Drosophila embryos, the asymmetric localisation of maternal mRNAs,
such as gurken (grk) and oskar (osk)
mRNAs, is essential for the formation of these axes. mRNA localisation
requires an organised microtubule network, and in this issue of
Development two papers investigate how microtubules are organised in
Drosophila oocytes. On p.
1477, Trudi
Schüpbach and colleagues identify a new protein – Spn-F –
that affects microtubule organisation and axis determination during
Drosophila oogenesis. spn-F was originally identified as a
mutation that affects the DV polarity of the eggshell. The researchers now
report that, in spn-F mutants, changes in the pattern of the eggshell
are due to defects in the localisation of grk mRNA during
mid-oogenesis. These arise because of defects in the organisation of the
microtubules that move grk mRNA around the oocyte. spn-F,
the authors report, encodes a coiled-coil protein that localises to the minus
end of oocyte microtubules, where it might, for example, be required for the
transport of grk RNA along microtubules. On p.
1467, Shapiro and
Anderson report that Drosophila Ik2 is also required for mRNA
localisation during oogenesis, and that it helps to link microtubule minus
ends to the oocyte cortex. Ik2 is an I
B kinase, which the researchers
expected to regulate the localisation of the early patterning determinant
Dorsal, an NF-B transcription factor. Instead, ik2 is
essential for the correct localisation of osk and grk mRNAs
in oocytes; its absence produces bicaudal and ventralised embryos that closely
resemble spn-F mutant embryos. In these mutant embryos, abnormal mRNA
localisation is accompanied by defects in the organisation of microtubule
minus ends and the oocyte actin cytoskeleton. Interestingly, given the
similarities between ik2 and spn-F mutants, both as embryos
and as adults, Schüpbach and colleagues show that Spn-F and Ik2 interact
directly in a global two-hybrid screen. Both research teams suggest,
therefore, that these proteins might cooperate to organise microtubules during
Drosophila oogenesis to ensure that axis determination goes
smoothly.
Related articles in Development:
- Drosophila Ik2, a member of the IB kinase family, is required for mRNA localization during oogenesis
- Risa S. Shapiro and Kathryn V. Anderson
Development 2006 133: 1467-1475.
[Abstract]
[Full Text]
- spn-F encodes a novel protein that affects oocyte patterning and bristle morphology in Drosophila
- Uri Abdu, Dikla Bar, and Trudi Schüpbach
Development 2006 133: 1477-1484.
[Abstract]
[Full Text]
