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Publications de l’équipe
Développement des cellules germinales
Année de publication : 2013
Nicolas Christophorou, Thomas Rubin, Jean-René Huynh (2013 Dec 19)
Synaptonemal complex components promote centromere pairing in pre-meiotic
germ cells.
PLoS genetics : e1004012 : DOI : 10.1371/journal.pgen.1004012
Résumé
Mitosis and meiosis are two distinct cell division programs. During mitosis, sister chromatids
separate, whereas during the first meiotic division, homologous chromosomes pair and then
segregate from each other. In most organisms, germ cells do both programs sequentially, as
they first amplify through mitosis, before switching to meiosis to produce haploid gametes.
Here, we show that autosomal chromosomes are unpaired at their centromeres in Drosophila
germline stem cells, and become paired during the following four mitosis of the
differentiating daughter cell. Surprisingly, we further demonstrate that components of the
central region of the synaptonemal complex are already expressed in the mitotic region of
the ovaries, localize close to centromeres, and promote de novo association of centromeres.
Our results thus show that meiotic proteins and meiotic organization of centromeres, which
are key features to ensure reductional segregation, are laid out in amplifying germ cells,
before meiosis has started.
Juliette Mathieu, Clothilde Cauvin, Clara Moch, Sarah J Radford, Paula Sampaio, Carolina N
Perdigoto, François Schweisguth, Allison J Bardin, Claudio E Sunkel, Kim McKim, Arnaud Echard,
Jean-René Huynh (2013 Aug 12)
Aurora B and cyclin B have opposite effects on the timing of cytokinesis
abscission in Drosophila germ cells and in vertebrate somatic cells.
Developmental cell : 250-65 : DOI : 10.1016/j.devcel.2013.07.005
Résumé
Abscission is the last step of cytokinesis that physically separates the cytoplasm of sister
cells. As the final stage of cell division, abscission is poorly characterized during animal
development. Here, we show that Aurora B and Survivin regulate the number of germ cells in
each Drosophila egg chamber by inhibiting abscission during differentiation. This inhibition is
mediated by an Aurora B-dependent phosphorylation of Cyclin B, as a phosphomimic form of
Cyclin B rescues premature abscission caused by a loss of function of Aurora B. We show
that Cyclin B localizes at the cytokinesis bridge, where it promotes abscission. We propose
that mutual inhibitions between Aurora B and Cyclin B regulate the duration of abscission
and thereby the number of sister cells in each cyst. Finally, we show that inhibitions of
Aurora B and Cyclin-dependent kinase 1 activity in vertebrate cells also have opposite
effects on the timing of abscission, suggesting a possible conservation of these mechanisms.
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 1
Publications de l’équipe
Développement des cellules germinales
Marlène Jagut, Ludivine Mihaila-Bodart, Anahi Molla-Herman, Marie-Françoise Alin, Jean-Antoine
Lepesant, Jean-René Huynh (2013 Mar 2)
A mosaic genetic screen for genes involved in the early steps of Drosophila
oogenesis.
G3 (Bethesda, Md.) : 409-25 : DOI : 10.1534/g3.112.004747
Résumé
The first hours of Drosophila embryogenesis rely exclusively on maternal information stored
within the egg during oogenesis. The formation of the egg chamber is thus a crucial step for
the development of the future adult. It has emerged that many key developmental decisions
are made during the very first stages of oogenesis. We performed a clonal genetic screen on
the left arm of chromosome 2 for mutations affecting early oogenesis. During the first round
of screening, we scored for defects in egg chambers morphology as an easy read-out of early
abnormalities. In a second round of screening, we analyzed the localization of centrosomes
and Orb protein within the oocyte, the position of the oocyte within the egg chamber, and
the progression through meiosis. We have generated a collection of 71 EMS-induced mutants
that affect oocyte determination, polarization, or localization. We also recovered mutants
affecting the number of germline cyst divisions or the differentiation of follicle cells. Here, we
describe the analysis of nine complementation groups and eight single alleles. We mapped
several mutations and identified alleles of Bicaudal-D, lethal(2) giant larvae, kuzbanian, GDPmannose 4,6-dehydratase, tho2, and eiF4A. We further report the molecular identification of
two alleles of the Drosophila homolog of Che-1/AATF and demonstrate its antiapoptotic
activity in vivo. This collection of mutants will be useful to investigate further the early steps
of Drosophila oogenesis at a genetic level.
Année de publication : 2010
Pierre Fichelson, Marlène Jagut, Sophie Lepanse, Jean-Antoine Lepesant, Jean-René Huynh (2010
Feb 12)
lethal giant larvae is required with the par genes for the early polarization of
the Drosophila oocyte.
Development (Cambridge, England) : 815-24 : DOI : 10.1242/dev.045013
Résumé
Most cell types in an organism show some degree of polarization, which relies on a
surprisingly limited number of proteins. The underlying molecular mechanisms depend,
however, on the cellular context. Mutual inhibitions between members of the Par genes are
proposed to be sufficient to polarize the C. elegans one-cell zygote and the Drosophila
oocyte during mid-oogenesis. By contrast, the Par genes interact with cellular junctions and
associated complexes to polarize epithelial cells. The Par genes are also required at an early
step of Drosophila oogenesis for the maintenance of the oocyte fate and its early
polarization. Here we show that the Par genes are not sufficient to polarize the oocyte early
and that the activity of the tumor-suppressor gene lethal giant larvae (lgl) is required for the
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 2
Publications de l’équipe
Développement des cellules germinales
posterior translocation of oocyte-specific proteins, including germline determinants. We also
found that Lgl localizes asymmetrically within the oocyte and is excluded from the posterior
pole. We further demonstrate that phosphorylation of Par-1, Par-3 (Bazooka) and Lgl is
crucial to regulate their activity and localization in vivo and describe, for the first time,
adherens junctions located around the ring canals, which link the oocyte to the other cells of
the germline cyst. However, null mutations in the DE-cadherin gene, which encodes the main
component of the zonula adherens, do not affect the early polarization of the oocyte. We
conclude that, despite sharing many similarities with other model systems at the genetic and
cellular levels, the polarization of the early oocyte relies on a specific subset of polarity
proteins.
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 3