Research axis Groups Job opportunities How to reach us Version française
Groups
Group ARRIGO
Group BAKLOUTI
Group CASTELLANI
Group LOPPIN
Group DURAND
Group EPSTEIN
Group GANDRILLON
Group GIESELER
Group LAMARTINE
Group LOMONTE
Group MORLE
Group MOUCHIROUD
Group SEGALAT

Epigenetics and zygote formation

Group composition

Leader:
Benjamin LOPPIN

Staff members:
Benjamin LOPPIN, CR 1 CNRS
Pierre COUBLE, DR 1 CNRS, HDR
Elisabeth CORTIER, AI UCBL
Laure SAPEY-TRIOMPHE, AI, CDD
Jérôme SCHMITT, AJT UCBL

Non permanent members:
Guillaume ORSI, PhD student

Scientific themes

Chromatin assembly at early development in Drosophila

Our main research interest is the study of the functional organization of the nucleus during development, using a classical genetic approach in Drosophila. We are particularly interested in the fate of the paternal nucleus during spermatogenesis and fertilization. The differentiation of spermatid nuclei after meiosis is accompanied by a dramatic reorganization of the paternal chromatin, with the replacement of core histones with sperm specific chromosomal proteins. At fertilization the reverse process must rapidly take place during the decondensation of the sperm chromatin into a replication-competent male pronucleus.
We are working on a gene, Hira, which encodes a WD repeat protein conserved in all eucaryotes. In vitro studies have recently demonstrated that HIRA is required for the assembly of chromatin independent of DNA replication. We identified the first mutant allele of Hira, called (ssm). In eggs produced by (ssm) mutant females, the sperm nucleus is unable to fully decondense its chromatin and does not participate in zygote formation. We have shown that histones are not deposited in the sperm nucleus in ssm eggs, which strengthens the chromatin assembly function of HIRA established in vitro. We are analysing the function of Hira in various Drosophila tissues where the gene is expressed, including testis. Our current hypothesis is that HIRA is required in very different situations to assemble nucleosome on DNA outside S phase. This activity seems to be correlated with global nuclear reorganization (spermiogenesis, fertilization) or transcriptional regulation (male and female germline, various differentiated cells).
A complementary approach is to determine the molecular composition of the various HIRA complexes that are assembled in vivo. We aim also at identifying the partner proteins of the HIRA complex.
We are also working on others mutants that affect the integration of paternal chromosomes in the zygote nucleus. maternal haploid (mh) is a maternal effect mutation that prevents the correct separation of paternally-derived sister chromatids at anaphase of the first zygotic division. This phenotype is shared with ms(3)K81 (K81) that is one of the rare paternal effect embryonic lethal mutants. The phenotype associated with the mh and K81 mutations suggests a defect in paternal chromatin assembly or organization. We recently identified the K81 gene which appears to be a small, rapidly evolving gene that is restricted to a few Drosophila species. This is quite surprising considering that this gene is essential for male fertility. The evolutionary scenario for K81 is under investigation.

Transcriptome analysis of silk gland cells in the silkworm B. mori We use also the silkworm to study the narrow specialization of the posterior and median cells of the silk gland, toward the production of fibroin and sericins, respectively. We analyse the transcriptome of each category of cells to measure the variations in gene expression that specify each of them.. With Jérôme Briolay of the DTAMB plateform, we develop a SAGE (Serial Analysis of Gene Expression) approach, and work together with the group of Olivier Gandrillon in the CGMC which develop bioinformatic tools for SAGE data interpretation.
A similar approach has been undertaken on the salivary gland of the mosquito Anopheles gambiae with the group of Paul Brey at the Pasteur Institute in Paris. The objective is to compare the transcriptomes of the salivary gland of blood-fed females, infected or not by Plasmodium berghei, the rodent pathogen model of malaria. The available genomic sequences of A. gambiae and of P. falciparum will help interpret the salivary gland cell response to the vection of the parasite.
In close collaboration with the National Sericulture Unit from INRA (la Mulatière), we also pursue the biotechnological exploitation of silkworm transgenesis (Tamura et al., 2000) toward diverse industrial applications.


Publications


Orsi GA, Couble P, Loppin B (2009) Epigenetic and replacement roles of histone variant H3.3 in reproduction and development. Int J Dev Biol 53: 231-243.

Landmann F, Orsi GA, Loppin B, Sullivan W. (2009) Wolbachia-mediated cytoplasmic incompatibility is associated with impaired histone deposition in the male pronucleus. PLoS Pathog. 2009 Mar;5(3):e1000343.

Loppin B, Oakey R. (2009) Genomic imprinting in Singapore. Workshop on Genomic Imprinting. EMBO Rep. 10(3):222-7.

Bonnefoy E, Orsi GA, Couble P, Loppin B (2007) The essential role of Drosophila HIRA for de novo assembly of paternal chromatin at fertilization. PLoS Genet 3: 1991-2006.

Pannebakker BA, Loppin B, Elemans CP, Humblot L, Vavre F (2007). Parasitic inhibition of cell death facilitates symbiosis. Proc Natl Acad Sci U S A. 104(1):213-5.

Loppin, B et Couble, P. (2006). Hira, une molécule de l'œuf qui contrôle la formation du pronucleus mâle. Médecine/Sciences 22(6-7):565-6.

Loppin B., Bonnefoy E., Anselme C., Laurençon A., Karr T.L. and Couble P. (2005). The histone H3.3 chaperone HIRA is essential for chromatin assembly in the male pronucleus. Nature 437,1386-90.

Loppin B, Lepetit D, Dorus S, Couble P, Karr TL. (2005). Origin and neofunctionalization of a Drosophila paternal effect gene essential for zygote viability.Curr Biol. 26;15(2):87-93.

Loppin, B., and Karr, T.L. (2004). Molecular Genetics of Insect Fertilization. In Comprehensive Insect Molecular Science, L.B. Gilbert and K. Iatrou, eds. (Oxford: Elsevier).

Bossin, H., Fournier, P., Royer, C., Barry, P., Gimenez, S., Couble, P., Bergoin, M. (2003) JcDNV-based plasmids for stable transgene expression in Sf9 lepidopteran cells: influence of the densovirus sequences on the integration pattern. J. Virology, 77, 11060-71.

Julien, E., Coulon-Bublex, M., Garel,A., Prudhomme J.C., Couble P. (2003) Bombyx silk gland development and regulation of silk protein-encoding genes. In : Comprehensive in Insect Biochemistry. (L. Gilbert, S. Gill & K. Iatrou, Edts).

Prudhomme, J.C., Couble, P. (2002) Perspective in silkworm (Bombyx mori) trasngenesis. Current Science, 83, 4332-438.

Julien, E., Bordeaux, M.C., Garel, A., Couble, P. (2002). Fork head alternative binding drives stage specific expression in the silk gland of Bombyx mori. Insect Biochem Molecul. Biol. 32, 377-387.

Dedeine, F., Vavre, F., Fleury, F., Loppin, B., Hochberg, M.E., Bouletreau, M. (2001). Removing the symbiotic bacteria Wolbachia inhibits oogenesis in a parasitic wasp. Proc. Natl. Acad. Sci USA 98, 6247-6252.
Loppin, B., Berger, F., Couble, P. (2001). The Drosophila maternal gene sésame is required for sperm chromatin remodeling at fertilization Chromosoma 110, 430-440.

Loppin, B., Berger, F., Couble, P. (2001). Paternal chromosome incorporation into the zygote nucleus is controlled by maternal haploid in Drosophila. Dev. Biol. 231, 383-396.

Loppin, B., Docquier, M., Bonneton, F., Couble, P. (2000). The maternal effect mutation sésame affects the formation of the male pronucleus in Drosophila melanogaster. Dev Biol 222, 392-404.

Tamura, T., Thibert, C., Royer, C., Kanda, T., Abraham, E., Kamba, M., Kômoto, N., Thomas, J.-L., Mauchamp, B., Chavancy, G., Shirk, P., Fraser, M., Prudhomme, J.-C., Couble, P. (2000) Germ-line transformation in the silkworm, Bombyx mori L using a piggyBac transposon-derived vector Nature Biotechnology. 18, 81-84.

Last modified : 10/01/2009