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Meiosis and Morphogenesis

Contact : Denise ZICKLER

CNRS Emeritus Senior Scientist - Team Robert DEBUCHY

Thematic : Meiosis and Morphogenesis

Phone : +33 1 69 15 70 13
Email : denise.zickler(AT)igmors.u-psud.fr

Building 400, Room n°206/208

Laboratory members

present members (arrival)

Denise ZICKLER, Senior Scientist DR1 Emeritus, CNRS
Eric ESPAGNE, Lecturer, University of Paris-Sud 11
Sophie TESSE, ingenieur CDD (02/2013)
Michel FLIPPHI, post-doc (01/2013)

former members (arrival-departure)

Arnaud de MUY, post-doc (06/2011-10/2012)
Christelle VASNIER, assistante ingénieur CNRS (01/2009-12/2012)
Esther de BOER, post-doc (09/2011-09/2013)


1) Meiotic recombination and pairing

A central feature of meiosis is recombination-mediated communication between homologous chromosomes. Meiotic recombination initiates after DNA replication via programmed double-strand breaks (DSBs). These DSBs then interact preferentially with a homolog chromatid, rather than with the sister chromatid as in mitosis.
Our laboratory has shown recently that recombination complexes are associated with recombination axes (Storlazzi et al, Genes&Dev., 2008; Cell, 2010). Moreover, analysis of three recombination proteins (the helicase Mer3, and the mismatch repair proteins Msh4 and Mlh1) allowed to demonstrate that initial DSB/partner interactions mediate not only recombination per se but also the recognition of homologous chromosomes for pairing and ensuing presynaptic alignment (Storlazzi et al., Cell, 2010). This study showed also that those recombination complexes form inter-axis bridges, which, by progression allow homolog pairing. We proposed that one end of each DSB is released from the “donor” to search for a partner “recipient” while the second end remains donor-associated, yielding an ends-apart configuration as suggested by Hunter (2006). Moreover, the crossover-designated interactions likely nucleate the installation of the pairing structure called the synaptonemal complex (SC). After initiation the SC spreads along the homolog axes as a close-packed array of transverse filaments, linking homologous chromosomes at a 100nm distance all along their lengths (Zickler, 2006; Storlazzi et al., 2008, 2010; Espagne et al., 2011). Crossovers plus axis cohesion provide the physical connections between homologous chromosomes that ensure their regular segregation at division I.

2) Chromosome pairing and resolution of entanglements

The organization of chromosomes within the nucleus can have a profound impact on gene expression and chromosome inheritance. This is particularly important during prophase of meiosis where homologous chromosomes must identify one another and pair along their lengths in a process essential for reducing diploid chromosome numbers to a precise haploid complement in preparation for sexual reproduction.
Our laboratory focuses on three aspects of chromosome dynamics during meiotic prophase: (i) roles of chromosome structure in interplay with chromosome dynamics, (ii) identification of homology and juxtaposition of homologous chromosomes in space (homolog pairing) and (iii) spatial patterning of recombination-related interactions along chromosomes. We showed that the recombination proteins Mer3 and Msh4 are not only directly implicated in homology searching and recognition but also in spatial juxtaposition of homologous chromosomes (Storlazzi et al., Cell, 2010). Our study also revealed that specific features of the pairing process minimize the formation of entanglements during the chromosome movements through the nucleus. These movements are required for pairing, but they generate also entanglements among unrelated chromosomes. We showed that Mer3 is involved in the early process of pairing and thus plays likely a role of avoidance of entanglements, while Mlh1 has a later role in the resolution of entanglements/interlockings. In Sordaria 20% of zygotene nuclei show interlockings, which are all resolved at pachytene when synapsis is complete. We suggested that when entanglements are trapped by SC formation and interhomolog recombination interactions, entrapped chromosomes move out via the dynamic movements which occur at that stage, with concomitant adjustment of the SC (de-polymerization and re-polymerization). We discovered that resolution of entanglements requires Mlh1, revealing a completely unknown function for this recombination protein involved in the crossover process. It also revealed for the first time the requirement of resolution of the recombination interactions at the DNA level during the interlocking resolution process (Storlazzi et al., 2010).
We are currently analyzing the formation of interlockings in several meiotic mutants in relation with the recombination process. Use of anti-skeleton drugs, which alter chromosome movements, showed the importance of chromosome movements and especially of actin in interlock resolution (manuscript in preparation). We are also exploring the pathway of interlock resolution over time, using two SC central components (Espagne et al, PNAS 2011) and by analyzing the interplay between telomere motion and DNA resolution. We are also currently using live imaging to follow in time both loading of the SC components and the resolution of interlocks in collaboration with Nancy Kleckner (Harvard University, USA).

3) Meiotic chromosome structure and dynamics

We discovered the first protein (Spo76/Pds5) involved in sister chromatid cohesion (van Heemst et al Cell 1999, PNAS, 2001). We next analyzed the meiosis-specific cohesin Rec8 and its relationship with the cohesin-associated protein Spo76. This study revealed three new aspects of cohesin functions: (i) Both are required for chromatin compactness, (ii) in absence of Rec8, Spo76 is lost locally at sites of the recombination protein Msh4 (involved in crossover resolution) with a concomitant tendency for loosening of inter-sister and inter-homolog connectedness at the affected sites. This implies that information flows locally from the recombination complex to the underlying chromosome axis. (iii) Rec8 is essential for maintenance of sister cohesion along arms and at centromere regions. This finding underlined the human “maternal age effect” of loss of sister-chromatid cohesiveness found in human aneuploid gametes and suggested that Rec8 could be an attractive target for this effect (Storlazzi et al., 2008; Kleckner et al., 2011).
We are currently studying the SC components of Sordaria and their relationships both with cohesin components and telomeres proteins. The Sordaria genome being sequenced (Nowrousian et al 2010) bioinformatic-based search for SC components allowed the discovery of three new SC components. Our recent study showed that one of the SC central component (Sme4) is also a component of the Spindle Pole Body (SPB), the fungal equivalent of centrosome. In both cases (SC and SPB) the protein mediates spatial juxtaposition of two major structures: linkage of homolog axes through the SC and a change in the SPB morphology from a planar to a bent conformation. Corresponding mutant exhibits defects in SC and SPB morphologies with down-stream consequences for recombination, astral microtubule nucleation, nuclear migration and sporulation. Interestingly Sme4 is also required for reorganization of the recombination complex (Rad51, Mer3 and Msh4) from an on-axis position to a between-axis (on SC) position concomitant with SC installation (Espagne et al., PNAS, 2011).
We are currently studying the links between two other SC components, the SPB and the nuclear envelope. New mutants involved in both telomere-nuclear-envelope attachments and chromosome movements will allow decipher their roles in the chromosome movements required for both pairing and interlock resolution.

Key-words: Meiosis, meiotic recombination, synaptonemal complex, pairing, chromosome structure, cohesin complex, SPB, Cytogenetic, Sordaria, Ascomycètes

Last publications

Thématique "Méiose et morphogénèse"

Espagne E, Vasnier C, Storlazzi A, Kleckner N, Silar P, Zickler D and Malagnac F (2011) Sme4 coiled-coil protein mediates synaptonemal complex assembly, recombinosome relocalization and spindle pole body morphogenesis. Proc. Natl. Acad. Sci. U.S.A. 26 : 10614-10619.

Kleckner N, Zhang L, Weiner B and Zickler D (2011) Meiotic chromosome dynamics. Chapter 19 in « Genome Organization », pp1-82, ed. Rippe, John Wiley-VCH Verlag, Mannheim.

Storlazzi A, Gargano S, Ruprich-Robert G, Falque M, David M, Kleckner N and Zickler D, (2010), Recombination proteins mediate meiotic spatial chromosome organization and pairing, Cell 141(1) : 94-106.

Nowrousian M, Stajich JE, Chu M, Engh I, Espagne E, Halliday K, Kamerewerd J, Kempken F, Knab B, Kuo HC, Osiewacz HD, Pöggeler S, Read ND, Seiler S, Smith KM, Zickler D, Kück U, Freitag M, (2010), De novo assembly of a 40 Mb eukaryotic genome from short sequence reads : Sordaria macrospora, a model organism for fungal morphogenesis, PLoS Genet 6:e1000891.

Zickler D, (2009), Observing meiosis in filamentous fungi : Sordaria and Neurospora, Methods Mol Biol. 558, 91-114, S. Keeney ed. The Human Press Inc. Totowa, New Jersey, USA.

Storlazzi A, Tesse S, Ruprich-Robert G, Gargano S, Poggeler S, Kleckner N and Zickler D, (2008), Coupling meiotic chromosome axis integrity to recombination, Genes Dev 22(6) : 796-809.

Zickler D, (2006), From early homologue recognition to synaptonemal complex formation, Chromosoma 115:158-174.
Shiu PK, Zickler D, Raju NB, Ruprich-Robert G, Metzenberg RL, (2006), From the Cover : SAD-2 is required for meiotic silencing by unpaired DNA and perinuclear localization of SAD-1 RNA-directed RNA polymerase, Proc Natl Acad Sci 103 : 2243-2248.

Zickler D (2006) Meiosis in mycelial fungi. pp 415-438. The Mycota I. Growth, differentiation and sexuality. Kuse and Fisher eds. Springer -Verlag Berlin Heidelberg.

Kleckner , Zickler D, Jones GH, Henle J, Dekker J, Hutchinson J, (2004), A mechanical basis for chromosome function, Proc Natl Acad Sci USA 101 : 12592-12597.

Bishop D.K., Zickler D, (2004), Meiotic crossover interference prior to stable strand exchange and synapsis, Cell 117:9-15.

Thématique "Organelles et programmes cellulaires"

Peraza-Reyes L, Arnaise S, Zickler D, Coppin E, Debuchy R, Berteaux-Lecellier V, (2011), The importomer peroxins are differentially required for peroxisome assembly and meiotic development in Podospora anserina: insights into a new peroxisome import pathway, Mol Microbiol In press.

Peraza-Reyes L, Espagne E, Arnaise S., Berteaux-Lecellier V, (2010) « Peroxisome » In "Cellular and Molecular Biology of filamentous fungi". Ebbole D and Borkovich K (eds). American society for microbiology.

Boisnard S, Espagne E, Zickler D, Bourdais A, Riquet AL and Berteaux-Lecellier V, (2009), Peroxisomal ABC transporters and beta-oxidation during the life cycle of the filamentous fungus Podospora anserina, Fungal Genet Biol 46(1) : 55-66.

Peraza-Reyes L, Espagne E, Arnaise S and Berteaux-Lecellier V, (2009), The role of peroxisomes in the regulation of Podospora anserina sexual development. In : Emergent functions of peroxisomes, Terlecky and Titorenko (eds). Research Signpost (1st ed).

Peraza-Reyes L, Zickler D and Berteaux-Lecellier V, (2008), The Peroxisome RING-Finger Complex is Required for Meiocyte Formation in the Fungus Podospora anserina, Traffic 9(11):1998-2009.

Arnaise S, Zickler D, Bourdais A, Dequard-Chablat M, Debuchy R, (2008), Mutations in mating-type genes greatly decrease repeat-induced point mutation process in the fungus Podospora anserina, Fungal Genetics and Biology 45 : 207-220.

Espagne E, Lespinet O, Malagnac F, Da Silva C, Jaillon O, Porcel B M, Couloux A, Ségurens B, Poulain J, Anthouard V, Grossetete S, Khalili H, Coppin E, Dequard-Chablat M, Picard M, Contamine V, Arnaise S, Bourdais A, Berteaux-Lecellier V, Gautheret D, de Vries R P, Battaglia E, Coutinho P M, Danchin E G.J, Henrissat B, El Khoury R, Sainsard-Chanet A, Boivin A, Pinan-Lucarré B, Sellem C H, Debuchy R, Wincker P, Weissenbach4 J, Silar P, (2008), The Genome Sequence of the Model Ascomycete Fungus Podospora anserina, Genome Biology 9(5) : R77.

Bonnet C, Espagne E, Zickler D, Boisnard S, Bourdais A, Berteaux-Lecellier V, (2006), The peroxisomal import proteins PEX2, PEX5 and PEX7 are differently involved in Podospora anserina sexual cycle, Mol. Microbiol. 62 : 157-169.