How do meiotic cells navigate the precarious transition between two M-Phases?
Lead Research Organisation:
Newcastle University
Department Name: Northern Institute for Cancer Research
Abstract
Keywords: Meiosis, kinase, signalling, ageing
Abstract: Sexual reproduction depends on the transmission of exactly one copy of each chromosome by the male and female gametes during fertilisation. Gametes become haploid during meiosis, which uniquely involves two rounds of chromosome segregation following a single round of DNA replication. The mechanisms by which this is accomplished are fundamental to our survival.
The mitotic cell cycle comprises alternating rounds of DNA replication during S phase and chromosome segregation during M-Phase. These events depend on the interplay between cell cycle kinases, phosphatases and ubiquitin ligases, acting as pacemakers to control the activities of chromatin-associated proteins. Accumulating evidence indicates that the meiotic divisions employ many elements of the mitotic machinery. A central aim of this project is to investigate how meiotic cells modify the cell cycle machinery to accomplish two successive rounds of chromosome segregation without an intervening S Phase. To tackle this question, we will combine expertise in structural biology with expertise in chromosome segregation in mouse and human oocytes. Mouse oocytes provide an ideal experimental system for investigating the Meiosis I (MI) to Meiosis II (MII) transition as they readily express fluorescently-tagged proteins, are amenable to high resolution live cell imaging, and enter a natural state of arrest at metaphase of Meiosis II.
Our work indicates that complete inactivation of CDK1-cyclinB1 is essential for chromosome segregation during MI in mouse oocytes. Moreover, live cell imaging during the MI-MII transition reveals that the condensation of chromosomes (typical of M Phase) precedes the accumulation of cyclinB1 during MII. These observations indicate that cell cycle regulators other than CDK1 act to orchestrate the MI-MII transition. In order to interrogate which catalytic and/or scaffolding functions of CDK-cyclin complexes underpin this behaviour, we will adopt a structurally-informed approach, exploiting our detailed understanding of the structures of CDK-cyclin complexes that control the mitotic cell cycle, alone and in combination with various regulators.
The specific aims of this project are (i) To apply insights from the structural biology of CDKs to further interrogate their proposed role in recruiting condensin to chromosomes during the transition from MI to MII, (ii) To determine the functional significance of rapid condensation of chromosomes following exit from MI and (iii) To investigate the mechanisms by which CDKs might mediate recruitment of condensin during the MI to MII transition. The findings of the project will shed new light on how the cell cycle machinery is modified to generate haploid gametes from diploid progenitors.
Abstract: Sexual reproduction depends on the transmission of exactly one copy of each chromosome by the male and female gametes during fertilisation. Gametes become haploid during meiosis, which uniquely involves two rounds of chromosome segregation following a single round of DNA replication. The mechanisms by which this is accomplished are fundamental to our survival.
The mitotic cell cycle comprises alternating rounds of DNA replication during S phase and chromosome segregation during M-Phase. These events depend on the interplay between cell cycle kinases, phosphatases and ubiquitin ligases, acting as pacemakers to control the activities of chromatin-associated proteins. Accumulating evidence indicates that the meiotic divisions employ many elements of the mitotic machinery. A central aim of this project is to investigate how meiotic cells modify the cell cycle machinery to accomplish two successive rounds of chromosome segregation without an intervening S Phase. To tackle this question, we will combine expertise in structural biology with expertise in chromosome segregation in mouse and human oocytes. Mouse oocytes provide an ideal experimental system for investigating the Meiosis I (MI) to Meiosis II (MII) transition as they readily express fluorescently-tagged proteins, are amenable to high resolution live cell imaging, and enter a natural state of arrest at metaphase of Meiosis II.
Our work indicates that complete inactivation of CDK1-cyclinB1 is essential for chromosome segregation during MI in mouse oocytes. Moreover, live cell imaging during the MI-MII transition reveals that the condensation of chromosomes (typical of M Phase) precedes the accumulation of cyclinB1 during MII. These observations indicate that cell cycle regulators other than CDK1 act to orchestrate the MI-MII transition. In order to interrogate which catalytic and/or scaffolding functions of CDK-cyclin complexes underpin this behaviour, we will adopt a structurally-informed approach, exploiting our detailed understanding of the structures of CDK-cyclin complexes that control the mitotic cell cycle, alone and in combination with various regulators.
The specific aims of this project are (i) To apply insights from the structural biology of CDKs to further interrogate their proposed role in recruiting condensin to chromosomes during the transition from MI to MII, (ii) To determine the functional significance of rapid condensation of chromosomes following exit from MI and (iii) To investigate the mechanisms by which CDKs might mediate recruitment of condensin during the MI to MII transition. The findings of the project will shed new light on how the cell cycle machinery is modified to generate haploid gametes from diploid progenitors.
Organisations
Publications
Lodge C
(2020)
Oocyte aneuploidy-more tools to tackle an old problem
in Proceedings of the National Academy of Sciences
Mengoli V
(2021)
Deprotection of centromeric cohesin at meiosis II requires APC/C activity but not kinetochore tension.
in The EMBO journal
Studentship Projects
Project Reference | Relationship | Related To | Start | End | Student Name |
---|---|---|---|---|---|
MR/N013840/1 | 30/09/2016 | 29/09/2025 | |||
1797416 | Studentship | MR/N013840/1 | 23/10/2016 | 22/04/2020 | Christopher Lodge |
Title | Quantitative Proteomic database of mouse oocytes at various meiotic stages in young and aged mice |
Description | Proteomics database containing datasets from mouse oocytes at prophase-arrest, metaphase I, and metaphase II, from young and aged mice. Quantitative analysis of the MS/MS spectra performed to look at differences in expression of proteins between stages of oocyte maturation and between the oocytes of young and aged mice |
Type Of Material | Database/Collection of data |
Year Produced | 2020 |
Provided To Others? | No |
Impact | Database has only recently been compiled - to be published. Any impact from publishing will be focused around how any differential expression may contribute to the maternal age effect in which oocytes become less able to faithfully transmit their genome with advancing age. Database also shows an improvement in minimising the amounts of mice needed for this type of work. Previously published work used 7000 oocytes in LC-MS/MS to obtain non-quantitative proteomes containing ~2900 proteins. Here only 10 oocytes were used to obtain up to ~1000 proteins - this was then repeated 6 times to give confidence in the proteins identified. |
Description | Poster presentation at NEPG |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Postgraduate students |
Results and Impact | Presented a poster as part of the annual North East Postgrad Conference in Newcastle |
Year(s) Of Engagement Activity | 2017 |