Our goal is to understand the mechanism of chromosome segregation during meiosis, particularly initiation of pairing of homologous chromosomes. The maize male meiocyte is the only cell where there is a large collection of mutants that affect meiosis, and it is possible to do superb cytology. We have shown that pairing is initiated at the transition between leptotene and zygotene and is associated with transitory changes in chromosome morphology. We call this stage pre- zygotene. We will describe the changes in chromosome structure and arrangement in the nucleus that occur during meiotic prophase, using the computerized light microscope workstation developed by John Sedat and David Agard (UCSF) that is capable of recording three dimensional images of multiple cellular components in fixed and living cells. The distinctive chromomeres, chromomeres, knobs and centromeres along with the use of paining probes, telomere probes, probes for individual genes and fluorescence in situ hybridization (FISH) will allow us to identify each individual chromosome arm. We will follow the behavior of one region of the same chromosome as it pairs with its homolog. This data will also be used to develop a cytological map of the maize genome. We will use antibodies against functionally important proteins involved in recombination to describe their location during pairing. We will also develop methods to study pairing in living cells. This analysis will allow us to understand the relevance of nuclear envelope associated telomere movements to initiation of pairing and locate the sites on chromosomes where pairing is initiated. We will culture meiocytes or anthers and determine whether microtubule depolymerizing agents applied during prezygotene interfere with telomere movements and the pairing process. We will analyze mutant meiocytes defective in the initiation of pairing to determine whether any of the have abnormal pre-zygotene chromosome morphology or abnormal telomere clustering. Analysis of mutants will eventually allow us to link changes in chromosome morphology and distribution to the corresponding molecular events required for homology recognition and synapsis. We are continuing a screening program to isolate and cytologically characterize new meiotic mutants induced by Mu or Ac transposon mutagenesis. Our highest priority is to find new mutants deficient in the pairing process. Meiosis is essential for all sexually reproducing organisms and the studies described here will further our understanding of this process not only in maize but in all organisms. The mechanism of meiosis is a topic of major medical interest since inaccurate chromosome segregation (aneuploidy) is causal in several congenital malformations and a major cause of premature termination of pregnancy. An improved understanding of meiosis in maize will allow us to understand the basis of abnormal chromosomal segregation during human gamete production.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
3R01GM048547-04S1
Application #
2835874
Study Section
Molecular Cytology Study Section (CTY)
Project Start
1994-08-01
Project End
1999-06-30
Budget Start
1998-08-01
Budget End
1999-06-30
Support Year
4
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of California Berkeley
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
094878337
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Golubovskaya, Inna N; Wang, C J Rachel; Timofejeva, Ljudmilla et al. (2011) Maize meiotic mutants with improper or non-homologous synapsis due to problems in pairing or synaptonemal complex formation. J Exp Bot 62:1533-44
Wang, Chung-Ju Rachel; Carlton, Peter M; Golubovskaya, Inna N et al. (2009) Interlock formation and coiling of meiotic chromosome axes during synapsis. Genetics 183:905-15
Gustafsson, Mats G L; Shao, Lin; Carlton, Peter M et al. (2008) Three-dimensional resolution doubling in wide-field fluorescence microscopy by structured illumination. Biophys J 94:4957-70
Golubovskaya, Inna N; Hamant, Olivier; Timofejeva, Ljuda et al. (2006) Alleles of afd1 dissect REC8 functions during meiotic prophase I. J Cell Sci 119:3306-15
Jin, Ye; Mancuso, Joel J; Uzawa, Satoru et al. (2005) The fission yeast homolog of the human transcription factor EAP30 blocks meiotic spindle pole body amplification. Dev Cell 9:63-73
Hamant, Olivier; Golubovskaya, Inna; Meeley, Robert et al. (2005) A REC8-dependent plant Shugoshin is required for maintenance of centromeric cohesion during meiosis and has no mitotic functions. Curr Biol 15:948-54
Franklin, Amie E; Golubovskaya, Inna N; Bass, Hank W et al. (2003) Improper chromosome synapsis is associated with elongated RAD51 structures in the maize desynaptic2 mutant. Chromosoma 112:17-25
Jin, Ye; Uzawa, Satoru; Cande, W Z (2002) Fission yeast mutants affecting telomere clustering and meiosis-specific spindle pole body integrity. Genetics 160:861-76
Bass, H W; Riera-Lizarazu, O; Ananiev, E V et al. (2000) Evidence for the coincident initiation of homolog pairing and synapsis during the telomere-clustering (bouquet) stage of meiotic prophase. J Cell Sci 113 ( Pt 6):1033-42
Kaszas, E; Cande, W Z (2000) Phosphorylation of histone H3 is correlated with changes in the maintenance of sister chromatid cohesion during meiosis in maize, rather than the condensation of the chromatin. J Cell Sci 113 ( Pt 18):3217-26

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