Research Summary

Molecular Genetics of Meiotic Recombination

Meiosis is the process by which the chromosome number is divided precisely in half. When defects occur in the meiotic process the oocyte or sperm receives an abnormal number of chromosomes (aneuploidy). Aneuploidy is usually catastrophic and is the leading cause of infertility in women and the cause of disorders such as Down's syndrome. Research in my laboratory is directed towards understanding meiosis in the model organism Drosophila melanogaster. By utilizing the experimental benefits of Drosophila, mutations that disrupt various steps in the meiotic program can be isolated and characterized. Currently, the lab focuses on two of the most important aspects of meiosis: i) the repair of programmed double strand breaks (DSB) in the DNA into crossovers, and ii) the involvement of crossovers in the segregation of homologous chromosomes. Since crossovers physically link homologous chromosomes together on a meiotic spindle, they direct segregation and ensure the precise splitting of the diploid genetic content into the gametes.

Our most profitable approach to dissect the different steps of meiotic recombination and chromosome segregation has been to identify genes using unbiased genetic screens for recessive mutants causing nondisjunction of the sex chromosomes. However, the group of mutants we have characterized still represents only a fraction of the total number of genes required for meiotic recombination. Thus, in the future we will continue to identify new meiotic genes from large-scale genetic screens. In addition, we are pursuing new genetic schemes in order to identify genes which would not be found in conventional recessive mutant hunts. Our genetic studies have been complemented by the development of antibodies to important meiotic proteins. These antibodies have alleviated many of the limitations we previously faced and have resulted in a host of new experiments. For example, an antibody to a histone that is phosphorylated in response to a double-strand break (ϒ-His2Av) has been particularly useful and has been very powerful in the analysis of mutants. With this antibody, we have been able to determine how many DSBs are generated and the dynamics of their repair. Many other researchers have found this antibody useful and we have sent aliquots to more than 20 laboratories. We have identified genes required for DSB formation and repair and are beginning to understand the mechanisms that regulate meiotic recombination, including the critical questions of how and when a DSB is fated to become a crossover. We have also identified genes required for chromosome segregation during the first meiotic division.

Publications

McKim, K. S., Joyce, E. F., and Jang, J. K., 2009. Cytological analysis of meiosis in fixed Drosophila ovaries in the Methods in Molecular Biology, S. Keeney (Ed). Humana Press, Totowa, NJ, in press.

Joyce, E. F. and McKim, K. S., 2009. Drosophila PCH2 is required for a pachytene checkpoint that monitors DSB-independent events leading to meiotic crossover formation. Genetics, 181(1):39-51.

Joyce, E.F., Tanneti, N. S., and McKim, K. S., 2009. Drosophila HDM protein is required for a subset of meiotic crossovers and interacts with repair endonuclease complex subunits MEI-9 and ERCC1. Genetics, 181:335-40.

Colombie, N., Cullen,C. F., Brittle,A. L., Jang,J. K., Earnshaw, W. C., Carmena, M. ,McKim,K. S. and Ohkura, H., 2008. Dual roles of Incenp critical to the assembly of the acentrosomal metaphase spindle in female meiosis, Development, 135:3239-46.

Wu, C., Singaram, V., and McKim, K. S., 2008. mei-38 is required for chromosome segregation during meiosis in Drosophila females, Genetics, 180:61-72.

Doubilet S., and McKim, K.S. 2007. Spindle assembly in the oocytes of mouse and Drosophila - similar solutions to a problem. Chromosome Res. 15:681-696

Jang, J.K., Rahman, T., Kober, V.S., Cesario, J. and McKim, K.S. 2007. Misregulation of the Kinesin-like protein Subito induces meiotic spindle formation in the absence of chromosomes and centrosomes. Genetics 177:267-280.

Mehrotra, S., Hawley, R.S. and McKim, K.S. 2007. Synapsis, double strand breaks and domains of crossover control in females, pp. 125-152 in Recombination and meiosis, crossing-over and disjunction, edited by R. Egel and D.Springer-Verlag, Berlin.

Trowbridge K, McKim, K.S. Bril, S.J. and Sekelsky, J. 2007. Synthetic lethality in the absence of the Drosophila MUS81 endonuclease and the DmBlm helicase is associated with elevated apoptosis. Genetics 176:1993-2001.

Mehrotra, S. and K.S. McKim. 2006 Temporal Analysis of Meiotic DNA Double-Strand Break Formation and Repair in Drosophila Females PLoS
Genet: in press

Cesario, J., B. Redding, N. Shah, T. Rahman, J.K. Jang and K. S. McKim. 2006 Subito, a Kinesin 6 family member, participates in mitotic spindle assembly and interacts with mitotic regulators such as Polo kinase and the Passenger proteins. J.
Cell Sci., in press

Horner, V.L., Z. Czank, J.K. Jang, N. Singh, B.C. Williams, J. Puro, E. Kubli, S.D. Hanes, K.S. McKim, M.F. Wolfner, and M.L. Goldberg, 2006 The Drosophila Calcipressin Sarah is Required for Several Aspects of Egg Activation.
Curr Biol 16: 1441-1446.

Gong, W.J, K.S. McKim and R.S. Hawley RS, 2005 All Paired Up with No Place to Go: Pairing, Synapsis, and DSB Formation in a Balancer Heterozygote.
PLoS Genet: 1: 589 - 602

McKim, K.S., 2005 When Size Does Not Matter: Pairing Sites during Meiosis.
Cell: 123(6):989-92.

Jang, J.K., T. Rahman and K. S. McKim, 2005 The kinesinlike protein subito contributes to central spindle assembly and organization of the meiotic spindle in Drosophila oocytes. Mol. Biol. Cell.: 16:4684-4694

Dorsett D., J.C. Eissenberg, Z. Misulovin, A. Martens, B. Redding and K.S. McKim, 2005 Effects of sister chromatid cohesion proteins on cut gene expression during wing development in Drosophila. Development: 132:4743-4753

Anderson, L.K., S.M. Royer, S.L. Page, K.S. McKim, A. Lai, M.A. Lilly and R.S. Hawley, 2005 Juxtaposition of C(2)M and the transverse filament protein C(3)G within the central region of Drosophila synaptonemal complex.
Proc. Natl. Acad. Sci. USA: 102:4482-4487

Sherizen, D. E., J.K. Jang, N. Kato, and K. S. McKim, 2005 Translocations are dominant meiotic crossover suppressors due to a defect early in the recombination pathway. Genetics: 169: 767-81

R. Bhagat, E. A. Manheim, D. E. Sherizen and K. S. McKim, 2004 Studies on crossover specific mutants and the distribution of crossing over in Drosophila females. Cytogenet Genome Res 107: 160-171

J.K. Jang, Sherizen, D.E., R. Bhagat, E.A. Manheim and Kim S. McKim, 2003 Relationship of DNA double-strand breaks to synapsis in Drosophila. J. Cell Science 116: 3069-3077

Manheim E. A. and K. S. McKim, 2003 C(2)M, a novel component of the synaptonemal complex, regulates meiotic crossing over. Curr. Biol. 13: 276-285

McKim, K.S., E.A. Manheim and J.K. Jang 2002 Meiotic recombination and chromosome segregation in Drosophila females, Annu. Rev. Genet. 36: 205- 232

Liu, H., J.K. Jang, N. Kato and K. S. McKim, 2002 mei-P22 encodes a chromosome-associated protein required for the initiation of meiotic recombination in Drosophila melanogaster. Genetics 162: 245-258

Guinta, K., J.K. Jang, E.A Manheim, G. Subramanian and K. S. McKim, 2002 subito encodes a kinesin-like protein required for meiotic spindle pole formation in Drosophila melanogaster. Genetics 160: 1489-1501

Manheim, E.A. J. K. Jang and K. S. McKim, 2002 Cytoplasmic localization and regulation of MEI-218, a protein required for meiotic crossing over in Drosophila. Mol. Biol. Cell 13: 84-95

Liu, H., J.K. Jang, J. Graham, K. Nycz, K. and K.S. McKim, 2000 Two genes required for meiotic recombination are expressed from a dicistronic message.
Genetics 154: 1735-1746

Page, S.L., K.S. McKim, B. Deneen, T. L. Van Hook, and R. S. Hawley, 2000 Genetic studies of mei-P26 reveal a link between the processes that control germ cell proliferation in both sexes and those that control meiotic exchange in Drosophila. Genetics 155:1757-72

McKim, K.S., J.K. Jang, J.J. Sekelsky, A. Laurencon, and R. S. Hawley, 2000 mei-41 is required for precocious anaphase in Drosophila females.
Chromosoma 109: 44-49

Sekelsky, J.J., K. S. McKim, L. Messina, R.L. French, W.D Hurley, T. Arbel, G.M. Chin, B. Deneen, S.J. Force, K.L. Hari, J.K. Jang, A.C. Laurencon, L.D. Madden, H.J. Matthies, D.B. Milliken, S.L. Page, A.D. Ring, S.M. Wayson, C.C. Zimmerman and R.S. Hawley, 1999 Identification of novel Drosophila meiotic genes recovered in a P-element screen. Genetics 152: 529-542.

McKim, K.S. and A. Hayashi-Hagihara, 1998 mei-W68 in Drosophila melanogaster encodes a Spo11 homolog: Evidence that the mechanism for initiating meiotic recombination is conserved. Genes & Dev. 12: 2932-2942.

McKim, K.S., B. Green-Maroquin, G. Chin, J. J. Sekelsky and R. S. Hawley, 1998 Meiotic Synapsis in the Absence of Recombination. Science 279: 876-878.

McKim, K.S., J.B Dahmus and R.S. Hawley, 1996 Cloning of the Drosophila melanogaster meiotic recombination gene mei-218: A genetic and molecular analysis of interval 15E. Genetics 144: 215-228.

McKim, K.S. and R.S. Hawley, 1995 Chromosomal control of meiotic cell division. Science 270: 1595-1601.

Lab Support

Janet Jang, Laboratory Researcher

Sarah Radford, Post-Doctoral Associate

Jeffry Cesario, Graduate Student

Eric Joyce, Graduate Fellow

Benson Fan, Undergraduate Student

Apple Long, Undergraduate Student

Audrey Reusch, Undergraduate Student

Shree Tanneti, Undergraduate Student