Tim L. Kroft, Assistant Professor

B.A. 1993, Miami University
Ph.D. 2001, Northwestern University

tkroft@d.umn.edu
252A SSB, 726-7796

Research

Genetics of gametogenesis, sperm-egg interactions and fertilization in C. elegans

Our research focuses on the cell-cell communication and associated signal transduction pathways that function during fertilization. We use genetic, molecular and cell biological tools to investigate how spermatozoa and eggs recognize each other, bind and fuse to form a new organism.

The unusual reproductive biology of the small free-living nematode C. elegans makes it an excellent model system for studies of sperm-egg interactions during fertilization. The primary reproductive mode of C. elegans hermaphrodites is internal self-fertilization, but a hermaphrodite’s eggs can also be fertilized by sperm transferred from a male. In a background of nearly 100% self-fertility, spermatogenesis defective (spe) hermaphrodites are readily identified by their oocyte-laying phenotype. The sterility defect of a spe hermaphrodite can be rescued by sperm from a wild type male because the defect is sperm-specific. We use this simple but powerful screen to discover genes that are necessary for spermatogenesis and/or fertilization.

We are currently studying a group of mutants that produce morphologically wild type spermatozoa yet cannot fertilize oocytes despite making direct sperm-oocyte contact. Our long term goal is to use the data we gather to develop a molecular model of the cell-cell interactions leading to fertilization.

Recent Publications

• Gleason, E.J., Lindsey, W.C., Kroft, T.L., Singson, A.W. and L’Hernault, S.W. 2006. spe-10 encodes a DHHC-CRD zinc finger membrane protein required for ER/Golgi membrane morphogenesis during Caenorhabditis elegans spermatogenesis. Genetics 172: 145-158.
• Kroft, T.L., Gleason, E.J., Lamitina, S.T. and L’Hernault, S.W. 2006. fer-14 encodes a sperm transmembrane protein required for fertilization in Caenorhabditis elegans. In Preparation.
• Kroft, T.L., Gleason, E.J. and L’Hernault, S.W. 2005. The spe-42 gene is required for sperm-egg interactions during C. elegans fertilization and encodes a sperm-specific transmembrane protein. Dev Biol. 286: 169-181.
• Kroft, T.L., Li, S., Doglio, L. and Goldberg, E. 2003. A transgenic analysis of mouse lactate dehydrogenase c promoter activity in the testis. J. Androl. 24: 843-852.
• Kroft, T.L., Patterson, J., Won Yoon, J., Doglio, L., Walterhouse, D.O., Iannaccone, P.M. and Goldberg, E. 2001. GLI1 localization in the germinal epithelial cells alternates between cytoplasm and nucleus: upregulation in transgenic mice blocks spermatogenesis in pachytene. Biol Reprod. 65: 1663-1671.
• Kroft, T.L., Jethanandani, P., McLean, D.J. and Goldberg, E. 2001. Methylation of CpG dinucleotides alters binding and silences testis-specific transcription directed by the mouse lactate dehydrogenase c promoter. Biol Reprod. 65: 1522-1527.

  Undergraduate students

  Lindsey Magnuson, Complementation testing of new Caenorhabditis elegans spermatogenesis defective mutants. 2006 – present.

  
  Teaches

  BIOL 2202 Genetics Laboratory
  BIOL 4231 Molecular Biology