Research Interests:
The germ cell complement and the processes of germ cell development determine reproductive potential. Factors that reduce germ cell number or interfere with gametogenesis can limit or even preclude reproduction, leading to infertility. Studies of sterile mutants in lower organisms have shed new light on the processes that control mammalian germ cell development. We are interested in understanding the molecular mechanisms that govern mouse gametogenesis, and our studies of CTF18 are based on work originating in the fly that has disclosed a novel gene, which regulates germ cell development.

Cutlet/CTF18 encodes an evolutionarily conserved protein that is crucial for germline development in the fly. Loss of function of cutlet in the fly results in a sterile phenotype due to failure of the germline stem cells to proliferate. CTF18 was first identified in Saccharomyces cerevisiae as a sister chromatid cohesion factor that is essential for the faithful transmission of chromosomes during DNA replication. CTF18 protein functions in an alternative and novel Replication Factor C-related complex in human cells and in yeast. We have cloned and characterized the human and mouse CTF18 orthologues of the Drosophila melanogaster gene, cutlet. We have demonstrated that CTF18 mRNA is expressed in human testis and ovary, and that CTF18 protein is highly expressed in the germ cells of mouse testis and ovary. We hypothesize a unique biological role for CTF18 in mammalian germ cell development based on its mammalian germline-enriched expression, high degree of evolutionary conservation, and role in DNA replication and chromosomal stability in yeast. Given the fly sterile phenotype, CTF18 could play a critical role in the fertility of mammals.

We believe that a better understanding of the role of CTF18 in mammals will broaden our knowledge of the underlying molecular aspects of gametogenesis, and in doing so will shed light on the molecular basis of infertility in mammals. We also strive to better elucidate the processes of DNA replication, recombination, and repair in germ cells and thus, provide insight into an area of germ cell development that is essential for mammalian gametogenesis, but in which little is currently known.

The goal of our project is to assess the function of mammalian CTF18 in germ cell proliferation and gametogenesis in vivo. To directly determine the role of CTF18 in vivo we are generating a mouse model that lacks CTF18. Gene targeting by homologous recombination will generate mice lacking a functional CTF18 allele. Given the fly mutant phenotype, we expect that mice generated by this classic knockout strategy will be viable. However, should the CTF18 null mutation lead to early lethality due to the role of cutlet in other tissues, we will employ tissue-specific gene deletion using the loxP/Cre recombinase system to generate mice that lack CTF18 only in the germline. We will then analyze the phenotypic consequences of CTF18 gene deletion. In order to characterize CTF18 null mice we are currently beginning with a detailed analysis of CTF18 expression in embryonic and postnatal wild-type mouse testes and ovaries.

Recent Representative Presentations
Berkowitz, KM and Jongens, TA. Germline-Enriched Expression of Mammalian CTF18: an Evolutionarily Conserved Protein Required for Germ Cell Proliferation in the Fly, submitted.

Berkowitz, KM and Jongens, TA: Characterization of Mammalian Cutlet, a Homologue of a Fly Gene Required for Germ Cell Proliferation. Presented at the 51st Annual Meeting of the Society for Gynecologic Investigation, March 24-27, 2004, Houston, TX,

Berkowitz, KM and Jongens, TA: Characterization of Mammalian Cutlet, An Orthologue of a Fly Gene Required for Germ Cell Proliferation. Presented at the WRHR Scholars’ Research Symposium, March 31-April 1, 2003, Washington, DC

Berkowitz, KM and Jongens, TA. Cloning and Characterization of the Human Cutlet Gene, a Homologue of a Drosophila Gene Required for Germ Cell Proliferation Presented at the 47th Annual Meeting of the Society for Gynecologic Investigation, March 22-25, 2000, Chicago, Illinois

Berkowitz, KM and Sondheimer, SJ "Progestins: Fertility Control and Other Uses" in Endocrinology of the Reproductive System and Fertility, Contemporary Endocrinology series, Santoro, N, Spratt, D., Conn, M. editors. Humana Press, in press.

Pfeifer SM, Berkowitz K Imperforate hymen with complete septate uterus, duplicated cervix and longitudinal vaginal septum diagnosed by Magnetic Resonance Imaging. Presented at the North American Society for Pediatric and Adolescent Gynecology, June 1999

Berkowitz KM and Pfeifer SM Uterine artery embolization as the treatment for cervical ectopic pregnancy Presented at the American Society for Reproductive Medicine/ The Canadian Fertility and Andrology Society 1999 Conjoint Annual Meeting September 25-30, 1999 Toronto, Ontario, Canada

Lee, G, Bahtiyar O, Berkowitz K, Ward D, Olive D. Aneuploidy Determination in the Human Fetal Ovary. Presented at the 45th Annual Meeting of the Society for Gynecologic Investigation, March 11-14, 1998 Atlanta, Georgia

Markowitz, C.E., Berkowitz, K.M., Jaffe, S.B., Wardlaw, S.L.: Effect of Opioid Receptor Antagonism on Proopiomelanocortin Peptide Levels and Gene Expression in the Hypothalamus. Molecular and Cellular Neurosciences Vol. 3 184-190(1992). Presented at the National Endocrine Society Meeting June 19-22, 1991 Washington D.C.