Debra J. Wolgemuth, PhD

Research Summary

MOLECULAR DEVELOPMENTAL GENETICS OF MAMMALIAN GAMETOGENESIS; CELL CYCLE REGULATION DURING MEIOSIS AND LEUKEMOGENESIS

Cell Cycle Regulation during Gametogenesis

We have identified a novel mammalian A-type cyclin, cyclin Al, which we have shown to be expressed at highest levels if not exclusively in the testis in mice and humans. Targeted mutagenesis of the gene for cyclin A1 results in viable progeny but male sterility, while females are fully fertile. Cyclin A1-deficient male germ cells arrest at the G2/M transition of meiotic prophase I. The cells do not form haploid spermatids and rather, exhibit properties suggestive of a rapid entry into an apoptotic cell death. Our hypothesis is that there is a primary cell death response that is specifically activated in response to cell cycle arrest. We wish to understand the transcriptional control cyclin A1 in the male germ line, the kinase partners and substrates of cyclin A1 protein, and the functional redundancy of the two mammalian A-type cyclins. Our current projects include:

Identifying regulatory elements required for the proper in vivo expression of cyclin A1
Asking if cyclin A2 can rescue the cyclin A1-deficient phenotype of meiotic arrest in spermatogenesis, in transgenic mice in vivo
Studying the function of cyclin A1in human spermatogenesis by screening for mutations in the gene for cyclin A1 in infertile men
Examining the role of p53 in the cell cycle arrest-induced apoptosis that occurs in the absence of cyclin A1
Determining the downstream effector molecules responsible for the cell death that occurs in the absence of cyclin A1
Identifying proteins that interact with cyclin A1 in the germ line
Identifying molecules that could inhibit cyclin A1/Cdk activity

Cyclin A1 and Leukemogenesis

Cyclin A1 is highly expressed in human leukemic cells from patients with acute myeloid leukemia. To test the hypothesis that the aberrant high levels of cyclin A1 were causal in the leukemic phenotype, i.e., acting as an oncogene, we generated transgenic mice in which cyclin A1 was expressed under the direction of the human cathepsin G promoter in myeloid precursor cells. The transgenic animals exhibited abnormal myelopoiesis and developed acute myeloid leukemia. We have also recently observed high levels of cyclin A1 expression in testicular tumors of the highly invasive embryonal carcinoma class but not in the more common and less invasive seminoma. We propose that cyclin A1 represents a novel target for drug intervention in cancer therapy. Our current projects include:

Asking if inhibiting the expression of cyclin Al in leukemic cells can revert the leukemic phenotype
Developing in vitro kinase assays for screening pharmacological targets for inhibition specifically for cyclin A1/Cdk function
Examining the sub-cellular distribution of cyclin A1 in leukemic versus normal cells
Studying the role of cyclin A1 in normal hematopoiesis in cyclin A1-deficient mice

Retinoid Signaling and Development of the Reproductive System

Dietary retinal is required for spermatogenesis (and vision) in mammals. Studies generating mutations in specific receptors for vitamin A metabolites have clearly shown a role for the retinoid receptors RAR alpha and RXR beta in spermatogenesis. Our current projects include:

Characterizing the phenotypic abnormalities resulting in male sterility in mice mutated in the RAR alpha gene, with particular emphasis on the developmental etiology of the abnormalities in the testis
Testing the hypothesis that the mutations in the RAR alpha gene are essentially phenocopied by the effects of vitamin A deficiency by comparing the spermatogenic abnormalities in the mutant mice with those in mice which have been vitamin A-deficient from birth
Identifying targets of the RAR alpha receptor in specific populations of cells in the testis
Examining cell-specific functions of RAR alpha by generating conditional mutations in particular cell types

The FSRG Bromodomain-containing Proteins and Reproductive Tissues

We have characterized some properties of Fsrg1, a bromodomain-containing mouse gene that is homologous to the Drosophila gene female sterile homeotic. Fsrg1 is a member of a small sub-family of bromodomain-containing genes that appear to be involved in chromatin remodeling and possibly regulating transcription. Our current projects include:

Determining the subcellular distribution of the Fsrg2, Fsrg3, and Fsrg4 proteins in reproductive tissues
Characterizing the biochemical properties of the Fsrg family of proteins by identifying proteins with which they associate in vivo, particularly in the germ line
Determining the effect of targeted mutagenesis of Fsrg1 and Fsrg3, with particular focus on spermatogenesis and oogenesis

Selected Publications

Persson JL, Zhang Q, Wang XY, Ravnik SE, Muhlrad S, Wolgemuth, DJ (2005). Distinct roles for the mammalian A-type cyclins during oogenesis. Reproduction, 130(4): 411-422.

Chung SS, Wang X, Wolgemuth DJ (2005). Male sterility in mice lacking retinoic acid receptor alpha involves specific abnormalities in spermiogenesis. Differentiation, 73(4): 188-198.

Ekberg J, Landberg G, Holm C, Richter J, Wolgemuth DH, Persson JL (2004). Regulation of the cyclin A1 protein is associated with its differential subcellular localization in hematopoietic and leukemic cells. Oncogene, 23(56): 9082-9089.

Lele KM, Wolgemuth DH (2004). Distinct regions of the mouse cyclin A1 gene, Ccna1, confer male germ-cell specific expression enhancer funcation. Biol. Reprod, 71(4): 1340-1347.

Chaudry HW, Dashoush NH, Tang H, Zhang L, Wang X, Wu EX, Wolgemuth DJ (2004). Cyclin A2 mediates cardiomyocyte mitosis in the postmitotic myocardium. J. Biol. Chem, 279(34): 35858-35866.

Wolgemuth DJ, Lele KM, Jobanputra V, Salazar G (2004). The A-type cyclins and the meiotic cell cycle in male germ cells. Int J Androl, 27(4): 192-199. Review.