This proposal describes a five-year training program for the development of an academic career in Anatomic Pathology. The Principal Investigator has completed the required residency training in Anatomic Pathology at the University of Pennsylvania and now, will expand upon his scientific skills through a unique integration of interdepartmental resources. This program will promote the command of chronobiology and male reproductive biology. Amita Sehgal, Ph.D. will mentor the Principal Investigator's scientific development. Dr. Sehgal is a recognized leader in the field of circadian rhythms. She is an Associate Professor of Neuroscience and has trained numerous post-doctoral fellows and graduate students. To enhance the training, the program will enlist the expertise of Gregory Kopf, Ph.D. Dr. Kopf is the Celso-Ramon Professor in the Center for Research on Reproduction and Women's Health, and is a leader in the field of spermatogenesis research. In addition, an advisory committee of highly regarded medical scientists will provide scientific and career advice. Research will focus on the role of circadian clock proteins in peripheral organs. Specifically, the role of one such protein, PER1, in spermatogenesis will be examined. The specific aims include: 1) Determining the spatial and temporal distribution of PER1 in the murine testis, 2) Determining the role of a PER1 interacting protein, RanBPM in the spermatogenesis, and 3) Identifying other PER1 interacting proteins in the murine testis through a yeast two- hybrid screen. The Pathology Department of the University of Pennsylvania provides an ideal setting for training physician scientists by incorporating expertise from diverse resources into customized programs. Such an environment maximizes the potential for the Principal Investigator to establish a scientific niche from which an academic career can be constructed.