PARENT SESSION

(T377) STRAIN DIFFERENCES IN THE TIMING AND RATE OF CYST BREAKDOWN AND THE ASSOCIATED APOPTOSIS IN DEVELOPING OOCYTES OF NEONATAL MICE.

Medico, Leonard¹, Wilson, Krystal¹, Pepling, Melissa¹, ¹ Syracuse University, Syracuse, NY

ABSTRACT- In the developing mouse ovary, primordial germ cells migrate to the presumptive gonad, and form clusters of interconnected cells, called cysts. Soon after birth, these cysts break apart to form unconnected germ cells concurrent with a two-thirds reduction in the germ cell population. Studies of the cyst breakdown process have been done in the CD-1 strain of mice. However, most mutant strains have been generated in the C57BL/6 background and most transgenics are made in the FVB background. In mice of these genetic backgrounds, it is not known if there are differences in the number of germ cells before and after neonatal programmed cell death, in the timing of onset of cyst breakdown, and in the rate of death and cyst breakdown. The purpose of this study is to determine the timing and progression of cell death and cyst breakdown in the FVB and C57BL/6 strains and compare them to the previously characterized CD-1 strain. Cyst breakdown and oocyte survival were analyzed by immunocytochemistry, with the oocyte marker STAT-3, in ovaries from postnatal day 7 females of the C57BL/6, FVB, and CD-1 strains. We found that the rate of cyst breakdown was faster in FVB mice as compared to CD-1 mice. In contrast, the rate of cyst breakdown in C57BL/6 mice was slower. In conclusion, genetic determinants for progression of oogenesis exist in different strains, such that the rates and kinetics differ among different strains. The knowledge of these differences will facilitate the comparisons of phenotypes among transgenic mice of different strains.

KEY WORDS: Cyst Breakdown, Apoptosis, Genetic Determinants, Strain Differences