Gene expression of the tyrosine kinase receptor c-kit during ovarian development in the brushtail possum (Trichosurus vulpecula).

Ovarian development and function have been extensively studied in eutherian species, with stem cell factor and its receptor, c-kit, having been shown to play key roles at various stages of these processes. In contrast, relatively little is known regarding ovarian development in marsupials. The aims of this study were, first, to establish the timing of key events during germ cell maturation and follicular development and, second, to determine the timing and cellular localization of gene expression for c-kit in the ovaries of a marsupial, the brushtail possum (Trichosurus vulpecula). For this study, ovaries were collected from possums ranging in age from Day 1 after birth to adult. Using stereology, the number of germ cells was found to increase rapidly during the first 60-100 days of life. This was followed by a sharp decline in number, wherein almost 90% of germ cells had disappeared by Day 180. From histological examinations, the time of initiation of meiosis, follicular formation, and follicular growth were determined to occur on Days 35, 50, and 60, respectively. Using in situ hybridization, c-kit gene expression was localized to germ cells and somatic cells during the first 15 days of life; however, after Day 30 and into adult life, c-kit expression was exclusive to germ cells. Results from this study suggest that the pattern of ovarian development is similar in marsupials to eutherians, and that c-kit may play a key role in germ cell development at various stages throughout life.