Gene Expression of the Tyrosine Kinase Receptor c-kit During Ovarian Development in the Brushtail Possum (Trichosurus vulpecula)1

Abstract

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.

Cellular and spatial changes in the anuran superior olive across metamorphosis

“…Widely divergent coefficients of error are equivalent to widely divergent squared estimation errors (which are equal to the total variance in an unbiased study) and are statistically undesirable. While some of the newer developmental stereologic studies reduced fluctuations in the number of cells counted per developmental stage and thus in the coefficient of error by adjusting one or more parameters of the sampling scheme over development (e.g., Bendsen et al, 2003;Lewandowski et al, 2003;Samuelsen et al, 2003), others did not or did not provide enough information to judge whether any such adjustments were made (e.g., Duffell et al, 2000;Eckery et al, 2002). We altered the scan grid size over larval development to accommodate the widely varying numbers of cells in the SO by using an adjustment formula.…”

Culture conditions for bovine embryonic stem cell-like cells isolated from blastocysts after external fertilization

“…Those cultured in medium II or III formed bubble-like structures and trophoblast growth was faster; because c-kit proteins present in the trophoblast cells expanded in vitro, the combination of SCF and c-kit promoted the expansion of the blastocyst surface area (Eckary et al 2002). SCF induced relatively fast growth of the trophoblast after embryo adherence, and large globular structures were seen in the cultivation system.…”

Determination of Steroidogenic Potential of Ovarian Cells of the Brushtail Possum (Trichosurus vulpecula)1

“…The follicular classification system was based on that previously described for the brushtail possum [18]. Primordial follicles (type 1) were classified as oocytes surrounded by a layer of flattened or mixed flattened and cuboidal granulosa cells.…”

“…In the brushtail possum, ovarian follicular development begins around Day 50 of pouch life, and antral follicles are common after Day 190 [18], which is shortly after the young has permanently left the pouch [19]. Numerous antral follicles are present throughout both the follicular phase (9-11 days duration) and luteal phase (16-18 days duration) of the estrous cycle (25-28 days duration) and during pregnancy (16-18 days duration, identical to the luteal phase of the estrous cycle).…”