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Gonocytes in testes of neonatal rats express the c-kit gene
1Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
Abstract:
Information gathered from mutant mouse models and from studies on normal puberal and adult animals points to the product of the c-kit gene, a tyrosine kinase surface receptor, and the kit-ligand (KL) as important for gametogenesis in males. In fetuses, KL serves as a survival factor for primordial germ cells, at least in vitro, and in adults activity of the c-kit gene has been indirectly related to survival and subsequent development of differentiating spermatogonia. However, because of the structural complexity of the seminiferous epithelium in adults, c-kit mRNA has not yet been definitively localized to one or more types of spermatogenic cells. In addition, no information is currently available regarding the possible involvement of the c-kit protein and its ligand in mediating germ cell development and/or Sertoli-germ cell interactions immediately after birth when events critical for later onset of spermatogenesis are ongoing. Thus, the aims of the current study were (1) to determine whether the c-kit gene is expressed in testes of neonatal and adult rats and, if so, by what specific cell types, and (2) to determine if those cells expressing the gene also produce the c-kit receptor protein. For this, we isolated total RNA from testes of pups aged days 1-5 and from adult rat testes, and probed for the presence of c-kit mRNA with Northern analysis. We identified the cells containing the c-kit message by carrying out in situ hybridization with digoxigenin-labeled probes, thus allowing the colorimetric signal to be assigned beyond doubt to individual cells in sections of testes. We also utilized Western analysis and immunolocalization to confirm the presence of the c-kit receptor protein in testes at these ages and to identify those cells types producing it. Our findings indicate that (1) neonatal gonocytes express the c-kit gene and produce the receptor protein on postnatal days 1 through 5, spanning the time when they resume dividing and migrating, and (2) spermatogonia and, to a lesser extent, spermatocytes and spermatids of adults express the gene but c-kit protein is present in detectable amounts only in spermatogonia and possibly a few early primary spermatocytes.
Insights
The c-kit gene and its ligand are crucial for male gametogenesis. This study found c-kit gene expression and protein production in neonatal rat gonocytes and adult spermatogonia, crucial for germ cell development.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Molecular Endocrinology
Background:
- The c-kit gene product, a tyrosine kinase receptor, and its ligand (KL) are implicated in male gametogenesis.
- Previous studies suggest KL is a survival factor for fetal germ cells, and c-kit activity aids adult spermatogonia survival and development.
- However, definitive localization of c-kit mRNA and protein in specific spermatogenic cells, especially during the critical neonatal period, remains unclear.
Purpose of the Study:
- To investigate c-kit gene and protein expression in neonatal and adult rat testes.
- To identify the specific cell types expressing c-kit mRNA and protein.
- To elucidate the role of c-kit in germ cell development and Sertoli-germ cell interactions during early postnatal life.
Main Methods:
- Northern analysis to detect c-kit mRNA in neonatal (days 1-5) and adult rat testes.
- In situ hybridization using digoxigenin-labeled probes to localize c-kit mRNA within testicular cells.
- Western analysis and immunolocalization to confirm c-kit receptor protein presence and identify producing cell types.
Main Results:
- Neonatal gonocytes express c-kit gene and produce the receptor protein from postnatal days 1-5, coinciding with their migration and division.
- In adult testes, c-kit gene is expressed in spermatogonia, spermatocytes, and spermatids.
- Detectable c-kit protein in adults is primarily found in spermatogonia and potentially early primary spermatocytes.
Conclusions:
- The c-kit gene is expressed in neonatal gonocytes and adult spermatogonia, with protein production confirmed in these cell types.
- These findings highlight the role of c-kit signaling in critical early developmental stages of male germ cells.
- The study provides definitive cellular localization of c-kit expression, advancing understanding of gametogenesis regulation.