Biomedical subjects

C Tilmann

Publications and source records attributed to C Tilmann.

3 recordsLinked to original sources

PubMed1999

Mesonephric cell migration induces testis cord formation and Sertoli cell differentiation in the mammalian gonad.

In mammals a single gene on the Y chromosome, Sry, controls testis formation. One of the earliest effects of Sry expression is the induction of somatic cell migration from the mesonephros into the XY gonad. Here we show that mesonephric cells are required for cord formation and male-specific gene expression in XY gonads in a stage-specific manner. Culturing XX gonads with an XY gonad at their surface, as a 'sandwich', resulted in cell migration into the XX tissue. Analysis of sandwich gonads revealed that in the presence of migrating cells, XX gonads organized cord structures and acquired male-specific gene expression patterns. From these results, we conclude that mesonephric cell migration plays a critical role in the formation of testis cords and the differentiation of XY versus XX cell types.

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PubMed1998

Sry and the testis: molecular pathways of organogenesis.

The gene Sry acts as a switch, initiating pathways leading to the differentiation of a testis rather than an ovary from the indifferent gonad (genital ridge) in mammals. The early events following Sry expression include rapid changes in the topographical organization of cells in the XY gonad. Sry must therefore initiate signaling pathways that direct male-specific patterns of proliferation, migration, cell-cell organization, and vascularization. We have identified an increase in male-specific proliferation by 12.0 days post coitum, while proliferation in the female gonad declines. We have also observed male-specific cell migration from the mesonephros into the gonad in a composite organ culture system in which gonads from wild-type mice (CD1) and mesonephroi from a transgenic strain expressing beta-galactosidase in all its cells (ROSA26) were grafted together in vitro at the indifferent stage of gonadogenesis. Migration depends on an active signal that requires the presence of a Y chromosome in the gonadal portion of the graft. The signals that trigger migration operate over considerable distances, suggesting either a long-range diffusible factor or the involvement of a rapid and efficient relay mechanism. Identification of the somatic cells contributed from the mesonephros with cell-specific markers indicated that some of the migrating cells were endothelial, revealing differences in processes of vascularization between male and female gonads. A second distinct population of migrating cells lay in close apposition to endothelial cells, and a third population occupied positions circumscribing areas of condensing Sertoli cells.

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PubMed1997

Male-specific cell migration into the developing gonad.

BACKGROUND: The gene Sry acts as a developmental switch, initiating a pathway of gene activity that leads to the differentiation of testis rather than ovary from the indifferent gonad (genital ridge) in mammalian embryos. The early events following Sry expression include rapid changes in the topographical organization of cells in the XY gonad. To investigate the contribution of mesonephric cells to this process, gonads from wild-type mice (CD1), and mesonephroi from a transgenic strain ubiquitously expressing beta-galactosidase (ROSA26), were grafted together in vitro. After culture, organs were fixed and stained for beta-galactosidase activity to identify cells contributed from the mesonephros to the male or female gonad. RESULTS: Migration of mesonephric cells occurred into XY but not XX gonads from 11.5-16.5 days post coitum (dpc). Somatic cells contributed from the mesonephros were distinguished by their histological location and by available cell-specific markers. Some of the migrating cells were endothelial; a second population occupied positions circumscribing areas of condensing Sertoli cells; and a third population lay in close apposition to endothelial cells. CONCLUSIONS: OFFgration from the mesonephros to the gonad is male specific at this stage of development and depends on an active signal that requires the presence of a Y chromosome in the gonad. The signals that trigger migration operate over considerable distances and behave as chemoattractants. We suggest that migration of cells into the bipotential gonad may have a critical role in initiating the divergence of development towards the testis pathway.

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