title: Stage-specific tissue and cell interactions play key roles in mouse germ cell specification.
abstract: Primordial germ cells (PGCs) in mice have been recognized histologically as alkaline phosphatase (AP) activity-positive cells at 7.2 days post coitum (dpc) in the extra-embryonic mesoderm. However, mechanisms regulating PGC formation are unknown, and an appropriate in vitro system to study the mechanisms has not been established. Therefore, we have developed a primary culture of explanted embryos at pre- and early-streak stages, and have studied roles of cell and/or tissue interactions in PGC formation. The emergence of PGCs from 5.5 dpc epiblasts was observed only when they were co-cultured with extra-embryonic ectoderm, which may induce the conditions required for PGC formation within epiblasts. From 6.0 dpc onwards, PGCs emerged from whole epiblasts as did a fragment of proximal epiblast that corresponds to the area containing presumptive PGC precursors without neighboring extra-embryonic ectoderm and visceral endoderm. Dissociated epiblasts at these stages, however, did not give rise to PGCs, indicating that interactions among a cluster of a specific number of proximal epiblast cells is needed for PGC differentiation. In contrast, we observed that dissociated epiblast cells from a 6.5-b (6.5+15-16 hours) to 6.75 dpc embryo that had undergone gastrulation gave rise to PGCs. Our results demonstrate that stage-dependent tissue and cell interactions play key roles in PGC determination.
authors.affiliation: Department of Molecular Embryology, Research Institute, Osaka Medical Center for Maternal and Child Health, Murodo-cho, Izumi, Osaka 594-1101, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yoshimizu
authors.forename: M
authors.initials: M
authors.lastname: Obinata
authors.forename: Y
authors.initials: Y
authors.lastname: Matsui
mesh_terms: D000818:Animals; D015415:Biomarkers; D002450:Cell Communication; D002452:Cell Count; D002454:Cell Differentiation; D019070:Cell Lineage; D018920:Coculture Techniques; D046508:Culture Techniques / Q000379:methods; D004475:Ectoderm / Q000166:cytology; D005314:Embryonic and Fetal Development; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D005775:Gastrula / Q000166:cytology; D005854:Germ Cells / Q000166:cytology*; D005865:Gestational Age; D007150:Immunohistochemistry; D008297:Male; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains
chemical_list: D015415:Biomarkers; D005353:Fibronectins