Brown, A. F. | Search bioRxiv

bioRxiv2025

Long-term iododeoxyuridine labelling analysis finds no evidence of ovarian germline stem cell activity in adult or ageing mice

The purpose of this study was to determine whether ovarian germline stem cells or any adult mitotic cell type contribute to the adult oocyte pool in vivo from early adult through to aging mice. Long-term thymidine analogue labelling assays using iododeoxyuridine (IdU) were performed to identify mitotic cells and their descendants by immunohistochemistry for IdU and germline markers Ddx4 and Oct4. C57BL/6 mice at 10 weeks, 5 months and 12 months old were given IdU for 21-30 days through their drinking water to label all dividing cells, followed by washout periods of 0-10 weeks. Over 60,000 ovarian somatic cells and oocytes were scored in 111 ovaries. No double labelling of IdU with germline stem cell markers was found in oocytes at any stage of maturity, in mice at any age. In contrast, IdU exposure during embryogenesis resulted in large numbers of labelled oocytes in postnatal mice, as expected. We were therefore unable to confirm mitotic activity in stem cells or any other progenitor replenishing the oocyte pool in C57BL/6 mice. There is no evidence that quiescent stem cells are activated when the oocyte pool is depleted by age.

cell biology↗

bioRxiv2022

First genetic data for the Critically Endangered Cuban endemic Zapata Rail Cyanolimnas cerverai, and the taxonomic implications

The taxonomic affinity of the near-flightless Zapata Rail Cyanolimnas cerverai, a Critically Endangered and highly localized species endemic to Cuba, has long been debated. Morphological analyses have suggested that this species, which constitutes a monotypic genus, could be related either to the extinct Tahitian Cave Rails (Nesotrochis sp.) or to the South American rail tribe Pardirallini, i.e., the genera Neocrex, Mustelirallus, and Pardirallus. Whilst pronounced phenotypic convergence-and divergence-among rails have repeatedly proven morphology-based phylogenies unreliable, thus far no attempt to sequence DNA from the enigmatic Cyanolimnas has succeeded. In this study, we extracted historic DNA from a museum specimen collected in 1927 and sequenced multiple short fragments that allowed us to assemble a partial sequence of the mitochondrial cytochrome oxidase I gene. Phylogenetic analyses confirm that Cyanolimnas belongs in tribe Pardirallini as sister to genus Neocrex, from which it diverged about six million years ago. Their divergence from Mustelirallus was estimated at about eight million years ago. Based on morphology and our mitochondrial phylogeny, we conclude that it is unjustified to retain the monotypic genus Cyanolimnas and tentatively recommend that C. cerverai and the two Neocrex species are ascribed to genus Mustelirallus. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

zoology↗