Biology subjects

Collinson, J. M.

Publications and source records attributed to Collinson, J. M..

5 recordsLinked to original sources

bioRxiv2025

Genetic and morphological analysis shows the Nechisar Nightjar is a hybrid

The Nechisar Nightjar Caprimulgus solala was described only from a single wing collected as roadkill from Nechisar National Park in Ethiopia in 1990. To resolve its taxonomic status a sample was taken from the Nechisar Nightjar holotype and 53 other Afrotropical nightjars, and genomic DNA extracted for sequencing of one mitochondrial and three nuclear genes. The genetic analysis concluded that Nechisar Nightjar is most likely a hybrid, with mitochondrial DNA of Standard-winged Nightjar Caprimulgus longipennis and nuclear alleles from Standard-winged Nightjar and a second nightjar species that has not yet been sequenced. Morphometric and plumage analysis suggests that the paternal parent is Freckled Nightjar Caprimulgus tristigma, for which no nuclear sequence data are currently available.

zoology↗

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↗

bioRxiv2024

Sox9 prevents retinal degeneration and is required for limbal stem cell differentiation in the adult mouse eye

Sox9 is a transcription factor with multiple roles during development and in adult organ homeostasis. In the adult eye, Sox9 expression persists in several cell types, including the retinal pigmented epithelium cells and the Muller glial cells, as well as in the limbal and corneal basal epithelia. To uncover the role of Sox9 in these cell types, we induced the deletion of the gene in adult mice. We found that, after Sox9 ablation, mutant mice undergo a severe process of retinal degeneration characterized by the loss of Muller glial cells and complete depletion of the photoreceptors layer. Moreover, by combining single-cell RNA sequencing and Sox9 lineage tracing, we found that Sox9 is expressed in a basal limbal stem cell population with the ability to form two types of long-lived cell clones involved in stem cell maintenance and homeostasis. Mosaic analysis of Sox9 positive and negative cells confirmed that the gene is essential for limbal stem cell differentiation. Our results show that Sox9 is required for the maintenance of retinal integrity and for limbal stem cell differentiation in the adult mouse eye.

developmental biology↗

bioRxiv2024

Spiral-eyes: A soft active matter model of in vivo corneal epithelial cell migration

The mammalian cornea constantly regenerates its outer epithelial layer. Cells lost by abrasion are replaced by division of both corneal epithelial cells and stem cell populations around the corneal periphery, the limbus. Limbal-derived epithelial cells migrate into the cornea, maintaining equal rates of cell loss and replacement (the XYZ hypothesis). This process produces a striking stable spiral cell motion pattern across the corneal surface, with a central vortex. Here, we show that this spiral pattern can be explained by the interplay of limbus position, cell division, extrusion, and collective cell migration along the curved corneal surface. Using dissected LacZ mosaic murine corneas, we inferred the surface flow field by following stripe edges, revealing a tightening spiral. To explain these flow fields, we developed a cell-level in silico model treating corneal epithelial cells as soft, self-propelled particles with density-dependent proliferation and extrusion rates, and noisy alignment of migration direction. Even without global guidance cues, the model predicted stripes and spirals closely recapitulating experiment. A complementary continuum description generalised the XYZ hypothesis. Spiral formation was robust to curvature changes, but not topology, and sensitive to limbal stem cells and flocking alignment, showing how swarm physics on curved surfaces can explain tissue-scale biological processes.

biophysics↗

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↗