Metzger Bria M.

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Last Name
Metzger
First Name
Bria M.
ORCID
0000-0002-7721-3034

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  • Article
    Segment number threshold determines juvenile onset of germline cluster expansion in Platynereis dumerilii
    (Wiley, 2021-11-18) Kuehn, Emily ; Clausen, David S. ; Null, Ryan W. ; Metzger, Bria M. ; Willis, Amy D. ; Ozpolat, B. Duygu
    Development of sexual characters and generation of gametes are tightly coupled with growth. Platynereis dumerilii is a marine annelid that has been used to study germline development and gametogenesis. P. dumerilii has germ cell clusters found across the body in the juvenile worms, and the clusters eventually form the gametes. Like other segmented worms, P. dumerilii grows by adding new segments at its posterior end. The number of segments reflect the growth state of the worms and therefore is a useful and measurable growth state metric to study the growth-reproduction crosstalk. To understand how growth correlates with progression of gametogenesis, we investigated germline development across several developmental stages. We discovered a distinct transition period when worms increase the number of germline clusters at a particular segment number threshold. Additionally, we found that keeping worms short in segment number, by manipulating environmental conditions or via amputations, supported a segment number threshold requirement for germline development. Finally, we asked if these clusters in P. dumerilii play a role in regeneration (as similar free-roaming cells are observed in Hydra and planarian regeneration) and found that the clusters were not required for regeneration in P. dumerilii, suggesting a strictly germline nature. Overall, these molecular analyses suggest a previously unidentified developmental transition dependent on the growth state of juvenile P. dumerilii leading to substantially increased germline expansion.
  • Article
    Annelid adult cell type diversity and their pluripotent cellular origins
    (Nature Research, 2024-04-12) Alvarez-Campos, Patricia ; Garcia-Castro, Helena ; Emili, Elena ; Perez-Posada, Alberto ; del Olmo, Irene ; Peron, Sophie ; Salamanca-Diaz, David A. ; Mason, Vincent ; Metzger, Bria M. ; Bely, Alexandra E. ; Kenny, Nathan J. ; Ozpolat, B. Duygu ; Solana, Jordi
    Many annelids can regenerate missing body parts or reproduce asexually, generating all cell types in adult stages. However, the putative adult stem cell populations involved in these processes, and the diversity of cell types generated by them, are still unknown. To address this, we recover 75,218 single cell transcriptomes of the highly regenerative and asexually-reproducing annelid Pristina leidyi. Our results uncover a rich cell type diversity including annelid specific types as well as novel types. Moreover, we characterise transcription factors and gene networks that are expressed specifically in these populations. Finally, we uncover a broadly abundant cluster of putative stem cells with a pluripotent signature. This population expresses well-known stem cell markers such as vasa, piwi and nanos homologues, but also shows heterogeneous expression of differentiated cell markers and their transcription factors. We find conserved expression of pluripotency regulators, including multiple chromatin remodelling and epigenetic factors, in piwi+ cells. Finally, lineage reconstruction analyses reveal computational differentiation trajectories from piwi+ cells to diverse adult types. Our data reveal the cell type diversity of adult annelids by single cell transcriptomics and suggest that a piwi+ cell population with a pluripotent stem cell signature is associated with adult cell type differentiation.