Biology subjects

Null, R. W.

Publications and source records attributed to Null, R. W..

3 recordsLinked to original sources

bioRxiv2024

A genome resource for the marine annelid Platynereis dumerilii

The marine annelid Platynereis dumerilii is a model organism used in many research areas including evolution and development, neurobiology, ecology and regeneration. Here we present the genomes of P. dumerilii (laboratory culture reference and a single individual assembly) and of the closely related P. massiliensis and P. megalops (single individual assembly) to facilitate comparative genomic approaches and help explore Platynereis biology. We used long-read sequencing technology and chromosomal-conformation capture along with extensive transcriptomic resources to obtain and annotate a draft genome assembly of [~]1.47 Gbp for P. dumerilii, of which more than half represent repeat elements. We predict around 29,000 protein-coding genes, with relatively large intron sizes, over 38,000 non-coding genes, and 105 miRNA loci. We further explore the high genetic variation ([~]3% heterozygosity) within the Platynereis species complex. Gene ontology reveals the most variable loci to be associated with pigmentation, development and immunity. The current work sets the stage for further development of Platynereis genomic resources.

genomics↗

bioRxiv2024

Sex-biased gene expression precedes sexual dimorphism in the agonadal annelid Platynereis dumerilii

Gametogenesis is the process by which germ cells differentiate into mature sperm and oocytes, cells essential for sexual reproduction. The sex-specific molecular programs that drive spermatogenesis and oogenesis can also serve as sex identification markers. Platynereis dumerilii is a research organism that has been studied in many areas of developmental biology. However investigations often disregard sex, as P. dumerilii juveniles lack sexual dimorphism. The molecular mechanisms of gametogenesis in the segmented worm P. dumerilii are also largely unknown. In this study, we used RNA sequencing to investigate the transcriptomic profiles of gametogenesis in P. dumerilii juveniles. Our analysis revealed that sex-biased gene expression becomes increasingly pronounced during the advanced developmental stages, particularly during the meiotic phases of gametogenesis. We identified conserved genes associated with spermatogenesis, such as dmrt1, and a novel gene psmt, that is associated with oogenesis. Additionally, putative long non-coding RNAs were upregulated in both male and female gametogenic programs. This study provides a foundational resource for germ cell research in P. dumerilii, markers for sex identification, and offers comparative data to enhance our understanding of the evolution of gametogenesis mechanisms across species. Summary statementThis study provides insights into the mechanisms of gametogenesis in Platynereis dumerilii through comparative transcriptomics, unveiling sex-biased genes, including conserved and novel genes, governing this largely unexplored process.

developmental biology↗

bioRxiv2021

Segment number threshold determines juvenile onset of germline cluster proliferation in Platynereis dumerilii

Many animals rely on sexual reproduction to propagate by using gametes (oocytes and sperm). Development of sexual characters and generation of gametes are tightly coupled with the growth of an organism. Platynereis dumerilii is a marine segmented worm which has been used to study germline development and gametogenesis. Platynereis has 4 Primordial Germ Cells (PGCs) that arise early in development and these cells are thought to give rise to germ cell clusters found across the body in the juvenile worms. The germ cell clusters eventually form the gametes. The stages of germline development and how the 4 PGCs become the numerous germ cell clusters are not well-documented in the juvenile stages. Platynereis, like other segmented worms, grows by adding new segments at its posterior end. The number of segments generally reflect the growth state of the worms and therefore is a useful and easily measurable growth state metric. To understand how growth correlates with development and gametogenesis, we investigated germline development across several developmental stages using germline/multipotency markers. We found that segment number predicted the state of germline development and the abundance of germline clusters. Additionally, we found that keeping worms short in segment number via changing external conditions or via amputations supported segment number threshold requirement for germline development. Finally, we asked if these clusters in Platynereis 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 Platynereis, suggesting a strictly germline nature. Overall, these molecular analyses suggest a previously unidentified developmental transition dependent on the growth state in juvenile Platynereis when germline proliferation is substantially increased.

developmental biology↗