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

Abstract

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.

Nanos Is Expressed in Somatic and Germline Tissue during Larval and Post-Larval Development of the Annelid Alitta virens

“…The obtained results show the expression of a pluri-/multipotent stem cell marker (nanos) in the blastema from an early stage. These data also support the opinion that blastemal cells are mostly derived from cells of the segment adjacent to the amputation site, and that the cluster of PGCs is not required for regeneration in the nereid polychaetes [24,32,45].…”

“…In the annelid A. virens , at the sixth to seventh cleavage, a robust expression is detected in very small cells, although it is also detected at lower levels throughout the embryo. These cells are products of the first cell divisions of the mesoteloblasts (4d daughter blastomeres) [ 41 ] and are putative PGCs [ 41 , 42 , 43 , 44 , 45 ]. A broad Avi-nanos expression encompasses all 4d descendants, not only those which will give rise to the primordial germ cells but also the major derivative of mesoteloblasts: segmental mesoderm, which includes body wall, visceral muscle, and coelomic cavity linings.…”

Cell type diversity in a developing octopus brain

“…Probe sets were ordered for Ov-glut, Ov-th, Ov-vacht, Ov-LOC118767670 and Ov-apolpp from Integrated DNA Technologies, Inc (Data S6). Probe sets were designed with the insitu_probe_generator 26 followed by automated blasting and formatting to minimize off-target hybridization with a custom script 27 . Imaging was done either with a Leica DM6 upright microscope (IHC, colorimetric ISH) or an Olympus confocal microscope Fluoview FV1000 (HCR).…”

Comparisons of cell proliferation and cell death across life histories in the hemichordate Schizocardium californicum

“…Complementary DNA sequences specific to genes of interest were submitted to the in situ probe generator from the Ozpolat Lab (138). Gene orthology was determined by collecting sequences of interest from related species and then building gene trees.…”