Transcriptional profiling of laser captured gonadal tissue from the planarian Schmidtea mediterranea

Female germ cells develop into oocytes, with the capacity for totipotency. In most animals, these remarkable cells are specified during development and cannot be regenerated. By contrast, planarians, known for their regenerative prowess, can regenerate germ cells. To uncover mechanisms required for female germ cell development and regeneration, we generated gonad-specific transcriptomes and identified genes whose expression defines progressive stages of female germ cell development. Strikingly, early female germ cells share molecular signatures with the pluripotent stem cells driving planarian regeneration. We uncovered spatial heterogeneity within somatic ovarian cells and found that a regionally enriched FoxL homolog is required for oocyte differentiation, but not specification, suggestive of functionally distinct somatic compartments. Unexpectedly, a neurotransmitter-biosynthetic enzyme, AADC, is also expressed in somatic gonadal cells, and plays opposing roles in female and male germ cell development. Thus, somatic gonadal cells deploy conserved factors to regulate germ cell development and regeneration in planarians. Overall design: Acetone-fixed planarians were cryosectioned, then ovary, testis and non-gonadal tissue were collected using laser capture microdissection. Ovarian tissue samples were collected from 14 worms (10 worms used for cross- sections and 4 worms used for sagittal sections) for each replicate (3 replicates total). Testis and non-gonadal tissue samples were collected from 6 worms for each replicate (4 worms used for cross-sections and 2 worms used for sagittal sections). RNA was extracted using the Arcturus Picopure RNA isolation kit, followed by library generation and RNA-seq