Cellular, ultrastructural and molecular analyses of epidermal cell development in the planarian Schmidtea mediterranea

摘要

Abstract The epidermis is essential for animal survival, providing both a protective barrier and cellular sensor to external environments. The generally conserved embryonic origin of the epidermis, but the broad morphological and functional diversity of this organ across animals is puzzling. We define the transcriptional regulators underlying epidermal lineage differentiation in the planarian Schmidtea mediterranea , an invertebrate organism that, unlike fruitflies and nematodes, continuously replaces its epidermal cells. We find that Smed-p53 , Sox and Pax transcription factors are essential regulators of epidermal homeostasis, and act cooperatively to regulate genes associated with early epidermal precursor cell differentiation, including a tandemly arrayed novel gene family ( prog ) of secreted proteins. Additionally, we report on the discovery of distinct and previously undescribed secreted organelles whose production is dependent on the transcriptional activity of soxP-3 , and which we term Hyman vesicles. Highlights ? Uncover role in early epidermal progenitor specification for SOXP-3 and PAX-2/5/8. ? Identify putative binding sites for P53/SOX/PAX factors near loci of epidermal specification genes. ? Define a transcriptional hierarchy/network for epidermal differentiation in planarians. ? Developed an antibody specific for a family member of the strongly expressed PROG family of proteins. ? Presence of PROG-2-5 protein in epidermal and early progeny cells solidifies lineage relationship. ? Electron microscopy of epidermis and progenitors uncovers new organelle. ? We term new organelle Hyman vesicle in honor of the late zoologist.