Patterns of cellular localization of germline proteins in solitary and colonial tunicates

Author(s)

David dos Santos Soares

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2019-09-03

Examining board members

Federico David Brown Almeida; Emilio de Lanna Neto; Chao Yun Irene Yan

• Advisor: Federico David Brown Almeida

Abstract

Tunicata is a group of marine invertebrate chordates with solitary and colonial species. Recent phylogenies suggest that the colonial species of the Botryllus + Symplegma clade with both sexually and asexually reproduction capabilities evolved from a solitary, sexually reproducing ancestor. Germ Stem Cells (GSCs) are located in the gonads but also in the cells outside gonads of extant colonial botryllid ascidians. Vasa, Piwi, PL10 and YB1 are markers that were previously used to identify GSCs in ascidian. Our objective is to compare the occurrence of GSCs in the solitary ascidian Styela canopus and in the colonial Symplegma rubra, which represent two taxa relatively close to botryllids in the phylogeny. Using antibodies that specifically bind to germline proteins generated for other species of ascidians, we validate their specificity for the species of interest (Styela canopus and Symplegma rubra) using western blot and immunohistochemistry on histological sections of these species. According to expectations, we observed Vasa and Piwi expression in oocytes and PL10 and YB1 expression in both oocytes and testes. We have documented positive Vasa and Piwi cells in the circulatory system of the colonial S. rubra, as previously shown for botryllids. However, we also observed some Vasa and Piwi-positive cells in the hemocoel of solitary S. canopus in at least one blood cell type, and in other somatic tissues like gut, mantle and branchial sac. The presence of these germline proteins in cell types outside gonads of solitary S. canopus suggests that: (1) positive cells may represent undifferentiated (GSC-related) cell types involved in other developmental processes (e.g. regeneration) or (2) these GSC-expressing proteins have acquired functions in S. canopus somatic cells that remain unknown. According to literature reports for Ciona, we also observed the presence of YB1 in both solitary and colonial oocytes, however YB1 was present only in germ cells in the testis of the solitary S. canopus. Although the expression patterns reported here in the testes do not allow us to determine the function of YB1 in spermatogenic cells, it is possible to speculate that YB1 plays a role as RNA chaperone or in the regulation of translation during spermatogenesis (AU)

• FAPESP's process: 17/13758-0 - ncRNAs in colonial ascidians
• Grantee: David dos Santos Soares
• Support Opportunities: Scholarships in Brazil - Master