Comparative cellular biology of vertebrate primordial oocytes

• Autores: Laasya Dhandapani
• Directores de la Tesis: Elvan Boke (dir. tes.)
• Lectura: En la Universitat Pompeu Fabra ( España ) en 2022
• Idioma: español
• Tribunal Calificador de la Tesis: Oriol Gallego Moli (presid.), Felix Campelo Aubarell (secret.), Esteban Kleinman Hoijman (voc.)
• Programa de doctorado: Programa de Doctorado en Biomedicina por la Universidad Pompeu Fabra
• Materias:
  • Ciencias de la vida
    • Biología celular
• Enlaces
  • Tesis en acceso abierto en: TDX
• Resumen
  • español

    En este proyecto, hemos desarrollado métodos que permiten la caracterización comparativa basada en imágenes en vivo de ovocitos primordiales de humano, ratón y Xenopus. Mostramos que los ovocitos primordiales en las tres especies de vertebrados contienen lisosomas, aparato de Golgi y mitocondrias activos. Mientras que los ovocitos humanos y de Xenopus tienen el cuerpo de Balbiani caracterizado por una densa acumulación de mitocondrias en su citoplasma, en los ovocitos de ratón no encontramos un cuerpo de Balbiani. En cambio, demostramos que lo que se usó previamente como marcador para el cuerpo de Balbiani en ovocitos primordiales de ratón es, de hecho, un aparato de Golgi en forma de anillo que no está asociado funcionalmente con la latencia de los ovocitos. Nuestro trabajo proporciona los primeros conocimientos sobre la organización del citoplasma en los ovocitos primordiales de mamíferos y aclara las ventajas y limitaciones relativas de elegir diferentes organismos modelo para estudiar la latencia de los ovocitos.

  • English

    In sexually reproducing animals, female germline cells called primordial oocytes are formed before the time of birth. They represent the fixed reserve from which fertilizable eggs are produced during the entire reproductive lifespan of the animal. In mammals, primordial oocytes have the remarkable ability to remain dormant for a long time, spanning just a few weeks in mice to several decades in humans. As the donor of virtually all the organelles in the developing embryo, it is necessary to understand the mechanisms by which oocytes maintain fitness for decades and why they eventually fail with age. Moreover, in the primordial oocytes of several species studied thus far, a Balbiani body, a phase-separated compartment consisting of organelles including mitochondria and Golgi apparatus, and ribonucleoprotein (RNP) particles has been observed. The Balbiani body is present only in primordial oocytes and is disassembled in growing oocytes. Thus, the Balbiani body is linked to dormancy. However, the cellular biology of primordial oocytes still remains largely unexplored.

    In this project, we developed enabling methods for live-imaging based comparative characterization of Xenopus, mouse and human primordial oocytes. This allowed us to address key questions about the cell biology of primordial oocytes such as the activity and dynamics of organelles and their association with dormancy. We show that primordial oocytes in all three vertebrate species contain active lysosomes, Golgi apparatus and mitochondria. While human and Xenopus oocytes have a Balbiani body characterized by a dense accumulation of mitochondria in their cytoplasm, we did not find a Balbiani body in mouse oocytes. Instead, we demonstrate what was previously used as a marker for the Balbiani body in mouse primordial oocytes is in fact a ring-shaped Golgi apparatus that is not functionally associated with oocyte dormancy. Our work provides the first insights into the organisation of the cytoplasm in mammalian primordial oocytes, and clarifies relative advantages and limitations of choosing different model organisms for studying oocyte dormancy.