Dynamic relocalization of maternal transcripts during oocyte meiotic maturation

Hwang, Hyojeong

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https://hdl.handle.net/2142/117558 Copy

Description

Title

Dynamic relocalization of maternal transcripts during oocyte meiotic maturation

Author(s)

Hwang, Hyojeong

Issue Date

2022-11-29

Director of Research (if dissertation) or Advisor (if thesis)

Yang, Jing

Doctoral Committee Chair(s)

Yang, Jing

Committee Member(s)

• Bagchi, Indrani C.
• Flaws, Jodi A.
• Zhang, Kai

Department of Study

Comparative Biosciences

Discipline

VMS - Comparative Biosciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• RNA localization
• endoplasmic reticulum
• oocyte maturation
• oocyte-to-embryo transition
• maternal RNAs
• Dnd1
• germline development
• ubiquitin-independent proteasome
• phase transition
• Xvelo1
• Xenopus

Abstract

The oocyte, a fully differentiated single cell, is the unique cell that can re-acquire totipotency upon going through meiotic maturation and fertilization. After fertilization, the embryo divides and differentiates into a multicellular organism. Throughout this process, numerous mechanisms, including transcriptional, post-transcriptional, and post-translational regulation, govern cellular differentiation by precise spatiotemporal gene expression. Asymmetric localization of RNA, as one of the post-transcriptional regulation mechanisms, orchestrates gene expression in the appropriate time and space, ultimately achieving local translation during embryonic development. Therefore, the study of asymmetric RNA localization is essential to understand embryonic development. In this study, using the Xenopus laevis oocytes as our model, we revealed that the level of Dnd1, a master regulator of vertebrate germline development, is controlled by a novel vegetal-to-animal translocation of proteasome RNAs during the oocyte-to-embryo transition. Furthermore, in the course of understanding the mechanism by which the proteasome system is translocated to and restricted in the animal hemisphere, we discovered that the vast majority of the maternal transcripts are associated with the endoplasmic reticulum (ER) in the oocyte. Strikingly, ER-associated transcripts are released into the cytosol during oocyte meiotic maturation. We further showed that the changes in affinity between the RNA-binding proteins (RBPs) and their target RNAs are a potential mechanism that regulates this localization of RNA from the ER to the cytosol. Meanwhile, actin filament-dependent remodeling of the ER, which forms a tubular network in the animal hemisphere, is responsible for the asymmetric localization of proteasomal transcripts in mature eggs. Additionally, we found that germline-specific transcripts are abundant in the insoluble fraction of the Xenopus oocyte, but are solubilized largely during oocyte maturation. Furthermore, we propose the hypothesis that preserving germline transcripts in an insoluble phase serves as a mechanism for maintaining the pluripotency of germ cells against external stimuli. Collectively, this dissertation provides novel insights into the dynamic relocalization of maternal transcripts during oocyte meiotic maturation, which plays a crucial role in achieving proper embryonic development.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Hyojeong Hwang

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