Characterization of human extended pluripotent stem cells as a model for the initiation of X chromosome inactivation

• Grant number: 21/12318-1
• Support Opportunities: Scholarships in Brazil - Master
• Effective date (Start): March 01, 2022
• Effective date (End): September 30, 2023
• Field of knowledge: Biological Sciences - Genetics - Human and Medical Genetics
• Principal Investigator: Lygia da Veiga Pereira
• Grantee: Daniel Minatti Felismino
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

X Chromosome Inactivation (XCI) is an important cellular process that occurs naturally in females of several animal species, including placental mammals, preventing X-linked gene transcripts from being present twice as much in females than in males. It consists in the silencing of one of the two X chromosomes in female cells, acting as an epigenetic mechanism of genic dosage compensation. In humans, XCI begins at the first stages of embryonic development, between the 4-cell stage and preimplantation blastocyst, and even though there are several studies aiming to fully understand this process, there are still some difficulties in relation to, especially, its initiation in humans. That happens mostly because of the lack of in vitro models capable of reliably reproducing the first stages of human embryonic development, taking into consideration the ethical barriers related to the obtention of human embryos, added to the difficulties in generating, by cell differentiation, cell lines that are found in these initial stages of development. Recently, new studies aiming to differentiate blastocyst-derived human embryonic stem cells into stem cells from early stages of development, such as the naive Pluripotent Stem Cells (naive PSCs), have been published. However, further characterization of these cells, including analysis of the XCI state, for example, which is considered an important parameter for the identification of the real stage in which the cell is found, have shown both positive and negative aspects when compared to what would be expected in true naive-state human pluripotent stem cells. This project aims to analyze the XCI state in human Extended Pluripotent Stem Cells (hEPSCs), a recently described cell type which can be generated through differentiation from several human PSCs, and which have shown similar characteristics to what is expected from human embryonic stem cells from early stages of development.