Investigation of active histone marks as barriers to cell-fate changes during reprogramming

• Applicant: Dr. Eva Hörmanseder
• Subject Area: Developmental Biology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 494710866

Vertebrate eggs have the remarkable ability to induce the reprogramming of somatic cell nuclei to enable the production of all cell types of an organism upon nuclear transfer (NT) 1. This capacity to generate all cell types is referred to as totipotency. During NT, the memory of cells must be fully erased in order to enable efficient reprogramming and the consequent generatation of totipotent cells. This has a fundamental impact on regenerative medicine, as progress in understanding the molecular mechanisms of reprogramming to totipotency could allow the generation of any cell type needed for cell replacement therapies. Despite its enormous potential, the molecular mechanisms that allow or impede the conversion of a differentiated ‘donor’ cell to totipotency are not fully understood. Previously, my research revealed that the low efficiency of cell fate conversion via NT is linked to the retention of donor cell type specific memory of an active transcriptional state stabilized by specific histone modifications, namely H3K4 methylation 2. However, the extent to which ‘active’ transcriptional memory impedes or facilitates NT reprogramming is unknown. The overall goal of this proposal is to address the role of active histone modifications in stabilising differentiated cell fates and therefore preventing efficient reprogramming using Xenopus NT-embryos as a model system. Specifically, in the project presented here we propose to 1) develop ”digital reprogramming”, a novel approach based on machine learning to predict candidate active histone modification signatures as epigenetic barriers to reprogramming. 2) functionally characterise such candidate active histone modifications by addressing whether cell fate conversion upon NT is improved after loss-of-function approaches. Importantly, investigating whether active histone modifications can act as epigenetic barriers during reprogramming will enable us to manipulate and lower these barriers. This knowledge will be key to improve reprogramming efficiencies and allow a robust and complete switch in cell fate. The developed tools and the analysis of epigenetic mechanisms that prevent cell-fate reprogramming will give crucial insights into the mechanisms of cellular memory, which prevent unwanted changes in cell fate during development and that are impaired in disease.

• DFG Programme: Research Grants