Self-sabotage in the early mammalian embryo: investigating the interplay between DNA damage responses, splicing failure and zygotic reprogramming

Introduction

In mammals, oocyte fertilisation is followed by a dramatic epigenetic and transcriptomic reprogramming to prepare the newly formed embryo for subsequent development. Preserving genome integrity is critical at these early stages, when all cells have the potential to contribute to a large proportion of the embryo including the germ line.

Background

Despite this work by ourselves and others suggesting that the ATM kinase driven DNA damage response (DDR) to double strand breaks is dampened in the early embryo, the ATR kinase mediated DDR appears fully active. This may even function in zygotic reprogramming, as DNA damage acting through this pathway can reprogram embryonic stem cells to a more totipotent state reminiscent of the early post-fertilisation embryo.

Current Understanding

Beyond this, little is known about DDRs in the early embryo. However, we have recently identified a programmed splicing failure that accompanies the transcriptomic reprogramming of the embryo and disproportionately disrupts transcripts coding for DDR genes. Furthermore, splicing inhibition has been found to reprogram embryonic stem cells to a more totipotent state, and we have found this also inordinately disrupts DDR gene transcripts.

Research Questions

These findings raise three fundamental questions:

1. Why is a dampened ATM dependent DDR found in early cleavage stage embryos?
2. Does an ATR mediated DDR play a role in embryonic reprogramming and totipotency emergence?
3. What is the impact of the programmed splicing failure on embryo development and totipotency, and is it related to DDR regulation?

Methodology

We will take a multidisciplinary approach to answer these questions using a combination of high-throughput -omics and focused techniques in the early mouse embryo.

Expected Outcomes

The knowledge gained will represent a breakthrough in the understanding of early mammalian post-fertilisation development, allowing us to unravel the interaction between the unique cellular processes that occur at this time, genome integrity control, and splicing failure.