Piszczek, A. | bioRxiv Science

bioRxiv2025

AXL governs axolotl cardiac regeneration and directs mammalian cardiomyocyte dedifferentiation

Cardiac injury outcomes vary widely across species, from complete regeneration to irreversible scarring. Using single-nucleus multiomics and spatial transcriptomics, we generated a spatially resolved atlas of axolotl heart regeneration following injury, identifying a distinct border-zone cardiomyocyte population with a pro-regenerative transcriptional program. Ligand-receptor analysis of the border zone niche identified enrichment of the receptor tyrosine kinase AXL in injury-responsive cardiomyocytes and its ligand Gas6 in endothelial cells. Functional perturbation demonstrated AXL requirement for border-zone cardiomyocyte activation and axolotl heart regeneration. In murine cardiomyocytes, AXL overexpression induced sarcomere disassembly, metabolic rewiring, and immature gene expression without triggering proliferation. These findings show that AXL signaling induces cardiomyocyte dedifferentiation and uncouples dedifferentiation from cell cycle re-entry, providing mechanistic insight into cellular plasticity during heart regeneration.

cell biology↗

bioRxiv2020

A RIF1 and KAP1-based, double-bookmarking system generates a toggle switch that stabilises the identities of the active and inactive X chromosomes during random X inactivation in mouse

The onset of random X inactivation in mouse requires the switch from a symmetric to an asymmetric state, where the identities of the future inactive and active X chromosomes are assigned. Here we show that RIF1 and KAP1 are two fundamental factors for the definition of the asymmetry. Our data show that at the onset of mESC differentiation, upregulation of the long non-coding RNA Tsix weakens the symmetric RIF1 association with the Xist promoter, and opens a window of opportunity for a more stable association of KAP1. KAP1 is required to sustain high levels of Tsix, thus reinforcing and propagating the asymmetry, and, as a result, marking the future active X chromosome. Furthermore, we show that RIF1 association with the future inactive X chromosome is essential for Xist upregulation. This double-bookmarking system, based on the mutually exclusive relationships of Tsix and RIF1, and RIF1 and KAP1, thus coordinates the identification of the inactive and active X chromosomes and initiates a self-sustaining loop that transforms an initially stochastic event into a stably inherited asymmetric X chromosome state.

molecular biology↗