Miret-Cuesta, M. | Search bioRxiv

bioRxiv2023

A novel regulatory mechanism of actin cytoskeleton dynamics through a neural microexon in DAAM1 is necessary for memory formation

Actin cytoskeleton dynamics is critical for nervous system development and function, yet the role of alternative splicing in controlling these processes is poorly understood. A highly conserved subset of neuronal-specific microexons coordinates fundamental aspects of nervous system biology. A subset of these exons is enriched in genes involved in actin cytoskeleton, yet their functions are unknown. Here, we focus on a microexon in DAAM1, a member of the formin-homology-2 (FH2) domain class of proteins, which have diverse functions associated with the reorganization of the actin cytoskeleton. Remarkably, splicing of the microexon extends the linker region of the DAAM1 FH2 domain and leads to qualitative and quantitative changes in actin polymerization. Deletion of the microexon results in neuritogenesis defects and increased calcium influx in differentiated neurons. Moreover, mice harboring the deletion exhibit postsynaptic defects, reduced number of immature dendritic spines, impaired long-term potentiation, and deficits in memory formation. These deficits are associated with increased RHOA/ROCK signaling, pivotal in controlling actin-cytoskeleton dynamics, and were rescued by treatment with a ROCK inhibitor. We thus demonstrate that a conserved neuronal microexon in DAAM1 is critical for controlling actin dynamics through the RHOA/ROCK signaling pathway and is necessary for normal cognitive functioning.

neuroscience↗

bioRxiv2020

A developmentally programmed splicing failure attenuates the DNA damage response during mammalian zygotic genome activation

The transition from maternal to embryonic transcriptional control is a crucial step in embryogenesis. However, how alternative splicing is regulated during this process and how it contributes to early development is unknown. Using transcriptomic data from pre-implantation stages of human, mouse and cow, we show that the stage of zygotic genome activation (ZGA) exhibits the highest levels of exon skipping diversity reported for any cell or tissue type. Interestingly, much of this exon skipping is temporary, leads to disruptive non-canonical isoforms, and occurs in genes enriched for DNA damage response in the three species. We identified two core spliceosomal components, Snrpb and Snrpd2, as regulators of these patterns. These genes have low maternal expression at the time of ZGA and increase sharply thereafter. Consistently, microinjection of Snrpb/d2 mRNA into mouse zygotes reduces the levels of temporary exon skipping at ZGA, and leads to an increase in etoposide-induced DNA damage response. Altogether, our results suggest that mammalian embryos undergo an evolutionarily conserved and developmentally programmed specific splicing failure at the time of genome activation that attenuates cellular responses to DNA damage at these early stages.

developmental biology↗