Biology subjects

Casella, C. E.

Publications and source records attributed to Casella, C. E..

2 recordsLinked to original sources

bioRxiv2025

Trailer Hitch coordinates P-body organization and facilitates transcript-specific mRNA regulation through nuclear actin-mediated feedback loop

Processing bodies (P-bodies) are cytoplasmic granules that regulate mRNA storage, repression, and decay, yet how their internal organization supports selective mRNA regulation remains poorly understood. Here, we show that the conserved LSm protein Trailer Hitch (Tral) is a key organizer of P-body architecture and function in the Drosophila melanogaster female germline. Using quantitative confocal imaging, super-resolution microscopy, and chemical perturbation of intermolecular interactions, we demonstrate that Tral coordinates the incorporation and spatial organization of the core P-body proteins Me31B and Cup. Loss of Tral alters their partitioning into P-bodies, promotes demixing into distinct subdomains, and shifts condensates toward a less dynamic, structurally heterogeneous state. These organizational changes have functional consequences for mRNA storage: Tral depletion selectively releases maternal mRNA bicoid, while nanos mRNA remains P-body associated and stable. We further identify twinstar mRNA, encoding the actin regulator Cofilin, as a Tral-dependent P-body client whose localization and organization within P-bodies requires Tral:RNA interactions and electrostatic forces. Reduced twinstar mRNA levels in the absence of Tral are associated with decreased nuclear G-actin and altered transcription of me31B and cup, revealing a potential feedback mechanism that links cytoplasmic P-body organization to nuclear gene expression. Together, these findings establish Tral as a central regulator of P-body architecture that couples condensate organization to selective mRNA regulation and transcriptional homeostasis.

cell biology↗

bioRxiv2024

The role of ER exit sites in maintaining P-body organization and transmitting ER stress response during Drosophila melanogaster oogenesis

Processing bodies (P-bodies) are cytoplasmic membrane-less organelles which host multiple mRNA processing events. While the fundamental principles of P-body organization are beginning to be elucidated in vitro, a nuanced understanding of how their assembly is regulated in vivo remains elusive. Here, we investigate the potential link between ER exit sites and P-bodies in Drosophila melanogaster egg chambers. Employing a combination of live and super-resolution imaging, we found that P-bodies associated with ER exit sites are larger and less mobile than cytoplasmic P-bodies, indicating that they constitute a distinct class of P-bodies which are more mature than their cytoplasmic counterparts. Moreover, we demonstrate that altering the composition of ER exit sites has differential effects on core P-body proteins (Me31B, Cup, and Trailer Hitch) suggesting a potential role for ER exit sites in P-body organization. We further show that in the absence of ER exit sites, P-body integrity is compromised and the stability and translational repression efficiency of the maternal mRNA, oskar, are reduced. Finally, we show that ER stress is communicated to P-bodies via ER exit sites, highlighting the pivotal role of ER exit sites as a bridge between membrane-bound and membrane-less organelles in ER stress response. Together, our data unveils the significance of ER exit sites not only in governing P-body organization, but also in facilitating inter-organellar communication during stress, potentially bearing implications for a variety of disease pathologies.

cell biology↗