Biology subjects

Hurd, T. R.

Publications and source records attributed to Hurd, T. R..

5 recordsLinked to original sources

bioRxiv2026

A GSK3-dependent phosphorylation switch licenses BNIP3-mediated mitophagy

The turnover of mitochondria through mitophagy is essential for maintaining mitochondrial function and matching mitochondrial content to cellular demand. In many cells, this process is mediated by the paralogous mitochondrial receptors BNIP3 and BNIP3L, which recruit WIPI-family autophagy effectors to initiate mitophagosome formation. However, the mechanisms that activate BNIP3/L remain poorly understood. Here, we show that the kinase GSK3 directly phosphorylates BNIP3, licensing receptor activity and activating mitophagy. Phosphorylation promotes BNIP3 recruitment of WIPI proteins, thereby initiating mitophagosome formation. We identify the critical phosphorylation sites required for this regulation and demonstrate that disruption of these sites abolishes BNIP3-dependent mitophagy. Together, our findings identify phosphorylation as a molecular switch controlling BNIP3/L activity and suggest that receptor phosphorylation may temporally and spatially license mitophagosome formation and mitochondrial clearance.

cell biology↗

bioRxiv2026

A structure-selective endonuclease drives uniparental mitochondrial DNA inheritance

Maternal inheritance of mitochondrial DNA (mtDNA) is a near-universal feature of eukaryotes1, yet the mechanisms that ensure this by preventing paternal mtDNA inheritance have remained unclear. In both Drosophila and humans, mtDNA is actively eliminated from sperm during spermatogenesis, producing mature sperm whose mitochondria lack their genomes2-5. Here we identify Hotaru, a previously uncharacterized, testis-specific GIY-YIG endonuclease, as a central player in this process. We find that Hotaru is expressed in elongated spermatids, localizes to the mitochondrial matrix, and is required for paternal mtDNA elimination. In hotaru mutants, sperm retain mtDNA at levels comparable to those present before the elimination process. Genetic and biochemical analyses show that Hotaru selectively recognizes and cleaves cruciform DNA structures within the mtDNA control region. Together, these findings identify a dedicated nuclease that enforces mitochondrial genome elimination in the animal male germline and reveal that an unexpected structural feature of mtDNA serves as the molecular determinant of its destruction. By recognizing DNA structure rather than specific sequence motifs, this mechanism is inherently robust to the high mutation rate of mitochondrial genomes.

developmental biology↗

bioRxiv2026

Ataxin-2 regulates the synaptonemal complex to ensure chromosome pairing during female meiosis

Sexual reproduction relies on meiotic recombination and the accurate segregation of homologous chromosomes to generate viable, genetically diverse gametes. While the molecular mechanisms of recombination and chromosome segregation are well studied, the upstream regulatory cues that drive expression of key meiotic genes remain poorly understood, especially in metazoans. Emerging evidence suggests that post-transcriptional regulation plays a central role in initiating and coordinating the meiotic program in both fruit flies and mammals. Here, we identify the RNA-binding protein Ataxin-2 (Atx2) as a crucial regulator of meiosis in Drosophila melanogaster. We show that Atx2 positively regulates meiotic factors, especially components of the synaptonemal complex (SC), a structure essential for pairing, recombination and segregation of homologous chromosomes. In Atx2-depleted germ cells, SC component mRNA and protein levels are markedly reduced, leading to defective SC assembly and maintenance. Consequently, homologous chromosomes fail to pair properly, which is essential to ensure homolog segregation and prevent aneuploidy. These findings uncover Atx2 as a key regulator of the SC and highlight an underappreciated layer of gene regulation essential for accurate meiotic chromosome segregation and fertility.

genetics↗

bioRxiv2025

Ataxin-2 preserves oocyte genome integrity by promoting timely premeiotic DNA replication

The faithful reassortment and transmission of chromosomes across generations is fundamental to species survival. While much is known about chromosome pairing and recombination, the upstream regulators controlling entry into the meiotic program remain largely elusive. In many species, including Drosophila and mammals, the decision to enter meiosis occurs prior to premeiotic DNA replication and is governed by post-transcriptional regulation, by yet to be discovered factors. Here, we identify the RNA-binding protein Ataxin-2 as a crucial and previously unrecognized regulator of meiotic entry. We show that Ataxin-2 acts post-transcriptionally to promote the entry into meiosis by downregulating the conserved cell cycle inhibitor Dacapo, the Drosophila ortholog of p21/p27. In the absence of Ataxin-2, germ cells mis-regulate Dacapo leading to delayed premeiotic DNA replication and sterility. Strikingly, when DNA replication is delayed and extends into the next stage of meiosis, synaptonemal complex formation, oocytes incur severe genomic DNA damage, likely caused by collisions between replication forks and the synaptonemal complex. Our findings establish Ataxin-2 as a pivotal factor in regulating premeiotic DNA replication and safeguarding oocyte genome stability, shedding new light on the intricate regulatory mechanisms that ensure successful meiosis and fertility.

genetics↗

bioRxiv2018

PHASE TRANSITIONED NUCLEAR OSKAR PROMOTES CELL DIVISION OF DROSOPHILA PRIMORDIAL GERM CELLS

Germ granules are non-membranous ribonucleoprotein granules deemed the hubs for post-transcriptional gene regulation and functionally linked to germ cell fate across species. Little is known about the physical properties of germ granules and how these relate to germ cell function. Here we study two types of germ granules in the Drosophila embryo: cytoplasmic germ granules that instruct primordial germ cells (PGCs) formation and nuclear germ granules within early PGCs with unknown function. We show that cytoplasmic and nuclear germ granules are phase transitioned condensates nucleated by Oskar protein that display liquid as well as hydrogel-like properties. Focusing on nuclear granules, we find that Oskar drives their formation in heterologous cell systems. Multiple, independent Oskar protein domains synergize to promote granule phase separation. Deletion of Oskars nuclear localization sequence specifically ablates nuclear granules in cell systems. In the embryo, nuclear germ granules promote germ cell divisions thereby increasing PGC number for the next generation.

cell biology↗