Biology subjects

Angers, A.

Publications and source records attributed to Angers, A..

5 recordsLinked to original sources

bioRxiv2026

A mitochondrial orphan protein contributes to sperm development in bivalves

Lineage-specific genes, or orphan genes, are increasingly recognized as important drivers of evolutionary innovation, yet their functional characterization remains largely restricted to nuclear genomes of model organisms. Whether lineage-specific genes encoded by mitochondrial DNA contribute to phenotypic diversification remains virtually unexplored. Here we investigate MORF, a rapidly evolving ORFan protein encoded by the paternally transmitted mitochondrial genome of bivalves with doubly uniparental inheritance (DUI). Combining immunolocalization, functional neutralization, protein interaction assays and proteomics in the distantly related bivalves Mytilus edulis and Venustaconcha ellipsiformis, we characterize MORF localization, function and molecular associations during male germ cell development. MORF localizes to developing sperm cells and mature sperm mitochondria in both species and is additionally detected in the acrosome of M. edulis. In cultured M. edulis germ cells, antibody-mediated neutralization of MORF increases the frequency of spermatids displaying four rather than the canonical five mitochondria, providing functional evidence that MORF contributes to mitochondrial organization during spermatogenesis. Comparative proteomic analyses identify MORF-associated proteins involved in cytoskeletal organization, protein homeostasis and extracellular matrix organization. The association between MORF and laminin is independently supported by western blotting in both species. Despite extensive sequence divergence, the two MORF proteins display overlapping functional and molecular features. Together, these findings uncover a functional role for a rapidly evolving mitochondrial orphan protein and point to mitochondrial orphan genes as a potentially overlooked source of evolutionary novelty.

molecular biology↗

bioRxiv2024

MTALTCO1: a 259 amino acid long mtDNA-encoded alternative protein that challenges conventional understandings of mitochondrial genomics.

Mitochondrial alternative Open Reading Frames (ORFs) substantially broaden the functional scope traditionally attributed to mitochondrial DNA, encoding peptides and proteins that participate in diverse cellular processes. These newly identified ORFs are embedded within annotated sequences, both coding and non-coding, and reveal layers of overlapping genetic information. We here report the discovery of MTALTCO1, a 259 amino-acid protein, the longest mitochondrial alternative protein identified to date, encoded by an ORF located within the human cytochrome oxidase 1 gene, in the +3 reading frame. We confirm the expression and mitochondrial origin of MTALTCO1 through multiple independent lines of evidence, including a custom-designed antibody, mass spectrometry-derived peptides, sequence analysis, and inhibitors of mitochondrial expression. Despite encoding AGR codons as arginine, contrary to the prevailing view that these function as stop codons in the vertebrate mitochondrial genetic code, MTALTCO1 shows strong evidence of mitochondrial translation, challenging established models of mitochondrial codon usage and gene expression. Co-immunoprecipitations and pull-down assays delineate MTALTCO1s interaction landscape across major cellular pathways. Lastly, we present the first in-depth analysis of conservation for a mitochondrial alternative ORF overlapping a reference protein-coding gene and discuss the results in light of MTALTCO1s suggested role in protein scaffolding.

molecular biology↗

bioRxiv2023

In vitro proliferation of Mytilus edulis male germ cell progenitors

Our understanding of basic cellular processes has mostly been provided by mammalian cell culture, and by some non-mammalian vertebrate and few invertebrate cell culture models. Developing reliable culture conditions for non-model organisms is essential to allow investigation of more unusual cellular processes. Here, we investigate how cells isolated from different tissues of the marine mussel Mytilus edulis thrive and survive in vitro in the hope of establishing a suitable laboratory model for the investigation of cellular mechanisms specific to these bivalve mollusks. We found that cells dissociated from male mantle tissue attached to the culture vessels and proliferated well in vitro, whereas all other cell types, although remaining viable, did not maintain divisions over three to four weeks in culture. We used antibodies against the germ-line marker DEAD-box helicase 4 (DDX4), also known as VASA, and the epithelial cell marker cytokeratin to distinguish different cell types in culture. DDX4-positive cells were the only cells that significantly proliferated in culture, and only from male tissue samples. Overall, the culture conditions described here allow an efficient selection of male germ cells that could be used to study specific cellular mechanisms in vitro.

cell biology↗

bioRxiv2022

MTALTND4, a second protein coded by nd4 impacts mitochondrial bioenergetics

Recent evidence suggests that the coding potential of the mitogenome is underestimated. We found a downstream alternative ATG initiation codon in the +3 reading frame of the human mitochondrial nd4 gene. This newly characterized alternative open reading frame (altORF) encodes a 99-amino acids long polypeptide, MTALTND4, which is conserved in primates. This small protein is localized in mitochondria and cytoplasm and is also found in the plasma, and it impacts mitochondrial physiology. Alternative mitochondrial peptides such as MTALTND4 may offer a new framework for the investigation of mitochondrial functions and diseases.

molecular biology↗

bioRxiv2021

Role of the ubiquitin ligase ITCH in clathrin-mediated endocytosis of the epidermal growth factor receptor

Once activated by ligand, epidermal growth factor receptor (EGFR) is endocytosed in clathrin-coated pits. ITCH is an E3 ubiquitin ligase that interacts with and ubiquitinates several proteins involved in clathrin-mediated endocytosis (CME) including endophilin. To further investigate the function of ITCH in EGFR endocytosis, the internalization of fluorescent EGF was measured in ITCH-/- HeLa cells. In the absence of ITCH, there was a significant decrease in the CME of EGF. Rescue experiments using wild-type ITCH confirmed the importance of the protein for normal EGF uptake. ITCH point mutations that disrupt the interaction of ITCH with endophilin failed to rescue the defects in EGFR uptake, as did a non-catalytic form of ITCH. ITCH-/- cells also displayed a delay in the rate of phospho-EGFR degradation as well as prolonged ERK1/2 signaling. Our study uncovers a pathway regulating EGFR trafficking and reveals for the first time that the protein ITCH is required for CME of EGFR.

cell biology↗