Biology subjects

Bregy, I.

Publications and source records attributed to Bregy, I..

4 recordsLinked to original sources

bioRxiv2026

Streamlining large-scale high-resolution electron tomography with VolWeaver

Researchers using electron microscopy must often balance a trade-off between obtaining high-resolution structural information and preserving sufficient cellular context. At one end of this spectrum, single particle cryo-electron microscopy and cryo-electron tomography provide near-molecular detail but are typically limited to relatively small fields of view. At the other, volume electron microscopy approaches, such as scanning electron microscopy of resin-embedded specimens, capture large cellular volumes but generally at lower resolution. Consequently, linking nanoscale structural information to larger cellular architecture remains a significant challenge. To address this gap, we optimised a transmission electron tomography workflow for resin-embedded malaria parasites that allows us to visualise targeted regions of interest at nanometre-scale resolution while retaining several micrometres of surrounding cellular context. Here, we present our current best-practice pipeline for sample preparation, tomogram acquisition, and reconstruction. In addition, we introduce VolWeaver, a data-processing framework, that integrates high-resolution tomographic datasets into serial section volume reconstructions, enabling the visualisation and interpretation of ultrastructural features within their broader cellular environment.

cell biology↗

bioRxiv2025

Building without the architect: the dispensable role of MICOS in de novo cristae formation in malaria parasites

The malaria parasite mitochondria represent the only tractable, naturally occurring system in which cristae, the characteristic invaginations of the inner mitochondrial membrane, are known to be formed de novo. In traditional model organisms, the central complex involved in cristae organization is the mitochondrial contact site and cristae organizing system (MICOS). However, whether MICOS has an active role in the initial formation of cristae remains unclear. We identified two putative Plasmodium falciparum MICOS components, PfMIC19 and PfMIC60 and show that both genes are dispensable in asexual blood stages, gametocytes, and mosquito stages, albeit with a mild reduction in oocyst numbers. Immunofluorescence microscopy and electron tomography of gametocytes lacking either or both MICOS orthologues showed aberrant mitochondrial morphology and abnormal cristae, with a marked reduction of crista junctions. Thus, by utilizing the unique properties of P. falciparum, we confirmed the involvement of PfMIC19 and PfMIC60 in the organization of crista junctions, while providing evidence that MICOS is not required for the initial formation of cristae.

microbiology↗

bioRxiv2023

Cryo-electron tomography sheds light on the elastic nature of the Trypanosoma brucei tripartite attachment complex

Trypanosomes only contain a single mitochondrion per cell. Within that singular mitochondrion, the protist carries a single mitochondrial genome that consists of a complex DNA network, the kinetoplast DNA (kDNA). The replicated kDNA is segregated during cell division by the tripartite attachment complex (TAC), a multi-protein bridge that physically links each daughter kDNA to a basal body (BB). BB movements drive kDNA segregation prior to cell division. How the TAC accommodates constant BB movements while maintaining a stable kDNA anchor throughout the cell cycle has remained unclear. Here we used cryo-electron tomography to image the cytoplasmic part of the TAC in its native context. We resolved the BB, the mitochondrial membranes, and the exclusion zone filaments (EZFs) connecting the BB and pro-BB to the outer mitochondrial membrane (OMM) and quantified the geometry of the region across many cells. EZF lengths spanned 230 to 625 nm in zoid cells and up to 874 nm in NP40-treated cells, and the BB occupied a wide range of positions and orientations relative to the OMM, while the pro-BB sat closer and more constrained. Building on these observations and prior evidence that p197 alone defines the BB-OMM distance, we propose that p197 is a length-variable connector: the length of a tandem array of -helical repeats depends on their relative orientation, and filaments of different lengths coexist at one basal body. How that orientation is set remains open, but such a connector reconciles stable kDNA anchoring with the mechanical demands of BB movement during the cell cycle.

cell biology↗

bioRxiv2020

Characterization of two novel proteins involved in mitochondrial DNA anchoring

Trypanosoma brucei is a single celled eukaryotic parasite in the group of the Excavates. T. brucei cells harbor a single mitochondrion with a singular mitochondrial genome, that consists of a unique network of thousands of interwoven circular DNA molecule copies and is termed the kinetoplast DNA (kDNA). To ensure proper inheritance of the kDNA to the daughter cells the genome is linked to the basal body, the master organizer of the cell cycle in trypanosomes. The structure connecting the basal body and kDNA is termed the tripartite attachment complex (TAC). Using a combination of proteomics and RNAi (depletomics) we test the current model of hierarchical TAC assembly and identify TbmtHMG44 and Tb927.11.16120 as novel candidates of a structure that connects the TAC to the kDNA. Both proteins localize in the region of the unilateral filaments between TAC102 and the kDNA and depletion of each leads to a strong kDNA loss phenotype. TbmtHMG44 and Tb927.11.16120 stably associate with extracted flagella, even after DNase treatment however they do require the kDNA for initial assembly. Furthermore we demonstrate that recombinant Tb927.11.16120 is a DNA binding protein and thus a promising candidate to link the TAC to the kDNA.

cell biology↗