Biology subjects

De Niz, M.

Publications and source records attributed to De Niz, M..

8 recordsLinked to original sources

bioRxiv2026

Desmoglein-1 coordinates cell proliferation and actin dynamics to promote epidermal morphogenesis.

Skin development depends on coordinated biochemical and mechanical signaling to form a multilayered epidermal barrier. Our previous work demonstrated that the stratified tissue-specific desmosomal cadherin Desmoglein-1 (Dsg1) promotes epidermal differentiation in human in vitro models. Dsg1 first appears in the developing mouse epidermis around E14, coinciding with a developmental transition in stratification and the onset of terminal differentiation, raising the question of how Dsg1 contributes to epidermal morphogenesis in vivo. We generated a wild-type (WT) single-cell RNA sequencing (scRNA-seq) atlas of murine skin and integrated scRNA-seq data from Dsg1 knockout (Dsg1 KO) embryos spanning E14.5, E15.5, E16.5, and E18.5. Six keratinocyte subpopulations were annotated, including a Transitional subpopulation co-expressing basal and suprabasal markers, positioned between basal and differentiated states. Dsg1 KO epidermis exhibited reduced thickness at E14.5-E15.5, but recovered by E16.5-E18.5, suggesting compensatory adaptation. Differential gene expression analysis revealed enrichment of cell-cycle and actin-associated programs in Dsg1 KO during late development. EdU incorporation and PCNA staining confirmed increased proliferation in superficial layers accompanied by altered actin organization and changed cell morphology. Notably, actin and the Arp2/3 actin nucleation-promoting factor N-WASP exhibited marked changes in distribution during early and late development, respectively. Mechanistically, Dsg1 associates with Nck1, an adaptor linking N-WASP to Arp2/3-dependent actin polymerization. Silencing Nck1 or N-WASP reduced Dsg1-mediated stratification significantly, while a Nck1-binding-deficient Dsg1 mutant failed to rescue stratification in Dsg1-deficient keratinocytes in vitro. Together, these findings identify a Dsg1-Nck1-N-WASP axis linking desmosomal adhesion to cytoskeletal remodeling and support a model in which Dsg1 coordinates cell-cycle, cell morphology, and actin dynamics to drive epidermal morphogenesis.

cell biology↗

bioRxiv2023

Investigation of Trypanosoma-induced vascular damage sheds insights into Trypanosoma vivax sequestration

Multiple blood-borne pathogens infecting mammals establish close interactions with the host vascular endothelium as part of their life cycles. In this work, we investigate differences in the interactions of three Trypanosoma species: T. brucei, T. congolense and T. vivax with the blood vasculature. Infection with these species results in vastly different pathologies, including different effects on vascular homeostasis, such as changes in vascular permeability and microhemorrhages. While all three species are extracellular parasites, T. congolense is strictly intravascular, while T. brucei is capable of surviving both extra- and intravascularly. Our knowledge regarding T. vivax tropism and its capacity of migration across the vascular endothelium is unknown. In this work, we show for the first time that T. vivax parasites sequester to the vascular endothelium of most organs, and that, like T. congolense, T. vivax Y486 is largely incapable of extravasation. Infection with this parasite species results in a unique effect on vascular endothelium receptors including general downregulation of ICAM1 and ESAM, and upregulation of VCAM1, CD36 and E-selectin. Our findings on the differences between the two sequestering species (T. congolense and T. vivax) and the non-sequestering, but extravasating, T. brucei raise important questions on the relevance of sequestration to the parasites survival in the mammalian host, and the evolutionary relevance of both sequestration and extravasation.

cell biology↗

bioRxiv2023

Spatial confinement of Trypanosoma brucei in microfluidic traps provides a new tool to study free swimming parasites

Trypanosoma brucei is the causative agent of African trypanosomiasis and is transmitted by the tsetse fly (Glossina spp.). All stages of this extracellular parasite possess a single flagellum that is attached to the cell body and confers a high degree of motility. While several stages are amenable to culture in vitro, longitudinal high-resolution imaging of free-swimming parasites has been challenging, mostly due to the rapid flagellar beating that permanently twists the cell body. Here, using microfabrication, we generated various microfluidic devices with traps of different geometrical properties. Investigation of trap topology allowed us to define the one most suitable for single T. brucei confinement within the field of view of an inverted microscope while allowing the parasite to remain motile. Chips populated with V-shaped traps allowed us to investigate various phenomena in cultured procyclic stage wild-type parasites, and to compare them with parasites whose motility was altered upon knockdown of a paraflagellar rod component. Among the properties that we investigated were trap invasion, exploratory behaviour, and the visualization of organelles labelled with fluorescent dyes. We envisage that this "Tryp-Chip" will be a useful tool for the scientific community, as it could allow high-throughput, high-temporal and high-spatial resolution imaging of free-swimming T. brucei parasites.

microbiology↗

bioRxiv2023

The lymphatic system favours survival of a unique T. brucei population, and its invasion results in major host pathology.

Trypanosoma brucei colonize and multiply in the blood vasculature, as well as in various organs of the hosts body. Lymph nodes have been previously shown to harbour large numbers of parasites, and the lymphatic system has been proposed as a key site that allows T. brucei distribution through, and colonization of the mammalian body. However, visualization of host-pathogen interactions in the lymphatic system has never captured dynamic events with high spatial and temporal resolution throughout infection. In our work, we used a mixture of tools including intravital microscopy and ex vivo imaging to study T. brucei distribution in 20 sets of lymph nodes. We demonstrate that lymph node colonization by T. brucei is different across lymph node sets, with the most heavily colonized being the draining lymph nodes of main tissue reservoirs: the gonadal adipose tissue and pancreas. Moreover, we show that the lymphatic vasculature is a pivotal site for parasite dispersal, and altering this colonization by blocking LYVE-1 (i.e. surface receptor of lymphatic vessel endothelial cells) is detrimental for parasite survival. Additionally, parasites within the lymphatic vasculature have unique morphological and behavioural characteristics, different to those found in the blood, demonstrating a physical separation of environments across both types of vasculature. Finally, we demonstrate that the lymph nodes and the lymphatic vasculature undergoes significant alterations during T. brucei infection, resulting in oedema throughout the hosts body.

microbiology↗

bioRxiv2021

Organotypic endothelial adhesion molecules are key for Trypanosoma brucei tropism and virulence

Trypanosoma brucei is responsible for lethal diseases in humans and cattle in Sub-Saharan Africa. These extracellular parasites extravasate from the blood circulation into several tissues. The importance of the vasculature in tissue tropism is poorly understood. Using intravital imaging and bioluminescence, we found that gonadal white adipose tissue and pancreas are the two main parasite reservoirs. We show that reservoir establishment happens before vascular permeability is compromised, suggesting that extravasation is an active mechanism. Blocking endothelial surface adhesion molecules (E-selectin, P-selectins, or ICAM2) significantly reduced extravascular parasite load in all organs and delayed host lethality. Remarkably, blocking CD36 had a specific effect on adipose tissue tropism that was sufficient to delay lethality, suggesting that establishment of the adipose tissue reservoir is necessary for parasite virulence. This works demonstrates the importance of the vasculature in a T. brucei infection and identifies organ-specific adhesion molecules as key players for tissue tropism.

microbiology↗

bioRxiv2020

N6-methyladenosine in poly(A) tails stabilize VSG transcripts

RNA modifications are important regulators of gene expression. In Trypanosoma brucei, transcription is polycistronic and thus most regulation happens post-transcriptionally. N6-methyladenosine (m6A) has been detected in this parasite, but its function remains unknown. Here we show that [~]50% of the m6A is located in the poly(A) tail of the monoallelically expressed Variant Surface Glycoprotein (VSG) transcript. m6A residues are removed from the VSG poly(A) tail prior to deadenylation and mRNA degradation. Using genetic tools, we identified a 16-mer motif in the 3UTR of VSG that acts as a cis-acting motif required for inclusion of m6A in the poly(A) tail. Removal of this motif from the VSG 3 UTR results in poly(A) tails lacking m6A, rapid deadenylation and mRNA degradation. To our knowledge this is the first identification of an RNA modification in the poly(A) tail of any eukaryote, uncovering a novel post-transcriptional mechanism of gene regulation.

molecular biology↗

bioRxiv2019

Developing a xenograft model of human vasculature in the mouse ear pinna

Humanised xenograft models allow for the analysis of human tissue within a physiological environment in vivo. However, current models often rely on the angiogenesis and ingrowth of recipient vasculature to perfuse tissues, preventing analysis of biological processes and diseases involving human blood vessels. This limits the effectiveness of xenografts in replicating human physiology and may lead to issues with translating findings into human research. We have designed a xenograft model of human vasculature to address this issue. Human subcutaneous fat was cultured in vitro to promote blood vessel outgrowth prior to implantation into immunocompromised mice. We demonstrate that implants survived, retained human vasculature and anastomosed with the circulatory system of the recipient mouse. Significantly, by performing transplants into the ear pinna, this system enabled intravital observation of xenografts by multiphoton microscopy, allowing us to visualise the steps leading to vascular cytoadherence of erythrocytes infected with the human parasite Plasmodium falciparum. This model represents a useful tool for imaging the interactions that occur within human tissues in vivo and permits visualization of blood flow and cellular recruitment in a system which is amenable to intervention for various studies in basic biology together with drug evaluation and mechanism of action studies.

pathology↗

bioRxiv2019

3D imaging of undissected optically cleared Anopheles stephensi mosquitoes infected with Plasmodium parasites

Malaria is a life-threatening disease, caused by Apicomplexan parasites of the Plasmodium genus. The Anopheles mosquito is necessary for the sexual replication of these parasites and for their transmission to vertebrate hosts, including humans. Imaging of the parasite within the insect vector has been attempted using multiple microscopy methods, most of which are hampered by the presence of the light scattering opaque cuticle of the mosquito. So far, imaging of the Plasmodium mosquito stages depended on either sectioning or surgical dissection of important anatomical sites, such as the midgut and the salivary glands. Optical projection tomography (OPT) and light sheet fluorescence microscopy (LSFM) enable imaging fields of view in the centimeter scale whilst providing micrometer resolution. In this paper, we present reconstructions of the whole body of Plasmodium-infected, optically cleared Anopheles stephensi mosquitoes and their midguts. The 3D-reconstructions from OPT imaging show detailed features of the mosquito anatomy and enable overall localization of parasites in midguts. Additionally, LSFM imaging of mosquito midguts shows detailed distribution of oocysts in extracted midguts.

microbiology↗