Biology subjects

Buzgariu, W.

Publications and source records attributed to Buzgariu, W..

3 recordsLinked to original sources

bioRxiv2022

Apical-to-basal graded ROS metabolism in intact Hydra leads to distinct levels of injury-induced ROS signaling in apical and basal regenerating tips

After mid-gastric bisection, Hydra regenerates a head from the lower half and a basal disc from the upper one. What signals elicit two distinct regenerative responses in bisected Hydra remains unknown. A mathematical modeling approach based on quantitative data linked to MAPK activation and injury-induced cell death predicts an immediate release of a locally restricted short-lived signal in apical-regenerating tips. We found that Reactive oxygen species (ROS) fulfill this role as evidenced by the injury-induced production of hydrogen peroxide (H2O2), three-fold higher in apical-regenerating tips than in basal ones. By contrast, mitochondrial superoxide (mtO2.-) is similarly produced on each side of the cut, playing a positive role on wound healing as mtO2.- scavenging delays healing whereas knocking-down Super Oxide Dismutase (SOD) leads to mtO2.- accumulation and acceleration of wound-healing. In intact Hydra, the ROS-processing enzyme activities are inversely graded along the body column, basal-to-apical for SOD and apical-to-basal for catalase, explaining the asymmetrical levels of H2O2 after bisection. High H2O2 levels trigger injury-induced cell death via paracrine signaling in apical-regenerating tips, where NOX4 and CYBB enzymes amplify them. Hence, the asymmetrical regulation of H2O2 levels immediately after amputation is crucial to activate two distinct regenerative responses in Hydra.

developmental biology↗

bioRxiv2019

Generic and context-dependent gene modulations during Hydra whole body regeneration

The cnidarian Hydra is a classical model of whole-body regeneration. Historically, Hydra apical regeneration has received more attention than its basal counterpart, most studies considering these two regenerative processes independently. We present here a transcriptome-wide comparative analysis of apical and basal regeneration after decapitation and mid-gastric bisection, augmented with a characterization of positional and cell-type expression patterns in non-regenerating animals. The profiles of 25637 Hydra transcripts are available on HydrATLAS (https://hydratlas.unige.ch), a web interface allowing a convenient access to each transcript profile. These data indicate that generic impulse-type modulations occur during the first four hours post-amputation, consistent with a similar integration of injury-related cues on both sides of the amputation plane. Initial divergences in gene regulations are observed in regenerating tips between four and eight hours post-amputation, followed by a dramatic transcriptomic reprogramming between eight and 16 hours when regulations become sustained. As expected, central components of apical patterning, Wnt3 and HyBra1, are among the earliest genes up-regulated during apical regeneration. During early basal regeneration, a BMP signaling ligand (BMP5-8c) and a potential BMP inhibitor (NBL1) are up-regulated, suggesting that BMP signaling is involved in the basal organizer, as supported by higher levels of phosphorylated Smad in the basal region and by the LiCl-induced extension of NBL1 expression. By contrast, upon ectopic activation of Wnt/{beta}-catenin signaling, NBL1 is no longer expressed, basal differentiation is not maintained and basal regeneration is abolished. A tight cross-talk between Wnt/{beta}-catenin apically and BMP signaling basally appears necessary for maintaining and regenerating Hydra anatomy.

developmental biology↗

bioRxiv2017

Hydra, a model system for deciphering the mechanisms of aging and resistance to aging

The freshwater cnidarian polyp named Hydra, which can be mass-cultured in the laboratory, is characterized by a highly dynamic homeostasis with a continuous self-renewal of its three adult stem cell populations, the epithelial stem cells from the epidermis, the epithelial stem cells from the gastrodermis, and the multipotent interstitial stem cells, which provide cells of the nervous system, gland cells and germ cells. Two unusual features characterize these stem cells that cannot replace each other, they all avoid G1 to pause in G2, and the two epithelial populations are concomitantly multifunctional and stem cells. H. vulgaris that does not show any signs of aging over the years, resists to weeks of starvation and adapts to the loss of neurogenesis, providing a unique model system to study the resistance to aging. By contrast some strains of a distinct species named H. oligactis undergo a rapid aging process when undergoing gametogenesis or when placed in stress conditions. The aging phenotype is characterized by the rapid loss of somatic interstitial stem cells, the progressive reduction in epithelial stem cell self-renewal, the loss of regeneration, the disorganization of the neuro-muscular system, the loss of the feeding behavior, and the death of all animals within about three months. We review here the possible mechanisms that help H. vulgaris to sustain stem cell self-renewal and thus bypass aging processes. For this, FoxO seems to act as a pleiotropic actor, regulating stem cell proliferation, stress response and apoptosis. In H. oligactis, the regulation of the autophagy flux differs between aging-sensitive and aging-resistant animals, pointing to a key role for proteostasis in the maintenance of a large pool of active and plastic epithelial stem cells.

evolutionary biology↗