Biology subjects

Chandragiri, S.

Publications and source records attributed to Chandragiri, S..

5 recordsLinked to original sources

bioRxiv2025

Alizarin red perturbs skeletal patterning and biomineralization via Catalase inhibition

Alizarin Red S (AZ) is an anthraquinone dye that is commonly used in histological studies and textiles. Exposure to AZ results in morphological perturbations in several species, including rats, frogs, and dogs; however, the mechanisms by which AZ has these effects is largely unexplored, and little is known about its effect on development. We have previously shown that AZ is teratogenic to sea urchin larvae, and that AZ was the only calcium-binding mineralization marker among five tested that perturbed skeletal patterning. Here, we further characterize these defects and demonstrate that embryos exposed to AZ have abnormal skeletal element rotation, branching, and bending. Immunostains and polychrome labeling reveal delayed migration of primary mesenchyme cells and initiation of biomineralization. Although gross ectodermal dorsal-ventral specification, ciliary band restriction, and neuronal specification occur normally in the majority of AZ-treated embryos, we find abnormal patterning and connectivity of the serotonergic neurons. Temporal transcriptomics comparisons confirm delayed development and implicate changes in neuron-related GO terms with AZ treatment. Particle imaging velocimetry experiments show that ciliary beating normally directs fluid flow into the larval mouth, while AZ treatment perturbs the normal pattern of vortices and redirects flow away from the mouth. These changes in fluid flow have functional consequences for larval feeding behaviors in AZ-treated embryos. Finally, we show that the effects of AZ on skeletal patterning are largely due to its inhibition of catalase and subsequent elevation of reactive oxygen species. Specifically, catalase knockdown and transient hydrogen peroxide treatment are each sufficient to phenocopy the hallmark AZ-mediated skeletal patterning defects. This study is the first to define the teratogenic consequences of AZ exposure and show how its effects on catalase activity impact development, skeletal patterning, and biomineralization. Summary StatementAlizarin Red exposure produces teratogenic effects on skeletal and nervous systems primarily via catalase inhibition.

developmental biology↗

bioRxiv2025

Local alkalinity enhancement using artificial substrates increases survivorship of early-stage coral recruits

Efforts to restore coral reefs using sexually derived coral recruits are often hindered by their low survivorship and growth, hence scalable interventions to improve these parameters are urgently needed. Here, we developed novel settlement substrates that modify the local chemical and hydrodynamic environments to provide local alkalinity enhancement (AE) within the laminar boundary layer to aid in coral restoration. Cement tiles with four different chemistries and two different surface topographies were tested in a novel flume system to quantify their ability to change local pH under reef-like conditions and their effect on larval settlement, survivorship, and growth of the endangered Caribbean coral, Orbicella faveolata. Chemistry had a minimal effect on the initial settlement of coral larvae, and textured tiles were preferred over smooth tiles. However, substrates that created a more alkaline local environment increased post-settlement survivorship. The increased survivorship of O. faveolata recruits on AE tiles was not due to increased growth on AE tiles, although trends in growth were dependent on chemistry and topography of tiles. Our results indicate that mixing sodium bicarbonate or sodium carbonate into cement used to fabricate artificial reef structures could be an effective means to enhance the development of coral cover. Significance StatementReef-building coral populations in South Florida and the Caribbean are nearing crisis, with low survivorship rates of new recruits being identified as a critical bottleneck limiting their recovery. Since ocean acidification is known to stress corals and hinder their growth, we hypothesized that enhancing substrate alkalinity could help mitigate ocean acidification effects by boosting coral growth and increasing survivorship during their critical early stages. This hypothesis was experimentally tested by adding sodium bicarbonate or sodium carbonate to settlement substrates and studying coral settlement preference, and coral spat growth and survival. Our results showed significantly higher survivorship on alkalinity enhanced substrates, indicating that this could be a promising restoration intervention.

ecology↗

bioRxiv2024

PFAS Compounds PFOA and Gen X are Teratogenic to Sea Urchin Embryos

Per-and polyfluorinated substances (PFAS) are synthetic chemicals that are used to make fluoropolymer coatings found in many products, such as non-stick pans, clothing, cosmetics, and food packaging. These highly persistent molecules are known as "forever chemicals" since they neither degrade environmentally nor break down enzymatically within biological systems. PFAS compounds readily contaminate water sources, and as a result, certain PFAS molecules have bioaccumulated in exposed species including humans. The purpose of this study was to define the effect of two PFAS molecules, the ostensibly more toxic perfluorooctanoic acid (PFOA) and the more recent, reportedly safer chemical hexafluoropropylene oxide dimer acid (Gen X), on the development of Lytechinus variegatus sea urchin embryos. We examined the effects of PFOA and Gen X on development and patterning using morphological analysis, immunostaining, HCR-FISH, and Particle Image Velocimetry (PIV). The results show that both PFAS compounds are teratogenic to sea urchin embryos. PFOA and Gen X each function at different intervals during development and provoke distinct phenotypic and gene expression outcomes. Despite beliefs that Gen X would be a safer alternative, our findings indicate that Gen X has earlier and more severe effects on endomesoderm and dorsal-ventral axis specification, neural development and function, and pattern formation compared to PFOA. These results illustrate the dangerous teratogenic potential of environmentally accumulating PFAS like Gen X, underscoring the negative ecological implications that accompany continuing commercial and industrial use of PFAS in the absence of remediation strategies. HIGHLIGHTSO_LIGen X is more teratogenic in sea urchins than PFOA C_LIO_LIGen X acts earlier than PFOA and perturbs axial and germ layer specification C_LIO_LIEach PFAS reduces neural numbers and perturbs ciliary behavior and swimming C_LI

developmental biology↗

bioRxiv2024

AFG3L2-mediated proteolysis restricts mitochondrial biogenesis and gene expression in hypoxia

Mitochondria are metabolically rewired in hypoxia when cells switch to glycolytic growth. In addition to the well-established role of transcriptional and translational programs, there is increasing evidence that post-translational mechanisms contribute to the rapid adaptation of the mitochondrial proteome to hypoxia. Here, we have used a proteomic survey to define how the m-AAA protease AFG3L2, a proteolytic complex in the inner mitochondrial membrane, regulates mitochondrial proteostasis. Our experiments identify a broad spectrum of mitochondrial substrate proteins and show that AFG3L2 is activated in hypoxia along an HIF1-mTORC1 signaling axis. AFG3L2-mediated proteolysis restricts mitochondrial biogenesis and gene expression by degrading proteins, which are involved in mitochondrial protein import, mitochondrial transcription, mRNA processing, mRNA modification and stability, and RNA granule formation. Our experiments highlight the important contribution of proteolytic rewiring of the mitochondrial proteome for the adaptation to low oxygen tension and shed new light on the pathophysiology of several neurodegenerative disorders associated with mutations in AFG3L2.

cell biology↗

bioRxiv2021

Metabolic control of adult neural stem cell self-renewal by the mitochondrial protease YME1L

The transition between quiescence and activation in neural stem and progenitor cells (NSPCs) is coupled to reversible changes in energy metabolism with key implications for life-long NSPC self-renewal and neurogenesis. How this metabolic plasticity is ensured between NSPC activity states is unclear. We found that a state-dependent rewiring of the mitochondrial proteome by the peptidase YME1L is required to preserve NSPC self-renewal in the adult brain. YME1L-mediated proteome rewiring regulates the rate of fatty acid oxidation (FAO) for replenishing Krebs cycle intermediates and dNTP precursors, which are required to sustain NSPC amplification. Yme1l deletion irreversibly shifts the metabolic profile of NSPCs away from a FAO-dependent state resulting in defective self-renewal, premature differentiation and NSPC pool depletion. Our results disclose an important role for YME1L in coordinating the switch between metabolic states of NSPCs and suggest that NSPC fate is regulated by compartmentalized changes in protein network dynamics.

neuroscience↗