Biology subjects

Sammi, S. R.

Publications and source records attributed to Sammi, S. R..

6 recordsLinked to original sources

bioRxiv2026

Loss of autism-associated gene wac alters social behavior and identifies cho-1 as a modulator of cholinergic signaling in C. elegans

WAC is a chromatin-associated regulatory protein involved in transcriptional control and has been identified as an autism-associated gene in human genetic studies. However, its functional role in regulating behavior and synaptic processes remains incompletely understood. Using Caenorhabditis elegans, we investigated the consequences of wac deficiency on food-associated social behavior, growth-associated phenotypes, and cholinergic pathway function. wac-deficient worms showed a marked reduction in food-leaving behavior, supporting impaired behavioral responsiveness to food-associated environmental cues, while aggregation behavior was not significantly altered. PHX2587 wac deletion mutant worms also exhibited reduced body length, decreased pharyngeal pumping, and shortened lifespan, indicating broader growth and physiological impairment. Stage-resolved analysis of cholinergic pathway genes revealed stage-associated transcriptional changes, with coordinated upregulation of multiple presynaptic and postsynaptic cholinergic components (ace-1, cha-1, cho-1, lev-1, lev-10, unc-17, unc-29, unc-38, and unc-50) emerging most prominently at the young adult stage. Functional RNAi analysis further identified cho-1, which encodes the high-affinity presynaptic choline transporter, as a genotype-specific modifier of cholinergic sensitivity in PHX2587 worms. Importantly, cho-1 RNAi not only reduced aldicarb hypersensitivity but also partially suppressed the reduced body length phenotype and improved food-leaving behavior in PHX2587 worms, while having limited effects in wild-type N2. Together, these findings support a functional relationship between wac deficiency and cho-1-associated cholinergic modulation, suggesting that presynaptic choline transport contributes to selected behavioral and physiological consequences of wac loss. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/719318v2_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@cd8950org.highwire.dtl.DTLVardef@1f1e6adorg.highwire.dtl.DTLVardef@5f783dorg.highwire.dtl.DTLVardef@1cf0ed6_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

neuroscience↗

bioRxiv2026

Neurobehavioral impacts of the autism risk gene, WAC: Studies involving C. elegans and Mice

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by a broad spectrum of behavioral impairments. While multiple genetic and environmental factors are attributed to its cause, biological underpinnings are still poorly understood. We investigated an ASD-associated gene, WAC, for its neurobehavioral aspects using C. elegans and mice. Studies of C. elegans with wac gene deletions (wac-1.1 and wac-1.2) showed enhanced acetylcholine-associated behavior, as indicated by the aldicarb assay. No alteration in acetylcholine levels or acetylcholinesterase activity was observed. Upon further investigation, we found that the elevated cholinergic transmission resulted from increased activity of nicotinic acetylcholine receptors (nAChRs). Additionally, we observed reduced motility and dopamine-associated behaviors, along with a reduced ability to switch from crawling to swimming, a serotonin-dependent behavior. Upregulation in mRNA expression of the lev-1 gene was observed. Conversely, a feedback-counterbalancing response in the form of downregulated genes, acr-2, unc-17, unc-63, and unc-50, was also observed. Surprisingly, lev-1 RNAi did not reverse the enhanced cholinergic transmission in PHX2587 worms, indicating the involvement of other players. To validate our findings, we also assessed CHRNA7 levels in Wac+/- mice. While some genetic compensation was observed in heterozygous mice, we found a direct, inverse correlation between Wac mRNA expression and CHRNA7 levels in the mouse brain cortex, corroborating our findings from C. elegans. Overall, these studies indicate that wac gene deletion in C. elegans exhibits a neurotransmitter alteration that is relatable to ASD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=61 SRC="FIGDIR/small/709202v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1771dc4org.highwire.dtl.DTLVardef@1434b4eorg.highwire.dtl.DTLVardef@10525ecorg.highwire.dtl.DTLVardef@fcd8a9_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Brief report on differential toxicity of legacy and second-generation PFAS on dopaminergic neurons and mitochondria

Per/polyfluoroalkyl substances (PFAS) are anthropogenic chemicals that have shown extensive usage. Owing to widespread use and resistance to environmental degradation, they have become a hazard with respect to the environment and human health. While the legacy PFAS are being phased out, they are being replaced by second-generation PFAS that are considered safer alternatives. However, the lack of information pertaining to the underlying mechanisms for legacy and especially second-generation PFAS exacerbates the risk. This study investigates legacy and second-generation PFAS to determine their individual effects on neurotoxicity and mitochondrial respiration. Legacy PFAS, perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and second-generation PFAS, GenX, and ADONA were employed, and studies were conducted using Caenorhabditis elegans and mitochondria isolated from Rat brain for Complex I to IV. It was found that legacy PFAS, PFNA, and PFDA were neurotoxic, with neurotoxicity proportional to chain length. PFOA, PFNA, and PFDA also exhibited significant inhibition to most of the mitochondrial complexes. Whereas in the case of second-generation PFAS ADONA, and GenX, it was only limited to the inhibition of Complex IV. GenX only exhibited neurodegeneration at very high doses. Our findings conclude that the legacy and second-generation PFAS might have significant neurotoxic implications. While the targets are similar to some extent, the mechanisms between the two classes are distinct. Our study the sets the stage to evaluate further the combined effect of PFAS (legacy and emergent) to fill in informational gaps pertaining to their safety.

pharmacology and toxicology↗

bioRxiv2025

γ-glutamyl-cysteine is a critical intermediate in glutathione-led amelioration of PFOS-neurotoxicity

Perfluorooctane sulfonate (PFOS) is one of the most prevalent PFAS. Earlier studies using Caenorhabditis elegans indicated that glutathione (GSH) ameliorates PFOS-induced neurodegeneration. This study investigates the GSH synthesis pathway to elucidate critical neuroprotective mechanisms. We assessed the effects of GSH precursors, cysteine, glutamic acid, and cysteine + glutamic acid, and of the intermediate {gamma}-glutamyl-cysteine ({gamma}-Glu-Cys), on PFOS neurotoxicity. While cysteine showed slight neuroprotection, other GSH precursors, glutamate, and cysteine + glutamate did not demonstrate beneficial effects. However, the crucial GSH synthesis intermediate, {gamma}-Glu-Cys, conferred neuroprotection comparable to GSH. Notably, no changes were observed in the gene or protein expression of GSH synthesis enzymes in C. elegans and SH-SY5Y cells, respectively. Further, testing of the alternative pathway for 5-oxoproline-mediated GSH synthesis revealed that it is not involved in {gamma}-glutamyl-cysteine-mediated neuroprotection. Paradoxically, 5-oxoproline supplementation was neurotoxic, plausibly due to glutamate toxicity. Further, we tested the effect of acute PFOS exposure on mitochondrial complexes I, II, III, and IV. We observed significant inhibition of enzyme activity in mitochondrial complexes II, III, and IV. Next, we tested whether GSH and {gamma}-Glu-Cys could rescue PFOS-induced enzyme inhibition. We found that while both GSH and {gamma}-Glu-Cys could rescue enzyme inhibition in complex III, the rescuing effect was altogether absent for complex IV. Overall, our findings confirmed that both GSH and {gamma}-Glu-Cys can rescue PFOS-induced neurodegeneration and mitochondrial enzyme affliction. This study effectively uncovers a novel mechanism that addresses existing knowledge gaps pertaining to the role of the GSH pathway in curtailing PFOS neurotoxicity. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/657248v3_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1050eeborg.highwire.dtl.DTLVardef@11668e0org.highwire.dtl.DTLVardef@3f51ddorg.highwire.dtl.DTLVardef@1178865_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract {gamma}-glutamyl-cysteine is the critical intermediate in glutathione-modulated amelioration of PFOS-neurotoxicity Perfluorooctanesulfonate (PFOS) leads to dopaminergic cell loss in C. elegans. Glutathione (GSH) confers neuroprotection against PFOS neurotoxicity. Further investigation of the critical components involved in GSH biosynthesis identified that while precursors of GSH, Cysteine and glutamate fail to confer neuroprotection, only {gamma}-glutamyl-cysteine alleviates neuronal loss similar to GSH. C_FIG

neuroscience↗

bioRxiv2022

Complementary biological and computational approaches identify distinct mechanisms of chlorpyrifos versus chlorpyrifos oxon induced dopaminergic neurotoxicity

Organophosphate (OP) pesticides are widely used in agriculture. While acute cholinergic toxicity has been extensively studied, chronic effects on other neurons are less understood. Here, we demonstrated that the OP pesticide chlorpyrifos (CPF) and its oxon metabolite are dopaminergic neurotoxicants in Caenorhabditis elegans. CPF treatment led to inhibition of mitochondrial complex II, II + III, and V in rat liver mitochondria, while CPF oxon did not (complex II + III, and IV inhibition observed only at high doses). While the effect on C. elegans cholinergic behavior was mostly reversible with toxicant washout, dopamine-associated deficits persisted, suggesting dopaminergic neurotoxicity was irreversible. CPF reduced the mitochondrial content in a dose-dependent manner and the fat modulatory genes cyp-35A2 and cyp-35A3 were found to have a key role in CPF neurotoxicity. These findings were consistent with in vitro effects of CPF and CPF oxon on nuclear receptor signaling and fatty acid/steroid metabolism observed in ToxCast assays. Two-way hierarchical analysis revealed in vitro effects on estrogen receptor (ER,) pregnane X receptor (PXR), and peroxisome proliferator-activated receptor gamma (PPAR gamma) pathways as well as neurotoxicity of chlorpyrifos, malathion, and diazinon, while these effects were not detected in malaoxon and diazoxon. Taken together, our study suggests that mitochondrial toxicity and metabolic effects of CPF, but not CPF-oxon, have a key role of CPF neurotoxicity in the low-dose, chronic exposure. Further mechanistic studies are needed to examine mitochondria as a common target for all OP pesticide parent compounds, since this has important implications on cumulative pesticide risk assessment.

pharmacology and toxicology↗

bioRxiv2022

Heterocyclic aromatic amines (HAAs) target mitochondrial physiology

Heterocyclic aromatic amines (HAA) may be found naturally in plants or are formed through the Maillard reaction when meat is cooked at high temperatures. Previous studies have indicated HAAs are especially toxic to dopaminergic neurons, whereas specific exposures may also affect other neuronal populations such as cholinergic neurons. Biochemical mechanisms of neurotoxic action implicate elevated oxidative stress and afflicted mitochondria. Notably, these mechanisms are of importance in Alzheimers disease (AD) and Parkinsons disease (PD). Most neurodegenerative disease cases are sporadic, where environmental and dietary factors may modulate risk. To further investigate HAA neurotoxicity, we tested the effect of common HAA (harmane, harmine, norharmane, PhIP, and HONH-PhIP) exposure on mitochondrial physiology, a key pathogenic target in AD and PD. Upon assessing mitochondrial bioenergetics, we observed a significant reduction in basal respiration, ATP production, maximal respiratory capacity, and non-mitochondrial respiration, indicating that HAA negatively impacts mitochondrial respiration. Followed by more specific studies on individual mitochondrial complexes, it was found that harmane, harmine, norharmane specifically inhibit complex I enzyme activity, whereas HONH-PhiP, a reactive metabolite of PhIP, inhibits Complex III enzyme activity. Our findings provide significant advancement with respect to underlying mechanisms of toxicity, though also validating HAA exposure as a potential risk factor for AD and PD.

neuroscience↗