Biology subjects

Alam, H.

Publications and source records attributed to Alam, H..

8 recordsLinked to original sources

bioRxiv2026

Microinjection-based Single-Cell Toxicological Assessment Reveals How Physiological Levels of PFOS Impair Oocyte Maturation and Developmental Competence

Perfluorooctanesulfonic acid (PFOS) is a persistent environmental contaminant widely detected in human serum and follicular fluid and has been associated with reduced implantation rates and female fertility. However, its direct effects on mammalian oocyte maturation remain poorly understood. Here, we developed a microinjection-based single-oocyte toxicological assay to directly evaluate how physiologically relevant PFOS concentrations affect mouse oocyte maturation and early embryonic development. Microinjection of PFOS at follicular-fluid level (5.6 nM) and occupational exposure level (60 nM) significantly reduced germinal vesicle breakdown (GVBD) and polar body extrusion (PBE) rates compared with water-injected controls. Notably, all tested concentrations (2.4 nM serum level, 5.6 nM, and 60 nM) induced abnormal polar-body formation, disrupted meiotic spindle morphology, and increased the proportion of unhealthy oocytes. PFOS exposure also significantly elevated intracellular reactive oxygen species (ROS) levels and mitochondrial membrane potential at 5.6 nM, indicating oxidative stress and mitochondrial dysfunction. Cytological analyses revealed chromosome misalignment and widened metaphase I plates, suggesting chromosome missegregation and subsequent prometaphase II arrest with defective polar bodies. Single-cell RNA sequencing of PFOS-treated oocytes exhibiting abnormal small polar bodies identified distinct transcriptional signatures, including dysregulation of genes involved in mRNA processing, chromosome segregation, mitochondrial function, and cell division. Functionally, these oocytes failed to progress beyond the 2-cell stage following in vitro fertilization, indicating loss of developmental competence. Collectively, these findings demonstrate that PFOS directly disrupts meiotic progression through spindle defects, oxidative stress, and transcriptional dysregulation, ultimately compromising oocyte quality even at environmentally relevant exposure levels. Environmental ImplicationPFOS is a persistent environmental contaminant widely detected in human serum and follicular fluid. Our findings demonstrate that PFOS at physiologically relevant levels can impair oocyte maturation, disrupt meiotic chromosome segregation, and compromise early embryonic development. By using a single-oocyte toxicological assay, we reveal that even low-dose PFOS exposure can induce oxidative stress and transcriptional dysregulation. These results highlight the potential reproductive risks of chronic PFOS exposure and underscore the importance of stricter environmental monitoring and regulation to protect female reproductive health and fertility. This novel assay also has the potential to redefine safety thresholds for other environmental toxicants.

cell biology↗

bioRxiv2026

Effects of Phthalate Metabolite Mixture Exposure on Mouse Oocyte Development

Phthalates are pervasive endocrine-disrupting chemicals widely used in consumer products. The wide use of many phthalates results in chronic human exposure to complex mixtures rather than single compounds. Despite extensive studies on individual compounds, the combined effects of phthalate metabolites on oogenesis remain poorly understood. Here, we developed a precise microinjection-based single-oocyte toxicological assay to examine the impact of a defined phthalate metabolite mixture on meiotic progression. Phthalate mixture exposure markedly impaired oocyte maturation, as most oocytes failed to extrude the first polar body. Mechanistic analyses revealed severe meiotic defects, including disrupted spindle morphology, chromosome misalignment, disorganized actin cytoskeleton, and impaired mitochondrial function, accompanied by excessive reactive oxygen species (ROS) accumulation and DNA damage. Single-cell transcriptomic profiling further identified differentially expressed genes enriched in biological processes related to exocytosis, secretory pathway regulation, and cytoskeletal organization, as well as in MAPK, JAK-STAT, cGMP-PKG, and GnRH signaling pathways that are essential for follicular development and oocyte maturation. Together, these findings demonstrate that combined phthalate exposure directly compromises female gamete quality and underscore the importance of evaluating mixture effects when assessing risks to womens reproductive health.

cell biology↗

bioRxiv2026

Curcumin-Magnesium complex loaded DNA hydrogels: concentration dependent swelling kinetics and selective cytotoxicity via Oxidative Stress induced apoptosis

Curcumin is a naturally occurring polyphenol that demonstrates considerable anti-cancer activity, however the aqueous insolubility, rapid metabolism and relatively low bioavailability are limiting to its clinical application. As such, a curcumin-magnesium (Cur-Mg) coordination complex was synthesized and subsequently encapsulated within DNA hydrogels (Cur-Mg-Hgel). The Cur-Mg complex was fully characterized using UV-Vis spectroscopy, FTIR and X-ray diffraction (XRD). UV-Vis, FTIR and XRD all support the formation of a coordination complex and suggest a decreased level of crystallinity compared to free curcumin. DNA hydrogels were formed and characterized using atomic force microscopy, rheology and swelling kinetic studies. In vitro cytotoxicity studies utilizing an MTT assay demonstrate dose dependent inhibition of HeLa cell proliferation and a slightly better retention of RPE-1 viability at low concentrations (suggesting some difference in sensitivity) though significant cell death is seen at higher concentrations and both cells. Intracellular production of ROS was measured using the DCFH-DA assay and is seen to increase when HeLa cells are treated with Cur-Mg-Hgel in comparison to un-treated controls. Annexin V/PI staining demonstrates primarily late or early apoptotic activity with minimal necrosis following treatment with Cur-Mg-Hgel. The evidence presented strongly supports the notion that Cur-Mg-Hgel is a ROS-modulating, pro-apoptotic Hydrogel suitable for cancer treatment. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/724072v2_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@d23f8corg.highwire.dtl.DTLVardef@14a30f6org.highwire.dtl.DTLVardef@1d485e9org.highwire.dtl.DTLVardef@1a3adf7_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2026

Resource availability and dimensionality result in ecology-dependent selection in bacteriophage spatial expansions

In microbial populations, fitness, which is essential to understand and predict evolution, is often defined and measured as the net growth rate of a population in isolation. Applying the same definition to viruses is challenging, both because viral replication involves a host infection process, which is determined by several parameters that are context-dependent, and because viruses compete heavily for resources (susceptible cells). These challenges are particularly exacerbated in spatial range expansions, where multiplicity of infection is often high and resource availability varies in time and space. To assess different fitness definitions and their generalizability, we investigate a model of coupled partial differential equations for phage plaque expansion in one and two dimensions. We find that two commonly used metrics for phage fitness in plaque expansions, i.e., steady state phage densities and front expansion speed in isolation, are unable to reliably predict the winner in one- and two-dimensional direct competitions. More generally, we find that optimal phage traits depend on the dimensionality of the system and the make-up of the phage population, leading to unexpected behaviours, e.g., rock-paper-scissor dynamics and, in high dimensions, enhanced phage density due to the nearby presence of a competitor. We show that the phenomenon stems from the interplay between resource consumption and replication and thus may apply more broadly to any population competing for shared resources.

ecology↗

bioRxiv2023

The extent of regeneration is impacted by the stage of amputation in ladybird beetles: a case study in Cheilomenes sexmaculata

Regeneration is a topic of interest for centuries and arthropods are no exception. Trade-offs associated with regeneration are likely to indicate the reallocation of resources from other metabolic activities such as growth, development, or reproduction to regrowth of the lost body part. This may confer negative selection to some of the developmental traits of the organism despite regeneration being overall advantageous. Our hypothesis for the study was that the extent of regeneration and trade-offs associated with it may be stage-specific. To test this hypothesis, the right forelimb of all four larval stages of the ladybird beetle (Cheilomenes sexmaculata) was amputated. The amputated stages were reared till adulthood and all developmental transitions were recorded. Leg size was measured and compared with control. The result showed that the regenerated legs of all the treatments were smaller than the control and the regenerative potency of early larval stage was higher than late larval stages. Regeneration causes delay in post-amputation duration in all the treatments, increasing their total development period. However, insignificant difference was observed between the fresh body weight of regenerated and control adults. The length of unamputated left foreleg was reduced in regenerated beetles, showing some internal trade-off.

zoology↗

bioRxiv2021

CCNE1 amplification is synthetic-lethal with PKMYT1 kinase inhibition

Amplification of the gene encoding cyclin E (CCNE1) is an oncogenic driver in several malignancies and is associated with chemoresistance and poor prognosis. To uncover therapeutic targets for CCNE1-amplified tumors, we undertook genome-scale CRISPR/Cas9-based synthetic lethality screens in cellular models of CCNE1 amplification. Here, we report that increasing CCNE1 dosage engenders a vulnerability to the inhibition of the PKMYT1 kinase, a negative regulator of CDK1. To inhibit PKMYT1, we developed RP-6306, an orally bioavailable and selective inhibitor that shows single-agent activity and durable tumor regressions when combined with gemcitabine in models of CCNE1-amplification. RP-6306 treatment causes unscheduled activation of CDK1 selectively in CCNE1 overexpressing-cells, promoting early mitosis in cells undergoing DNA synthesis. CCNE1 overexpression disrupts CDK1 homeostasis at least in part through an early activation of the FOXM1/MYBL2/MuvB-dependent mitotic transcriptional program. We conclude that PKMYT1 inhibition is a promising therapeutic strategy for CCNE1-amplified cancers.

cancer biology↗

bioRxiv2018

Super-enhancer impairment is a link between MLL4 inactivated lung tumors and their vulnerability to glycolysis pathway inhibition

Epigenetic modifiers often harbor loss-of-function mutations in lung cancer, but their tumor-suppressive roles are poorly characterized. Here we show that lung-specific loss of the gene encoding the histone methyltransferase MLL4 (alias KMT2D; a COMPASS-like enzyme), which is ranked the most highly inactivated epigenetic modifier in lung cancer, strongly promotes lung adenocarcinoma in mice. Mll4 loss upregulated tumor-promoting programs, including glycolysis. The pharmacological inhibition of glycolysis preferentially impeded tumorigenic growth of human lung cancer cells bearing MLL4-inactivating mutations. Mll4 loss widely impaired epigenomic signals for super-enhancers and enhancers, including the super-enhancer for the circadian rhythm repressor gene Per2, and decreased Per2 expression. Per2 downregulated several glycolytic pathway genes. These findings uncover a distinct tumor-suppressive epigenetic mechanism in which MLL4 enhances Per2-mediated repression of pro-tumorigenic glycolytic genes via super-enhancer activation to suppress lung adenocarcinoma tumorigenesis and also implicate a glycolysis-targeting strategy as a therapeutic intervention for the treatment of MLL4- mutant lung cancer.

cancer biology↗

bioRxiv2018

Enhancer Reprogramming Confers Dependence on Glycolysis and IGF signaling in KMT2D Mutant Melanoma

Epigenetic modifiers have emerged as important regulators of tumor progression. We identified histone methyltransferase KMT2D as a potent tumor-suppressor through an in vivo epigenome-focused pooled RNAi screen in melanoma. KMT2D harbors frequent somatic point mutations in multiple tumor types. How these events contribute to tumorigenesis and whether they impart therapeutic vulnerability are poorly understood. To address these questions, we generated a genetically engineered mouse model of melanoma based on conditional and melanocyte-specific deletion of KMT2D. We demonstrate KMT2D as a bona fide tumor suppressor which cooperates with activated BRAF. KMT2D-deficient tumors showed substantial reprogramming of key metabolic pathways including glycolysis. Glycolysis enzymes, intermediate metabolites and glucose consumption rate were aberrantly upregulated in KMT2D mutant cells. The pharmacological inhibition of glycolysis reduced proliferation and tumorigenesis preferentially in KMT2D mutant cells. Mechanistically, KMT2D loss caused drastic reduction of H3K4me1-marked active enhancer states. Loss of distal enhancer and subsequent reduction in expression of IGFBP5 activated IGF1R-AKT to increase glycolysis in KMT2D-deficient cells. We conclude that KMT2D loss promotes tumorigenesis by facilitating increased usage of glycolysis pathway for enhanced biomass needs via enhancer reprogramming. Our data imply that inhibition of glycolysis or IGFR pathway could be a potential therapeutic strategy in KMT2D mutant tumors.

cancer biology↗