Biology subjects

Hassan, H.

Publications and source records attributed to Hassan, H..

At least 19 recordsLinked to original sources

bioRxiv2026

Extensive membrane lipid remodeling at the host-parasite interface of Toxoplasma gondii

Phosphoinositides regulate diverse membrane trafficking and signaling events in eukaryotic cells, yet their transbilayer distribution remains largely unexplored, particularly at host-parasite membrane interfaces. Here, we determined the membrane leaflet localization of phosphatidylinositol 4-phosphate (PtdIns(4)P) and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) in Toxoplasma gondii using quick-freezing freeze-fracture replica labeling combined with phosphoinositide-specific probes. Both phosphoinositides were predominantly localized to the cytoplasmic leaflet of the parasite plasma membrane, whereas only weak labeling was detected in the inner membrane complex. PtdIns(4)P, but not PtdIns(4,5)P2, was additionally detected on intracellular vesicles, while mature micronemes lacked detectable labeling for either phosphoinositide. Surprisingly, both phosphoinositides exhibited nearly symmetric distributions between the two leaflets of the parasitophorous vacuole membrane (PVM), in striking contrast to their asymmetric localization in the parasite plasma membrane. Together with our previous demonstration that phosphatidylserine and phosphatidylethanolamine also lose their transbilayer asymmetry in the PVM, these findings indicate that the PVM undergoes global membrane lipid remodeling that extends from major phospholipids to phosphoinositides. We propose that this extensive lipid reorganization represents a defining structural feature of the apicomplexan PVM and provides a new framework for understanding membrane identity at the host-parasite interface.

cell biology↗

bioRxiv2026

Spatio-temporally regulated maternal RNA decay factor essential for zebrafish development

Maternal mRNA decay is essential for the Maternal-to-Zygotic Transition (MZT), yet its impact on spatial regulation has remained largely unexplored. We identify Cth1 as the first maternally encoded RNA-decay factor regulated in a spatiotemporal manner outside the germline in zebrafish, driven by conserved 3'UTR cis-elements. RfxCas13-dmediated depletion of maternal cth1 revealed early developmental defects that could not be assessed with SpyCas9 mutants due to infertility from impaired gametogenesis. Mechanistically, Cth1 acts independently of zygotic genome activation, recognizing AUrich motifs in maternal 3'UTRs to promote deadenylation and decay in a spatio-temporal manner; deletion of these motifs or depletion of Cth1 stabilizes both reporter and endogenous transcripts. These findings establish Cth1 as a key component of the maternal program and provide the first direct evidence that spatio-temporally regulated mRNA decay, outside the germline, contributes to early vertebrate development.

developmental biology↗

bioRxiv2026

Parasitophorous vacuole membranes of Toxoplasma gondii and Plasmodium falciparum lack the lipid asymmetry characteristic of host cell plasma membranes

Apicomplexan parasites, including Toxoplasma gondii and Plasmodium falciparum, reside within a specialized compartment known as the parasitophorous vacuole (PV) during their intracellular life cycle. The PV membrane (PVM), which derives from the host plasma membrane upon invasion, serves as a selective barrier that permits nutrient acquisition while shielding the parasite from host defense mechanisms. Although the protein composition of the PVM has been studied extensively, its lipid organization remains poorly understood. Using the quick-freeze, freeze-fracture replica labeling (QF-FRL) method, we quantitatively analyzed the transbilayer distribution of phosphatidylserine (PtdSer), phosphatidylethanolamine (PtdEtn), and GM3 ganglioside in the PVM of T. gondii and P. falciparum. Unlike host cell plasma membranes, where these lipids exhibit strict asymmetry--PtdSer and PtdEtn confined to the cytoplasmic leaflet and GM3 to the exoplasmic leaflet--we found that all three lipids were symmetrically distributed across both leaflets of the PVM. This striking loss of lipid asymmetry suggests that the PVM undergoes profound remodeling during infection. The presence of PtdSer and PtdEtn in the luminal leaflet may facilitate the binding of perforin-like proteins (PLP1s) during egress. These findings reveal a unique feature of the PVM that redefines our understanding of host-parasite membrane biology.

cell biology↗

bioRxiv2026

Structure-function studies of HRIKD-{triangleup}KI, a Minimal Kinase Domain of Human Heme-Regulated Inhibitor Kinase

EIF2 kinase heme-regulated inhibitor (HRI) is a novel target for haematological malignancies with modulators reported to trigger cell death via the HRI-eIF2-ATF4 pathway. We report a protocol for producing the minimal kinase domain of full-length human HRI, termed HRIKD-{Delta}KI, where the unstructured 140 amino acid (aa) kinase insert (KI) within HRI kinase domain (HRIKD) is replaced with a 2aa glycine/serine (GS) linker. X-ray crystal structures were determined of apo-HRIKD-{Delta}KI and of its complex with ATP at 2.1 & 2.5 [A] resolution respectively. Both structures display a canonical bi-lobal kinase fold. However, they remain in a non-productive state with a displaced C-helix, disassembled R-spine, and a disordered activation segment hindering the substrate site. Biophysical assays (fluorescence based thermal shift & Synchrotron Radiation Circular Dichroism) demonstrate HRIKD-{Delta}KI retains its functional ligand-binding conformation. All together, these findings define structural and ligand-binding features of HRI to support ongoing drug discovery efforts in blood cancer.

biochemistry↗

bioRxiv2026

Isoform-Specific Functions of p73 Drive Survival and Chemoresistance in Diffuse Large B-Cell Lymphoma

Diffuse large B-cell lymphoma (DLBCL) represents 30-40% of non-Hodgkin lymphoma cases and is curable in >60% of patients; however, approximately one-third ultimately relapse. Although prior studies in normal B cells and lymphoma models implicate p73 in B-cell lymphomagenesis, the functional role of individual p73 isoforms in DLBCL remains poorly defined. TP73, a TP53 family member located on chromosome 1p36, encodes both transcriptionally active (TAp73) and dominant-negative ({Delta}Np73) isoforms that differentially regulate apoptosis and proliferation. In this study, we characterized p73 locus alterations, isoform-specific expression patterns, and their biological relevance in DLBCL. Chromosomal analysis revealed disruption of the 1p36 locus--predominantly via heterozygous deletion--in 35% of patient samples, which significantly correlated with elevated {Delta}Np73 expression. Immunohistochemical profiling demonstrated a positive association between TAp73 and cleaved caspase-3, and between {Delta}Np73 and Ki-67. Conversely, TAp73 expression negatively correlated with the anti-apoptotic proteins Bcl-2 and Bcl-6. Functional studies in DLBCL cell lines further confirmed that TAp73 enhances sensitivity to serum deprivation and doxorubicin, whereas {Delta}Np73 overexpression promotes survival and chemoresistance. Together, these findings identify p73 isoform imbalance as a key contributor to DLBCL pathogenesis and therapeutic response, highlighting {Delta}Np73 as a potential biomarker of aggressive disease and treatment resistance, and TAp73 as a tumor-suppressive axis warranting further investigation. SummaryDiffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma, yet relapse remains a major challenge. The p73 gene produces two key isoforms with opposing functions: TAp73, which promotes apoptosis, and {Delta}Np73, which inhibits cell death and supports tumor growth. In DLBCL samples, 1p36 chromosomal disruption occurred in 35% of cases and was associated with elevated {Delta}Np73. TAp73 expression correlated with apoptosis markers, whereas {Delta}Np73 correlated with proliferation. Functional studies showed TAp73 sensitizes DLBCL cells to stress and chemotherapy, while {Delta}Np73 enhances resistance. These findings highlight {Delta}Np73 as a potential biomarker and therapeutic target in DLBCL.

pathology↗

bioRxiv2025

Regulatory logic of neuronal identity specification in Drosophila

Combinations of terminal selector transcription factors (tsTFs) are thought to establish and maintain the unique identities of the numerous cell types found in nervous systems. However, it remains largely unclear how tsTF combinations are specified during development, and how they then coordinate the type-specific differentiation programs of each neuron. To investigate these regulatory mechanisms, we performed simultaneous single-cell RNA and ATAC sequencing on the Drosophila optic lobes at four stages of their development and identified over 250 distinct cell types. We characterized the common cis-regulatory features of neuronal enhancers and performed comprehensive inference of gene regulatory networks across cell types and stages. Our results reveal cell-type and stage-specific enhancers of many neuronal genes and the cooperative actions of tsTFs, pan-neuronal and ecdysone-responsive TFs on these enhancers. We show that the same effector genes are often regulated by different tsTF combinations acting through distinct enhancers in different neurons. During neurogenesis, tsTF codes are established within a brief critical period in newborn neurons, often through cell-type-specific enhancers that are not accessible in their progenitors. Accordingly, when neuroblast temporal patterning TFs are re-utilized as tsTFs in neurons, they are regulated independently through separate enhancers. Therefore, neuronal identity specification and differentiation is a multi-step regulatory program, wherein the same TFs enact distinct regulatory codes at different steps and across cell types.

neuroscience↗

bioRxiv2025

Early-Life Poultry-Derived Lactobacilli Drive Microbial Succession and Gut Immune Modulation in Broiler Chickens

Probiotic supplementation supports poultry gut health by modulating microbiome and promoting immune development, yet limited information is known about the effects of early, particularly embryonic, supplementation. In this study, we investigated the effects of administering a lactobacilli cocktail in ovo (embryonic day 18), post-hatch, or both on gut immunity and the succession of the cecal microbiota in broilers over five weeks. 16S rRNA gene-based sequencing of cecal contents revealed a steady increase in Shannon diversity during the first three weeks (PERMANOVA, p < 0.005), with community structure stabilizing by week 3 across all groups. In ovo lactobacilli administration improved early hatch rates and modulated microbial composition during early succession, including reductions in Klebsiella and Enterococcus, and enrichment of Lactobacillus, during the first two weeks (MaAsLin2, q < 0.25). These microbiome shifts were accompanied by a reduced expression of pro-inflammatory cytokines (IFN-{gamma}, IL-1{beta}, and IL-8) in cecal tonsils. These findings highlight the transient yet critical role of early-life probiotic interventions in shaping gut microbial colonization and immune response in broiler chickens. More importantly, a single in ovo lactobacilli dose yielded effects comparable to weekly oral or combined administration.

microbiology↗

bioRxiv2025

Modular regulation of the stem cell transcriptome defines self-renewal, differentiation, and dedifferentiation

Adult stem cells maintain tissue homeostasis, yet are themselves vulnerable to loss. One common mechanism to replace lost stem cells is dedifferentiation, in which progeny revert to stem cell identity. It is a paradox how stem cells and progeny retain the same stem cell potential while exhibiting distinct current identities of self-renewal, differentiation, and dedifferentiation. Here, we show that the Drosophila male germline lineage solves this paradox via two parallel and complementary mechanisms to separate potential and identity. First, differentiating progeny maintain stem cell potency by inheriting perdurant stem cell mRNAs without actively transcribing them. Second, two known niche signals (Bmp and Jak-Stat) activate distinct sets of targets, defining three identities (self-renewal, differentiation, and dedifferentiation) based on the combination of their on/off states. Together, this study reveals how a pool of dedifferentiation-competent progeny is maintained to regenerate stem cells as needed without resulting in stem cell overproduction, and resolves the puzzle of why most stem cell systems require multiple independent niche signals. Significance StatementDedifferentiation is a mechanism by which differentiating cells revert back to stem cell identity to compensate for the loss of stem cells, allowing for long-term tissue homeostasis. It remains poorly understood how stem cells and progeny retain the same stem cell potential while exhibiting distinct current identities of self-renewal, differentiation, and dedifferentiation. This study reveals two parallel mechanisms to separate cells potential and identity. First, differentiating progeny maintain stem cell potency by inheriting perdurant stem cell mRNAs. Second, two known niche signals (Bmp and Jak-Stat) activate distinct sets of targets, defining three identities (self-renewal, differentiation, and dedifferentiation) based on the combination of their on/off states. This study reveals how a pool of dedifferentiation-competent progeny is maintained to regenerate stem cells.

developmental biology↗

bioRxiv2024

Critical role of Spatio-Temporally Regulated Maternal RNAs in Zebrafish Embryogenesis

The maternal-to-zygotic transition shifts regulatory control from maternal to zygotic messenger RNAs (mRNA) through maternal mRNA degradation. While temporal aspects of maternal mRNA decay are known, spatial mechanisms remain underexplored. Using CRISPR-Cas9 and CRISPR-Cas13d systems, we functionally dissected the contribution of maternal versus zygotic fractions and overcame challenges of studying embryonic lethal genes. We identified differentially distributed maternal mRNAs in specific cells and evidenced the critical role of five maternal mRNAs, cth1, arl4d, abi1b, foxa and lhx1a, in embryogenesis. Further, we focused on the functionally uncharacterized cth1 gene, revealing its essential role in gametogenesis and embryogenesis. Cth1 acts as a spatio-temporal RNA decay factor regulating mRNA stability and accumulation of its targets in a spatio-temporal manner through 3UTR recognition during early development. Furthermore, Cth1 3UTR drives its spatio-temporal RNA localization. Our findings provide new insights into spatio-temporal RNA decay mechanisms and highlight dual CRISPR-Cas strategies in studying embryonic development. HighlightsO_LIDifferentially distributed marginal maternal RNAs have a critical role in early embryogenesis. C_LIO_LICas13d complements the Cas9 limitation to study the functions of embryonic lethal genes. C_LIO_LICth1 is essential for gametogenesis and early embryonic development. C_LIO_LICth1 is a maternal RNA decay factor required for spatio-temporal RNA regulation. C_LIO_LI3UTR of Cth1 drives its spatio-temporal RNA dynamics. C_LI

developmental biology↗

bioRxiv2024

Potential role of microRNAs in regulating transcriptional profile, and sculpting development and metabolism in cavefish.

Astyanax mexicanus, a species with both surface-dwelling and multiple cave-dwelling populations, offers a unique opportunity to study repeated adaptation to dark and resource-scarce environments. While previous work has identified large-scale changes in gene expression between morphs even under identical laboratory conditions, the regulatory basis of these expression differences remains largely unexplored. In this study, we focus on microRNAs (miRNAs) as key regulators of gene expression to understand cavefish adaptation nuances. Our analysis identified 683 miRNAs, which not only surpasses the number documented in related species but also provides the first comprehensive catalog of miRNAs for this species. We identified a unique subset of differentially expressed miRNAs common to all studied cave-dwelling populations, potentially orchestrating the nuanced gene expression patterns required for survival in the challenging cave milieu. Gene Ontology analysis of the predicted miRNA targets revealed involvement in developmental and metabolic pathways that are pivotal for thriving in nutrient-limited environments, such as the regulation of neuromast migration. Moreover, our study provides evidence for miRNA influence on circadian rhythm and oxidative stress response, both essential adaptations for the cave-dwelling lifestyle. The comprehensive miRNA catalog generated will guide future investigations into the intricate world of miRNA-mediated evolution of complex traits.

evolutionary biology↗

bioRxiv2023

Prioritization of The Zinc finger domain within BCL11A gene by the Amelioration capability of hemoglobinopathies using CRISPR-Cas9 technology

BCL11A/EVI9, a zinc-finger protein primarily expressed in brain and hematopoietic cells, plays a central role in lymphocyte development, gamma-globin suppression, spinal neuron development, sensory innervation, neuronal polarity, migration, and is associated with microcephaly and dysregulated brain-related genes, offering therapeutic potential for sickle cell disease. The function of the transcriptional regulator is intricately linked to its structural organization, which determines its ability to interact with specific DNA sequences and modulate gene expression. BCL11A boasts multiple domains, including six C2H2 zinc fingers, a C2HC zinc finger, a NuRD-interacting domain, an acidic domain, and a proline-rich domain. In the present study, we delve into the intricate structure and function of the zinc finger domains located in the BCL11A gene, which plays a crucial role in regulating the expression of gamma-globin gene. Specifically, three C2H2-type zinc finger domains, Znf4, Znf5, and Znf6, within BCL11A, are known to bind to DNA. Znf4 and Znf5 demonstrate a significant interaction with the TGACCA motif in the gamma-globin -115 HPFH region sequence, contributing substantially to DNA binding specificity. Although Znf3 and Znf6 also interact with DNA, their contributions are comparatively minor. Employing CRISPR-Cas9 technology, targeted genomic deletions of Znf4 exhibit high efficiency, opening doors for further research. Edited CD34+ cells successfully differentiate into erythrocytes without impairments, underscoring CRISPR-Cas9s suitability for studying gene functions in erythropoiesis. Furthermore, BCL11A knockdown via sgRNAs results in elevated gamma-globin expression, offering a promising therapeutic avenue for beta-hemoglobinopathies. HPLC analysis reveals a substantial increase in HbF levels, particularly upon Znf4 deletion, emphasizing BCL11A gene potential as a therapeutic target. These findings also highlight the connection between the function of BCL11A and its structural organization, which can be modulated, and this insight can potentially be extended to uncover its roles in various other domains.

molecular biology↗

bioRxiv2023

Emergence of the Novel Infectious bursal disease viruse Variant in Vaccinated Poultry Flocks in Egypt

Infectious bursal disease viruses (IBDVs) have a profound impact on poultry production worldwide, directly causing mortality rates of up to 100%, and indirectly through their immunosuppressive effects. Since the emergence of the antigenically modified very virulent IBDV (vvIBDV) in Egypt in late 1999, the country has experienced recurrent outbreaks with high mortality rates and typical vvIBDV gross lesions. However, a notable shift occurred in 2023, characterized by a substantial increase in reported subclinical IBDV cases exhibiting atrophied bursa and associated immunosuppression. To assess the field situation, we examined samples from 21 farms in 2023 and 18 farms from 2021 and 2022, all of which experienced IBD outbreaks based on clinical diagnosis. These samples were submitted to our laboratory for confirmatory testing and subsequently subjected to VP2-HVR sequencing. Phylogenetic analysis revealed that all samples collected in 2021 and 2022 clustered with classical virulent strains and very virulent IBDV. In 2023, one sample clustered with the Egyptian vvIBDV, while one sample clustered with classic virulent IBDV, and the remaining 2023 samples clustered with the Chinese novel variant IBDV (nVarIBDV). The alignment of deduced amino acid sequences for VP2 revealed that all Egyptian classic virulent strains were similar to the Winterfield or Leukert strains. In contrast, vvIBDV strains exhibited two out of the three typical residues found in Egyptian antigenically atypical vvIBDV, namely Y220F and G254S, but not A321T, and one sample was identical to the European vvIBDV (emerged in 1989). Meanwhile, all variant strains recognized in the present study exhibited typical residues found in variant IBDV, in addition to the three conserved amino acid residues found only in Chinese variant IBDVs. However, all Egyptian variant strains showed a mutation at position 321 (321V), which represents the most exposed part of the capsid and is known to have a massive impact on IBDV antigenicity, with the exception of one sample that had 318G instead. This report highlights the emergence of a new variant IBDV clustered with the Chinese new variant in Egypt, causing bursa atrophy and spreading subclinically in broiler farms over a wide geographic distance, resulting in massive economic losses due to immunosuppression.

microbiology↗

bioRxiv2023

3D spheroid culturing of Astyanax mexicanus liver-derived cell lines recapitulates distinct transcriptomic and metabolic states of in vivo tissue environment.

In vitro assays are crucial tools for gaining detailed insights into various biological processes, including metabolism. Cave morphs of the river-dwelling fish species, Astyanax mexicanus, have adapted their metabolism allowing them to thrive in the biodiversity-deprived and nutrient-limited environment of caves. Liver-derived cells from the cave and river morphs of Astyanax mexicanus have proven to be excellent in vitro resources to better understand the unique metabolism of these fish. However, the current 2D cultures have not fully captured the complex metabolic profile of the Astyanax liver. It is known that 3D culturing can modulate the transcriptomic state of cells when compared to its 2D monolayer culture. Therefore, in order to broaden the possibilities of the in vitro system by modeling a wider gamut of metabolic pathways, we cultured the liver-derived Astyanax cells of both surface and cavefish into 3D spheroids. We successfully established 3D cultures at various cell seeding densities for several weeks and characterized the resultant transcriptomic and metabolic variations. We found that the 3D cultured Astyanax cells represent a wider range of metabolic pathways, including cell cycle changes and antioxidant activities, associated with liver functioning as compared to its monolayer culture. Additionally, the spheroids also exhibited surface and cave-specific metabolic signatures, making it a suitable system for evolutionary studies associated with cave adaptation. Taken together, the liver-derived spheroids prove to be a promising in vitro model for widening our understanding of metabolism in Astyanax mexicanus and of vertebrates in general.

evolutionary biology↗

bioRxiv2023

The Mexican Cavefish Mount a Rapid and Sustained Regenerative Response Following Skeletal Muscle Injury

Physical injury and tissue damage is prevalent throughout the animal kingdom, with the ability to quickly and efficiently regenerate providing a selective advantage. The skeletal muscle possesses a uniquely large regenerative capacity within most vertebrates, and has thus become an important model for investigating cellular processes underpinning tissue regeneration. Following damage, the skeletal muscle mounts a complex regenerative cascade centered around dedicated muscle stem cells termed satellite cells. In non-injured muscle, satellite cells remain in a quiescent state, expressing the canonical marker Pax7 (Chen et al. 2020). However, following injury, satellite cells exit quiescence, enter the cell cycle to initiate proliferation, asymmetrically divide, and in many cases terminally differentiate into myoblasts, ultimately fusing with surrounding myoblasts and pre-existing muscle fibers to resolve the regenerative process (Chen et al. 2020).

evolutionary biology↗

bioRxiv2023

Circadian rhythm disruption is associated with skeletal muscle dysfunction within the blind Mexican Cavefish

Circadian control of physiology and metabolism is pervasive throughout nature, with circadian disruption contributing to premature aging, neurodegenerative disease, and type 2 diabetes (Musiek et al. 2016; Panda, 2016). It has become increasingly clear that peripheral tissues, such as skeletal muscle, possess cell-autonomous clocks crucial for metabolic homeostasis (Gabriel et al. 2021). In fact, disruption of the skeletal muscle circadian rhythm results in insulin resistance, sarcomere disorganization, and muscle weakness in both vertebrates and non-vertebrates - indicating that maintenance of a functional muscle circadian rhythm provides an adaptive advantage. We and others have found that cavefish possess a disrupted central circadian rhythm and, interestingly, a skeletal muscle phenotype strikingly similar to circadian knock-out mutants; namely, muscle loss, muscle weakness, and insulin resistance (Olsen et al. 2022; Riddle et al. 2018; Mack et al. 2021). However, whether the cavefish muscle phenotype results from muscle-specific circadian disruption remains untested. To this point, we investigated genome-wide, circadian-regulated gene expression within the skeletal muscle of the Astyanax mexicanus - comprised of the river-dwelling surface fish and troglobitic cavefish - providing novel insights into the evolutionary consequence of circadian disruption on skeletal muscle physiology.

evolutionary biology↗

bioRxiv2022

Comprehensive multi-omics characterization of gut microbiome extracellular vesicles reveals a connection to gut-brain axis signaling

Microbiota-gut-brain axis is an evident pathway of host-microbiota crosstalk that is linked to multiple brain disorders. Microbiota released extracellular vesicles (MEVs) has emerged as a key player in intercellular signaling in host microbiome communications. However, their role in gutbrain axis signaling is poorly investigated. Here, we performed a deep multi-omics profiling of MEVs content generated ex vivo and from stool samples in order to get some insights on their role in gut-brain-axis signaling. Metabolomics profiling identified a wide array of metabolites embedded in MEVs, including lipids, carbohydrates, amino acids, vitamins, and organic acids. Interestingly, many neurotransmitter-related compounds were detected inside MEVs, including arachidonyl-dopamine (NADA), gabapentin, glutamate and N-acylethanolamines. Next, we aimed to identify commensal microbes with psychobiotic activity. We isolated 58 Bacteroides strains assigned to four genera, 11 species, and 4 new species based on 16S rDNA sequencing. We performed whole genome sequencing of 18 representative isolates, followed by a comparative analysis of the structure of polysaccharide utilization loci (PUL) and glutamate decarboxylase (GAD), a genetic system involved in GABA production. Quantifying GABA was done using competitive ELISA, wherein three isolates (B. finegoldii, B. faecis, and B. caccae) showed high GABA production (4.5-7 mM range) in supernatant whereas 2.2 to 4 uM GABA concentration was detected inside microvesicles extracted using ultracentrifugation. To test the biodistribution of MEVs from the gut to other parts of the body, CACO-2, RIN-14 B, and hCMEC/D3 cells showed a capacity to internalize labeled MEVs through an endocytic mechanism. Additionally, MEVs exhibited a dose dependent paracellular transport through CACO-2 intestinal cells and hCMEC/D3 brain endothelial cells. In vivo results showed biodistribution of MEVs to liver, stomach and spleen. Overall, our results reveal the capabilities of MEVs to cross the intestinal and blood brain barriers to deliver their cargoes of neuroactive molecules to the brain as a new signaling mechanism in microbiota-gut-brain axis communications.

microbiology↗

bioRxiv2022

Hemisynthetic derivatives of the natural alkaloid trilobine are fast-acting antimalarial compounds with sustained activity in multi-drug resistant P. falciparum isolates

Malaria eradication requires the development of new drugs to combat drug-resistant parasites. The search for new chemical scaffolds that target novel pathways of the human malaria parasite Plasmodium falciparum is of highest priority. We identified bisbenzylisoquinoline alkaloids isolated from Cocculus hirsutus. (trilobine derivatives) as active in the nanomolar range against P. falciparum blood stages. Synthesis of a library of 94 hemi-synthetic derivatives allowed us to identify compound 84 that kills multi-drug resistant clinical isolates in the nanomolar range (median IC50 ranging from 35-88nM). Efforts were made to obtain compounds with significantly improved preclinical properties. Out of those, compound 125 delays the onset of parasitemia in P. berghei infected mice and inhibits P. falciparum transmission stages in vitro (culture assays) and in vivo using membrane feeding assay in the Anopheles stephensi vector. Compound 125 also impairs P. falciparum development in sporozoite-infected hepatocytes, in the low micromolar range. Finally, we used a chemical pull-down strategy to identify potential protein targets of this chemical family. Mass spectrometry analysis identified the parasite interactome with trilobine derivatives, identifying protein partners belonging to metabolic pathways that have not been previously targeted by antimalarial drugs or implicated in drug-resistance mechanisms.

pathology↗

bioRxiv2022

Molecular Control of Circuit Plasticity and the Permanence of Imprinted Odor Memory

Behavioral imprinting is a distinct form of learning that has a lifelong impact on social interactions and affectional behaviors1-4. Unlike other forms of memory, imprinting does not require conspicuous association of stimuli; exposure per se appears sufficient to induce memories that neither undergo extinction nor are altered by experience later in life. The site of storage of imprinted memory and the mechanisms that control its formation and permanence are unknown. Here we uncover a molecular mechanism that controls olfactory imprinting, which underlies behaviors including kin and nest recognition, maternal attachment, and homing5-10. We show that odor exposure during the perinatal period converts an innately aversive odor into a homing signal. The behavioral change is associated with odor-induced changes in the projection patterns of olfactory sensory neuron (OSN) expressing the cognate receptors for the exposed odor. We show that the Wnt signaling receptor Frizzled1 (Fzd1) acts as a master regulator of the critical period of OSN development and is responsible for closing the critical period to prevent further changes in the neural circuit. In Fzd1 knockout mice axon projection patterns are continually modified by sensory experience. As Fzd1 knockout abolishes the developmental critical period, it also abolishes odor imprinting. Specific knockout of Fzd1 in the OSNs have the same effect. Mechanistically, Fzd1 controls the critical period through an autoregulated shutdown and by controlling an activity-driven regulon in the OSNs. The transient expression and the subsequent downregulation of Fzd1 leads to the irreversible closure of the critical period to lock in circuits established during the critical period. The evidence suggests that imprinted odor memory is stored in the patterns of connectivity at the first synapse in the olfactory bulb. Early odor experience induces changes in the OSN projection to alter connectivity with innate circuits to establish a life-long memory.

neuroscience↗