Biology subjects

Ramirez, M. D.

Publications and source records attributed to Ramirez, M. D..

5 recordsLinked to original sources

bioRxiv2026

Phosphatidylserine receptors are critical for lethal infection by Crimean-Congo hemorrhagic fever virus

The tick-borne Crimean-Congo hemorrhagic fever virus (CCHFV) causes severe and often fatal hemorrhagic disease for which no approved countermeasures are available. Herein, we identify the phosphatidylserine receptors (PSRs) AXL, TIM-1, and TIM-4 as critical entry host factors for CCHFV in cell lines and liver-derived primary cell cultures. Small-molecule and antibody-based PSR inhibitors greatly reduced viral infection in cell culture. Germline knockout of individual PSR genes afforded partial protection against CCHFV infection, disease, and death in a murine model of lethal viral challenge. Mice engineered to lack two PSRs were completely protected from challenge, with viremia and viral replication, pathology, and inflammation in the liver and spleen reduced to baseline. Therefore, PSRs are collectively indispensable for CCHFV infection and pathogenesis. We conclude that PSRs are not just cell entry factors but bona fide determinants of infection, dissemination, and disease by CCHFV and legitimate targets for the development of new antiviral countermeasures.

microbiology↗

bioRxiv2023

Egg-laying hormone expression in identified neurons across developmental stages and reproductive states of the nudibranch Berghia stephanieae

Neuropeptides play essential roles in coordinating reproduction. Egg-laying hormone (ELH) is conserved in genetic sequence and behavioral function across molluscs, where neuronal clusters secrete ELH to modulate and induce egg-laying. Here we investigated ELH in the nudibranch mollusc, Berghia stephanieae. ELH preprohormone gene orthologs, which showed clade-specific differences at the C-terminus of the predicted bioactive peptide, were identified in brain transcriptomes across several nudipleuran species, including B. stephanieae. Injection of synthesized B. stephanieae ELH peptide into mature individuals induced egg-laying. ELH gene expression in the brain and body was mapped using in-situ hybridization chain reaction. Across the adult brain, 300-400 neurons expressed ELH. Twenty-one different cell types were identified in adults, three of which were located unilaterally on the right side, which corresponds to the location of the reproductive organs. Ten cell types were present in pre-reproductive juvenile stages. An asymmetric cluster of approximately 100 small neurons appeared in the right pedal ganglion of late-stage juveniles. Additional neurons in the pleural and pedal ganglia expressed ELH only in adults that were actively laying eggs and sub-adults that were on the verge of doing so, implicating their direct role in reproduction. Outside the brain, ELH was expressed on sensory appendages, including in presumptive sensory neurons. ELH shares deep homology with the corticotropin-releasing hormone gene family, which has roles broadly in stress response. Its widespread expression in the nudibranch B. stephanieae suggests that ELH plays a role beyond reproduction in gastropod molluscs. HighlightsO_LIEgg-laying hormone (ELH) preprohormone sequences were identified in the transcriptomes of several nudipleuran molluscs. C_LIO_LIMany ELH-expressing neurons and clusters in the brain could be individually identified based on soma position and morphology. C_LIO_LISome identified ELH-expressing neurons were not observed until later juvenile stages. C_LIO_LISome neurons expressed ELH in adults only when they were actively laying eggs. C_LIO_LIMany hundreds of ELH-expressing neurons were present in peripheral appendages. C_LI

neuroscience↗

bioRxiv2023

A chromosome-level genome for the nudibranch gastropod Berghia stephanieae helps parse clade-specific gene expression in novel and conserved phenotypes

How novel phenotypes originate from conserved genes, processes, and tissues remains a major question in biology. Research that sets out to answer this question often focuses on the conserved genes and processes involved, an approach that explicitly excludes the impact of genetic elements that may be classified as clade-specific, even though many of these genes are known to be important for many novel, or clade-restricted, phenotypes. This is especially true for understudied phyla such as mollusks, where limited genomic and functional biology resources for members of this phylum has long hindered assessments of genetic homology and function. To address this gap, we constructed a chromosome-level genome for the gastropod Berghia stephanieae (Valdes, 2005) to investigate the expression of clade-specific genes across both novel and conserved tissue types in this species. The final assembled and filtered Berghia genome is comparable to other high quality mollusk genomes in terms of size (1.05 Gb) and number of predicted genes (24,960 genes), and is highly contiguous. The proportion of upregulated, clade-specific genes varied across tissues, but with no clear trend between the proportion of clade-specific genes and the novelty of the tissue. However, more complex tissue like the brain had the highest total number of upregulated, clade-specific genes, though the ratio of upregulated clade-specific genes to the total number of upregulated genes was low. Our results, when combined with previous research on the impact of novel genes on phenotypic evolution, highlight the fact that the complexity of the novel tissue or behavior, the type of novelty, and the developmental timing of evolutionary modifications will all influence how novel and conserved genes interact to generate diversity.

genomics↗

bioRxiv2023

Mapping neuronal gene expression reveals aspects of ganglionic organization in a gastropod mollusc

Gastropod molluscs such as Aplysia, Lymnaea, and Tritonia have been important for determining fundamental rules of motor control, learning, and memory because of their large, individually identifiable neurons. Yet for the vast majority of gastropod neurons, as well as glia, there are no established molecular markers, limiting the ability to establish brain-wide structure-function relations. Here we combine high-throughput, single-cell RNA sequencing (scRNAseq) with in-situ hybridization chain reaction (HCR) in the nudibranch Berghia stephanieae to identify and visualize the expression of markers for cell types. Broad neuronal classes were characterized by genes associated with neurotransmitters, like acetylcholine, glutamate, serotonin, and GABA, as well as neuropeptides. These classes were subdivided by other genes including transcriptional regulators and unannotated genes. Marker genes expressed by neurons and glia formed discrete, previously unrecognized regions within and between ganglia. This study provides the foundation for understanding the fundamental cellular organization of gastropod nervous systems.

neuroscience↗

bioRxiv2019

Accelerated clearing and molecular labeling of large tissue samples using magnetohydrodynamic force

Here we report a strategy to efficiently render opaque biological tissues transparent and demonstrate that this approach can be modified to rapidly label intact samples with antibodies for large volume fluorescence microscopy. This strategy applies a magnetohydrodynamic (MHD) force to accelerate the removal of lipids from and the introduction of antibodies into tissue samples as large as an intact adult mouse brain. This strategy complements a growing array of tools that enable high-resolution 3-dimensional anatomical analyses in intact tissues using fluorescence microscopy. MHD-accelerated clearing and MHD-accelerated antibody labeling are fast, reliable, inexpensive, and compatible with existing strategies for high-quality fluorescence microscopy of intact tissues.

neuroscience↗