Biology subjects

Murphy, M. R.

Publications and source records attributed to Murphy, M. R..

8 recordsLinked to original sources

bioRxiv2026

A modular Bayesian framework for inferring transmission networks from polyclonal infections, with application to Plasmodium falciparum

MotivationMolecular surveillance and infectious disease transmission network reconstruction can provide compelling evidence for estimating public-health quantities that are difficult to observe directly, including importation, source-sink structure, and differences in onward transmission across locations or intervention strata. These quantities can be expressed as functions of the underlying transmission network, but individual transmission events are rarely observed and many networks may be consistent with the same data. Existing transmission network reconstruction methods leveraging genetic data are often built for settings in which each infection has one dominant source, one representative haplotype, and mutation-driven genetic divergence along transmission chains. These assumptions are poorly matched to polyclonal infections, in which hosts carry multiple genetically distinct clones and recipient infections may reflect contributions from multiple sources. Such infections are common in malaria, tuberculosis, HIV, and many parasitic infections. Methods are needed that can accommodate these data. ResultsWe present a modular Bayesian framework for estimating directed transmission on sampled cases, where an infection may have no sampled parent, one parent, or several parents, including sources outside the observed panel. Pathogen-specific modules supply likelihoods over candidate parent sets and connect to shared inference that yields marginal directed edge probabilities, posterior mean out-degree, and inclusion probabilities for unobserved parents. We demonstrate our framework with Plasmotrack, a transmission network model for Plasmodium falciparum that uses targeted amplicon sequencing data. We implemented these components with a per-locus allele-mixture transmission likelihood, an amplicon genotyping error model, and data augmentation allowing for unobserved parents. Simulations from a biologically informed generative model, under which the inferential per-locus allele-mixture likelihood is misspecified, showed recovery of aggregate network summaries including mean outdegree and mean unobserved-source inclusion, alongside high precision and recall for detecting directed transmission. Other pathogens can reuse the same modular composition after substituting transmission and observation likelihoods. AvailabilityThe Plasmotrack software and documentation are available at https://github.com/eppicenter/plasmotrack. Source code and example datasets are provided under an open-source license. Contactmaxwell.murphy@ucsf.edu

bioinformatics↗

bioRxiv2026

Decoding the MYC locus reveals a druggable ultraconserved RNA element

The human genome is dominated by noncoding sequences, most of which are poorly conserved across species. How genetic information is distributed between coding and noncoding regions remains a fundamental unresolved question. Using CRISPR saturation mutagenesis at base-pair resolution, we mapped the functional fitness landscape of the 10-kb human MYC locus with a near-PAMless, high-fidelity SpRY-Cas9. This unbiased interrogation revealed that the majority (67%) of functionally essential base-pairs in this locus are noncoding. Paradoxically, the phenotypic impact of noncoding sequences correlates inversely with evolutionary conservation, driven in part by rapidly diverging cis-regulatory DNA elements that remain functionally constrained in humans. Within this landscape, we identified an ultraconserved RNA element in the 3 untranslated region (UTR) that is indispensable for MYC-dependent cancer cells. Remarkably, steric-blocking antisense oligos targeting this RNA element selectively eliminate MYC-addicted cancer cells by suppressing MYC function without reducing MYC abundance. Mechanistically, this 3' UTR element promotes perinuclear localization of MYC mRNA and efficient nuclear import of the short-lived MYC protein, enabling its function as a nuclear transcription factor. Together, these findings highlight noncoding sequences as major carriers of functional genetic information, provide a comprehensive fitness map of the MYC locus, and uncover a therapeutically actionable RNA element that disables MYC-driven cancer.

genomics↗

bioRxiv2025

An optogenetic toolkit for robust activation of FGF, BMP, and Nodal signaling in zebrafish

Cell signaling regulates a wide range of biological processes including development, homeostasis, and disease. Accessible technologies to precisely manipulate signaling have important applications in basic and translational research. Here, we present an optogenetic toolkit for signaling manipulation in zebrafish embryos. We introduce a zebrafish-optimized optogenetic FGF signaling activator and a single-transcript Nodal signaling activator, and assess them together with a previously established BMP signaling activator. We thoroughly characterize this suite of tools and demonstrate light-dependent spatiotemporal control of signaling in vivo. In response to [~]455 nm (blue) light, zebrafish receptor kinase domains fused to blue light-dimerizing LOV domains enable robust signaling activation with minimal inadvertent activity in the dark or at wavelengths over 495 nm. Each optogenetic tool initiates pathway-specific signaling and activates known target genes. Signaling is activated with rapid on/off kinetics, and activation strength can be tuned by adjusting light irradiance. Finally, we demonstrate spatially localized signaling activation in vivo. Together, our results establish this optogenetic toolkit as a potent experimental platform and provide guidelines for rapid, direct, and adjustable activation of FGF, BMP, and Nodal signaling in zebrafish embryos.

developmental biology↗

bioRxiv2025

Recessive but damaging alleles of muscle-specific ribosomal protein gene RPL3L drive neonatal dilated cardiomyopathy

The heart employs a specialized ribosome in its muscle cells to translate genetic information into proteins, a fundamental adaptation with an elusive physiological role1-3. Its significance is underscored by the discovery of neonatal patients suffering from often fatal heart failure caused by severe dilated cardiomyopathy when both copies of the gene RPL3L are mutated4-9. RPL3L is a muscle-specific paralog1-3 of the ubiquitous ribosomal protein L3 (RPL3), which makes the closest contact of any protein to the ribosomes RNA-based catalytic center10. RPL3L-linked heart failure represents the only known human disease associated with tissue-specific ribosomes, yet the underlying pathogenetic mechanisms remain poorly understood. Intriguingly, disease is linked to a large number of mostly missense variants in RPL3L, and RPL3L-knockout resulted in no severe heart defect in either human or mice3, 11-13, challenging the prevailing view that autosomal recessive diseases are caused by loss-of-function mutations. Here, we report three new cases of RPL3L-linked severe neonatal heart failure and present a unifying pathogenetic mechanism by which a large number of variants in the muscle-specific ribosome led to disease. Specifically, affected families often carry one of two recurrent toxic gain-of-function variants alongside a family-specific putative loss-of-function variant. While the non-recurrent variants often trigger partial compensation of RPL3 similar to Rpl3l-knockout mice, both recurrent variants exhibit increased affinity for the RPL3/RPL3L chaperone GRWD114-16 and 60S biogenesis factors, sequester 28S rRNA in the nucleus, disrupt ribosome biogenesis, and trigger severe cellular toxicity that extends beyond the loss of ribosomes. These findings provide critical insights for genetic screening and therapeutic development of neonatal heart failure. Our results suggest that gain-of-toxicity mechanisms may be more prevalent in autosomal recessive diseases, and a combination of gain-of-toxicity and loss-of-function mechanisms could underlie many diseases involving genes with paralogs.

molecular biology↗

bioRxiv2023

Developmental remodeling repurposes larval neurons for sexual behaviors in adult Drosophila

Most larval neurons in Drosophila are repurposed during metamorphosis for functions in adult life, but their contribution to the neural circuits for sexually dimorphic behaviors is unknown. Here, we identify two interneurons in the nerve cord of adult Drosophila females that control ovipositor extrusion, a courtship rejection behavior performed by mated females. We show that these two neurons are present in the nerve cord of larvae as mature, sexually monomorphic interneurons. During pupal development, they acquire the expression of the sexual differentiation gene, doublesex, undergo doublesex-dependent programmed cell death in males, and are remodeled in females for functions in female mating behavior. Our results demonstrate that the neural circuits for courtship in Drosophila are built in part using neurons that are sexually reprogrammed from former sex-shared activities in larval life.

neuroscience↗

bioRxiv2023

Long Non-Coding RNA Generated from CDKN1A Gene by Alternative Polyadenylation Regulates p21 Expression during DNA Damage Response

Alternative Polyadenylation (APA) is an emerging mechanism for dynamic changes in gene expression. Previously, we described widespread APA occurrence in introns during the DNA damage response (DDR). Here, we show that a DNA damage activated APA event occurs in the first intron of CDKN1A, inducing an alternate last exon (ALE)-containing lncRNA. We named this lncRNA SPUD (Selective Polyadenylation Upon Damage). SPUD localizes to polysomes in the cytoplasm and is detectable as multiple isoforms in available high throughput studies. SPUD has low abundance compared to the CDKN1A full-length isoform and is induced in cancer and normal cells under a variety of DNA damaging conditions in part through p53 transcriptional activation. RNA binding protein (RBP) HuR and the transcriptional repressor CTCF regulate SPUD levels. SPUD induction increases p21 protein, but not CDKN1A full-length levels, affecting p21 functions in cell-cycle, CDK2 expression, and cell viability. Like CDKN1A full-length isoform, SPUD can bind two competitive p21 translational regulators, the inhibitor calreticulin and the activator CUGBP1; SPUD can change their association with CDKN1A full-length in a DDR-dependent manner. Together, these results show a new regulatory mechanism by which a lncRNA controls p21 expression post-transcriptionally, highlighting lncRNA relevance in DDR progression and cellcycle.

molecular biology↗

bioRxiv2021

RNA-guided cell targeting with CRISPR/RfxCas13d collateral activity in human cells

While single-cell sequencing has allowed rapid identification of novel cell types or states and associated RNA markers, functional studies remain challenging due to the lack of tools that are able to target specific cells based on these markers. Here we show that targeting a single marker RNA with CRISPR/RfxCas13d led to collateral transcriptome destruction in human cells, which can be harnessed to inhibit cell proliferation or to suppress cell state transition.

molecular biology↗

bioRxiv2017

Improved Aedes aegypti mosquito reference genome assembly enables biological discovery and vector control

Female Aedes aegypti mosquitoes infect hundreds of millions of people each year with dangerous viral pathogens including dengue, yellow fever, Zika, and chikungunya. Progress in understanding the biology of this insect, and developing tools to fight it, has been slowed by the lack of a high-quality genome assembly. Here we combine diverse genome technologies to produce AaegL5, a dramatically improved and annotated assembly, and demonstrate how it accelerates mosquito science and control. We anchored the physical and cytogenetic maps, resolved the size and composition of the elusive sex-determining \"M locus\", significantly increased the known members of the glutathione-S-transferase genes important for insecticide resistance, and doubled the number of chemosensory ionotropic receptors that guide mosquitoes to human hosts and egg-laying sites. Using high-resolution QTL and population genomic analyses, we mapped new candidates for dengue vector competence and insecticide resistance. We predict that AaegL5 will catalyse new biological insights and intervention strategies to fight this deadly arboviral vector.

genomics↗