Biology subjects

Byrne, A. B.

Publications and source records attributed to Byrne, A. B..

3 recordsLinked to original sources

bioRxiv2023

A single neuron in C. elegans orchestrates multiple motor outputs through parallel modes of transmission

Animals generate a wide range of highly coordinated motor outputs, which allows them to execute purposeful behaviors. Individual neuron classes in the circuits that generate behavior have a remarkable capacity for flexibility, as they exhibit multiple axonal projections, transmitter systems, and modes of neural activity. How these multi-functional properties of neurons enable the generation of highly coordinated behaviors remains unknown. Here we show that the HSN neuron in C. elegans evokes multiple motor programs over different timescales to enable a suite of behavioral changes during egg-laying. Using HSN activity perturbations and in vivo calcium imaging, we show that HSN acutely increases egg-laying and locomotion while also biasing the animals towards low-speed dwelling behavior over longer timescales. The acute effects of HSN on egg-laying and high-speed locomotion are mediated by separate sets of HSN transmitters and different HSN axonal projections. The long-lasting effects on dwelling are mediated by HSN release of serotonin that is taken up and re-released by NSM, another serotonergic neuron class that directly evokes dwelling. Our results show how the multi-functional properties of a single neuron allow it to induce a coordinated suite of behaviors and also reveal for the first time that neurons can borrow serotonin from one another to control behavior.

neuroscience↗

bioRxiv2022

Evidence-based calibration of computational tools for missense variant pathogenicity classification and ClinGen recommendations for clinical use of PP3/BP4 criteria

Recommendations from the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) for interpreting sequence variants specify the use of computational predictors as Supporting level of evidence for pathogenicity or benignity using criteria PP3 and BP4, respectively. However, score intervals defined by tool developers, and ACMG/AMP recommendations that require the consensus of multiple predictors, lack quantitative support. Previously, we described a probabilistic framework that quantified the strengths of evidence (Supporting, Moderate, Strong, Very Strong) within ACMG/AMP recommendations. We have extended this framework to computational predictors and introduce a new standard that converts a tools scores to PP3 and BP4 evidence strengths. Our approach is based on estimating the local positive predictive value and can calibrate any computational tool or other continuous-scale evidence on any variant type. We estimate thresholds (score intervals) corresponding to each strength of evidence for pathogenicity and benignity for thirteen missense variant interpretation tools, using carefully assembled independent data sets. Most tools achieved Supporting evidence level for both pathogenic and benign classification using newly established thresholds. Multiple tools reached score thresholds justifying Moderate and several reached Strong evidence levels. One tool reached Very Strong evidence level for benign classification on some variants. Based on these findings, we provide recommendations for evidence-based revisions of the PP3 and BP4 ACMG/AMP criteria using individual tools and future assessment of computational methods for clinical interpretation.

bioinformatics↗

bioRxiv2020

TIR-1/SARM1 Inhibits Axon Regeneration

An injured axon has two choices, regenerate or degenerate. In many neurons, the result is catastrophic axon degeneration and a failure to regenerate. To coerce the injured nervous system to regenerate, the molecular mechanisms that regulate both axon regeneration and degeneration need to be defined. We found that TIR-1/SARM1, a key regulator of axon degeneration, inhibits regeneration of injured motor axons. Loss of tir-1 function both reduces the frequency with which severed axon fragments degenerate and increases the frequency of axon regeneration. The increased regeneration in tir-1 mutants is not a secondary consequence of its effects on degeneration. Rather, TIR-1 carries out each of these opposing functions cell autonomously by regulating independent downstream genetic pathways. While promoting axon degeneration with the DLK-1 mitogen activated protein kinase (MAPK) signaling cascade, TIR-1 inhibits axon regeneration by activating the NSY-1/ASK1 MAPK signaling cascade. Our finding that TIR-1 regulates both axon regeneration and degeneration provides critical insight into how axons coordinately regulate the two key responses to injury, consequently informing approaches to manipulate the balance between these responses towards repair.

neuroscience↗