Detection of G Protein-coupled Receptor Expression in Mouse Vagal Afferent Neurons using Multiplex In Situ Hybridization
September 20th, 2021
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Multiplex in situ hybridization (ISH) was employed to simultaneously visualize the transcripts for two G protein-coupled receptors and one transcription factor in the entire vagal ganglionic complex of the adult mouse. This protocol could be used to generate accurate maps of the transcriptional profiles of vagal afferent neurons.
Overview
This study utilizes multiplex in situ hybridization (ISH) to visualize transcripts of two G protein-coupled receptors and one transcription factor within the vagal ganglionic complex of adult mice. By applying this protocol, accurate maps of the transcriptional profiles of vagal afferent neurons can be generated, enhancing our understanding of their complex roles.
Key Study Components
Area of Science
- Neuroscience
- Gene Expression
- Neuroanatomy
Background
- Transcriptional profiling of heterogeneous cell types is crucial for understanding their functions.
- G protein-coupled receptors play significant roles in neuronal signaling.
- Understanding vagal afferent neuron profiles can elucidate their involvement in various neural pathways.
- Multiplex ISH provides a sensitive method for examining multiple RNA transcripts simultaneously.
Purpose of Study
- To visualize and analyze the expression profiles of multiple genes in vagal ganglionic neurons.
- To improve mapping of transcriptional variations in afferent neurons.
- To understand the functional diversity within the vagal afferent neuron population.
Methods Used
- The primary technique used is multiplex in situ hybridization (ISH).
- The biological model consists of vagal ganglionic neurons extracted from adult mice.
- Key steps include dissection, sample preparation, incubation with specific probes, and image acquisition.
- Sections are cut and treated to visualize the transcripts of interest, followed by imaging with a confocal microscope.
Main Results
- Multiplex ISH revealed specific transcript accumulation patterns for GHSR and CCK1R in nodose ganglion neurons.
- Phox2b expression was identified in afferent neurons, contributing to understanding neuronal identity.
- CCK1R signals were detected in considerable densities among ganglionic neurons, indicating functional heterogeneity.
- Overall findings highlight significant variations in gene expression within vagal neurons, essential for further research.
Conclusions
- This study demonstrates a robust technique for mapping transcript diversity in neuronal populations.
- The findings enhance our grasp of neuroanatomical complexity and receptor dynamics.
- Such profiling methods may have broad implications for understanding neuronal roles in health and disease.
Frequently Asked Questions
What are the advantages of using multiplex ISH?
Multiplex ISH allows for simultaneous visualization of multiple RNA transcripts, providing a comprehensive view of gene expression within tissue samples.
How is the vagal ganglionic mass collected for analysis?
The vagal ganglionic mass is dissected from adult mice after careful removal of surrounding muscles and tissues to expose the relevant nerves and ganglia.
What types of data does this method provide?
This method delivers spatially resolved gene expression data, facilitating insights into the transcriptional profiles of specific neuron populations.
How can these findings be applied in future research?
Results can inform studies on neuronal signaling and pathways involved in various physiological and pathological conditions, enhancing our understanding of neural functions.
What limitations should be considered when interpreting the results?
Considerations include the potential for variability in transcript levels across different neuronal subtypes and the specific conditions under which samples were prepared and analyzed.
How can the results contribute to understanding neurological disorders?
The insights gained on gene expression profiles may uncover molecular mechanisms underlying various neurological disorders, guiding therapeutic strategies.
Executive Industry Relevance
Accurate transcriptional mapping of heterogeneous neuronal populations supports target de-risking in neurotherapeutic discovery. Multiplex ISH enables simultaneous detection of GPCR expression and neuronal identity markers, improving confidence in target validation for vagal afferent pathways. This approach aids in prioritizing mechanistically grounded targets for gastrointestinal and metabolic disease indications.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of GPCR expression patterns in defined neuronal subtypes to clarify therapeutic hypotheses.
- Operational Value: Provides spatially resolved transcript data that supports functional target validation in native tissue context.
- Predictive Value: Reduces mechanistic ambiguity by linking receptor expression to anatomically defined afferent neuron populations.
Screening & Assay Development
- Assay Readiness: Generates standardized, reproducible ISH protocols for multiplex detection of GPCRs and lineage markers in ganglion sections.
- Quantitative Output: Enables calculation of co-expression percentages to support assay optimization and screening readiness.
- Platform Reuse: Compatible with immunohistochemistry, allowing integration into multimodal screening workflows for neuroanatomy-based target screening.
Translational & Preclinical Research
- Disease Relevance: Supports mapping of GPCR expression in vagal afferent neurons involved in gut-brain axis signaling, relevant to metabolic and gastrointestinal disorders.
- Translational Continuity: Enables cross-species extrapolation of transcriptional profiles to inform preclinical model selection.
- Risk-Adjusted Advancement: Provides expression data to de-risk targets by confirming neuronal site of action before functional assays.
Pipeline & Workflow Integration
The method fits within the discovery continuum from target identification to preclinical validation by providing molecular phenotyping of neuronal populations.
- Discovery Biology: Supports hypothesis testing and pathway clarification by mapping GPCR expression to specific afferent neuron subtypes.
- Screening: Delivers quantitative, spatially resolved outputs that enable reliable evaluation of target engagement in native tissue.
- Analytics: Generates co-expression metrics and distribution patterns that help compare conditions and prioritize targets.
- Translational Research: Connects discovery findings to preclinical continuity through anatomically grounded transcriptional profiling.
- Enterprise Reuse: Establishes a standardized ISH workflow applicable across multiple GPCR targets and neuronal systems.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in target validation by reducing false positives from ectopic or low-specificity expression.
- Operational Value: Ensures standardization and reproducibility through fixed-section ISH with RNAscope technology.
- Strategic Value: Improves go/no-go decisions by confirming target expression in relevant neuronal populations early in discovery.
- Portfolio Impact: Enables risk-adjusted prioritization of GPCR targets based on validated neuronal expression patterns.
Implementation Considerations
- Requires expertise in tissue dissection, fixation, and cryosectioning of murine ganglia.
- Dependent on RNAscope-compatible probes, hybridization ovens, and confocal imaging infrastructure.
- Necessitates cross-team standardization for probe design, signal quantification, and background control.
- Adaptation across model systems may require optimization of retrieval and amplification steps.
- Practical limitations include signal detection sensitivity for low-abundance transcripts and tissue autofluorescence at high laser power.
Biopharma FAQs
Why does multiplex ISH matter for target validation in neuronal GPCR discovery?
Multiplex ISH allows simultaneous detection of GPCR transcripts and neuronal identity markers, enabling confirmation of target expression in defined afferent neuron populations. This reduces mechanistic ambiguity by linking receptor presence to anatomically validated cell types. The method supports target de-risking by providing spatially resolved expression data before functional screening.
How does independent variable isolation in multiplex ISH support the discovery pipeline?
By using cell-type-specific markers like Phox2b and Prdm12, the method isolates GPCR expression to distinct neuronal subpopulations, treating cell identity as an independent variable. This enables clear attribution of CCK1R or GHSR expression to nodose or jugular afferent neurons. Such isolation improves target confidence by clarifying which neuron types express receptors of interest.
What quantitative dependent variable measurements does multiplex ISH enable for target assessment?
The method enables calculation of the percentage of RNAscope-positive profiles expressing each transcript, such as CCK1R in Phox2b-positive neurons. These measurements provide quantitative readouts of co-expression frequency and distribution within ganglia. Such data supports comparative analysis across conditions and informs target prioritization based on expression prevalence.
Why do replication requirements in multiplex ISH matter for cross-functional collaboration?
Replication across sections and animals ensures consistent detection of GPCR expression patterns, which is essential for reliable data sharing between discovery, screening, and preclinical teams. Consistent results build confidence in target expression maps used for go/no-go decisions. Standardized replication supports alignment across functions by providing reproducible, auditable evidence of neuronal target engagement.
What statistical analysis capabilities are required before implementing multiplex ISH for target validation?
Implementation requires capability to quantify signal-positive cells, calculate co-expression percentages, and assess signal-to-noise ratios using negative controls. Statistical comparison of expression frequencies across neuronal subtypes or conditions depends on accurate counting and threshold setting. These capabilities ensure that expression data is robust enough to support target validation decisions and portfolio triage.
Chapters in this video
0:04
Introduction
0:39
The Mouse Jugular-nodose Ganglia Sample Collection
2:51
Pretreatment of the Slides and In Situ Hybridization (ISH)
4:51
Microscopy and Data Analysis
5:34
Results: Microscopic Analysis of the Mouse Vagal Afferent Neurons After Multiplex in Situ Hybridization
7:34
Conclusion
