RLN3 Antibody

What is RLN3 and why are antibodies against it important for research?

RLN3 (Relaxin-3) is a member of the relaxin family peptide hormones that belongs to the insulin gene superfamily. In humans, this protein is encoded by the gene RLN3 and may also be known as H3, RXN3, ZINS4, insl7, insulin-like peptide 7, and insulin-like peptide INSL7. The protein has a reported amino acid length of 142 and an expected mass of 15.5 kDa .

Unlike the widespread expression of related proteins RLN1 and RLN2, RLN3 is predominantly expressed in brain (particularly in the nucleus incertus) and to a lesser extent in the thymus, kidney and spleen . RLN3 antibodies are critical research tools for:

• Studying RLN3 distribution in neural tissues

• Investigating the role of RLN3 in neurophysiological processes

• Examining RLN3's involvement in various pathological conditions

• Validating gene expression data at the protein level

What are the common applications for RLN3 antibodies in research?

Based on the available data, RLN3 antibodies are used in multiple research applications:

What species reactivity should I consider when selecting an RLN3 antibody?

Most commercially available RLN3 antibodies show reactivity to human and mouse RLN3. Some antibodies may also react with RLN3 variants in other species including rat, monkey, and porcine models . When selecting an antibody, consider:

• The experimental model organism

• The degree of conservation of the target epitope across species

• Validated species reactivity (documented in product literature)

• Cross-reactivity with other members of the relaxin protein family

How should I optimize immunohistochemical detection of RLN3 in brain tissue?

Detecting RLN3 in brain tissue requires careful optimization:

• Tissue preparation: Use 4% formaldehyde fixation overnight at 4°C for best results

• Antigen retrieval: For paraffin sections, use TE buffer pH 9.0 or alternatively citrate buffer pH 6.0

• Blocking conditions: Use 4% normal donkey serum (NDS), 2% bovine serum albumin (BSA) and 0.2% Triton X100 in 0.01 M PBS for 1 hour at room temperature

• Primary antibody incubation:

  • For mouse anti-RLN3: Dilute 1:10 (HK4-144-10) or as recommended by manufacturer

  • For rabbit anti-RLN3: Use 1:50-1:500 dilution range

  • Incubate overnight at 4°C

• Signal detection: For chromogenic detection, use biotinylated secondary antibody followed by ABC complex and DAB/nickel sulfate for a black reaction product

• Controls: Include negative controls (omitting primary antibody) and positive controls (tissues known to express RLN3)

What is the optimal protocol for double-labeling RLN3 with other neuronal markers?

For co-localization studies of RLN3 with neuronal markers, the following protocol has been validated:

• Initial blocking: Use blocking media of TBS containing 4% NDS, 2% BSA and 0.1% Triton X-100 for 1 hour at room temperature

• Primary antibody mix: Combine mouse anti-RLN3 (1:10) with rabbit antibodies against neuronal markers:

  • PV (1:2,500)

  • CB-28kD (1:5,000)

  • CR (1:1,250)

  • Synaptic markers like Synaptophysin (1:1,000)

• Incubation: 48 hours at 4°C in TBS containing 2% NDS, 2% BSA and 0.2% Triton X100

• Secondary antibody mix: Use fluorescent-labeled secondary antibodies (1:200 dilution):

  • FITC-labeled anti-rabbit IgG

  • Texas Red-labeled anti-mouse IgG

  • For triple/quadruple labeling: Add Cy5-labeled secondary antibodies

• Mounting: Use FluorSave™ Reagent or similar anti-fade mounting medium

How can I verify the specificity of RLN3 immunolabeling in my experiments?

To ensure specificity of RLN3 immunolabeling:

• Antibody validation controls:

  • Use RLN3 knockout tissues as negative controls (as demonstrated in RLN3-/- mice models)

  • Perform preabsorption tests with the immunizing peptide

  • Compare labeling patterns with multiple antibodies targeting different epitopes

• Cross-reactivity assessment:

  • Evaluate potential cross-reactivity with other relaxin family members (RLN1, RLN2)

  • Confirm labeling matches known RLN3 distribution patterns

• Technical controls:

  • Include no-primary-antibody controls

  • Use isotype-matched irrelevant antibodies as negative controls

  • Verify concentration-dependent signal

• Complementary techniques:

  • Correlate antibody labeling with mRNA expression (in situ hybridization)

  • Confirm with RNAscope™ for simultaneous detection of RLN3 protein and mRNA

How can RLN3 antibodies be used to investigate the role of RLN3-RXFP3 signaling in neurophysiological processes?

RLN3 antibodies have been instrumental in elucidating the RLN3-RXFP3 signaling pathway in the brain:

• Anatomical mapping: RLN3 antibodies have helped map the distribution of RLN3-positive fibers in relation to RXFP3-expressing neurons, particularly in:

  • Parahippocampal cortex including medial and lateral entorhinal cortex

  • Paraventricular nucleus (PVN)

  • Other brain regions involved in stress, arousal, and cognitive functions

• Functional studies: Combined with electrophysiology to understand how RLN3-RXFP3 signaling affects:

  • Inhibition of magnocellular neurons

  • Activation of ERK1/2 signaling

  • Inhibition of TGF-β/SMAD signaling

• Receptor-ligand interaction studies:

  • Visualizing co-distribution of RLN3 fibers and RXFP3-expressing neurons using double-labeling techniques

  • Identifying synaptic contacts using RLN3 antibodies combined with synaptic markers (synaptophysin)

• Signal transduction analysis: Investigating downstream pathways by combining RLN3 immunolabeling with phospho-specific antibodies against:

  • Phosphorylated ERK1/2

  • Phosphorylated SMAD2

What methodological approaches are available for investigating RLN3's role in pathological conditions?

Research has implicated RLN3 in several pathological conditions, particularly adolescent idiopathic scoliosis (AIS). Methodological approaches include:

• Clinical samples analysis:

  • Measure RLN3 plasma levels using ELISA in patients vs. controls

  • Correlate RLN3 levels with clinical parameters (e.g., joint hypermobility in AIS)

  • Immunohistochemical analysis of ligament samples from patients

• Animal models:

  • Generate and characterize RLN3 knockout mice using CRISPR/Cas9

  • Establish disease models (e.g., bipedal ambulation-induced scoliosis in mice)

  • Evaluate phenotypic changes after genetic manipulation of RLN3 expression

• Pharmacological interventions:

  • Use RXFP3 antagonists (e.g., R3(B1-22)R) to block RLN3 signaling

  • Evaluate therapeutic potential in disease models

  • Combine with RLN3 antibodies to monitor changes in protein expression/distribution

• Cell culture systems:

  • Study effects of RLN3 on specific cell types (e.g., ligament fibroblasts)

  • Analyze cellular responses using immunocytochemistry with RLN3 antibodies

  • Investigate molecular pathways using combined immunolabeling approaches

How can I combine RLN3 antibodies with genetic approaches to study RLN3 function?

Integrating RLN3 antibodies with genetic approaches provides powerful insights:

• Validation of genetic models:

  • Confirm protein knockdown/knockout in RLN3-/- mice using RLN3 antibodies

  • Verify overexpression in transgenic models with quantitative immunohistochemistry

• RNAscope™ + immunohistochemistry:

  • Simultaneously detect RXFP3 mRNA and RLN3 protein:

    • Apply RNAscope™ in situ hybridization for RXFP3 mRNA

    • Follow with immunofluorescence detection of RLN3 protein

    • This approach revealed differential distribution of RLN3 fibers and RXFP3-expressing neurons in entorhinal cortex

• Single-cell analysis:

  • Combine patch-clamp electrophysiology with sc-RT-PCR and RLN3 immunocytochemistry

  • Correlate functional responses with gene/protein expression

• CRISPR-based approaches:

  • Create cell lines with edited RLN3 or RXFP3 genes

  • Validate edits using RLN3 antibodies to confirm protein changes

  • Study consequences on downstream signaling pathways

What are common issues with RLN3 antibody staining and how can they be resolved?

How can I quantify RLN3 expression in tissue samples?

Quantification of RLN3 expression can be performed using several approaches:

• Immunohistochemistry quantification:

  • Measure optical density of DAB staining in defined regions of interest

  • Count RLN3-positive cells/fibers per area

  • Use stereological methods for unbiased estimation of fiber density

• Western blot quantification:

  • Use validated RLN3 antibodies (observed at ~15-68 kDa depending on preparation)

  • Normalize to appropriate loading controls

  • Apply densitometric analysis with proper controls

• ELISA-based quantification:

  • For plasma/serum samples (as used in AIS studies showing elevated RLN3 levels)

  • Follow standardized protocols with appropriate dilution series

• Fluorescence-based quantification:

  • Measure fluorescence intensity of immunolabeled RLN3

  • Apply co-localization analysis with other markers

  • Use confocal microscopy for detailed quantitative analysis

What considerations are important when designing experiments to study RLN3-RXFP3 interactions?

When investigating RLN3-RXFP3 interactions:

• Receptor-ligand specificity:

  • RLN3 can bind to multiple receptors (RXFP1, RXFP3, RXFP4)

  • Use receptor-specific antagonists to distinguish receptor subtypes

  • Consider using R3(B1-22)R as a specific RXFP3 antagonist

• Appropriate controls:

  • Include receptor knockdown/knockout controls

  • Use peptide antagonists as negative controls

  • Include positive controls with known RLN3-RXFP3 signaling

• Downstream signaling analysis:

  • RLN3-RXFP3 activates ERK1/2 signaling but inhibits TGF-β/SMAD signaling

  • Consider monitoring multiple pathways simultaneously

  • Investigate both acute and long-term signaling events

• Experimental timing:

  • RLN3-RXFP3 signaling shows temporal dynamics

  • Design time-course experiments to capture signaling kinetics

  • Consider both immediate and delayed effects on target cells

How has research on RLN3-RXFP3 signaling advanced our understanding of neurophysiological processes?

Recent research has revealed important roles for RLN3-RXFP3 signaling:

• Inhibitory control of magnocellular neurons:

  • RLN3/RXFP3 signaling in the PVN inhibits magnocellular neurons via activation of potassium channels

  • This suggests a role in neuroendocrine regulation and stress responses

• Parahippocampal innervation patterns:

  • Detailed mapping shows RLN3 fibers concentrated in specific layers of medial and lateral entorhinal cortex

  • Distribution suggests involvement in memory and spatial navigation

• Molecular signaling mechanisms:

  • RLN3-RXFP3 activates neuronal nitric oxide synthase through the ERK1/2 pathway

  • Simultaneously inhibits TGF-β/SMAD signaling in target cells

• Behavioral regulation:

  • Evidence for RLN3's involvement in feeding, metabolism, stress responses

  • Suggested roles in arousal, learning, and memory formation

What are the implications of RLN3's role in adolescent idiopathic scoliosis (AIS)?

Recent research has revealed unexpected connections between RLN3 and adolescent idiopathic scoliosis:

• Clinical correlations:

  • Significantly increased RLN3 plasma levels in AIS patients compared to controls

  • Positive correlation between joint hypermobility and RLN3 plasma levels

• Animal model validation:

  • Bipedal C57BL/6J mice showed higher relaxin-3 plasma levels compared to normal group

  • RLN3 knockout significantly decreased scoliosis prevalence in this model

• Cellular mechanism:

  • RLN3 exhibits anti-fibrotic effects on spinal ligament fibroblasts

  • Inhibits TGF-β via RXFP3 receptor activation

  • Increases expression of matrix metalloproteinases (MMP2 and MMP9) via the TGF-β/Smad2 and MAPK-ERK1/2 pathway

• Therapeutic potential:

  • RXFP3 antagonist R3(B1-22)R significantly decreased scoliosis prevalence in mouse models

  • Suggests potential for prophylactic treatment of AIS through RXFP3 antagonism

How are advanced techniques enhancing RLN3 research?

Cutting-edge techniques are expanding RLN3 research capabilities:

• Combined RNAscope™ and immunohistochemistry:

  • Simultaneous visualization of RXFP3 mRNA and RLN3 protein

  • Revealed differential distribution patterns in entorhinal cortex layers

• Single-cell RT-PCR with electrophysiology:

  • Correlating RXFP3 expression with functional neuronal responses

  • Investigating co-expression of RXFP3 with potassium channel subunits (KCNQ)

• CRISPR/Cas9 genetic models:

  • Generation of RLN3 knockout mice to study physiological roles

  • Assessment of phenotypic changes in disease models

• High-resolution imaging:

  • Detailed mapping of RLN3-positive fibers in relation to specific neuronal populations

  • Quantitative analysis of synaptic contacts between RLN3 terminals and target neurons