Recombinant Human Probable G-protein coupled receptor 149 (GPR149)

What is the basic molecular structure of human GPR149?

GPR149 is a Class-A rhodopsin-like G-protein coupled receptor (GPCR) consisting of 731 amino acids with a molecular mass of approximately 80,984 Da in humans. It features seven transmembrane domains characteristic of GPCRs. Uniquely, GPR149 possesses a highly conserved 360 amino acid C-terminal domain with no homology to other proteins, which may play a critical role in downstream signaling pathways . Phylogenetic analysis indicates GPR149 shows closest sequence homology to GPCRs that utilize peptides as their ligands, suggesting it may function as a neuropeptide receptor .

How conserved is GPR149 across species?

GPR149 demonstrates significant evolutionary conservation across vertebrates from fish to mammals. The high degree of sequence conservation, particularly in the C-terminal domain, suggests an important biological function that has been maintained throughout vertebrate evolution . When designing experiments involving animal models, researchers should note that mouse GPR149 closely resembles the human ortholog in both structure and tissue distribution patterns, making mouse models valuable for translational research .

What are the known molecular functions of GPR149?

While GPR149 remains an orphan receptor with unidentified endogenous ligands, molecular analysis suggests functions including G-protein coupled receptor activity and neuropeptide binding capabilities . Based on structural homology with other GPCRs, it likely couples to G-proteins and activates downstream signaling cascades involving cyclic nucleotide second messengers . Research examining GPR149 signaling should consider potential pathway interactions involving:

What is the tissue distribution pattern of GPR149?

Quantitative PCR (qPCR) analysis reveals that GPR149 expression is predominantly observed in the central nervous system (CNS), with the strongest expression in the striatum, hypothalamus, brainstem, and spinal cord . The highest non-neuronal expression is found in the pituitary gland, with lower levels detected in the gastrointestinal tract and female reproductive organs . Expression appears to be neuronal rather than glial in the adult brain, with no discernible signals in white matter tracts, meninges, or epithelia .

Which specific brain regions show the highest GPR149 expression?

In situ hybridization studies demonstrate that at least 80 brain regions express GPR149 at varying levels . The strongest expression is observed in:

• Islands of Calleja and surrounding nuclei (including the olfactory tubercle)

• Ventromedial hypothalamus

• Rostral interpeduncular nucleus

• Select brainstem nuclei (e.g., sphenoid nucleus)

Moderate-to-low expression is found across the basal forebrain, striatum, hypothalamus, brainstem, and spinal cord, with only low expression in cortical and subcortical regions such as the hippocampus . This expression pattern supports potential roles in regulating basic motivated behaviors, autonomic outflow, and sensory processes .

How can researchers accurately map GPR149 expression in experimental models?

For comprehensive mapping of GPR149 expression, researchers should employ multiple complementary approaches:

• Quantitative PCR (qPCR): Provides quantitative measurement of mRNA expression across different tissues .

• In situ hybridization (ISH): Enables cellular-level visualization of expression patterns within tissues. Fluorescent RNAscope ISH is particularly effective for detailed brain mapping .

• Reporter mouse models: Transgenic approaches such as Cre-loxP systems (e.g., Gpr149-Cre crossed with tdTomato reporter lines) allow for genetic labeling of GPR149-expressing cells .

• Validation in knockout models: To confirm probe specificity, researchers should validate results in GPR149 knockout models .

The methodological approach used by researchers in recent studies involved CRISPR-Cas9 technology to generate both Gpr149-null alleles and Cre-P2A-Gpr149 lines for reporter studies .

How does GPR149 affect female fertility?

GPR149 functions as a negative regulator of fertility in female mice. Knockout studies demonstrate that GPR149-deficient female mice exhibit enhanced fertility characterized by increased ovulation rates . Molecular analysis shows that deletion of GPR149 leads to:

• Increased oocyte Gdf9 mRNA levels

• Elevated FSH receptor expression in granulosa cells

• Enhanced cyclin D2 mRNA levels in granulosa cells

• Normal folliculogenesis despite altered fertility parameters

These findings indicate that GPR149 may serve as a potential target for fertility enhancement therapies in assisted reproductive technologies .

What is the developmental expression pattern of GPR149 in reproductive tissues?

GPR149 displays dynamic expression throughout ovarian development. Expression levels are low in newborn ovaries but progressively increase throughout folliculogenesis . This temporal regulation suggests stage-specific functions during oocyte development and maturation. Researchers investigating GPR149 in reproduction should consider developmental timing when designing experiments, as expression patterns change throughout reproductive development .

What methodological approaches can assess GPR149 function in oocyte development?

To investigate GPR149's role in oocyte physiology, researchers should employ a multi-faceted approach:

• Gene expression analysis: Measure transcriptional changes in oocyte-specific genes (e.g., Gdf9) and granulosa cell markers upon GPR149 deletion or overexpression .

• Folliculogenesis assays: Quantify follicle numbers at different developmental stages in wildtype versus knockout models.

• Superovulation studies: Assess ovulation rates and oocyte quality following hormonal stimulation.

• Molecular signaling analysis: Examine the impact on downstream pathways affecting oocyte growth and maturation.

• In vitro culture systems: Use isolated oocytes or follicles to study direct effects of GPR149 modulation .

What evidence suggests GPR149 involvement in energy balance regulation?

Multiple lines of evidence implicate GPR149 in energy homeostasis:

• Strong expression in brain regions controlling energy balance, particularly the ventromedial hypothalamus .

• Enrichment in vagal afferents, which transmit peripheral metabolic signals to the brain .

• Preliminary metabolic phenotyping of male GPR149-knockout mice reveals alterations in energy balance parameters .

• Expression in hypothalamic nuclei known to regulate glucose homeostasis .

These findings collectively suggest GPR149 participates in neural circuits regulating feeding behavior, energy expenditure, and metabolic homeostasis.

How does GPR149 deficiency affect metabolic parameters in male mice?

While comprehensive metabolic characterization of GPR149-knockout models remains limited, preliminary findings indicate that male GPR149-deficient mice exhibit alterations in energy homeostasis parameters . Researchers investigating the metabolic functions of GPR149 should design studies examining:

• Body weight and composition

• Food intake and energy expenditure

• Glucose tolerance and insulin sensitivity

• Hypothalamic expression of neuropeptides regulating energy balance

• Autonomic regulation of peripheral metabolism

What methodological considerations are important when studying GPR149 in metabolic regulation?

When investigating GPR149's role in metabolism, researchers should:

• Control for sex differences: GPR149 may have sex-specific metabolic effects, so both male and female models should be evaluated separately .

• Consider age-dependent phenotypes: Metabolic phenotypes may emerge or change with age.

• Use comprehensive metabolic phenotyping: Include measurements of energy expenditure (indirect calorimetry), body composition analysis, glucose and insulin tolerance tests, and feeding behavior.

• Examine neuronal activation patterns: Use c-Fos immunostaining or other neuronal activity markers to assess activation of GPR149-expressing neurons under different metabolic conditions.

• Perform circuit-specific manipulations: Use Cre-dependent viral approaches in Gpr149-Cre mice to manipulate specific neural populations .

How can researchers generate GPR149 knockout models for functional studies?

Modern genetic engineering approaches enable efficient generation of GPR149 knockout models. A validated methodology includes:

• CRISPR-Cas9 genome editing: Design guide RNAs targeting exon 1 of GPR149. Specific guide sequences that have proven successful include:

  • 5′ Guide: 5′-CUUAUAACUGGUCACCUAUGUGUUUUAGAGCUAUGCU-3′

  • 3′ Guide: 5′-UUGGUAGUUAACGAGACCCCGUUUUUAGAGCUAUGCU-3′

• Pronuclear injection: Administer guides, tracrRNA, and Cas9 protein through pronuclear injection in C57Bl/6N mouse embryos .

• Founder screening: Screen potential founders using PCR and Sanger sequencing to identify successful deletion events .

• Genotyping protocol: Validate knockout using the following primers:

  • Gpr149 1: 5′-GCTGCTTGTAATGTGTGCAGAGAG-3′

  • Gpr149 2: 5′-GTCTACTCATGGCAGACCAAAGTAATGG-3′

  • Gpr149 3: 5′-GTCTCTTGGTGCTAGAGATGGGTG-3′

  • Expected results: WT band of 200 bp and GPR149 KO band of 350 bp

What approaches are available for generating reporter models to visualize GPR149-expressing cells?

Cre-loxP based reporter systems provide powerful tools for visualizing and manipulating GPR149-expressing cells. A successful approach involves:

• Targeting endogenous GPR149 locus: Design guide RNA (5′-AAGUCAUAAUUCUACGGAGAGUUUUAGAGCUAUGCU-3′) to target the start codon .

• Insertion of Cre recombinase: Prepare a donor template with homology arms flanking a Cre-P2A sequence for insertion at the GPR149 ATG start site .

• Pronuclear co-injection: Administer guide RNA and donor template into pronuclei of mouse embryos .

• Crossing with reporter lines: Mate Gpr149-Cre mice with fluorescent reporter lines (e.g., Rosa26-LSL-tdTomato) to visualize GPR149-expressing cells .

What methodological approaches can detect GPR149 expression at the cellular level?

For cellular-level detection of GPR149 expression, researchers should consider:

• RNAscope in situ hybridization: This technique offers single-cell resolution detection of GPR149 mRNA with high specificity. Protocols have been validated using the RNAscope Multiplex Fluorescent v2 Assay with probe #318071 .

• Processing parameters:

  • Apply probe at 40°C for 2 hours

  • Use Opal570 for fluorescence assays or FastRed for chromogenic detection

  • Counterstain with DAPI (fluorescence) or hematoxylin (chromogenic)

• Validation controls: Always include GPR149 knockout tissues as negative controls to confirm probe specificity .

What evidence links GPR149 to prostatic cancer?

Preliminary research suggests GPR149 may participate in prostatic carcinogenesis, potentially serving as a marker for prostatic cancer . While detailed mechanisms remain to be elucidated, alterations in GPR149 expression or function could contribute to disease progression. Researchers investigating this association should:

• Compare GPR149 expression levels in normal versus cancerous prostate tissues

• Analyze correlations between GPR149 expression and clinical outcomes

• Evaluate functional impacts of GPR149 modulation in prostate cancer cell lines

• Investigate potential interactions with established prostate cancer pathways

Could GPR149 serve as a therapeutic target for neurological disorders?

GPR149's enrichment in specific brain regions, particularly the striatum, suggests potential relevance to striatum-related neurological diseases . As an orphan GPCR, it represents a class of proteins amenable to pharmacological modulation. Researchers exploring GPR149 as a therapeutic target should:

• Characterize behavioral phenotypes in GPR149 knockout models

• Develop high-throughput screening assays to identify potential ligands

• Assess region-specific functions using conditional knockout approaches

• Evaluate functional coupling to downstream signaling pathways

• Consider potential side effects based on GPR149's distribution pattern

What methodological approaches could identify endogenous ligands for GPR149?

Deorphanizing GPR149 represents a critical research challenge. Approaches to identify potential ligands include:

• Reverse pharmacology screening: Express GPR149 in cell lines with various readout systems (calcium mobilization, cAMP production, β-arrestin recruitment) and screen candidate ligand libraries.

• Bioinformatic prediction: Apply in silico approaches to predict potential ligands based on structural homology with related receptors.

• Tissue extract fractionation: Prepare extracts from tissues with high GPR149 expression (e.g., hypothalamus, pituitary) and test fractions for receptor activation.

• Proximity-based labeling: Employ techniques like APEX2 or BioID fused to GPR149 to identify proteins interacting with the receptor in its native environment.

• Genetic screening: Use CRISPR activation/interference libraries to identify genes affecting GPR149 signaling.

How might single-cell transcriptomics advance our understanding of GPR149 function?

Single-cell RNA sequencing could provide unprecedented insights into GPR149 biology by:

• Precisely defining the cellular identity of GPR149-expressing neurons

• Revealing co-expression patterns with other receptors and signaling molecules

• Identifying cell type-specific transcriptional signatures in GPR149-positive versus negative cells

• Tracking developmental trajectories of GPR149-expressing cells

• Assessing transcriptional responses to physiological challenges or disease states

Researchers should consider applying single-cell approaches to tissues with established GPR149 expression, particularly hypothalamic and striatal regions, to advance our understanding of its functional context.

What is known about the regulation of GPR149 expression?

Limited information exists regarding the transcriptional regulation of GPR149. Current evidence shows developmental regulation in reproductive tissues, with expression increasing throughout folliculogenesis . Future research should address:

• Transcription factors controlling GPR149 expression

• Epigenetic modifications of the GPR149 promoter region

• Hormonal and metabolic regulation of GPR149 transcription

• Alternative splicing or post-transcriptional regulatory mechanisms

• Sex-specific regulatory patterns, given the observed reproductive phenotypes

How can contradictory data regarding GPR149 function be reconciled?

As with many emerging research areas, studies on GPR149 may produce seemingly contradictory results. When faced with inconsistent findings, researchers should:

• Carefully evaluate methodological differences: Consider variations in knockout strategies, genetic backgrounds, age of animals, and environmental conditions.

• Consider sexual dimorphism: GPR149 functions appear to differ between males and females, particularly regarding reproductive versus metabolic phenotypes .

• Assess developmental timing: Phenotypic manifestations may vary with developmental stage.

• Evaluate compensatory mechanisms: Chronic genetic deletion may trigger compensatory changes not observed with acute manipulations.

• Design studies with appropriate controls: Include littermate controls and sufficient sample sizes to account for individual variation.

• Employ conditional approaches: Use temporal and spatial specific deletion/activation to disentangle primary from secondary effects.