FOLR2 Human

What is FOLR2 and what is its genomic location?

FOLR2 (Folate Receptor Beta) is a protein encoded by the FOLR2 gene located on human chromosome 11. This protein belongs to the folate receptor family with high affinity for folic acid and several reduced folic acid derivatives, mediating the delivery of 5-methyltetrahydrofolate to cell interiors . The encoded protein shares 68% sequence homology with FOLR1 and 79% with FOLR3, indicating evolutionary relationships while maintaining distinct functional profiles .

What is the tissue distribution pattern of FOLR2?

While FOLR2 was initially thought to be expressed exclusively in the placenta, subsequent research has identified significant expression in immune-related tissues including the spleen, bone marrow, and thymus . This expanded tissue distribution suggests important roles in immune function beyond reproductive biology. Understanding this distribution pattern is critical for researchers designing tissue-specific experiments and interpreting expression data in different physiological contexts.

What are the recommended methods for detecting and quantifying FOLR2 in human samples?

For quantitative determination of FOLR2 in human samples, enzyme-linked immunosorbent assay (ELISA) is the preferred method. When collecting plasma samples, researchers should use citrate or heparin as anticoagulants rather than EDTA, which is not recommended for FOLR2 assays . The standard ELISA approach employs wells coated with antibodies specific for human FOLR2, where target protein binds to immobilized antibodies, followed by detection with biotinylated anti-human FOLR2 antibody and HRP-conjugated streptavidin, with color development proportional to FOLR2 concentration .

How can researchers evaluate the specificity of their FOLR2 detection methods?

Specificity validation is critical for FOLR2 research given its homology with other folate receptors. Researchers should conduct cross-reactivity tests against related proteins, particularly FOLR1 and FOLR3. Commercial ELISA kits typically demonstrate no cross-reactivity with various human proteins including ALK-1, B7-H2, BLAME, BMP-8, CD28, Common beta Chain (CD131), and numerous other cytokines and receptors . When developing new detection methods, specificity should be verified against recombinant standards of all three folate receptors to ensure target specificity.

What approaches are recommended for studying FOLR2 in complex tissue environments?

Single-cell RNA sequencing represents the gold standard for studying FOLR2 in heterogeneous tissues. Analysis of datasets such as GSE152048 has successfully identified FOLR2 expression across different cell clusters in complex samples from osteosarcoma patients . This approach allows researchers to precisely map FOLR2 expression to specific cellular populations and correlate it with other markers. For optimal results, researchers should integrate single-cell data with bulk RNA sequencing and protein-level detection methods to obtain comprehensive expression profiles across multiple analytical scales.

What sample processing considerations are critical for accurate FOLR2 measurement?

Sample processing significantly impacts FOLR2 detection accuracy. For recombinant protein work, lyophilized FOLR2 should be reconstituted at 100 μg/mL in PBS and stored properly to avoid repeated freeze-thaw cycles . For clinical samples, plasma should be collected using citrate or heparin anticoagulants rather than EDTA . Researchers should validate recovery rates in their specific sample types, with published data showing average recovery rates of 110.8% in serum (range 84-134%), 74.20% in plasma (range 71-76%), and 103.7% in cell culture media (range 81-120%) .

What are the key considerations for data analysis in FOLR2 expression studies across different patient cohorts?

When analyzing FOLR2 expression across patient cohorts, researchers should implement rigorous bioinformatic approaches. For differential expression analysis, packages such as limma, edgeR, or DESeq2 should be employed with appropriate thresholds (|Fold change| > 1.5 and adjusted p < 0.05) . Patient stratification should consider immune infiltration levels, with survival comparisons conducted using appropriate statistical packages. For mechanistic insights, researchers should perform functional enrichment analysis including Gene Ontology to identify biological processes associated with FOLR2 expression patterns .

How should researchers interpret linearity differences in FOLR2 detection across sample types?

FOLR2 detection linearity varies significantly across sample types, requiring careful interpretation of dilution studies. Published data shows that at 1:2 dilution, the average percentage of expected FOLR2 recovery is 97.77% for serum (range 95-100%), 114.6% for plasma (range 91-138%), and 93.53% for cell culture media (range 85-103%) . At 1:4 dilution, these values change to 106.8% for serum (range 105-109%), 130.2% for plasma (range 118-143%), and 99.10% for cell culture media (range 83-115%) . These differences highlight the importance of matrix-specific calibration when comparing FOLR2 levels across different sample types.

What approaches help distinguish between FOLR2-specific effects and general folate metabolism in experimental outcomes?

To differentiate FOLR2-specific effects from general folate metabolism consequences, researchers should implement parallel experimental designs that include: (1) comparative analysis with other folate receptors (FOLR1, FOLR3); (2) functional studies using receptor-specific blocking antibodies; (3) genetic manipulation approaches (siRNA, CRISPR) targeting FOLR2 specifically; and (4) correlation of outcomes with folate levels in experimental systems. This comprehensive approach helps isolate receptor-specific functions from broader metabolic effects.

How can single-cell and bulk RNA sequencing data be effectively integrated for FOLR2 research?

Integration of single-cell and bulk RNA sequencing provides comprehensive insights into FOLR2 biology. Researchers should locate FOLR2 among major cell clusters identified from single-cell data (as demonstrated in dataset GSE152048 with 99,668 individual cells from osteosarcoma patients) . This cellular distribution data should then be contextualized with bulk RNA findings from datasets like GSE21257 and GSE32981, where samples can be divided into high and low immune infiltration groups . This multi-scale approach connects cellular-level expression patterns with tissue-level outcomes and clinical correlations.

What are the functional implications of FOLR2's differential expression across immune cell subtypes?

FOLR2's expression in immune-related tissues (spleen, bone marrow, thymus) suggests specialized functions in immune biology . Future research should focus on characterizing FOLR2's role in specific immune cell subtypes, particularly myeloid lineages where it may influence differentiation, activation, or functional polarization. The contradictory findings regarding FOLR2-expressing cells in tumor environments highlight the need for deeper functional characterization of receptor activity in different immune contexts .

How might FOLR2 interact with the tumor microenvironment to influence disease progression?

FOLR2's potential role in tumor-associated macrophages presents an important research frontier. Researchers should explore how FOLR2-expressing macrophages interact with tumor cells and other components of the tumor microenvironment. Analysis approaches should include clustering osteosarcoma samples into distinct groups based on component 1q positive macrophage markers and comparing their survival outcomes . This may reveal whether FOLR2 represents a potential therapeutic target or prognostic biomarker in certain cancer contexts.

What is the relationship between FOLR2 genetic variants and disease susceptibility or treatment response?

The genetic basis of FOLR2 variation and its relationship to disease remains underexplored. Future studies should investigate potential polymorphisms in the FOLR2 gene (located on chromosome 11) and their association with folate metabolism disorders, immune dysfunction, or cancer susceptibility. This research direction requires integration of genomic data with functional studies to establish causative relationships between genetic variants and phenotypic outcomes.

Table 1: Molecular Characteristics of Human FOLR2

Table 2: FOLR2 Detection Performance in Various Sample Types

Table 3: Linearity of FOLR2 Detection Methods