Recombinant Mouse Membrane-spanning 4-domains subfamily A member 13 (Ms4a13)

What is MS4A13 and how does it relate to other MS4A family members?

MS4A13 is a member of the Membrane-spanning 4-domains subfamily A (MS4A) gene cluster, which encodes a family of transmembrane proteins sharing structural similarities with CD20. The MS4A gene family consists of at least 16 members including MS4A1 (CD20), MS4A2, MS4A3, MS4A4A, MS4A6A, and MS4A13 . These proteins typically contain four transmembrane domains with intracellular N- and C-termini.

Research indicates that most MS4A proteins function as ion channels that regulate calcium transport . While MS4A13's specific function isn't fully characterized, other MS4A family members play roles in:

• Cell signaling

• Protein trafficking in microglia

• Immune cell regulation

• Calcium channel modulation

Unlike some of its family members (such as MS4A4A and MS4A6A) that have been extensively studied in relation to Alzheimer's disease, MS4A13's physiological role remains less characterized .

What expression patterns have been observed for MS4A13 in mouse tissues?

MS4A13 exhibits a tissue-specific expression pattern that differs from some other MS4A family members:

While the search results don't provide comprehensive expression data specifically for MS4A13, research indicates it has a more restricted expression pattern compared to MS4A4A and MS4A6A, which are widely expressed in microglia and immune cells .

When designing experiments with recombinant MS4A13, consider using tissue-specific cells that naturally express this protein to ensure physiologically relevant results.

What expression systems are optimal for producing recombinant mouse MS4A13?

For successful production of functional recombinant mouse MS4A13, consider these expression systems based on research with related MS4A proteins:

• Mammalian expression systems (recommended):

  • HEK293T cells have been successfully used for producing other mouse recombinant proteins with similar transmembrane domains .

  • CHO cells provide proper post-translational modifications essential for transmembrane protein folding.

• E. coli systems (limited application):

  • While E. coli can express segments of MS4A proteins, full-length transmembrane proteins like MS4A13 typically require eukaryotic expression systems for proper folding and function.

  • Consider E. coli only for expressing soluble domains or peptide fragments.

• Methodology for optimal expression:

  • Use codon-optimized sequences for improved expression efficiency

  • Include appropriate signal sequences for membrane targeting

  • Consider fusion tags (His, FLAG, MYC) positioned to avoid interference with transmembrane domains

  • Employ detergent screening for optimal solubilization during purification

For example, other recombinant mouse proteins have been successfully expressed with C-terminal tags in HEK293T cells, as shown with the fibromodulin (Fmod) protocol where the predicted MW was 43.1 kDa and purification achieved >80% as determined by SDS-PAGE .

Purification Approach:

• Initial solubilization:

  • Use mild detergents (DDM, CHAPS, or digitonin) to solubilize membrane fractions

  • Progressive detergent screening is crucial for maintaining native conformation

• Chromatography sequence:

  • Affinity chromatography utilizing His-tag or other fusion tags

  • Ion exchange chromatography for removing contaminating proteins

  • Size exclusion chromatography for final polishing and buffer exchange

• Buffer optimization:

  • Consider including glycerol (10%) for stability

  • Phosphate or Tris-based buffers at physiological pH (7.2-7.4)

  • Addition of reducing agents (DTT or β-mercaptoethanol) to maintain disulfide bonds

Validation Methods:

Physical validation:

• SDS-PAGE for purity assessment (target >80% purity)

• Western blotting with anti-MS4A13 antibodies

• Mass spectrometry for confirmation of protein identity and post-translational modifications

Functional validation:

• Calcium flux assays (as MS4A proteins may function as calcium channels)

• Binding assays with potential interaction partners

• Structural integrity assessment via circular dichroism

Based on protocols for similar recombinant proteins, storage in 25 mM Tris-HCl, 100 mM glycine, pH 7.3 with 10% glycerol has proven effective for maintaining stability .

How does MS4A13 potentially relate to neurological disease pathways compared to other MS4A family members?

While MS4A13 itself hasn't been directly implicated in neurological diseases based on the available search results, other MS4A family members show significant disease associations:

• MS4A4A and MS4A6A in Alzheimer's disease:

  • Genome-wide significant genetic association exists between MS4A gene region and soluble TREM2 (sTREM2) levels in cerebrospinal fluid

  • The top SNP rs1582763 (located near MS4A4A) showed significant association with CSF sTREM2 (P = 1.15×10−15)

  • MS4A4A and TREM2 colocalize on lipid rafts at the plasma membrane

• Potential research directions for MS4A13:

  • Investigate whether MS4A13 participates in similar cellular pathways as MS4A4A

  • Examine possible interaction with TREM2 or related proteins

  • Explore expression changes in disease models

The MS4A gene region contains independent signals with opposing effects on CSF sTREM2 levels. For instance, rs1582763 is associated with elevated CSF sTREM2, while rs6591561 (MS4A4A p.M159V) is associated with reduced CSF sTREM2 levels . This complexity suggests the need for careful genetic analysis when studying any MS4A family member's role in disease.

What experimental approaches can determine functional interactions between MS4A13 and other proteins?

To investigate MS4A13's interaction partners and functional relationships, consider these methodological approaches:

• Co-immunoprecipitation (Co-IP):

  • Express tagged MS4A13 in relevant cell types

  • Immunoprecipitate using anti-tag antibodies

  • Identify binding partners via mass spectrometry

  • Validate specific interactions with targeted Western blotting

• Proximity labeling:

  • Generate fusion proteins of MS4A13 with BioID or APEX2

  • Identify proteins in close proximity through biotinylation

  • This approach is particularly valuable for membrane proteins like MS4A13

• Microscopy-based colocalization:

  • Dual immunofluorescence with potential partners

  • Super-resolution microscopy for detailed localization

  • FRET/BRET for direct interaction assessment

• Functional assays:

  • Calcium mobilization assays (as MS4A4A has been linked to calcium signaling)

  • Gene expression analysis following MS4A13 overexpression or knockdown

  • Trafficking studies using fluorescently tagged constructs

Research with MS4A4A showed it colocalizes with TREM2 in intracellular structures and on the plasma membrane . Similar approaches could be applied to MS4A13 to explore its interactions and trafficking patterns.

What considerations are important when designing gene knockout or knockdown studies for MS4A13?

When designing MS4A gene manipulation studies, consider these methodological approaches based on successful MS4A family research:

• CRISPR/Cas9 knockout approaches:

  • Target early exons to ensure complete loss of function

  • Verify specificity to avoid affecting other MS4A family members

  • Consider conditional knockout systems if constitutive deletion is lethal

  • Example: The CRISPR/Cas9-mediated deletion of the Mup gene cluster in C57BL/6N mice provides a methodological template

• siRNA/shRNA knockdown strategy:

  • Test multiple siRNA sequences for optimal knockdown efficiency

  • Include scrambled controls and rescue experiments

  • Verify specificity across MS4A family members with high sequence homology

  • Assess knockdown at both mRNA and protein levels

• Validation approaches:

  • RT-qPCR for mRNA expression

  • Western blotting for protein levels

  • Immunohistochemistry for tissue localization patterns

  • Functional assays specific to hypothesized MS4A13 roles

• Special considerations:

  • Potential compensatory upregulation of other MS4A family members

  • Tissue-specific effects requiring targeted approaches

  • Developmental timing if MS4A13 has stage-specific functions

Studies on other genes have revealed that genetic manipulation can lead to unexpected compensatory mechanisms. For example, the knockout of the Mup gene cluster revealed sex-specific metabolic changes with 461 differentially expressed genes (DEG) in male knockout mice compared to 137 DEG in female knockout mice .

How can recombinant MS4A13 be used for antibody development and validation?

Developing and validating high-quality antibodies against MS4A13 requires careful planning:

• Antigen design strategy:

  • Select unique extracellular domains or C-terminal regions

  • Avoid highly conserved transmembrane regions shared with other MS4A proteins

  • Consider both peptide antigens and folded domain constructs

  • Example: The immunogen sequence "LTIIELSHFNSVSYRNYGQAKLGREVSRI" has been used for generating MS4A13 antibodies

• Antibody development approaches:

  • Monoclonal antibodies provide specificity and reproducibility

  • Polyclonal antibodies may recognize multiple epitopes

  • Consider species reactivity requirements (mouse-specific vs. cross-reactive)

• Validation methodologies:

  • Western blotting against recombinant protein and tissue lysates

  • Immunoprecipitation efficiency testing

  • Immunohistochemistry with positive and negative control tissues

  • Testing with knockout/knockdown tissues or cells

• Quality control metrics:

  • Establish specificity through testing against other MS4A family members

  • Determine optimal working dilutions for each application

  • Document lot-to-lot consistency

Commercial MS4A13 antibodies are available for research applications including Western blotting, ELISA, and immunohistochemistry, with rabbit polyclonal antibodies showing reactivity to both human and mouse MS4A13 .

What cell-based assays can evaluate MS4A13 function in relation to calcium signaling?

Since MS4A family proteins have been implicated in calcium signaling, these methodological approaches can assess MS4A13's potential role:

• Real-time calcium imaging:

  • Load cells with calcium indicators (Fluo-4, Fura-2)

  • Monitor calcium flux following stimulation

  • Compare MS4A13-expressing cells with controls

  • Analyze both amplitude and kinetics of calcium responses

• Patch-clamp electrophysiology:

  • Directly measure ion channel properties

  • Determine conductance, selectivity, and gating characteristics

  • Assess effects of potential modulators on channel function

• Store-operated calcium entry (SOCE) assays:

  • Deplete ER calcium stores with thapsigargin

  • Measure subsequent calcium influx

  • Compare SOCE in MS4A13-expressing versus control cells

• Calcium-dependent signaling pathways:

  • Monitor phosphorylation of calcium-dependent kinases (CaMKII, PKC)

  • Assess activation of calcium-responsive transcription factors (NFAT, CREB)

  • Examine calcium-dependent gene expression changes

MS4A1 has been documented to participate in store-operated Ca²⁺ entry , suggesting that MS4A13 may have similar functions that could be evaluated using these methodological approaches.

What are the key considerations for experimental design when investigating MS4A13 in immune cell function?

When designing experiments to study MS4A13 in immune contexts, consider these methodological approaches:

• Immune cell expression profiling:

  • Analyze MS4A13 expression across immune cell subsets using:

    • Flow cytometry with validated antibodies

    • Single-cell RNA sequencing

    • Immunohistochemistry of immune tissues

  • Compare expression patterns with other MS4A family members

• Functional assessment in immune cells:

  • Proliferation and survival assays

  • Cytokine production profiling

  • Migration and chemotaxis assessment

  • Phagocytosis and antigen presentation (for myeloid cells)

• Stimulation conditions to consider:

  • Cytokine treatments (particularly IL-4, which increases MS4A4A expression)

  • Toll-like receptor (TLR) activation

  • T cell receptor (TCR) or B cell receptor (BCR) engagement

  • Colony-stimulating factors (M-CSF)

• In vivo model systems:

  • Conditional MS4A13 knockout in specific immune lineages

  • Adoptive transfer experiments

  • Immune challenge models (infection, inflammation)

  • Age-dependent immune phenotyping

Several MS4A family members have established roles in immune function. For example, MS4A1 (CD20) is crucial for B-cell differentiation, proliferation and activation , while MS4A4A expression increases with IL-4 stimulation in human macrophages .

How does MS4A13 compare genetically to other MS4A family members in various species?

Understanding the evolutionary relationships and genetic variations of MS4A13 across species provides important context:

• Evolutionary conservation:

  • MS4A13 is conserved across mammalian species, including primates

  • The gene has been identified in various species including mice, humans, and northern white-cheeked gibbon (Nomascus leucogenys)

  • The mouse MS4A gene cluster is located on chromosome 19, while the human cluster is on chromosome 11q12.2

• Comparative genetic structure:

  • The mouse MS4A13 gene produces a membrane-spanning protein with four transmembrane domains

  • In northern white-cheeked gibbon, the MS4A13 coding region is 459bp in length

  • The gene structure includes conserved exons encoding the transmembrane domains

• Genetic variation and disease association:

  • While some MS4A family members show significant disease associations, specific MS4A13 variants linked to disease have not been prominently reported

  • For comparison, MS4A4A contains variants like rs6591561 (p.M159V) that significantly impact sTREM2 levels

  • MS4A13 has been found to contain rare variants including a frameshift mutation (MS4A13:NM_001012417:exon7:c.403–1G>T) identified in control subjects

• Expression regulation:

  • Regulatory elements controlling MS4A13 expression may differ from those controlling other MS4A genes

  • Tissue-specific expression patterns suggest distinct promoter regulation across family members

This comparative analysis highlights that while MS4A13 shares structural features with other family members, its genetic variation patterns and expression regulation may be distinct.

What reconstitution and storage protocols are recommended for maintaining MS4A13 stability?

Based on established protocols for similar recombinant membrane proteins, these methodological approaches are recommended:

• Reconstitution methodology:

  • Reconstitute lyophilized protein in sterile PBS to a concentration of 100 μg/mL

  • Allow complete dissolution at room temperature with gentle swirling (avoid vortexing)

  • For transmembrane proteins, consider adding 0.1% detergent (e.g., DDM or CHAPS) to maintain solubility

  • Filter through 0.22 μm filter for sterility if intended for cell culture applications

• Storage recommendations:

  • Store reconstituted protein in small aliquots to avoid freeze-thaw cycles

  • Maintain at -80°C for long-term storage

  • For short-term use (1-2 weeks), 4°C storage may be suitable

  • Include carrier protein (e.g., 0.1% BSA) for dilute solutions to prevent adsorption to container surfaces

• Stability considerations:

  • Avoid repeated freeze-thaw cycles that significantly reduce activity

  • Monitor protein stability through functional assays over time

  • Consider adding protease inhibitors for protection during storage

  • Buffer composition for optimal stability: 25 mM Tris-HCl, 100 mM glycine, pH 7.3, with 10% glycerol

• Quality control measures:

  • Validate protein activity after reconstitution

  • Check for aggregation using dynamic light scattering or size exclusion chromatography

  • Confirm protein concentration using BCA or Bradford assay

Similar recombinant proteins are typically shipped lyophilized or in solution at ambient temperature but must be stored appropriately upon receipt .

What techniques are most effective for monitoring MS4A13 expression changes in experimental models?

To accurately measure MS4A13 expression changes in various experimental conditions, consider these methodological approaches:

When analyzing MS4A gene expression in mice, research has shown that experimental conditions such as IL-4 stimulation can significantly increase expression of MS4A family members like MS4A4A , suggesting similar approaches may be valuable for studying MS4A13.

How can researchers address the challenges of working with multi-transmembrane domain proteins like MS4A13?

Working with transmembrane proteins like MS4A13 presents unique challenges that require specific methodological approaches:

• Solubilization strategies:

  • Systematic detergent screening (starting with DDM, CHAPS, digitonin)

  • Nanodiscs or SMALPs (styrene-maleic acid lipid particles) for native-like membrane environment

  • Amphipol stabilization for structural studies

  • Bicelle formulations for NMR applications

• Expression optimization:

  • Use expression vectors with strong promoters designed for membrane proteins

  • Consider inducible expression systems to minimize toxicity

  • Test multiple fusion tag positions to identify optimal construct

  • Evaluate different cell lines for highest functional expression

• Structural characterization approaches:

  • Cryo-electron microscopy for 3D structure determination

  • FTIR spectroscopy for secondary structure analysis

  • Circular dichroism to assess proper folding

  • Limited proteolysis to identify stable domains

• Functional characterization:

  • Reconstitution into liposomes for functional assays

  • Fluorescence-based assays for monitoring conformational changes

  • Binding studies with potential interaction partners

  • Site-directed mutagenesis of key residues

When working with MS4A13, researchers should particularly note that the protein contains four transmembrane domains and may form oligomeric structures similar to MS4A1 (CD20), which forms tetramers .

What disease models are appropriate for investigating MS4A13's potential roles in pathology?

Based on known functions of MS4A family members, consider these methodological approaches for investigating MS4A13 in disease contexts:

• Neurodegenerative disease models:

  • Alzheimer's disease mouse models (given the role of MS4A4A in modulating TREM2)

  • Neuroinflammation models assessing microglial function

  • Age-dependent expression changes in brain tissues

  • Cell-based models using microglia or macrophages

• Immunological disorder models:

  • Inflammatory disease models (considering MS4A family roles in immune cells)

  • Allergic response models (MS4A2/FcεRIβ is involved in mast cell responses)

  • Autoimmune conditions with aberrant immune activation

  • Infection models examining innate immune responses

• Cancer research applications:

  • Expression analysis in tumor vs. normal tissues

  • Functional analysis in cancer cell lines

  • Tumor microenvironment studies

  • Potential biomarker evaluation

• Methodological considerations:

  • Cell-type specific conditional knockouts rather than global deletion

  • Temporal control of gene manipulation (inducible systems)

  • Careful phenotyping across multiple physiological systems

  • Integration of 'omics approaches (transcriptomics, proteomics)

Research on MS4A family members shows their involvement in cancer biology. For example, MS4A members display altered expression in lung cancer, with MS4A2, MS4A4A, MS4A4E, MS4A6A, MS4A6E, MS4A7, MS4A8, MS4A14, and MS4A15 significantly decreased in lung cancer tissues compared to normal tissues .