Recombinant Mouse Protein FAM118A (Fam118a)

What is mouse FAM118A and what are its basic molecular characteristics?

Mouse FAM118A (family with sequence similarity 118, member A) is encoded by the Fam118a gene (Gene ID: 73225) and has aliases including 3110048E14Rik and C230014M12Rik . The protein is referenced in databases with mRNA Refseq NM_133750.4 and Protein Refseq NP_598511.1, with UniProt ID Q91YN1 . The protein's function is still being characterized, but research indicates it may play a role in bone mineral density regulation based on genetic association studies .

Mouse Fam118a is typically studied using recombinant protein expression systems, where the full-length or partial-length protein can be produced with various tags for detection and purification purposes. The protein sequence begins with "MESVEKTTNRSEQKCRKFLKSLIRKQPQDLLLVIGTVRAQLWPQASERAVALEEAHAAVIEAAEQLEVLHPGDVAEFRRKVMKDRDLLVVAHDLIRKMSARVG..." as can be seen in the available sequence data .

How is recombinant mouse FAM118A protein typically produced for research applications?

Recombinant mouse FAM118A is predominantly produced using mammalian cell expression systems to ensure proper folding and post-translational modifications . This approach is preferred over bacterial systems for studying mammalian proteins where functional activity is crucial. The production typically involves:

• Cloning the Fam118a gene into an appropriate expression vector (e.g., pCMV6-Entry)

• Transfection into mammalian cell lines

• Selection of stable transfectants using antibiotics such as Neomycin

• Expression induction and protein harvesting

• Purification using affinity chromatography, often utilizing His-tag affinity

The resulting protein can achieve purity levels >80% with endotoxin levels below 1.0 EU per μg as determined by the LAL method . Some preparations require custom production with lead times between 5-9 weeks depending on specific requirements and modifications .

What are the optimal storage and handling conditions for recombinant FAM118A?

For maintaining recombinant mouse FAM118A stability and activity, specific storage conditions are recommended:

The protein is typically supplied in PBS buffer, which helps maintain stability . When working with lyophilized preparations, reconstitution should be performed gently to prevent protein denaturation, and aliquoting is recommended to avoid repeated freeze-thaw cycles which can degrade protein quality. Handling should include standard precautions for research-grade proteins, including the use of sterile techniques to prevent contamination .

What tags and modifications are available for recombinant mouse FAM118A protein?

Various tagged versions of recombinant mouse FAM118A are available for different experimental applications:

The choice of tag depends on the experimental requirements. His-tagged versions are useful for routine purification and antibody detection, while Avi-tagged versions allow for site-specific biotinylation. Myc/DDK-tagged versions provide flexibility for detection with commercially available antibodies. Untagged versions are preferable when studying the native function without potential tag interference .

How can I validate the expression and activity of recombinant FAM118A in experimental systems?

Validating recombinant FAM118A expression and activity requires multiple complementary approaches:

• Western blotting: Using anti-FAM118A or anti-tag antibodies to confirm size and expression level

• Mass spectrometry: For sequence confirmation and identification of post-translational modifications

• Functional assays: Based on putative functions such as:

  • Protein-protein interaction studies through co-immunoprecipitation

  • Gene expression analysis in cells overexpressing FAM118A

  • Analysis of downstream signaling pathways

For activity validation specifically, researchers should consider downstream effects, particularly in bone-related cell lines, given the association with bone mineral density . This might include assessing osteoblast differentiation markers or calcium signaling pathways when FAM118A is overexpressed or knocked down.

It is important to include appropriate controls in these experiments:

• Untransfected/mock-transfected controls

• Cells expressing an irrelevant protein with the same tag

• Dose-response relationships to establish specificity

What is known about the association between FAM118A and bone mineral density?

Research has identified significant associations between FAM118A and bone mineral density (BMD) through both genome-wide association studies (GWAS) and expression quantitative trait loci (eQTL) analyses . Key findings include:

• The SNP rs136564 has been identified as playing an important regulatory role in the expression of a novel transcript of FAM118A

• This same SNP (rs136564) has been reported to be related to BMD based on GWAS analysis

• Mendelian randomization approaches have been applied to confirm the causal relationship between FAM118A expression and BMD variation

This dual identification through both GWAS and eQTL studies strengthens the evidence for FAM118A's involvement in bone metabolism pathways. The exact molecular mechanism remains under investigation, but researchers hypothesize that FAM118A may influence osteoblast or osteoclast function, potentially through regulatory roles in gene expression or protein interactions within bone remodeling pathways .

How does mouse FAM118A compare to human FAM118A in terms of structure and function?

While the search results don't provide direct comparative data between mouse and human FAM118A, we can address this question based on available information and general principles of protein homology:

Mouse FAM118A (UniProt ID: Q91YN1) and human FAM118A likely share significant sequence homology and conserved domains, as is typical for orthologous proteins between these species . This conservation suggests similar fundamental functions across species, particularly in highly conserved biological processes like those affecting bone metabolism.

Both human and mouse FAM118A appear to be involved in similar pathways related to bone mineral density regulation, as evidenced by:

• Genetic variants affecting FAM118A expression being associated with BMD in human studies

• The applicability of mouse models for studying these relationships

Researchers should be aware that despite these similarities, species-specific differences might exist in:

• Expression patterns across tissues

• Regulatory mechanisms controlling the gene

• Protein interaction partners

• Post-translational modifications

When designing experiments using mouse FAM118A as a model for human conditions, these potential differences should be considered and validated when possible.

How can I design experiments to investigate FAM118A's role in bone mineral density regulation?

Designing comprehensive experiments to investigate FAM118A's role in bone mineral density regulation requires a multi-faceted approach:

• Genetic Association Validation:

  • Confirm the association between rs136564 and FAM118A expression in bone cells

  • Perform targeted genotyping of this SNP in cohorts with BMD measurements

  • Use Mendelian randomization approaches to validate causality

• Molecular Mechanisms:

  • Generate FAM118A overexpression and knockout models in bone-related cell lines

  • Analyze differential gene expression using RNA-seq to identify affected pathways

  • Perform ChIP-seq if FAM118A is suspected to have DNA-binding properties

  • Conduct proteomics studies to identify interaction partners

• Functional Studies in Cell Models:

  • Assess effects on osteoblast differentiation markers (ALP, RUNX2, OCN)

  • Measure mineralization capacity using Alizarin Red staining

  • Evaluate osteoclast differentiation and activity when FAM118A is modulated

• In Vivo Models:

  • Generate conditional knockout models targeting FAM118A in bone-specific cells

  • Perform micro-CT analysis to measure bone parameters

  • Conduct histomorphometric analysis of bone formation and resorption

  • Assess mechanical strength through biomechanical testing

The integration of these approaches will provide a comprehensive understanding of how FAM118A influences bone mineral density at the molecular, cellular, and organismal levels .

What techniques can be used to study protein-protein interactions involving FAM118A?

Several complementary techniques can be employed to study protein-protein interactions involving FAM118A:

• Co-Immunoprecipitation (Co-IP):

  • Using tagged recombinant FAM118A (His-tagged, Myc/DDK-tagged)

  • Followed by mass spectrometry to identify binding partners

  • Verification through reverse Co-IP with antibodies against identified partners

• Proximity-Based Labeling:

  • BioID or TurboID fusion with FAM118A

  • APEX2-based proximity labeling

  • These approaches identify proteins in close proximity to FAM118A in living cells

• Yeast Two-Hybrid Screening:

  • Using FAM118A as bait to screen for interactors

  • Domain-specific interactions can be mapped using truncated constructs

• Protein Microarrays:

  • Probing protein arrays with purified recombinant FAM118A

  • Can identify interactions with hundreds of proteins simultaneously

• FRET/BRET Analysis:

  • For studying dynamic interactions in living cells

  • Requires fluorescent or bioluminescent protein fusions

• Surface Plasmon Resonance (SPR):

  • For quantitative binding kinetics measurements

  • Requires purified FAM118A protein (>80% purity)

Each method has strengths and limitations, so combining multiple approaches provides the most robust evidence for protein interactions. The availability of different tagged versions of recombinant FAM118A facilitates these diverse experimental approaches .

How can single-cell transcriptomics approaches be leveraged to understand FAM118A function in specific cell populations?

Single-cell transcriptomics offers powerful approaches to understand FAM118A function in heterogeneous tissues and cell populations:

• Cell Type-Specific Expression Profiling:

  • Identify cell populations with high FAM118A expression

  • Compare expression patterns across different tissues and developmental stages

  • Similar to approaches used in immune cell transcriptional landscapes

• Response to Perturbations:

  • Analyze FAM118A expression changes following stimuli

  • Compare wild-type vs. FAM118A knockout effects at single-cell resolution

  • Identify cell populations most affected by FAM118A modulation

• Trajectory Analysis:

  • Map FAM118A expression changes during differentiation processes

  • Particularly relevant for osteoblast or osteoclast differentiation given BMD associations

  • Identify temporal dynamics of expression during cell state transitions

• Co-expression Network Analysis:

  • Identify genes consistently co-expressed with FAM118A across single cells

  • Infer potential functional relationships and pathways

  • Construct regulatory networks involving FAM118A

Implementation would involve:

• Single-cell RNA sequencing of relevant tissues (bone, bone marrow)

• Computational analysis using algorithms like Seurat, Monocle, or SCENIC

• Integration with other single-cell modalities (ATAC-seq, protein measurements)

• Validation of findings using in situ techniques or sorted cell populations

This approach could reveal cell-specific functions of FAM118A that might be masked in bulk tissue analyses, similar to the identification of specific immune cell subtypes in disease contexts .

What are the best approaches for generating FAM118A knockdown or knockout models?

For generating FAM118A knockdown or knockout models, several approaches can be considered based on experimental goals:

• Transient Knockdown:

  • siRNA or shRNA targeting FAM118A mRNA

  • Advantages: Quick, relatively inexpensive, works in difficult-to-transfect cells

  • Limitations: Temporary effect, potential off-target effects

  • Validation: qRT-PCR and Western blot to confirm knockdown efficiency

• Stable Knockdown:

  • Lentiviral shRNA delivery for long-term expression

  • Selection with appropriate antibiotics

  • Advantages: Sustained knockdown, can be used for long-term studies

  • Limitations: Variable knockdown efficiency, potential for compensation

• CRISPR-Cas9 Knockout:

  • Complete gene disruption using guide RNAs targeting critical exons

  • Can be performed in cell lines or animal models

  • Advantages: Complete loss of protein expression, specific targeting

  • Validation requires sequencing confirmation and protein expression analysis

• Conditional Knockout:

  • Cre-loxP or similar system for tissue-specific or inducible deletion

  • Essential for studying genes where germline knockout may be lethal

  • Allows temporal control of gene deletion

  • Particularly valuable for studying FAM118A in specific bone cell populations

• Domain-Specific Mutagenesis:

  • Targeted modification of specific functional domains

  • Useful for dissecting protein function without complete deletion

  • Can generate hypomorphic or dominant-negative variants

For bone-related studies of FAM118A, conditional approaches targeting osteoblasts (using Osx-Cre or Col1a1-Cre) or osteoclasts (TRAP-Cre) would be particularly informative given the association with bone mineral density .

How can I integrate genetic and functional data to understand FAM118A's biological role?

Integrating genetic and functional data for FAM118A requires a systematic approach combining multiple data types:

• Genetic Association Integration:

  • Compile GWAS data linking FAM118A variants to phenotypes (e.g., rs136564 with BMD)

  • Gather eQTL data showing how these variants affect FAM118A expression

  • Use Mendelian randomization to establish causality between expression and phenotype

• Multi-omics Data Integration:

  • Transcriptomic data: RNA-seq from relevant tissues

  • Proteomic data: Interaction partners and post-translational modifications

  • Epigenomic data: Regulatory elements affecting FAM118A expression

  • Metabolomic data: Downstream metabolic effects of FAM118A modulation

• Computational Methods:

  • Network analysis to place FAM118A in biological pathways

  • Machine learning approaches to predict functional relationships

  • Similar to approaches described for BMD-related genes

• Experimental Validation:

  • Test predictions from integrated analyses using targeted experiments

  • Validate in multiple model systems (cell lines, primary cells, animal models)

  • Use recombinant protein to confirm direct interactions

This integrated approach has been successfully applied to identify BMD-related genes and could reveal FAM118A's role in bone metabolism or other biological processes . The combination of genetic evidence with functional validation provides the strongest support for biological mechanisms.

What experimental controls should be included when working with recombinant FAM118A protein?

When working with recombinant FAM118A protein, rigorous experimental controls are essential for meaningful and reproducible results:

• Protein Quality Controls:

  • Purity assessment: SDS-PAGE and mass spectrometry to confirm >80% purity

  • Endotoxin testing: Ensure levels <1.0 EU per μg using LAL method

  • Aggregation assessment: Size exclusion chromatography or dynamic light scattering

  • Batch-to-batch comparison: Validate consistency between preparations

• Negative Controls:

  • Heat-denatured FAM118A: To distinguish between specific activity and non-specific effects

  • Irrelevant protein with same tag: To control for tag-mediated effects

  • Buffer-only controls: To account for buffer component effects

  • Untransfected/mock-transfected cells in expression studies

• Positive Controls:

  • Known interacting partners (when identified)

  • Positive readouts in functional assays

  • Reference standards with established activity metrics

• Dosage Controls:

  • Dose-response experiments to establish specificity

  • Titration series to determine EC50/IC50 values

  • Time-course experiments to determine optimal treatment duration

• System-Specific Controls:

  • Cell-type specific responses: Compare effects across multiple cell lines

  • Species-specific differences: Compare mouse and human protein effects when possible

  • Environmental variables: Temperature, pH, ionic strength controls

Including these controls helps distinguish specific FAM118A-mediated effects from artifacts and ensures the reliability and reproducibility of experimental findings. Given the high purity (>80%) of commercially available recombinant FAM118A , researchers should be able to obtain consistent results when proper controls are implemented.