Recombinant Human Uncharacterized protein C17orf78 (C17orf78)

What is the genomic structure and location of the C17orf78 gene?

C17orf78 (Chromosome 17 Open Reading Frame 78) is located on the long arm cytogenetic band 17q12 of human chromosome 17. The genomic sequence spans from base pair position 37,375,985 to 37,392,708 on the forward strand, constituting a length of 16,723 base pairs. The gene contains 7 exon regions and 6 intron regions spanning its sequence. It is positioned near neighboring genes including TADA2A, DUSP14, and ACACA .

For researchers designing primers or gene editing strategies, understanding this genomic architecture is essential for appropriate experimental design. When targeting specific regions of C17orf78, consideration of exon-intron boundaries is critical for successful amplification or modification.

What are the known protein isoforms of C17orf78 and their structural characteristics?

C17orf78 has two identified splice variant isoforms with distinct structural characteristics:

The primary sequence has an isoelectric point of 9.62, indicating it is basic in nature . This characteristic should be considered when designing protein purification protocols, as the protein will carry a positive charge at physiological pH.

When working with recombinant C17orf78, researchers should specify which isoform they are investigating, as the structural and potentially functional differences between isoforms may impact experimental outcomes.

What is the tissue expression pattern of C17orf78 in humans?

C17orf78 demonstrates a highly tissue-specific expression pattern. It is predominantly expressed in the human small intestine, with particularly high levels in the duodenum. Lower expression levels have been detected in the testes and other tissues. Interestingly, fetal expression of C17orf78 decreases in most tissues during development, with the notable exception of intestinal tissues, where expression increases over time .

For researchers interested in studying C17orf78 function, the duodenum represents the most relevant physiological context. Cell lines derived from intestinal tissue would likely provide the most appropriate in vitro model systems for functional studies.

What antibodies are available for C17orf78 research and how should they be optimized for different applications?

Several validated antibodies are available for C17orf78 research, with optimization parameters for different applications:

The commonly used antibody is a polyclonal antibody raised in rabbits against recombinant human C17orf78 protein (amino acids 1-186) . For immunohistochemistry, human spleen tissue has been successfully used as a positive control. For immunofluorescence, the A549 cell line has been validated .

When optimizing antibody protocols, researchers should:

• Begin with the manufacturer's recommended dilutions

• Perform titration experiments to determine optimal concentration for specific sample types

• Include appropriate positive controls (human spleen tissue for IHC; A549 cells for IF)

• Include negative controls (secondary antibody only; isotype controls)

• Be aware that the buffer system (50% Glycerol, 0.01M PBS, pH 7.4) may affect antibody performance in some applications

How can CRISPR-Cas9 technology be effectively utilized to study C17orf78 function?

For CRISPR-Cas9 gene editing of C17orf78, lentiviral vectors containing sgRNA and Cas9 are available with titers >1×10^7 IU/mL. The vector backbone typically used is pLenti-U6-sgRNA-SFFV-Cas9-2A-Puro, which includes a puromycin selection marker for generating stable cell lines .

Methodological considerations for CRISPR-Cas9 editing of C17orf78:

• Target selection: Design sgRNAs targeting early exons (preferably exons 1-3) to maximize disruption of all isoforms

• Cell line selection: Consider intestinal cell lines where C17orf78 is naturally expressed

• Delivery method: Lentiviral transduction provides high efficiency in most cell types

• Validation strategy:

  • PCR and sequencing of the targeted region

  • Western blot analysis of protein levels using validated antibodies

  • qRT-PCR to assess mRNA expression levels

• Control generation: Create parallel cell lines with non-targeting sgRNAs

Note that the SFFV promoter controlling Cas9 expression works for most cell types but is not recommended for ES cells or iPS cells . For these specialized cell types, alternative promoters should be considered.

What methodologies are appropriate for detecting C17orf78 variants and their potential functional consequences?

The C17orf78 gene can harbor variants with potential functional implications. For example, the NM_173625.5(C17orf78):c.391G>A variant results in a p.(Ala131Thr) amino acid substitution .

Methodological approach for variant analysis:

• PCR amplification and Sanger sequencing of specific exons

• Next-generation sequencing for comprehensive variant detection

• Bioinformatic analysis using prediction tools to assess potential impact:

  • SIFT, PolyPhen-2 for missense variants

  • SpliceAI for variants near splice sites (like c.391G>A, which is 1 bp from a donor site)

• Functional validation through:

  • Site-directed mutagenesis of expression constructs

  • Cell-based assays comparing wild-type and variant proteins

  • RNA analysis to detect potential splicing alterations

For the c.391G>A variant specifically, its position near a splice donor site (1 bp from donor) suggests potential impact on splicing efficiency, which should be experimentally validated using minigene assays or RT-PCR analysis of patient samples if available .

What is known about the potential role of C17orf78 in immune regulation?

Current evidence suggests C17orf78 may function as a regulator of immune responses, though its precise mechanism remains to be elucidated. The protein's high expression in intestinal tissues, particularly the duodenum, suggests a potential role in gut immunity or barrier function .

Research approaches to investigate immune regulatory functions:

• Cytokine profiling in C17orf78-knockout cells under various immune stimulation conditions

• Co-immunoprecipitation studies to identify protein-protein interactions with known immune regulators

• Transcriptomic analysis of immune gene expression in C17orf78-depleted versus control cells

• Investigation of C17orf78 expression changes during inflammatory challenges

• Assessment of intestinal barrier function in models with altered C17orf78 expression

Given its potential role in immune regulation, C17orf78 represents a promising target for studies investigating diseases with immune components, including inflammatory bowel diseases, autoimmune disorders, and certain cancers .

How might the intestine-specific expression pattern of C17orf78 relate to its biological function?

The tissue-specific expression of C17orf78, with predominance in the small intestine and particularly the duodenum, suggests specialized functions in this tissue. The developmental pattern, with increasing expression in intestinal tissues during fetal development while decreasing in other tissues, further supports a specific role in intestinal biology .

Research strategies to explore function based on expression pattern:

• Single-cell RNA sequencing of intestinal tissues to identify specific cell types expressing C17orf78

• Spatial transcriptomics to map expression along the intestinal axis

• Comparative analysis with genes showing similar expression patterns

• Investigation of expression changes in intestinal disease states

• Developmental studies examining the timing of C17orf78 expression in relation to intestinal maturation

• Organoid models to study C17orf78 function in a physiologically relevant context

The duodenum-specific expression might indicate roles in nutrient sensing, absorption, or local immune regulation at this critical intestinal site, which represents the first major site of interaction between ingested material and the gastrointestinal tract.

What are the experimental challenges in studying uncharacterized proteins like C17orf78?

Investigating uncharacterized proteins presents several methodological challenges:

• Limited reference data: Without established functional assays, researchers must develop novel approaches to assess protein function

• Lack of structural information: Without crystal structures or models, predicting functional domains becomes challenging

• Antibody validation: With limited characterization, confirming antibody specificity requires rigorous controls

• Phenotype subtlety: Knockout or overexpression may produce subtle phenotypes easily overlooked in standard assays

• Unknown interactors: Difficulty in designing appropriate co-IP or pull-down experiments without knowledge of potential binding partners

Recommended approach for uncharacterized protein research:

• Begin with bioinformatic analyses to predict domains and potential functions

• Perform evolutionary analysis to identify orthologs in model organisms

• Use proximity labeling methods (BioID, APEX) to identify neighboring proteins

• Employ unbiased screening approaches (transcriptomics, proteomics) following perturbation

• Consider compensatory mechanisms when analyzing knockout models

For C17orf78 specifically, leveraging its tissue-specific expression pattern may provide insights into potential functions and guide experimental design toward intestinal-specific processes.

How can researchers effectively design experiments to elucidate the function of C17orf78?

A comprehensive experimental strategy to determine C17orf78 function should include:

• Subcellular localization studies:

  • Fluorescent protein tagging

  • Subcellular fractionation followed by Western blotting

  • Immunofluorescence with validated antibodies

• Interactome analysis:

  • Immunoprecipitation followed by mass spectrometry

  • Yeast two-hybrid screening

  • Proximity labeling (BioID or APEX2)

• Gene expression profiling:

  • RNA-seq following knockdown or overexpression

  • ChIP-seq if nuclear localization is confirmed

  • Single-cell RNA-seq in intestinal tissue

• Functional assays based on expression pattern:

  • Intestinal epithelial barrier function

  • Nutrient absorption assays

  • Immune cell interactions

• In vivo models:

  • Conditional knockout in intestinal epithelium

  • Humanized mouse models for tissue-specific studies

  • Organoid cultures from human intestinal tissue

Each experimental approach should include appropriate controls and validation strategies to ensure reproducibility and reliability of results.

What potential disease associations might C17orf78 have, based on its expression pattern and predicted functions?

Given C17orf78's high expression in the small intestine and potential role in immune regulation, several disease associations warrant investigation:

• Inflammatory Bowel Diseases (IBD):

  • Expression analysis in Crohn's disease and ulcerative colitis samples

  • Genetic association studies examining C17orf78 variants in IBD cohorts

  • Functional studies in intestinal inflammation models

• Intestinal Cancers:

  • Expression analysis in duodenal and small intestinal adenocarcinomas

  • Examination of somatic mutations in cancer databases

  • Assessment of prognostic value in patient cohorts

• Celiac Disease:

  • Expression changes in response to gluten challenge

  • Potential role in intestinal barrier function

  • Involvement in local immune responses

• Infectious Enteric Diseases:

  • Response to pathogen challenge

  • Role in antimicrobial peptide production

  • Contribution to recovery after infection

• Malabsorption Syndromes:

  • Potential roles in nutrient transport or processing

  • Expression changes in malabsorption conditions

  • Interaction with transport proteins

For each potential disease association, researchers should consider both genetic and functional approaches, integrating findings from patient samples with mechanistic studies in model systems.

How can structural biology approaches be applied to uncharacterized proteins like C17orf78?

For uncharacterized proteins like C17orf78, structural biology can provide crucial insights into function:

• Protein expression and purification strategy:

  • Expression in E. coli, insect cells, or mammalian cells

  • Affinity tags for purification (His, GST, MBP)

  • Consideration of protein solubility and stability

• Structural determination methods:

  • X-ray crystallography requiring protein crystallization

  • Cryo-electron microscopy for complex structures

  • NMR spectroscopy for smaller domains

  • AlphaFold2 or other AI-based structure prediction

• Functional domain analysis:

  • Limited proteolysis to identify stable domains

  • Thermal shift assays to assess protein stability

  • Circular dichroism to analyze secondary structure

  • Small-angle X-ray scattering for solution structure

• Structure-guided functional studies:

  • Identification of potential binding pockets

  • Site-directed mutagenesis of conserved residues

  • Design of truncated constructs for domain-specific analysis

  • Virtual screening for potential binding partners

For C17orf78 specifically, structural studies would benefit from focusing on individual domains if the full-length protein proves challenging to express or crystallize. The recombinant fragment (amino acids 1-186) used as an immunogen for antibody production could serve as a starting point for structural studies .

What are the optimal conditions for expressing and purifying recombinant C17orf78 protein?

Based on the protein's characteristics and available information, the following protocol is recommended for recombinant C17orf78 expression and purification:

• Expression system selection:

  • E. coli BL21(DE3) for basic studies

  • Mammalian expression (HEK293) for studies requiring post-translational modifications

  • Baculovirus-infected insect cells for improved solubility

• Construct design considerations:

  • Full-length (275 amino acids) vs. truncated constructs

  • N-terminal vs. C-terminal tags based on predicted structure

  • Inclusion of TEV or PreScission protease sites for tag removal

  • Codon optimization for the selected expression system

• Purification strategy:

  • Initial capture: Ni-NTA affinity chromatography for His-tagged protein

  • Intermediate purification: Ion exchange chromatography (cation exchange given pI of 9.62)

  • Polishing: Size exclusion chromatography

  • Buffer optimization: Consider pH 7.0-7.5 with moderate salt concentration

• Quality control:

  • SDS-PAGE and Western blot using validated antibodies

  • Mass spectrometry for identity confirmation

  • Dynamic light scattering for homogeneity assessment

  • Circular dichroism for secondary structure analysis

The isoelectric point of 9.62 indicates C17orf78 will be positively charged at physiological pH, which should be considered when designing purification strategies and buffer systems .

How should researchers approach the validation of C17orf78 knockdown or knockout models?

Rigorous validation of C17orf78 knockdown or knockout models is essential for reliable functional studies:

• Genetic validation:

  • PCR and sequencing of the targeted locus

  • Analysis of potential off-target modifications

  • Assessment of genomic integrity around the target site

• Transcript validation:

  • qRT-PCR with primers spanning multiple exons

  • RNA-seq to assess complete transcriptome and detect potential cryptic splicing

  • Analysis of both isoforms to ensure complete knockout

• Protein validation:

  • Western blot using antibodies targeting different epitopes

  • Immunofluorescence to confirm absence in relevant cell compartments

  • Mass spectrometry-based proteomics to confirm complete absence

• Functional validation:

  • Rescue experiments with wild-type C17orf78 expression

  • Comparison of multiple independent knockout/knockdown clones

  • Correlation of phenotype severity with knockdown efficiency in partial knockdowns

• Control considerations:

  • Use of non-targeting sgRNAs for CRISPR controls

  • Scrambled siRNA controls for knockdown studies

  • Isogenic wild-type cell lines as the most appropriate controls

For C17orf78 specifically, validation in intestinal cell lines is recommended given the protein's high expression in this tissue type .

What considerations should be made when designing experiments to identify C17orf78 interacting partners?

Identifying protein interaction partners is critical for understanding C17orf78 function:

• Co-immunoprecipitation (Co-IP) strategy:

  • Use multiple validated antibodies targeting different epitopes

  • Consider both endogenous IP (in intestinal cells) and overexpression systems

  • Include appropriate controls (IgG control, lysate input)

  • Gentle lysis conditions to preserve protein complexes

  • Crosslinking for transient interactions

• Proximity-based approaches:

  • BioID: Fusion of C17orf78 with biotin ligase for labeling proximal proteins

  • APEX2: Peroxidase-based proximity labeling

  • Split-BioID for monitoring conditional interactions

  • Controls with BioID/APEX2 alone or fused to unrelated proteins

• Yeast two-hybrid considerations:

  • Use of both N- and C-terminal fusions to activation/binding domains

  • Library selection from intestinal tissue where C17orf78 is expressed

  • Stringent confirmation of positive interactions

  • Mammalian two-hybrid validation

• Mass spectrometry analysis:

  • SILAC or TMT labeling for quantitative comparison

  • Filtering against CRAPome database to remove common contaminants

  • Validation of key interactions by reciprocal IP

  • Network analysis to identify enriched pathways

• Subcellular context:

  • Consider compartment-specific interactome analysis

  • Fraction cells before IP to enrich for relevant compartments

  • Use organelle-specific proximity labeling approaches

For C17orf78, focusing on intestinal cell types and considering its potential role in immune function should guide the design of interaction studies and interpretation of results .