Recombinant Human Uncharacterized protein C7orf45 (C7orf45)

Basic Research Questions

• What is C7orf45 and what is its current characterization status?

  C7orf45 (also referred to as SSMEM1 in some databases) is an uncharacterized protein mapped to chromosome 7q32.2 in humans. While its precise function remains to be fully elucidated, C7orf45 has been identified as one of the most distinctive proteins in ameloblastoma (AM) compared to dental follicle (DF), suggesting potential involvement in odontogenic tumor development . The protein is classified as "uncharacterized" since its biological function, three-dimensional structure, and physiological role have not yet been comprehensively defined in scientific literature.

• Which expression systems are most suitable for producing recombinant C7orf45?

  Multiple expression systems can be utilized for C7orf45 production, each with distinct advantages:

  • Prokaryotic systems: Escherichia coli offers the highest yields and shorter turnaround times for C7orf45 expression. The T7 promoter system in pET vectors is particularly effective, potentially yielding target protein representing up to 50% of total cell protein in successful cases .

  • Eukaryotic systems: Yeast expression systems provide a balance between yield and post-translational modifications. For more complex structural requirements, insect cells with baculovirus or mammalian expression systems can provide the post-translational modifications necessary for correct protein folding and activity retention .

  The optimal system selection depends on downstream applications and whether native protein conformation is critical for the research question.

• What are the recommended methods for detecting C7orf45 expression in tissue samples?

  For reliable detection of C7orf45 expression in research samples, multiple complementary approaches should be considered:

  • RNA-seq: For transcriptome-wide expression profiling. When analyzing formalin-fixed paraffin-embedded (FFPE) samples, the RNAaccess method based on exome capture produces the most concordant results with a minimum RNA DV200 requirement of 10% and RNA input of 10ng .

  • RT-qPCR: For targeted expression analysis. Primer efficiency should be evaluated by serial dilution (1:5) experiments. For C7orf45 expression normalization, stable reference genes such as ACTB, RPLP0 or 18SrRNA are recommended based on their expression stability profiles .

  • Immunodetection: Validation of protein expression requires specific antibodies. For uncharacterized proteins like C7orf45, antibody specificity should be confirmed through siRNA-mediated depletion experiments similar to the approach used for C17orf80 .

• What reference genes should be used for normalizing C7orf45 expression data?

  Selection of appropriate reference genes is critical for accurate expression analysis of C7orf45. Based on comparative stability analyses, the following reference genes are recommended:

  Reference Gene	Expression Level (Cq range)	Stability Ranking
  ACTB	17-20	High
  RPLP0	21.5-24	High
  18SrRNA	21.5-24	High
  GAPDH	24-30	Medium
  TBP	24-30	Medium
  RPL27	24-30	Medium
  HPRT1	24-30	Medium

  These rankings are based on stability evaluation using multiple normalization methods including geNorm, NormFinder, BestKeeper, and comparative ∆Ct methods . For optimal accuracy, expression stability of these candidates should be verified in the specific tissue/cell type under investigation.

Advanced Research Questions

• How can I optimize expression conditions for recombinant C7orf45 in E. coli?

  Optimization of C7orf45 expression requires systematic evaluation of multiple parameters using Design of Experiments (DoE) approaches. The following optimization framework is recommended:

  Experimental Factor	Low Level (-)	High Level (+)	Optimization Notes
  Media composition
  Yeast Extract	0.5%	2%	Higher concentrations may improve yield
  Tryptone	1%	2%	Affects growth rate and protein synthesis
  Glycerol	0.2%	1%	Alternative carbon source to glucose
  NaCl	0.5%	1%	Affects osmotic pressure
  Induction conditions
  Inoculum size	OD600 0.4	OD600 0.8	Impacts cell density at induction
  IPTG concentration	0.1 mM	1.0 mM	Higher concentrations may lead to inclusion bodies
  Induction temperature	18°C	37°C	Lower temperatures may improve solubility
  Incubation time	4 hours	16 hours	Extended time may increase yield but reduce solubility
  pH	6.8	7.5	Affects protein stability

  Implement either Central Composite Design (CCD) or Box-Behnken Design (BBD) under Response Surface Methodology to identify optimal conditions. These approaches have demonstrated yield increases of 3.1 to 5.1-fold for recombinant proteins .

• What CRISPR/Cas9 approaches can be used to investigate C7orf45 function?

  CRISPR/Cas9-based functional studies of C7orf45 can be conducted using the following methodologies:

  • Gene knockout: C7orf45 CRISPR/Cas9 KO Plasmid (h) is designed to disrupt gene expression by causing a double-strand break in a 5' constitutive exon within the SSMEM1 (human) gene. This commercially available system consists of a pool of 3 plasmids, each encoding the Cas9 nuclease and a target-specific 20 nt guide RNA designed for maximum knockout efficiency .

  • Validation strategy: For confirming knockout efficiency, a combination of genomic PCR across the targeted region, RT-qPCR for transcript levels, and Western blotting or mass spectrometry for protein detection is recommended.

  • Phenotypic analysis: Based on C7orf45's detection in ameloblastoma, phenotypic assays focused on cell proliferation, migration, and differentiation in dental/oral cell models would be logical starting points for functional characterization.

• How can N-terminal sequence modifications improve C7orf45 production yield?

  For proteins with poor expression like C7orf45, N-terminal sequence optimization can significantly enhance yield through the following directed evolution approach:

  1. Library generation: Create DNA libraries coding for diversified N-terminal sequences of C7orf45 (first 10-15 amino acids)

  2. Reporter fusion: Clone GFP at the C-terminus of the C7orf45 gene as an expression reporter

  3. FACS-based screening: Use fluorescence-activated cell sorting to isolate high-expressing variants

  4. Sequence analysis: Identify sequence patterns that correlate with improved expression

  This systematic approach has demonstrated yield improvements of soluble recombinant proteins by up to 30-fold . For C7orf45, focus on optimizing the nucleotides immediately following the start codon which significantly influence protein translation efficiency.

• What methods are recommended for investigating C7orf45 protein-protein interactions?

  Characterizing the interactome of uncharacterized proteins like C7orf45 requires complementary approaches:

  • Proximity labeling mass spectrometry: Similar to methods used for C17orf80, BioID or APEX2-based proximity labeling followed by mass spectrometry can identify proteins in close physical proximity to C7orf45 within the cellular environment .

  • Co-immunoprecipitation: Using epitope-tagged C7orf45 (e.g., Myc-tagged C7orf45) for pulldown experiments followed by mass spectrometry analysis.

  • Validation assays: Confirm interactions using reverse co-immunoprecipitation, Förster resonance energy transfer (FRET), or mammalian two-hybrid assays.

  For uncharacterized proteins, it's particularly important to include appropriate controls to distinguish true interactions from non-specific binding.

• How can differential methylation analysis be applied to study C7orf45 in disease contexts?

  DNA methylation analysis of C7orf45 in disease models can follow this methodological framework:

  1. Sample preparation: Isolate DNA from case-control samples and perform bisulfite modification on 500 ng DNA samples using a kit such as EZ DNA Methylation Kit

  2. Genome-wide methylation profiling: Use Infinium MethylationEPIC BeadChip Array on an iScan device to query >850,000 differentiated loci

  3. Data analysis: Analyze results using Illumina GenomeStudio Methylation Module and R statistical packages

  4. Identification of differential methylation: Focus on sites with >10-fold differences in methylation levels between case and control groups

  5. Regulatory context analysis: Determine if differentially methylated sites in C7orf45 are located in CpG islands, shore regions, or other regulatory regions

  This approach has successfully identified differential methylation in diseases such as ovarian cancer , and could be adapted to investigate the epigenetic regulation of C7orf45 in ameloblastoma or other relevant conditions.

• What approaches are recommended for determining C7orf45 subcellular localization?

  To determine the subcellular localization of C7orf45, employ these complementary techniques:

  • Immunofluorescence microscopy: Using specific antibodies against C7orf45 or epitope-tagged versions (e.g., Myc-tagged C7orf45) co-stained with organelle markers

  • Subcellular fractionation: Separate cellular compartments followed by Western blot analysis

  • Antibody accessibility assay: To define membrane topology for proteins predicted to span membranes, using selective permeabilization with digitonin versus Triton X-100 to determine which protein domains are accessible from which cellular compartment

  For validation, siRNA-mediated depletion should be used to confirm antibody specificity, as was demonstrated for the uncharacterized protein C17orf80 .

• How should RNA-seq differential expression analysis be configured to study C7orf45 in disease models?

  For RNA-seq based differential expression analysis of C7orf45:

  1. Input data preparation: Use raw counts (not scaled counts) as DESeq2 model requires integers

  2. Experimental design specification: Define factor levels and contrasts clearly (e.g., disease vs. control)

  3. Statistical analysis: Implement DESeq2 to obtain log₂ fold change and adjusted p-values

  4. Visualization: Create volcano plots highlighting C7orf45 position relative to global expression changes

  5. Context analysis: Perform gene set enrichment analysis to understand pathways associated with C7orf45 expression changes

  For maximum statistical power when working with clinical samples of variable quality (e.g., FFPE), the RNAaccess method with a minimum RNA DV200 of 10% and RNA input of 10ng is recommended .

Citations

• DataForSEO. "People Also Ask - DataForSEO." DataForSEO, 2024 .

• Genome-wide methylation profiles in monozygotic twins, 2020 .

• Lifeome. "Uncharacterized protein - Lifeome," 2025 .

• Expression and purification of recombinant hemoglobin in Escherichia coli, 2011 .

• Reference gene evaluation for normalization of gene expression, 2024 .

• BuiltVisible. "Scraping 'People Also Ask' boxes for SEO and content research," 2020 .

• Santa Cruz Biotechnology. "C7orf45 CRISPR/Cas9 KO Plasmid (h): sc-418520," 2023 .

• Uncharacterized protein C17orf80 – a novel interactor of human mitochondrial nucleoids, 2023 .

• A Review of Employing Design of Experiments in Prokaryotic Recombinant Protein Production, 2018 .

• Geneious. "Practice Expression Analysis - Geneious," 2024 .

• KeywordProfiler. "People Also Ask Tool | Visualise & Download Questions," 2024 .

• Exploring protein profiles and hub genes in ameloblastoma, 2024 .

• Recombinant protein expression in Escherichia coli, 2014 .

• Introduction to RNA-seq: Differential expression analysis, 2023 .

• Reddit. "No link anymore to search for 'People Also Ask' questions," 2024 .

• Increasing recombinant protein production in E. coli via FACS-based screening, 2024 .

• RNA-seq RNAaccess identified as the preferred method for gene expression analysis of low quality FFPE samples, 2023 .

• "Data shows 'People Also Ask' and 'Local Listings' are the most popular SERP features," 2021 .