Recombinant Pan troglodytes Psoriasis susceptibility 1 candidate gene 1 protein homolog (PSORS1C1)

What is PSORS1C1 and what is its significance in autoimmune disease research?

PSORS1C1 (Psoriasis Susceptibility 1 Candidate 1) is a susceptibility gene located within the major histocompatibility complex (MHC) on chromosome 6p21.3, spanning approximately 180 to 250 kb in humans. It has been identified as a significant genetic determinant for several autoimmune conditions, most notably psoriasis . The importance of this gene extends beyond psoriasis to other autoimmune diseases, including potential associations with Graves' disease (GD), as demonstrated in studies of Chinese Han populations . The gene contains multiple single nucleotide polymorphisms (SNPs) that have been linked to disease susceptibility, making it an important target for understanding the genetic basis of autoimmunity. The Pan troglodytes homolog provides valuable comparative data for evolutionary studies of immune function and disease susceptibility across primates.

What are the key structural and functional characteristics of the PSORS1C1 protein?

The PSORS1C1 protein is encoded by a 459 bp open reading frame in Pan troglodytes, as referenced in the NCBI database (accession NM_001128140.1) . The protein shares significant homology with its human counterpart, though with species-specific variations that may influence its functionality. Studies of gene expression patterns have shown that PSORS1C1 is under-expressed in psoriatic patients compared to normal controls, suggesting potential regulatory roles in immune function . The protein is part of the PSORS1 locus, which contains several genes, including protein-coding genes, non-protein-coding genes, and pseudogenes, many of which have variants associated with autoimmune conditions. The specific molecular mechanisms through which PSORS1C1 influences disease susceptibility remain an active area of investigation, with current evidence pointing toward roles in immune regulation and response.

What is the evolutionary relationship between human and Pan troglodytes PSORS1C1?

The evolutionary relationship between human and Pan troglodytes PSORS1C1 reflects the rapid evolution of major histocompatibility complex (MHC) class I genes in primates. Comparative sequencing studies have revealed that insertions/deletions represent the major path to genomic divergence between human and chimpanzee MHC class I regions . The PSORS1C1 gene in Pan troglodytes (GenBank accession NM_001128140.1) shows significant homology to its human counterpart, though with species-specific variations. This evolutionary pattern is consistent with the "hitchhiking diversity" phenomenon described by Shiina et al. (2006), where new disease alleles in humans may have emerged through this evolutionary process . The rapid evolution of these genes likely reflects adaptive immune responses to species-specific pathogen pressures, making comparative studies between human and chimpanzee PSORS1C1 valuable for understanding both disease mechanisms and evolutionary immunology.

Which PSORS1C1 SNPs have been most strongly associated with autoimmune diseases?

Several single nucleotide polymorphisms (SNPs) within the PSORS1C1 gene have been associated with autoimmune conditions. In studies of autoimmune thyroid disease (AITD), the rs3778638 polymorphism showed significant associations, with different genotype distributions between AITD patients and healthy controls (p = 0.046). Specifically, the genotype frequencies in AITD patients were AA: 2.67%, AG: 19.15%, and GG: 78.18%, compared to controls (AA: 1.52%, AG: 22.2%, and GG: 75.87%) . This SNP showed a stronger association with Graves' disease (p = 0.039) than with Hashimoto's thyroiditis.

In psoriasis research, three key SNPs within the PSORS1 locus have been investigated:

• rs1062470 (within PSORS1C1/CDSN genes)

• rs887466 (within PSORS1C3 gene)

• rs10484554 (within LOC105375015 gene)

Among these, rs10484554 demonstrated the strongest association with psoriasis risk, with its C/T genotype conferring 5.63 times higher likelihood of developing psoriasis under codominant comparison. The T allele was 3 times more likely to be associated with psoriasis under allelic comparison . For rs887466, the G/G genotype appeared to have a protective effect, being 0.4 times less likely to be associated with psoriasis under a codominant comparison model .

How do PSORS1C1 expression patterns differ between disease states and normal conditions?

Studies examining PSORS1C1 expression have revealed significant differences between disease states and normal conditions. In psoriatic patients, PSORS1C1 was found to be under-expressed compared to normal controls, suggesting potential regulatory involvement in disease pathogenesis . This under-expression pattern was determined through relative gene expression profiling using reverse transcription followed by real-time PCR with the following specific primers:

• Forward primer: 5′-CTGACCGACTTTGCCACATGGA-3′

• Reverse primer: 5′-GTGGGAAGAGGGAACCAGGATA-3′

GAPDH was used as the endogenous control in these experiments, exhibiting uniform and stable expression in plasma samples with no significant difference between psoriatic patients and controls . The differential expression observed in disease states suggests that PSORS1C1 may function in immune regulation pathways relevant to autoimmunity, though the specific molecular mechanisms require further investigation. This expression pattern provides a potential biomarker for disease states and offers insight into the functional consequences of genetic variations within this locus.

What is the linkage disequilibrium pattern of PSORS1C1 SNPs in different populations?

Linkage disequilibrium (LD) patterns for PSORS1C1 SNPs show notable population-specific variations. In the Chinese Han population study of autoimmune thyroid disease patients, no significant linkage disequilibrium was observed among the four investigated SNPs (rs3130983, rs3778638, rs3815087, and rs4959053) in PSORS1C1 . This finding suggests independent inheritance patterns for these polymorphisms in this population.

In contrast, studies in other populations, particularly Egyptian cohorts, have examined different SNPs within the broader PSORS1 locus, including rs1062470 (PSORS1C1/CDSN), rs887466 (PSORS1C3), and rs10484554 (LOC105375015) . While complete LD data for these specific markers was not fully detailed in the available research, the differential association of these SNPs with psoriasis risk suggests potentially complex LD patterns within the PSORS1 region.

The population-specific nature of these LD patterns highlights the importance of considering ethnic background in genetic association studies of PSORS1C1. These differences may reflect unique evolutionary histories and selective pressures on the MHC region in different human populations, potentially influencing disease susceptibility and progression in a population-specific manner.

What are the optimal methods for cloning and expressing recombinant Pan troglodytes PSORS1C1?

For optimal cloning and expression of recombinant Pan troglodytes PSORS1C1, a systematic approach using contemporary molecular biology techniques is recommended. Based on available information, the following protocol would provide efficient results:

• Gene Synthesis and Vector Selection:

  • The complete PSORS1C1 ORF (459 bp) from Pan troglodytes can be synthesized based on the reference sequence NM_001128140.1 .

  • For expression studies, pcDNA3.1-C-(k)DYK or equivalent mammalian expression vectors are recommended, providing a C-terminal DYKDDDDK (FLAG) tag for detection and purification .

• Cloning Strategy:

  • Seamless cloning technologies (such as CloneEZ™) have proven effective for inserting the PSORS1C1 ORF into expression vectors .

  • The linear insert structure allows for precise incorporation without unwanted modifications to the coding sequence.

• Expression System Selection:

  • For functional studies, mammalian cell lines (particularly primate-derived) provide the most physiologically relevant post-translational modifications.

  • HEK293T cells have been successfully used for expression of MHC-region proteins, offering good yield and appropriate processing.

• Protein Purification:

  • The C-terminal FLAG tag allows for single-step affinity purification using anti-FLAG antibody columns.

  • Size exclusion chromatography as a second purification step is recommended to achieve higher purity for functional studies.

This approach ensures production of recombinant protein that closely resembles the native form, facilitating meaningful functional and structural analyses.

What PCR and genotyping approaches are most reliable for studying PSORS1C1 polymorphisms?

For reliable analysis of PSORS1C1 polymorphisms, multiplex PCR technology has been validated in multiple studies . Based on the research literature, the following methodological approach is recommended:

• DNA Isolation:

  • Standard DNA extraction methods from peripheral blood are suitable, with quality assessment via spectrophotometry (260/280 ratio of 1.8-2.0).

• SNP Selection and Primer Design:

  • Include validated SNPs such as rs3130983, rs3778638, rs3815087, and rs4959053 for AITD association studies .

  • For psoriasis studies, include rs1062470, rs887466, and rs10484554 .

  • Design primers with Tm values within 2-3°C of each other, GC content of 40-60%, and minimal secondary structure formation.

• Genotyping Methods:

  • Multiplex PCR has shown high reliability in detecting PSORS1C1 SNPs .

  • Real-time PCR with SYBR Green detection offers quantitative assessment for expression studies .

  • For higher throughput studies, consider microarray-based genotyping platforms that can simultaneously assess multiple SNPs across the PSORS1 locus.

• Controls and Validation:

  • Include known genotype controls in each assay run.

  • Validate results by sequencing a subset (5-10%) of samples to confirm genotype calls.

  • Use Hardy-Weinberg equilibrium tests to ensure genotyping quality.

For expression studies, the validated primers for PSORS1C1 are:

• Forward: 5′-CTGACCGACTTTGCCACATGGA-3′

• Reverse: 5′-GTGGGAAGAGGGAACCAGGATA-3′

With GAPDH as endogenous control .

These approaches provide robust and reproducible results for studying PSORS1C1 polymorphisms in diverse population samples.

How can PSORS1C1 gene expression be accurately quantified in experimental models?

Accurate quantification of PSORS1C1 gene expression requires a carefully optimized protocol combining RNA isolation, reverse transcription, and real-time PCR analysis. Based on validated methodologies from recent studies, the following comprehensive approach is recommended:

• RNA Isolation and Quality Assessment:

  • Extract total RNA using specialized kits designed for the specific tissue/cell type.

  • Assess RNA integrity using Bioanalyzer or gel electrophoresis (RIN > 8.0 preferred).

  • Ensure RNA purity with A260/280 ratios of 1.8-2.0 and A260/230 > 1.7.

• Reverse Transcription Protocol:

  • Polyadenylate the RNA using poly(A) polymerase.

  • Convert to cDNA using reverse transcriptase with oligo-dT priming.

  • Perform RT reactions at 37°C for 1 hour, followed by enzyme inactivation at 95°C .

• qPCR Methodology:

  • Utilize a SYBR Green-based real-time PCR system.

  • Perform reactions in triplicate using validated PSORS1C1-specific primers:

    • Forward: 5′-CTGACCGACTTTGCCACATGGA-3′

    • Reverse: 5′-GTGGGAAGAGGGAACCAGGATA-3′

  • Run reactions on standard real-time PCR platforms such as the StepOne system.

• Reference Gene Selection and Normalization:

  • GAPDH has been validated as a suitable reference gene, showing uniform expression between patient and control samples .

  • For higher accuracy, consider using multiple reference genes (such as ACTB, B2M, or HPRT1) and geometric averaging of normalization factors.

• Data Analysis:

  • Calculate relative expression using the 2^(-ΔΔCt) method.

  • Apply appropriate statistical tests based on data distribution (parametric or non-parametric).

This methodology provides a robust framework for accurate quantification of PSORS1C1 expression across various experimental models and clinical samples.

How might epigenetic modifications influence PSORS1C1 function in disease pathogenesis?

Epigenetic modifications likely play a significant role in regulating PSORS1C1 function and its contribution to disease pathogenesis, though this remains a largely unexplored frontier. The under-expression of PSORS1C1 observed in psoriatic patients compared to controls suggests potential epigenetic dysregulation . Several mechanisms may be involved:

• DNA Methylation Patterns:

  • The PSORS1 locus is situated within the MHC region on chromosome 6p21.3, which is known to undergo differential methylation in autoimmune conditions.

  • Hypermethylation of CpG islands near the PSORS1C1 promoter could contribute to the observed under-expression in disease states.

• Histone Modifications:

  • Changes in chromatin accessibility through histone acetylation/deacetylation or methylation marks may alter PSORS1C1 expression.

  • The MHC region is subject to complex regulation through bivalent histone marks that maintain genes in poised states, potentially affecting PSORS1C1 transcription in response to immune stimuli.

• Non-coding RNA Regulation:

  • The PSORS1 locus contains non-protein-coding genes that may produce regulatory RNAs influencing PSORS1C1 expression .

  • miRNAs targeting PSORS1C1 mRNA could contribute to post-transcriptional regulation in disease contexts.

• Environmental Triggers and Epigenetic Changes:

  • Environmental factors known to trigger psoriasis and other autoimmune conditions may exert their effects through epigenetic modifications of susceptibility genes like PSORS1C1.

  • Stress, infection, and certain medications could potentially alter the epigenetic landscape at this locus.

Future research employing bisulfite sequencing, ChIP-seq for histone modifications, and integrated multi-omics approaches would be valuable for elucidating the specific epigenetic mechanisms regulating PSORS1C1 in health and disease.

What protein-protein interactions are critical for PSORS1C1 function in immune regulation?

The protein-protein interaction network for PSORS1C1 in immune regulation remains incompletely characterized, representing an important area for future investigation. Based on its location within the MHC region and associations with autoimmune conditions, several potential interaction mechanisms can be hypothesized:

• MHC Class I Protein Interactions:

  • Given the proximity of PSORS1C1 to HLA genes within the MHC complex, it may interact with components of the antigen presentation machinery.

  • Potential interactions with tapasin, TAP proteins, or other peptide-loading complex components could influence antigen presentation and T cell responses.

• Cytokine Signaling Networks:

  • The under-expression of PSORS1C1 in psoriatic conditions suggests possible interactions with inflammatory cytokine pathways .

  • PSORS1C1 may function in IL-17, IL-23, or TNF-α signaling cascades that are central to psoriasis pathogenesis.

• Nuclear Protein Interactions:

  • If PSORS1C1 functions in transcriptional regulation, it may interact with chromatin remodeling complexes or transcription factors.

  • Potential binding partners might include STAT proteins, NF-κB components, or other immune-related transcription factors.

• Pathway Integration Points:

  • The genetic association with both psoriasis and autoimmune thyroid diseases suggests PSORS1C1 may function at the intersection of shared pathways in autoimmunity .

  • Interactions with pattern recognition receptors or downstream adaptors could link PSORS1C1 to innate immune activation.

Systematic investigation using techniques such as co-immunoprecipitation followed by mass spectrometry, proximity labeling methods (BioID or APEX), or yeast two-hybrid screening would be valuable approaches to identifying the PSORS1C1 interactome. Additionally, CRISPR-based genetic screens could help identify synthetic lethal interactions that reveal functional relationships.

How do structural differences between human and Pan troglodytes PSORS1C1 impact functional studies?

The structural differences between human and Pan troglodytes PSORS1C1 proteins have important implications for functional studies and interpretation of experimental results. These differences reflect the rapid evolution of MHC-related genes in primates and may influence protein functionality in species-specific ways:

• Sequence Variation and Functional Domains:

  • Comparative sequencing studies of human and chimpanzee MHC class I regions have revealed that insertions/deletions represent the major path to genomic divergence .

  • These sequence variations may affect critical functional domains, protein folding, or post-translational modification sites.

• Expression Regulation Differences:

  • Promoter and enhancer elements may differ between species, potentially resulting in different expression patterns and responses to stimuli.

  • Studies by Shiina et al. (2006) indicated that rapid evolution of MHC class I genes in primates generates new disease alleles in humans via hitchhiking diversity .

• Interaction Partner Specificity:

  • Species-specific amino acid differences may alter binding interfaces with interaction partners.

  • This could affect the assembly of protein complexes, potentially resulting in different signaling outcomes or regulatory functions.

• Methodological Considerations for Cross-Species Studies:

  • When using Pan troglodytes PSORS1C1 as a model for human disease processes, researchers should account for:

    • Potential differences in antibody epitopes affecting detection methods

    • Altered protein stability or solubility properties

    • Different post-translational modification patterns

    • Possible divergence in subcellular localization

For researchers conducting functional studies, these considerations necessitate careful validation of cross-species findings. Experiments comparing the human and chimpanzee proteins directly in the same cellular context would provide valuable insights into functional conservation and divergence, ultimately informing the translational relevance of findings from non-human primate models.

What evolutionary insights can be gained from comparing PSORS1C1 across primate species?

Comparative analysis of PSORS1C1 across primate species offers valuable evolutionary insights into immune system development and autoimmune disease susceptibility. The available research highlights several key evolutionary patterns:

• Rapid Evolution within the MHC Region:

  • Studies by Shiina et al. (2006) and Anzai et al. (2003) demonstrate that MHC class I genes, including those in the PSORS1 locus, undergo rapid evolution in primates .

  • Insertions/deletions represent the major path to genomic divergence between human and chimpanzee MHC regions, suggesting dynamic evolutionary processes .

• Hitchhiking Diversity Mechanism:

  • The rapid evolution of MHC genes generates new disease alleles in humans via a mechanism termed "hitchhiking diversity" .

  • This process may explain why certain PSORS1C1 variants are associated with autoimmune conditions in humans but not necessarily in other primates.

• Balancing Selection Pressures:

  • The maintenance of polymorphisms within PSORS1C1 across primate species suggests balancing selection, likely driven by pathogen pressures.

  • Different environmental exposures and pathogen challenges faced by various primate species may have shaped species-specific variations in PSORS1C1.

• Functional Divergence and Conservation:

  • While the Pan troglodytes PSORS1C1 protein shows homology to its human counterpart, the functional consequences of species-specific variations remain to be fully characterized.

  • The 459 bp ORF in chimpanzees suggests potential structural and functional differences from the human protein .

These evolutionary insights have important implications for understanding human autoimmune diseases and for designing appropriate animal models. The dynamic evolution of this region may partially explain why certain autoimmune conditions appear to be predominantly human diseases, with limited representation in non-human primates despite genetic similarities.

What novel therapeutic approaches might target PSORS1C1 or its pathways in autoimmune diseases?

Emerging research on PSORS1C1's role in autoimmune diseases suggests several promising therapeutic approaches that could target this gene or its associated pathways:

• Gene Expression Modulation:

  • Given the under-expression of PSORS1C1 observed in psoriatic patients , epigenetic modifiers that enhance PSORS1C1 expression might restore normal immune function.

  • Targeted CRISPR activation (CRISPRa) systems could potentially upregulate PSORS1C1 expression in affected tissues.

• SNP-Targeted Approaches:

  • Allele-specific therapeutics could target disease-associated SNPs like rs10484554, which shows strong association with psoriasis (OR = 5.63 for C/T genotype) .

  • Antisense oligonucleotides or small molecules that modulate splicing or expression in an allele-specific manner represent a precision medicine approach.

• Pathway Intervention:

  • The association of PSORS1C1 variants with both psoriasis and autoimmune thyroid diseases suggests common inflammatory pathways that could be targeted .

  • Inhibition of downstream effectors in these shared pathways might address multiple autoimmune conditions simultaneously.

• Protein Replacement or Supplementation:

  • For loss-of-function variants, administration of recombinant PSORS1C1 protein or peptide mimetics could potentially restore normal immune regulation.

  • Exosome-delivered PSORS1C1 mRNA might provide a targeted delivery approach to affected tissues.

• Combinatorial Approaches:

  • Given the complex genetic architecture of autoimmune diseases, combination therapies targeting multiple susceptibility genes including PSORS1C1 might prove most effective.

  • Personalized approaches based on individual genotyping of PSORS1C1 and other susceptibility loci could optimize treatment selection.

What future research directions would advance our understanding of PSORS1C1 in disease mechanisms?

Several critical research directions would significantly advance our understanding of PSORS1C1's role in disease mechanisms and potentially lead to novel therapeutic approaches:

• Comprehensive Functional Characterization:

  • Define the molecular function of PSORS1C1 protein through systematic knockout/knockin studies in relevant cell types.

  • Determine subcellular localization and dynamic changes in response to immune stimulation.

  • Establish a complete protein interactome using proximity labeling approaches and mass spectrometry.

• Cross-Disease Comparative Studies:

  • Expand genetic association studies of PSORS1C1 SNPs across multiple autoimmune conditions beyond psoriasis and AITD .

  • Conduct meta-analyses to identify shared and disease-specific genetic associations.

  • Investigate potential pleiotropic effects of PSORS1C1 variants across different organ systems.

• Advanced Genomic and Epigenomic Profiling:

  • Apply single-cell multi-omics approaches to characterize PSORS1C1 expression and regulation at cellular resolution.

  • Map the complete epigenetic landscape around the PSORS1 locus in health and disease states.

  • Utilize long-read sequencing to resolve complex structural variations in this genomic region.

• Translational Models and Therapeutic Development:

  • Develop humanized mouse models incorporating disease-associated PSORS1C1 variants.

  • Establish patient-derived iPSC models representing different PSORS1C1 genotypes.

  • Screen for small molecules or biologics that modulate PSORS1C1 expression or function.

• Clinical Translation and Precision Medicine:

  • Evaluate PSORS1C1 variants as biomarkers for disease risk, progression, or treatment response.

  • Incorporate PSORS1C1 genotyping into clinical trials for autoimmune disease therapeutics.

  • Develop genotype-guided treatment algorithms that consider PSORS1C1 status.

These research directions would address current knowledge gaps regarding PSORS1C1's biological function and disease relevance. The integration of multi-omics data with functional validation studies and clinical correlations would provide a comprehensive understanding of this gene's role in autoimmunity and potentially reveal new therapeutic targets.