Codon-Usage Bias and Genomic Architecture of 79 Psoriasis-Susceptibility Genes: Implications for Expression...

Psoriasis is a chronic autoimmune skin disorder with a complex genetic basis. However, the codon usage patterns and nucleotide features of psoriasis-related genes remain unexplored, despite their potential to influence gene expression and disease progression.

We analyzed 79 psoriasis-associated genes to investigate codon usage bias (CUB) and nucleotide composition. Metrics included GC content, effective number of codons (ENC), and relative synonymous codon usage (RSCU). Evolutionary influences were assessed using correspondence analysis, parity rule 2 (PR2) plots, and neutrality plots.

Functional enrichment analysis identified pathway involvement. Comparative genomic analysis evaluated differences in coding sequence and UTR lengths and GC content relative to the genome-wide background. Psoriasis-related genes showed high GC content (mean = 53.3 ± 9.3%) with a strong preference for GC-ending codons, especially at the third codon position (GC3 = 60.6 ± 16.1%). RSCU analysis revealed frequent use of GCC (alanine), CTG (leucine), and GTG (valine). While the mean ENC (46.2 ± 9.9) suggested moderate codon bias, several genes displayed strong bias (ENC < 30). Selection pressure accounted for 71% of codon usage variation, with mutation pressure contributing 29%. Functional enrichment showed significant involvement in IL-17 (FDR = 3.4×10^-3), JAK-STAT (FDR = 3.4×10^-3), and TNF (FDR = 8.0×10^-³) signaling pathways. These genes also tended to have shorter coding sequences and 5'UTRs and higher GC content compared to genome-wide averages.

In conclusion, this study reveals that psoriasis-related genes are under strong selective pressure, enriched in key inflammatory pathways, and exhibit codon and nucleotide features that may optimize expression in inflamed tissues. These insights have translational relevance for designing codon-optimized mRNAs, gene therapies, and diagnostic tools tailored to autoimmune diseases like psoriasis.