Unveiling the Role of Histone Methyltransferases in Psoriasis Pathogenesis: Insights from Transcriptomic Analysis.

Psoriasis involves complex epigenetic alterations, but detailed studies on histone methyltransferases and their role in disease progression are limited. We conducted a comprehensive analysis of nearly 300 transcriptomes, focusing mainly on differential expression of protein isoform-coding transcripts within the SET domain family of histone methyltransferases. Consistent with previous findings, EZH2 transcripts showed increased expression in lesional skin, indicating altered H3K27 methylation that may enhance gene silencing, promoting keratinocyte proliferation and inflammatory responses. In the SET2 family, ASH1L exhibited reversed expression patterns between non-lesional and lesional skin, while NSD1 and NSD2 were upregulated, and SETD2 downregulated in lesions, suggesting disrupted H3K36 methylation that may affect immune responses and keratinocyte proliferation. Among H3K9 methyltransferases, SUV39 members, SUV39H2 was upregulated in lesions, whereas EHMT1 transcripts increased in non-lesional skin, and SETDB2 decreased in lesions. Additionally, PRDM family members such as PRDM2, MECOM (PRDM3), PRDM6, and PRDM8 showed altered expression in lesional skin. The H4K20 methylating SUV4-20 subfamily member, a SUV420H1 transcript, and SETD8 belonging to the other SET domain-containing family of methyltransferases were significantly increased in non-lesional skin and in lesions, respectively. Overall, aberrant expression and isoform variability of histone methyltransferases likely contribute to psoriasis pathogenesis by dysregulating proliferation, differentiation, and immune responses.