Molecular mechanisms controlling the expression of the HLA-Cw*06 psoriasis susceptibility allele

Psoriasis is an inflammatory skin disorder that is inherited as a common and complex trait. Linkage studies have repeatedly identified a primary disease susceptibility locus (PSORS1) spanning 250 kb within the Major Histocompatibility Complex. Deep sequencing experiments and genome-wide association scans have highlighted HLA-C as the most likely PSORS1 gene and unambiguously demonstrated that the HLA-Cw*0602 allele confers increased disease risk in a wide range of populations. In this context, the aim of this project was to investigate the impact of PSORS1 genetic variation on HLA-C transcription, with a particular focus on HLA-Cw*0602 expression. In the first part of the study, genetic variants mapping to the regulatory elements of different HLA-C alleles were characterized, by measuring the basal and cytokineinduced reporter activity driven by the HLA-Cw*0602, -Cw*0702 and -Cw*0304 promoters. These experiments identified two regulatory polymorphisms that virtually abolished the response to TNF-α (rs2524094) and IFN-γ (rs10657191) in HLA-Cw*0602<br/>constructs. The existence of a differential cytokine response was also confirmed by the real-time PCR analysis of primary keratinocytes treated with TNF-α and IFN-γ. Since little is known about the role of epigenetic factors in the regulation of HLA-C expression, the presence of HLA-Cw*0602 specific modification patterns was examined in the second part of the project. The methylation status of the five PSORS1 CpG islands (CGIs) was initially investigated. This targeted approach revealed lack of methylation at four CGIs, two of which mapped within the HLA-C gene region. Partial methylation was detected at a fifth CGI, lying upstream of POU5F1. To complement these data, a methylation profile of the entire PSORS1 locus was generated in two HLA Cw*0602,-Cw*0702 heterozygous individuals. <br/><br/>This showed that the majority of methylated cytosines mapped between the POU5F1 and C6orf15 transcripts, and upstream of HLA-C. Neither the targeted CGI analysis nor the systematic profiling of the entire PSORS1 region revealed any substantial differences in the methylation status of haplotypes bearing different HLA-C alleles. Taken together, the results of this study indicate that HLA-C expression is tightly controlled by promoter variants and immunological stimuli. Further studies will be required to fully explore the impact of genetic variation on DNA methylation and to determine whether PSORS1 epigenetic modifications play a role in psoriasis susceptibility.

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

King's College London

Year dc:date.issued

2013

Author dc:creator

• Bertoni, Anna

Advisors dc:contributor.advisor

• Trembath, Richard Charles
• Capon, Francesca

Language dc:language

eng

Identifier

oai:kclpure.kcl.ac.uk:studenttheses/9ab9c311-68f1-4519-913f-45872a59d164

OAI identifier oai:identifier

oai:kclpure.kcl.ac.uk:studenttheses/9ab9c311-68f1-4519-913f-45872a59d164