Genetic evidence for a pathogenic role for the vitamin D3 metabolizing enzyme CYP24A1 in multiple sclerosis

Adaikalavan Ramasamy, Daniah Trabzuni, Paola Forabosco, Colin Smith, Robert Walker, Allissa Dillman, Sigurlaug Sveinbjornsdottir, John Hardy, Michael E. Weale, Mina Ryten

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)

Abstract

Background
Multiple sclerosis (MS) is a common disease of the central nervous system and a major cause of disability amongst young adults. Genome-wide association studies have identified many novel susceptibility loci including rs2248359. We hypothesized that genotypes of this locus could increase the risk of MS by regulating expression of neighboring gene, CYP24A1 which encodes the enzyme responsible for initiating degradation of 1,25-dihydroxyvitamin D3.

Methods
We investigated this hypothesis using paired gene expression and genotyping data from three independent datasets of neurologically healthy adults of European descent. The UK Brain Expression Consortium (UKBEC) consists of post-mortem samples across 10 brain regions originating from 134 individuals (1231 samples total). The North American Brain Expression Consortium (NABEC) consists of cerebellum and frontal cortex samples from 304 individuals (605 samples total). The brain dataset from Heinzen and colleagues consists of prefrontal cortex samples from 93 individuals. Additionally, we used gene network analysis to analyze UKBEC expression data to understand CYP24A1 function in human brain.

Findings
The risk allele, rs2248359-C, is strongly associated with increased expression of CYP24A1 in frontal cortex (p-value=1.45×10−13), but not white matter. This association was replicated using data from NABEC (p-value=7.2×10−6) and Heinzen and colleagues (p-value=1.2×10−4). Network analysis shows a significant enrichment of terms related to immune response in eight out of the 10 brain regions.

Interpretation
The known MS risk allele rs2248359-C increases CYP24A1 expression in human brain providing a genetic link between MS and vitamin D metabolism, and predicting that the physiologically active form of vitamin D3 is protective. Vitamin D3's involvement in MS may relate to its immunomodulatory functions in human brain.

Funding
Medical Research Council UK; King Faisal Specialist Hospital and Research Centre, Saudi Arabia; Intramural Research Program of the National Institute on Aging, National Institutes of Health, USA.

Keywords
Multiple sclerosis; Genetics; Vitamin D; CYP24A1; Expression quantitative trait loci; Genome-wide association studies
Original languageEnglish
Pages (from-to)211-219
Number of pages9
JournalMultiple Sclerosis and Related Disorders
Volume3
Issue number2
DOIs
Publication statusPublished - Mar 2014

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