Discovery of potential new gene variants and inflammatory cytokine associations with fibromyalgia syndrome by whole exome sequencing

Abstract

Fibromyalgia syndrome (FMS) is a chronic musculoskeletal pain disorder affecting 2% to 5% of the general population. Both genetic and environmental factors may be involved. To ascertain in an unbiased manner which genes play a role in the disorder, we performed complete exome sequencing on a subset of FMS patients. Out of 150 nuclear families (trios) DNA from 19 probands was subjected to complete exome sequencing. Since >80,000 SNPs were found per proband, the data were further filtered, including analysis of those with stop codons, a rare frequency (<2.5%) in the 1000 Genomes database, and presence in at least 2/19 probands sequenced. Two nonsense mutations, W32X in C11orf40 and Q100X in ZNF77 among 150 FMS trios had a significantly elevated frequency of transmission to affected probands (p = 0.026 and p = 0.032, respectively) and were present in a subset of 13% and 11% of FMS patients, respectively. Among 9 patients bearing more than one of the variants we have described, 4 had onset of symptoms between the ages of 10 and 18. The subset with the C11orf40 mutation had elevated plasma levels of the inflammatory cytokines, MCP-1 and IP-10, compared with unaffected controls or FMS patients with the wild-type allele. Similarly, patients with the ZNF77 mutation have elevated levels of the inflammatory cytokine, IL-12, compared with controls or patients with the wild type allele. Our results strongly implicate an inflammatory basis for FMS, as well as specific cytokine dysregulation, in at least 35% of our FMS cohort.

Figure 1. Plasma chemokine/cytokine levelsin FMS patients with C11orf40 or ZNF77 mutations.

Ctrl: unrelated healthy controls, n = 77 (female = 48 and male = 29). WT: FMS patients with wild type (non-variant) C11orf40 and ZNF77, n = 53 (female = 45 and male = 8). C11orf40: FMS patients with C11orf40 mutation W32X, n = 20 (female = 13 and male = 7). ZNF77: FMS patients with ZNF77 mutation Q100X, n = 9 (female = 7 and male = 2). P values in the first row are in comparison with unrelated healthy controls; P values in the second row are in comparison with wild type (non-variant) C11orf40 and/or ZNF77 genes.Discovery of Potential New Gene Variants and Inflammatory Cytokine Associations with Fibromyalgia Syndrome by Whole Exome Sequencing.

Figure 2. Cytokine secretion of TLR-ligand-treated monocytes transfected with wild type or mutated C11orf40 gene.

Human monocytes were transfected with empty vector (V),wild type C11orf40 (WT) or the W32X truncated mutant gene (T) and challenged with three TLR ligands, LPS (TLR4), CL075 (TLR7/8), and Pam3CSK (TLR 1/2), followed by measurement of secreted cytokine 24 hrs. later. P values are for comparison to vector control (**, P = 0.005) or WT (^##, P = 0.005).