A functional polymorphism in COL11A1, which encodes the alpha 1 chain of type XI collagen, is associated with susceptibility to lumbar disc herniation

Abstract

Lumbar disc herniation (LDH), degeneration and herniation of the nucleus pulposus of the intervertebral disc (IVD) of the lumbar spine, is one of the most common musculoskeletal diseases. Its etiology and pathogenesis, however, remain unclear. Type XI collagen is important for cartilage collagen formation and for organization of the extracellular matrix. We identified an association between one of the type XI collagen genes, COL11A1, and LDH in Japanese populations. COL11A1, which encodes the alpha 1 chain of type XI collagen, was highly expressed in IVD, but its expression was decreased in the IVD of patients with LDH. The expression level was inversely correlated with the severity of disc degeneration. A single-nucleotide polymorphism (c.4603C-->T [rs1676486]) had the most significant association with LDH (P=3.3 x 10(-6)), and the transcript containing the disease-associated allele was decreased because of its decreased stability. These observations indicate that type XI collagen is critical for IVD metabolism and that its decrease is related to LDH.

Figure 1.

Case-control association study and linkage-disequilibrium mapping. a, Association of COL11A1 with LDH. The −log₁₀ transformation of the corrected P value (allele 1 vs. allele 2) was plotted on the Y-axis. The asterisk (*) indicates c.4603C→T. b, Pairwise linkage disequilibrium between SNPs in and around COL11A1 measured by D′ and Δ in 465 controls. The COL11A1 region is divided into two linkage-disequilibrium blocks.

Figure 2.

Difference in transcription and stability of COL11A1 mRNA containing the LDH-associated SNP. a, Relative cDNA expression of c.4603C→T evaluated by real-time PCR. Data represent the ratios of cDNA to genomic DNA, and expression of the C allele is converted to 1 (an asterisk [*] indicates P<.05, by Student's t test). Data represent the mean ± SD in triplicate assays. b, Sequential change of COL11A1 mRNA analyzed by northern blotting. “4603C” and “4603T” indicate COL11A1 mRNA produced by in vitro transcription with c.4603C and c.4603T, respectively. c, Rate of degradation of the transcripts. Diamonds indicate the transcript with c.4603C; squares indicate the transcript with c.4603T. The difference of the rate of degradation was significant at both 5 min and 10 min after the reaction (an asterisk (*) indicates P<.05, by Student's t test). Data represent the mean ± SD in triplicate assays.

Figure 3.

Type XI collagen expression in human. a, COL11A1 expression in different tissues. COL11A1 mRNA was predominantly expressed in IVD. b, Inverse correlation between COL11A1 expression and severity of degeneration of IVD in patients with LDH (an asterisk [*] indicates P<.05, by Student's t test). The degree of disc degeneration is evaluated by MRI and is scored according to the classification of Schneiderman. c and d, Immunostaining of type XI collagen in IVDs from an unaffected individual (c) and a patient with LDH (Schneiderman’s grade 3) (d). Ubiquitous and intense staining was found in the normal disc. In contrast, the staining was found only in and around the territorial matrices of clustered cells in the degenerative disc. The white scale bar indicates 50 nm.