Genome-Wide Association Identifies TBX5 as Candidate Gene for Osteochondrosis Providing a Functional Link to Cartilage Perfusion as Initial Factor

Abstract

Osteochondrosis (OC) is an orthopedic syndrome of the joints that occurs in children and adolescents and domestic animals, particularly pigs, horses, and dogs. OC is the most frequent cause of leg weakness in rapidly growing pigs causing animal welfare issues and economic losses. In this study, a genome-wide association study (GWAS) was performed using the Porcine 60k SNPChip in animals of the breed Large White (n = 298) to identify chromosome regions and candidate genes associated with OC lesion scores. A total of 19 SNPs on chromosomes (SSC) 3, 5, 8, 10, 14, and 18 were significantly associated with OC lesion scores (p-values ≤ 10−5). The SNPs MARC0098684, MARC00840086, MARC0093124, and ASGA0062794 at SSC14 36.1–38.2 Mb encompass a region of six linkage disequilibrium (LD) blocks. The most significant SNP ASGA0062794 is located in a LD block spanning 465 kb and covering the gene encoding T-box transcription factor 5 (TBX5). A SNP (c.54T > C) identified in TBX5 was significantly associated with OC lesion scores in a single-marker analysis. TBX5 c.54T > C showed highest LD with ASGA00627974 (r2 = 0.96) and superior association with OC lesion scores over other SNPs when included in the genome scan, whereas its treatment as an additional fixed effect in the GWAS statistical model led to a drop of significance of nearby markers. Moreover, real-time PCR showed different transcript abundance of TBX5 in healthy and defect cartilage. The results imply that the association signal obtained on SCC14 is largely attributable to TBX5 c.54T > C likely to be in LD with a regulatory polymorphism of TBX5. The transcription factor TBX5 interacts with GJA5 and MEF2C both being involved in vascularization. This study provides evidence for epistatic interaction of TBX5 and MEF2C, thus supporting deficiency of blood supply to growth cartilage as being fundamental for the initiation of OC.

Gene expression profiling of articular cartilage reveals functional pathways and networks of candidate genes for osteochondrosis in pigs

“…On SSC14, there were three genes that overlapped with expression data and GWAS data, including chromosome 12 open reading frame 49 (C12orf49), mediator complex subunit 13-like (MED13L), and T-box 5 (TBX5). We have previously described an association of the SNP TBX5 c.54TϾC with OC lesion scores in pigs (48 (Fig. 2), we found that TBX5 is indirectly related to BMPR1A, which was is functionally significant during chondrogenesis (73).…”

“…The average age at slaughter was 177.6 Ϯ 15.6 days. Articular cartilage samples of 292 animals were obtained from the medial part of condylus humeri (CMH) or condylus medialis femoris (CMF), where serial sections of cartilage were histopathologically inspected for OC lesions, as previously described (29,47,48). In brief, slices of the articular cartilage surface of macroscopically nonaffected areas and affected regions, if present, were stored at Ϫ80°C for RNA isolation and at Ϫ20°C for histopathological assessment, to consider the criteria of appearance and texture of cartilage surface, hyperplasia and vascularization of the hyaline cartilage, as well necrosis and ossification of the hyaline cartilage.…”

“…In addition to relating results of the microarray expression study with a previous QTL study performed in the same population, we investigated DE genes within these QTL regions that were close to significantly trait-associated SNPs identified in a GWAS of commercial herds ( Table 4). The GWAS revealed multiple significant SNPs on SSC2, SSC10, and SSC14 that were overlapping with the QTL for OC lesion scores (48). For SSC2, LYSMD3 and LOX are highlighted above because these genes exhibited Ͼ1.5-fold difference in transcript abundance between OCnegative and OC-positive cartilage.…”

Pathogenesis of osteochondrosis dissecans: How does this translate to management of the clinical case?

“…However, in another study no relation of genetic polymorphism of the Ihh gene with OC could be demonstrated in Polish Halfbreds (Zabek et al 2013). In the pig the gene encoding T-box transcription factor 5 was shown to be associated with OC (Rangkasenee et al 2013). This is potentially interesting as this transcription factor is involved in vascularisation, but no data on the horse exist thus far.…”

“…In the pig the gene encoding T‐box transcription factor 5 was shown to be associated with OC (Rangkasenee et al . ). This is potentially interesting as this transcription factor is involved in vascularisation, but no data on the horse exist thus far.…”