Abstract
Objectives:
Anterior cruciate ligament (ACL) injuries are one of the most common knee injuries requiring surgery in the United States with over 120,000 ACL injuries estimated to occur each year. Selection pressures over the past tens of millennia have led to genetic adaptations that influence various traits, including musculoskeletal health. The knee’s complex structure and function evolved over 300 million years. Variations in physical activity patterns, diet, and lifestyle among ancestral human populations have shaped the genetic landscape related to bone and ligament structure and function. Evolutionary genetic signatures in human populations enable the genome-wide association study (GWAS) approach to identify associations between genetic variants and traits such as ACL injury risk. Understanding the genetics of ACL injury is crucial for uncovering the underlying genetic factors that contribute to injury risk, enabling the development of targeted prevention and treatment strategies. This study aimed to use GWAS in both a European and an African cohort to illuminate genes over-represented in a population with a history of ACL injury in comparison to healthy controls and create a preliminary polygenic risk score (PRS) based on identified single nucleotide polymorphisms (SNPs).
Methods:
We conducted a GWAS in two independent cohorts, a cohort with African ancestry and a cohort with European ancestry. The African cohort included 108 cases (72 males and 36 females) and 1080 controls without ACL injury (720 males and 360 females). The European cohort included 232 cases (114 males and 118 females) and 2320 controls (1140 males and 1180 females). The cases and controls were selected as unrelated (kinship coefficient < 0.0442). The ancestries were all confirmed using the well-established Admixture 1.3 Software to determine maximum likelihood estimation of individual ancestries from multilocus SNP genotype datasets. The genotyping was done using the Illumina Genotyping BeadChips with at least 550,000 SNPs genotyped. Genome-wide imputation was performed with the TOPMed Imputation Server (https://imputation.biodatacatalyst.nhlbi.nih.gov/#) using the TOPMed (Version R2 on GRC38) Reference Panel. To score the subjects for their genetic risk of ACL injury, index SNPs were identified with P<1E-04 and r2<0.1 in each 250kb distance.
Results:
In this study, 2789 SNPs had P<1E-04 in the African cohort, and 1801 SNPs had P<1E-04 in the European cohort (Figure 1). Altogether, 2053 genes mapped to these loci. Three genes, GMNN, RREB1, and TBC1D7, related to abnormal patella morphology were highlighted by over-representation analysis in both the African cohort and the European cohort. In addition, using SNPs identified in the European population, we observed significantly lower PRS in Europeans than in African subjects (Table 1).
Conclusions:
Over-representation of the genes GMNN, RREB1, and TBC1D7 in a population with a history of ACL rupture has not previously been reported in either an African or a European cohort. These findings are the first to indicate that GMNN, RREB1, and TBC1D7 may potentially be key genes associated with risk of ACL injury. Further, this study represents the largest of its kind to evaluate potential genetic associations with ACL injury risk in an African cohort. Additionally, the lower PRS for European subjects suggests that genetic variants contributing to ACL injury may have been subject to negative selection in the European population, causing removal of deleterious alleles.
