Polymorphisms in PTK2 are associated with skeletal muscle specific force: an independent replication study

The aim of the study was to investigate two single nucleotide polymorphisms (SNP) in PTK2 for associations with human muscle strength phenotypes in healthy men.

Measurement of maximal isometric voluntary knee extension (MVC_KE) torque, net MVC_KE torque and vastus lateralis (VL) specific force, using established techniques, was completed on 120 Caucasian men (age = 20.6 ± 2.3 year; height = 1.79 ± 0.06 m; mass = 75.0 ± 10.0 kg; mean ± SD). All participants provided either a blood (n = 96) or buccal cell sample, from which DNA was isolated and genotyped for the PTK2 rs7843014 A/C and rs7460 A/T SNPs using real-time polymerase chain reaction.

Genotype frequencies for both SNPs were in Hardy-Weinberg equilibrium (X ² ≤ 1.661, P ≥ 0.436). VL specific force was 8.3% higher in rs7843014 AA homozygotes than C-allele carriers (P = 0.017) and 5.4% higher in rs7460 AA homozygotes than T-allele carriers (P = 0.029). No associations between either SNP and net MVC_KE torque (P ≥ 0.094) or peak MVC_KE torque (P ≥ 0.107) were observed.

These findings identify a genetic contribution to the inter-individual variability within muscle specific force and provides the first independent replication, in a larger Caucasian cohort, of an association between these PTK2 SNPs and muscle specific force, thus extending our understanding of the influence of genetic variation on the intrinsic strength of muscle.