Decreased YBX1 causes mis-splicing in genes crucial for endochondral ossification, including Fgfr3, Vegfa, Idua, and P2rx7. These findings underscore the regulatory role of SMN in gene expression and alternative splicing during endochondral ossification, elucidating the upstream molecular events contributing to impaired bone development in SMA. Here, P2RX7 is linked to proximal spinal muscular atrophy.