PTPDC1 and obstructive sleep apnea syndrome: Non-etheless, among the 41 OSA-associated GWAS variants, some trace back to genes involved in cytoskeletal structure and dynamic functionality, such as CDH4 (a calcium-dependent cell-cell adhesion glycoprotein that plays a role in muscle development), similarly to the PTPDC1 and TMDO4 genes mutated in Family B, which exhibit mainly structural functions important for muscle cell functionality.