CHEK2 and obstructive sleep apnea syndrome: Chromosomal instability observed here in canine OSA could be explained by the loss of cell cycle checkpoint integrity (e.g. WRN, CDKN2A/B and RB1), apoptotic (e.g. FAS) and DNA damage response pathways (e.g. TP53, CHEK2 and WRN), SVs in CFSs and short telomeres.