FOXO1 and intervertebral disk degenerative disorder: Similar cellular changes were also found in degenerated NP tissues of SM/J mice (an early-onset IDD mouse strain), naturally aged mice, and multiple knockout mice (such as Bgn, or Foxo1/3/4, Tnmd, Nfat5, or Mkx knockout mice) [4–6, 8, 9, 31].