PNKP and Hand-foot syndrome: Quantification showed that while 2–5-mo-old WT mice maintained a normal HF structure in all cases (Fig 2I; n = 89 HFs from four mice), the DP was detached in 46.3% of HFs from sex- and age-matched Pnkp KO mice, and a further 29.2% of HFs showed a complete absence of DP (Fig 2I; n = 82 HFs from five mice).