CHEK2 and neoplasm: In an analogous manner, the frequency and severity of epithelial pathologies associated to Trf1 deficiency such as hair follicle atrophy, skin interfollicular dysplasia and esophagus dysplasia were also significantly rescued in Trf1Δ/ΔK5Cre Chk2−/− newborns (1–2 day old mice) compared to the Trf1Δ/ΔK5Cre Chk2+/+ age-matched controls (Fig 1D,E).