The work further suggests that the NK cell phenotype in XLPDR may be linked to the effects of POLA1 expression on MCM4. As shown here, cells derived from patients with XLPDR are partially deficient in MCM4, and interestingly, deficiency of either POLA1 or MCM4 in primary NK cells or NK cell lines results in a functional defect in NK cell cytotoxicity. This evidence concerns the gene MCM4 and X-linked reticulate pigmentary disorder.