PNKP and hydrops fetalis: Pnkp deletion was initiated at 3 wk of age, and this led to a progressive age-dependent phenotype in which Pnkp-deficient mice exhibited: (i) alopecia resulting from hair follicle (HF) degeneration followed by progressive hyperpigmentation, (ii) a complete absence of spermatogenesis, and (iii) loss of brain subventricular zone neural progenitors and diminished neurogenesis.