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Poly(ADP-ribose) glycohydrolase (Parg) is a central enzyme for poly(ADP-ribose) degradation. We established a Parg+/− mice strain by deletion of a part of exon 1 and around 0.4-kb upstream of sequences of the Parg gene. Parg−/− embryos obtained by intercrossing the Parg+/− mice died in utero between 4.5 and 9.5 days postcoitum. We examined whether poly(ADP-ribose) polymerase-1 (Parp-1) deficiency could rescue embryonic lethality of Parg−/− mice. Parg−/−Parp-1−/− mice were born viable at a reduced frequency from the expected mendelian ratio in the intercross progeny of Parg+/−Parp-1−/− mice. The results suggest a possibility that the presence of Parp-1 is responsible for the lethality of Parg−/− embryos, and Parg molecules or Parg activity degrading poly(ADP-ribose) might be important for embryogenesis. In Parg−/−Parp-1−/− mice, Parg protein was not detected in various tissues, and the protein level of Timm23, a 5’-upstream gene of Parg, was reduced compared with that in Parg+/+Parp-1−/− mice. Parg−/−Parp-1−/− mice showed retarded growth compared with Parg+/+Parp-1−/− mice, and died within 3 months of age accompanied with severe renal failure. Glomerular sclerosis, tubular dilatation, and hyaline casts in the kidney were observed in Parg−/−Parp-1−/− mice. An increase in blood urea nitrogen (p < 0.05), a marked increase of albumin level in urine (p < 0.01) and its concomitant decrease in serum (p < 0.05) were also detected in Parg−/−Parp-1−/− mice compared with the Parg+/+Parp-1−/− counterpart. The results imply that the combined Parg and Parp-1 loss with a hypomorphic state of Timm23 leads to the development of severe renal failure.