Poly(ADP-ribosyl)ation is involved in pro-survival autophagy in porcine blastocysts

Poly(ADP-ribosyl)ation (PARylation) prevents apoptosis through its involvement in pro-survival autophagy in cultured cells; whether or not the same is true for pre-implantation embryos has not yet been documented. In this study, we investigated the participation of PARylation and autophagy in in vitro porcine pre-implantation embryo development. The transcript levels of autophagy-related genes and poly(ADP-ribose) polymerase 1 (PARP1), an enzyme required for PARylation, were transiently up-regulated by fertilization, decreased at the late 1-cell stage, and maintained until the blastocyst stage. LC3, a marker of autophagosomes, and poly(ADP-ribose) (PAR) polymer were present in all stages of pre-implantation development. Exposure of embryos to 3-methyladenine, an autophagy inhibitor, or 3-aminobenzamide, a PARP inhibitor, suppressed the development of blastocysts. Pharmacological inhibition of PARylation further suppressed pro-survival autophagy by decreasing the expression of autophagy-related genes (ATG5, BECLIN1, and LC3) and decreasing LC3 protein abundance while increasing the rate of apoptosis in blastocysts. Deficiency in autophagy also induced abnormal accumulation of SQSTM1/p62 aggregates in porcine blastocysts. Collectively, these data suggest that PARylation is involved in selective autophagic degradation of ubiquitinated proteins, functioning in a pro-survival role, in porcine in vitro-produced embryos. These pro-survival regulatory mechanisms may be important for the control of embryo quality.