Specifically, PNLDC1, a PARN-like 3′-to-5′ exonuclease located at the membrane of the mitochondria in a mouse, is critical to the processing of piRNAs and PNLDC1 disrupted in mice would lead to azoospermia and male infertility ultimately [38, 39]. The gene discussed is PNLDC1; the disease is male infertility.