PNLDC1 is a poly(A)-specific 3'-5' exonuclease that functions primarily in mRNA decay and non-coding RNA biogenesis 1. As a deadenylase, it degrades poly(A) tails of mRNAs, often initiating eukaryotic mRNA decay and silencing maternal mRNAs during oocyte maturation and early embryonic development 1. PNLDC1 exhibits discrete expression in embryonic stem cells, germ cells, and early embryonic tissues, with promoter methylation by DNMT3B suppressing expression during differentiation 1. A critical function involves piRNA biogenesis, where PNLDC1 trims 3' ends of pre-piRNAs to generate mature 21-35 nucleotide piRNAs essential for transposable element silencing and genomic stability in germ cells 23. PNLDC1 participates in a mitochondrial complex with PIWIL3 and TDRKH for piRNA loading 4. Mutations in PNLDC1 cause nonobstructive azoospermia (NOA) through impaired piRNA processing, resulting in spermiogenesis arrest, meiotic errors, and derepression of retrotransposons like LINE1 25. PNLDC1 mutations also produce amorphous sperm head morphology 6. A balanced translocation disrupting PNLDC1 segregates with affective psychosis in one family, suggesting potential neuropsychiatric associations 7. Clinical significance centers on male infertility diagnosis and potential therapeutic targeting of piRNA dysregulation.