PPP1R7 (protein phosphatase 1 regulatory subunit 7) is a regulatory subunit that modulates protein phosphatase 1 (PP1) activity through direct protein-protein interactions mediated by 11 tandem leucine-rich repeats 1. PPP1R7 functions as a localization and substrate specificity factor for PP1, with cardiac tissue showing the highest PP1c binding affinity for PPP1R7 among all PP1 interactors 2. In sperm, PPP1R7 associates with the testis-specific PP1γ2 isoform during epididymal maturation, with dynamic binding changes regulating sperm motility development 3. The human PPP1R7 gene spans 33 kb on chromosome 2 with 11 exons generating up to four different protein isoforms through alternative splicing 1. PPP1R7 is ubiquitously expressed across cancer cell lines, though somatic mutations and polymorphisms suggest involvement in multistep carcinogenesis 4. Cardiac-specific PPP1R7 knockdown causes dysfunction and disrupted sarcoplasmic reticulum calcium release, indicating essential roles in heart function 2. In ionizing radiation responses, phosphorylation at serine 12 (S12-PPP1R7) represents a novel phospho-signaling mode regulating mitotic exit and G2/M checkpoint control 5. PPP1R7 has been identified as a fusion partner in rare acute myeloid leukemia cases with t(2;16) translocation 6.