PTPDC1 (protein tyrosine phosphatase domain containing 1) is a gene located on chromosome 9 with putative roles in cellular signaling and cilia biology. The protein contains a tyrosine phosphatase domain and may participate in cilia formation and/or maintenance [UniProt annotation]. PTPDC1 exhibits protein binding activity and is localized to the cytoplasm where it may influence cilium assembly through its phosphatase function [GO annotations]. Clinically, PTPDC1 has emerged as a disease-associated locus in multiple contexts. A genome-wide association study identified PTPDC1 as one of 22 potential loci implicated in sporadic Parkinson's disease susceptibility in Han Chinese populations, suggesting involvement in neurodegeneration pathways 1. More prominently, a circular RNA derived from PTPDC1 (circ-PTPDC1) is significantly upregulated in gastric cancer tissues and serum, where it promotes cancer cell proliferation, migration, and invasion through a miR-139-3p/ELK1 regulatory axis 2. Elevated circ-PTPDC1 correlates with advanced clinical stage, invasion depth, and poor patient survival, establishing it as a prognostic biomarker for gastric cancer 2. Additionally, PTPDC1-derived peptides show altered abundance in breast cancer plasma compared to controls and other diseases 3. These findings suggest PTPDC1 functions in both normal biological processes and disease pathogenesis, with particular relevance as a cancer biomarker.