IGSF21 and nonpapillary renal cell carcinoma: Furthermore, scATAC-seq has identified cell subtype-specific chromatin accessibility regions in ccRCC, with increased chromatin openness at protein-coding genes specific to tumor cells[such as heparanase 2 (HPSE2), attractin—like 1 (ATRNL1), immunoglobulin superfamily member 21 (IGSF21)], rRNA, and certain long non-coding RNAs (lncRNAs) (such as RP11-661C8.2, CTB-164N12.1) [255].