CD274 and hypoparathyroidism-retardation-dysmorphism syndrome: Mutational signatures also impacted cellular interactions, as predicted by higher receptor–ligand co-expression of PD-L1 (CD274) in myeloid clusters and PD-1 (PDCD1) in T and NK cell clusters in HRD subtypes derived from scRNA-seq data (Extended Data Fig. 13f).