HHIP and chronic obstructive pulmonary disease: Our integrative analysis of COPD GWAS with our scRNAseq data (CELLECT) also identified AT2B cells as key epithelial mediators of COPD heritability, in part because AT2B cells are major expressors of SERPINA1 (along with monocyte and macrophage populations), SFTPD, and HHIP. Previous GWAS firmly established an association between HHIP polymorphisms and COPD-related traits23; while animal studies have shown haploinsufficient Hhip mice are prone to oxidative stress and emphysema24.