The protein expression profile of ACE2 in human tissues

Feria Hikmet; Loren Méar; Mathias Uhlén; Cecilia Lindskog

Early studies based on multi-tissue Northern blotting and QRT-PCR suggested moderate to high transcript expression in kidney, testis, heart and the intestinal tract, with most prominent in small intestine and lower levels in colon and/or rectum 3, 4 . No or low expression of ACE2 was observed in human lung. By the introduction of microarray analysis, whole-body maps quantifying global gene expression patterns based on mRNA transcripts were launched, such as BioGPS 5 , soon followed by several large-scale transcriptomics efforts based on next-generation sequencing in samples representing most major human organs and tissues. Three such recent initiatives include the Human Protein Atlas (HPA) consortium 6 and the genome-based tissue expression (GTEx) consortium 7 based on RNA-seq, and the FANTOM5 consortium based on cap analysis gene expression (CAGE) 8 . The HPA consortium aims at characterizing the entire human proteome in tissues, organs, cells and organelles using a combination of transcriptomics and antibody-based proteomics. In the open-access database www.proteinatlas.org, expression profiles based on both external and internal datasets are shown, together with primary data, criteria used for validation and original high-resolution images of immunohistochemically stained human tissue samples. The HPA displays mRNA expression data from HPA, GTEx and FANTOM5, and also summarizes the three datasets as normalized expression levels (NX) across 37 tissues and organs covering all major parts of the human body, including human blood 9, 10 . The consensus of these three datasets show medium or high expression levels in kidney, testis and the intestinal tract, together with low expression in heart and adipose tissue and lack of expression in most other normal organs, including lung ( Figure 1 ).