Data from primary manuscripts and microscopy screenings were used to assign a confidence level to the likelihood of different subcellular locations expressing ACE2.  This study showed that the extracellular space and plasma membrane are the most likely places to express ACE2 (confidence = 5), and the Golgi apparatus is the least likely (confidence = 1) out of these listed locations.  

Subcellular Expression of ACE2

- drug mediators
- non-drug mediators
- genetic mediators
- disease states

Mediators that Infleunce ACE2 Expression

- comparing expression levels in different tissues
- comparing expression levels by sex
- coexpression of TMPRSS2 and ACE2 

Comparing TMPRSS2 and ACE2 Expression

- Increased Concentrations of Circulating ACE2 is Associated with Mild COVID-19 Symptoms 
- Circulating ACE2 expression compared to circulating ACE

Expression of Circulating ACE2 and COVID-19

Pregnant mice were used to assess the expression levels of the following genes associated with SARS-CoV-2, inflammation, and other viral diseases:

- ACE2: cellular receptor for the SARS-CoV-2 virus
- TMPRSS2: serine protease involved in cellular entry of the SARS-CoV-2 virus
- St3gal4: related to the influenza virus
- St6gal1: related to the influenza virus
- Ifngr1: related to inflammation
- Tnfrsf1a: related to inflammation

Mice were sacrificed at the following timepoints:

- E12.5: embryonic day 12 (gravid females are sacrificed)
- E14.5: embryonic day 14 (gravid females are sacrificed)
- P1: day pups are born (pups are sacrificed)

Epithelium (Epi) and mesenchyme (Mes) tissue were collected from the soft pallets (SP) and tongues (T) of the different developmental stages.  Notably, ACE2 expression was only observed in large quantities in P1 mice, and TMPRSS2 expression increased throughout the developmental process.  FPKM: fragments per kilobase million reads

ACE2 and Other SARS-CoV-2 Related Gene Expression in Mouse Development

- cancer tissue
- human airway epithelium tissue
- human brain expression
- protein and mRNA expression
- relationship to COVID-19

ACE2 Expression in Tissue and Organs

- subcellular expression
- tissue and organ expression
- mediators that influence expression
- comparing to TMPRSS2 expression
- circulating expression
- expression in embryonic development

Michigan State University

Smith College

ACE2 is located on the X chromosome (Xp22), and belongs to a subset of genes that escapes X-inactivation, showing a heterogenous sex bias and evolutionary characteristics of tissue specificity and expression (Tukiainen et. al). However, expression differences in distinct tissues suggest presence of X-inactivation, though incomplete.

The figure below shows ACE2 preferential expression in males (blue). 

ACE2 Chromosomal Localization and Activation.

ACE2 Expression

Allelic variants in the ACE2 gene has been observed in different ethinic populations, as well as in case-control studies within ethnic groups. However, these are present in relatively low frequencies. Functional studies are encouraged to characterize the relationship between ACE2 variants and COVID-19 severity, but no causal relationship can be made to date.

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