hACE2-KI mice have human ACE2 cDNA replacing the endogenous mouse Ace2 sequences. The endogenous Ace2 regulatory elements direct expression of human ACE2, the receptor used for cellular entry by several coronaviruses, including severe acute respiratory syndrome coronavirus-1 (SARS-CoV) and -2 (SARS-CoV-2). Because hACE2-KI are susceptible to SARS-CoV-2, they are useful for studying antiviral therapies to COVID-19.
These mice should be handled in a manner consistent with CDC/ABSA/WHO guidelines for prevention of human infection with the SARS-CoV-2 virus. Proper PPE and handling methods should be used at all times when working with these mice. Additional important guidelines for using SARS-CoV-2 susceptible mouse lines.
Of note, ACE2-GR (Stock No. 035800) has some similarities, but the human ACE2 gene replaces the endogenous sequence (expression directed by human regulatory elements) and is not floxed. Also available are K18-hACE2 transgenic mice with human ACE2 expression directed to epithelia (Stock No. 034860).
David Wentworth, Center for Disease Control
hACE2-KI mice have a loxP-flanked human ACE2 cDNA sequence replacing the endogenous mouse Ace2 sequences on the X Chromosome. These mice express human ACE2 in place of mouse Ace2, as directed by endogenous regulatory elements of the mouse Ace2 locus. Homozygous females and hemizygous males are viable and fertile.
Human ACE2 is the receptor used for cellular entry by several coronaviruses, including severe acute respiratory syndrome coronavirus-1 (SARS-CoV), severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2; 2019 novel coronavirus) and HCoV-NL63. This hACE2-KI mouse model may be useful in studying antiviral therapies for these coronaviruses, particularly SARS-CoV-2 pathogenesis and the disease outbreak COVID-19.
The donating investigator reports that initial studies with 10-13 week old hACE2-KI heterozygous females are susceptible to SARS-CoV-2, and the virus replicates efficiently in respiratory tissues. Specifically, heterozygous females were infected intranasally with wildtype SARS-CoV-2 variants [a 1:1 ratio of SARS-CoV-2(S-614D) and SARS-CoV-2(S-614G), using 1x10^5 plaque forming units of each variant] and samples were collected at days 2-4 post-infection. This revealed high viral RNA loads in the nasal conchae and lungs. Virus RNA was also detected in olfactory bulbs and at lower levels in brain tissues. Low to undetectable levels of virus were observed in spleen, small intestine, kidneys and feces. Heterozygous females did not exhibit morbidity or mortality (e.g., no weight loss) when infected with typical wildtype SARS-CoV-2 viruses. [Zhou et al. bioRxiv October 2020]
We will update this description as more information becomes available.
These hACE2-KI mice (Stock No. 035000) have loxP sites flanking the human ACE2 cDNA sequence. Upon exposure to Cre recombinase, the human ACE2 cDNA will be deleted - generating a knock-out allele.
Of note, ACE2-GR (Stock No. 035800) has some similarities, but differs in that it has the human ACE2 coding and regulatory/non-coding sequences replacing the endogenous mouse Ace2 coding and regulatory/non-coding sequences, and it does not have the loxP sites.
The hACE2-KI allele has exon 2 of the X-linked angiotensin I converting enzyme (peptidyl-dipeptidase A) 2 gene [Ace2] replaced with a human ACE2 cDNA inserted in-frame with the endogenous initiation codon. First, a targeting vector was designed with a loxP site upstream of exon 2, human ACE2 cDNA in-frame with the endogenous initiation codon, frt-flanked neomycin resistance (neo) cassette and a second loxP site. The construct was electroporated into 129Sv/Pas embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts. Chimeric males were bred to C57BL/6J Flp-expressing females to excise the frt-flanked neomycin selection cassette. The resulting hACE2-KI colony was backcrossed to C57BL/6J mice for seven generations prior to arrival at The Jackson Laboratory Repository in 2020. Upon arrival, the colony was backcrossed to C57BL/6J (Stock No. 000664) at least two additional generations [October 2020].
|Allele Name||targeted mutation 1, David Wentworth|
|Allele Type||Targeted (Inserted expressed sequence, Humanized sequence)|
|Allele Synonym(s)||hACE2 KI|
|Gene Symbol and Name||Ace2, angiotensin I converting enzyme (peptidyl-dipeptidase A) 2|
|Strain of Origin||129S2/SvPas|
|Molecular Note||The targeting construct is designed to replace exon 2 with a human ACE2 cDNA inserted in-frame with the endogenous initiation codon. in addition, a loxP site is placed upstream of the ACE2 cDNA and a FRT-flanked neomycin resistance (neo) cassette and a second loxP site is placed downstream of the ACE2 cDNA. Flp-mediated recombination removed the FRT-flanked neo cassette.|
Ace2 is X-linked. Homozygous females and hemizygous males are viable and fertile.
When using the hACE2-KI mouse strain in a publication, please cite the originating article(s) and include JAX stock #035000 in your Materials and Methods section.