B6.Cg-Tg(FCGRT)32Dcr Fcgrt^tm1Dcr Ace2^em4Lutzy/J

Stock number: 035448
Product name: FcRn-/- hFcRn (32) Tg ; Ace2^H353K
Strain synonyms: FcRn-/- hFcRn (32) Tg Ace2^H353K
Research areas: Developmental Biology Research, Immunology, Inflammation and Autoimmunity Research, Internal/Organ Research, Research Tools, Virology Research

Description

Ace2^H353K knockin mice express an H353K (histidine to lysine) amino acid substitution in the Ace2 (angiotensin I converting enzyme (peptidyl-dipeptidase A) 2) locus on the hFcRn Tg32 background (B6.Cg-Fcgrt^tm1Dcr Tg(FCGRT)32Dcr/DcrJ, Stock No. 014565). The FcRn-/- targeted mutation and hFcRn (32) transgene function to enhance the human-like protection of humanized IgG and potentially make these mice useful for developing antibody-based therapeutics against SARS-CoV, including assessing half-life, selecting efficacious variants and determining dosage for clinical trials. Ace2 is the receptor used for cellular entry by several coronaviruses, including severe acute respiratory syndrome coronavirus-1 (SARS-CoV) and -2 (SARS-CoV-2).

This strain may be useful for the study of 2019 novel coronavirus (SARS-CoV-2) pathogenesis as well as cardiovascular disease.

Detailed description

Please note, 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.

Stock No. 035448 FcRn-/- hFcRn (32) Tg ; Ace2^H353K is a multiple mutant strain created by CRISPR/cas9 genome editing of the Ace2 locus in FcRn mice (Stock No. 014565). In an attempt to offer popular alleles together, mouse lines may be bred together for purpose of researchers to study and characterize. It should be noted that the phenotype of Stock No. 035448 could vary from that originally described for the individual mouse lines used to assemble it. We may modify the strain description if necessary as published results become available. Each mutant allele is briefly described below.

The Ace2^H353K knock-in allele was created using CRISPR/cas9 genome editing to express the H353K (histidine to lysine) amino acid substitution in the mouse 353 codon of the Ace2 (angiotensin I converting enzyme (peptidyl-dipeptidase A) 2) locus on the X chromosome. Ace2 encodes a dipeptidyl carboxydipeptidase involved in cleavage of angiotensin I and II. Mouse Ace2 has high homology to human ACE2. 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. A lysine is present at position 353 of ACE2 in humans, non-human primates, bats and ferrets, while mice and rats have a histidine at this position. In mice, the Ace2 H353K mutation has been found to confer susceptibility to SARS-CoV-2 infection in vivo - see Stock No. 034903.

hFcRn Tg32 or FcRn-/- hFcRn line 32 Tg; Stock No. 014565) carries a knock-out mutation for the mouse Fcgrt gene (Stock No. 003982) in addition to a transgene expressing the human FCGRT gene under the control of its own native promoter. It is a humanized mouse model that can be used to predict the pharmacokinetics (PK) of IgG antibodies in humans with an accuracy comparable to non-human primates (NHPs) and is a valuable model for use when maximum half-life data is required. The transgene, integrated on mouse Chromosome 2, displays a physiological human FCGRT expression pattern (Latvala et al., 2017). Serum albumin levels are slightly above those seen in C57BL/6J mice, while mouse IgG levels are low due to the species-specific activity of human FCGRT.

Development

The Ace2^H353K allele was created by Dr. Cathy Lutz (The Jackson Laboratory) using constructs designed by Dr. Paul B. McCray (University of Iowa). CRISPR/Cas9 genome editing was used to create an amino acid substitution at position 353 (histidine to lysine, H353K) in the Ace2 locus on the X chromosome. Single guide RNA and cas9 endonuclease were introduced into FcRn-/- hFcRn (32) Tg [Stock No. 014565] derived fertilized eggs by pronuclear injection. Embryos were transferred to pseudopregnant females, and correctly targeted pups were bred to Stock No. 014565 for germline transmission.

Stock No. 014565 FcRn-/- hFcRn (32) Tg mice have a knock-out mutation for the mouse Fc receptor, IgG, alpha chain transporter gene (Fcgrt) on chromosome 7 and a transgene expressing the human FCGRT gene under the control of its own native promoter (hTg32) on chromosome 2 (101,081,712-101,081,713; mouse genome mm10). See Stock No. 014565 for more information on transgene copy number and other human genes in this transgene.

Allele

Symbol: Ace2^em4Lutzy
Name: endonuclease-mediated mutation 4, Cathy Lutz
MGI accession ID: MGI:6865646
Generation method: Endonuclease-mediated
Attributes: Humanized sequence
Synonyms: Ace2^H353K
Marker symbol: Ace2
Marker name: angiotensin I converting enzyme (peptidyl-dipeptidase A) 2
Marker synonyms: 2010305L05Rik; ACEH
Chromosome: X
Strain of origin: B6.Cg-Fcgrt^tm1Dcr Tg(FCGRT)32Dcr/DcrJ
Molecular note: CRISPR/cas9 genome editing was used to create an amino acid substitution at position 353 (histidine to lysine, H353K). A lysine is present at position 353 of ACE2 in humans, non-human primates, bats and ferrets, while mice and rats have a histidine at this position.

Allele

Symbol: Fcgrt^tm1Dcr
Name: targeted mutation 1, Derry C Roopenian
MGI accession ID: MGI:3511510
Generation method: Targeted
Attributes: Null/Knockout
Synonyms: FcRn^-
Marker symbol: Fcgrt
Marker name: Fc receptor, IgG, alpha chain transporter
Marker synonyms: alpha-chain; FcgammaRn; FCRN; neonatal Fc receptor
Chromosome: 7
Strain of origin: 129X1/SvJ
Molecular note: Sequence from exon 1 and part of exon2 was replaced with a PGK-neo cassette. Quantitative PCR of liver cDNA indicated the absence of mRNA. Western blot analysis of neonatal intestinal extracts failed to reveal protein product.

Allele

Symbol: Tg(FCGRT)32Dcr
Name: transgene insertion 32, Derry C Roopenian
MGI accession ID: MGI:4944199
Generation method: Transgenic
Attributes: Inserted expressed sequence; Humanized sequence
Synonyms: hFcRn(32) vhFcRn (32) Tg hFcRn (32) Tg; Tg32
Marker symbol: Tg(FCGRT)32Dcr
Marker name: transgene insertion 32, Derry C Roopenian
Chromosome: 2
Strain of origin: C57BL/6J
Expressed genes: FCGRT,Fc fragment of IgG receptor and transporter,human
Site of expression: The transgene expresses human FCGRT from the native human promoter, and displays a physiological human FCGRT expression pattern (Latvala et al., 2017).
Molecular note: A 34Kb fragment of a BAC containing the entire human FCGRT , Fc fragment of IgG, receptor, transporter, alpha, gene (approximately 11kb) and approximately 10kb of flanking sequence was sublconed into a SuperCos vector. The resulting cosmid was microinjected into fertilized C57BL/6J mouse eggs. Founder line 32 was established. Transgene insertion occurred on Chr 2.