(A/J x B6.Cg-Tg(K18-ACE2)2Prlmn/J)F1/J

Stock number: 035940
Product name: A/J x K18-hACE2
Strain synonyms: A/JxK18-hACE2
Research areas: Developmental Biology Research, Immunology, Inflammation and Autoimmunity Research, Internal/Organ Research, Mouse/Human Gene Homologs, Research Tools, Virology Research

Description

The COVID Diversity Platform is a humanized mouse panel of first generation (F1) hybrid offspring created by breeding different inbred strain females to the C57BL/6-congenic K18-hACE2 transgenic males.

Stock No. 035940 A/J x K18-hACE2 are the F1 progeny of breeding A/J females (Stock No. 000646) to C57BL/6-congenic males hemizygous for the K18-hACE2 transgene (Stock No. 034860).

K18-hACE2 transgenic mice express human ACE2, the receptor used by severe acute respiratory syndrome coronavirus (SARS-CoV) to gain cellular entry. The human keratin 18 promoter directs expression to epithelia, including airway epithelia where infections typically begin. Because K18-hACE2 are susceptible to SARS-CoV-2 and SARS-CoV viruses, they are useful for studying antiviral therapies to COVID-19 and SARS.

Please see the K18-hACE2 datasheet (Stock No. 034860) for important safety/handling and any updated information on K18-hACE2 mice in SARS-CoV-2 research.

Detailed description

Please see the K18-hACE2 datasheet (Stock No. 034860) for important safety/handling and any updated information on K18-hACE2 mice in SARS-CoV-2 research.

For this A/J x K18-hACE2 mouse line (Stock No. 035940), The Jackson Laboratory will distribute the first generation (F1) offspring created by breeding A/J inbred females (Stock No. 000646) to C57BL/6-congenic males homozygous for the K18-hACE2 transgene (Stock No. 034860).

The COVID Diversity Platform is a humanized mouse panel of first generation (F1) hybrid offspring created by breeding different inbred strain females to the C57BL/6-congenic K18-hACE2 transgenic males. The inbred females include some of the inbred founder strains used for the Collaborative Cross (CC), and as such the different F1 progeny are collectively referred to as CCxK18-hACE2 F1 mice.
While the K18-hACE2 transgene on a C57BL/6 genetic background (Stock No. 034860) confers high susceptibility to the severe acute respiratory syndrome coronavirus responsible for the COVID-19 pandemic (SARS-CoV-2) [PMID:33166988, PMID:33465158, PMID:32723427], this response is mitigated by other genetic background contributions (see below). The COVID Diversity Platform panel is a valuable resource for studying the effects of genetic background diversity on the K18-hACE2 transgenic model, producing a spectrum of SARS-CoV-2 infection/disease responses to allow additional therapeutic investigation.

The COVID Diversity Platform panel was originally characterized in a collaboration between Nadia A. Rosenthal (The Jackson Laboratory) and Sonja M. Best (National Institute of Allergy and Infectious Diseases (NIAID)) funded by the Division of Intramural Research, National Institutes of Health, NIAID in Robertson et al. 2021. The different CCxK18-hACE2 F1 progeny displayed a spectrum of weight loss, survival, infection dynamics, histopathology and cytokine profiles, some of which were sex-specific. Importantly, the timing of type I interferon and other cytokines in the lung was closely associated with sensitivity of mice to lethal disease. Thus, dynamics of inflammatory responses observed in COVID-19 are recapitulated in diverse mice that provide a genetically tractable platform for establishing biomarkers of disease severity, characterizing antiviral immune responses and evaluating countermeasures. The publication's preliminary findings for this F1 mouse line are summarized below.

Stock No. 035940 A/J x K18-hACE2: As of August 2021, the preliminary findings summarized below are the result of SARS-CoV-2 intranasal inoculation [10³ pfu nCoV-WA1-2020 (MN985325.1)] and monitoring the results for 21 days post-infection (dpi). These F1 mice exhibited a highly sensitive phenotype, with rapid weight loss (~20% 4-7 dpi) and 55% death 5-10 dpi [2/5 females; 4/6 males]. They sustained high titers of virus replication in lung (at 3 dpi) and CNS (at 6 dpi). No significant differences between sexes were apparent. Surviving mice exhibited weight gain and appeared to recover by 21 dpi.

Development

The ~6.8 kb K18-hACE2 transgene was designed with, from 5' to 3', 2.5 kb of genomic sequence, including the promoter, and the first intron (with a mutation in the 3' splice acceptor site to reduce exon skipping) from the human keratin 18 (KRT18) gene, and a translational enhancer (TE) sequence from alfalfa mosaic virus. This was followed by the human angiotensin I converting enzyme (peptidyl-dipeptidase A) 2 (hACE2) coding sequence, and exons 6-7 and the poly(A) signal of the human K18 gene. This transgene was microinjected into fertilized (C57BL/6J x SJL/J)F2 oocytes. K18-hACE2 mice from founder line 2, with 8 copies of the transgene, were subsequently maintained by breeding transgenic mice with C57BL/6 mice for at least two generations (the genetic background of the mice sent to The Jackson Laboratory was later determined to be C57BL/6N via SNP testing). Upon arrival, three backcrosses to C57BL/6J (Stock No. 000664) were then performed to rederive, establish, and expand a congenic colony as Stock No. 034860 at The Jackson Laboratory.

This strain (Stock No. 035940) is part of a panel of first generation (F1) offspring created by breeding mice from the C57BL/6-congenic K18-hACE2 transgenic strain (Stock No. 034860) to mice from 9 different inbred strains - with the goal being to generate genetically diverse but isogenic F1 offspring. The Jackson Laboratory will distribute first generation (F1) offspring as this line, created by breeding A/J (Stock No. 000646) females to hemizygous C57BL/6-congenic K18-hACE2 males.

In May 2020, analysis commissioned by The Jackson Laboratory determined that multiple copies of the Tg(K18-ACE2)2Prlmn transgene integrated at a single site on chromosome 2 (99,209,508-99,220,724; mouse mm10). An ~11 kb duplication of the host genome (chr2:99,209,508-99,220,724) is present at both ends of the integrated transgene array. Currently, there are no genes annotated in this region. The transgene copy number of the hemizygous mouse is estimated to be 8 full copies (or 12-30 partial copies).

Allele

Symbol: Tg(K18-ACE2)2Prlmn
Name: transgene insertion 2, Stanley Perlman
MGI accession ID: MGI:6389235
Generation method: Transgenic
Attributes: Inserted expressed sequence; Humanized sequence
Synonyms: K18-hACE2
Marker symbol: Tg(K18-ACE2)2Prlmn
Marker name: transgene insertion 2, Stanley Perlman
Chromosome: 2
Strain of origin: (C57BL/6J x SJL/J)F2
Site of expression: Epithelia, including airway epithelia.
Molecular note: The ~6.8 kb transgene was designed with, from 5' to 3', 2.5 kb of genomic sequence, including the promoter, and the first intron (with a mutation in the 3' splice acceptor site to reduce exon skipping) from the human K18 gene, and a translational enhancer (TE) sequence from alfalfa mosaic virus. This was followed by the human angiotensin I converting enzyme (peptidyl-dipeptidase A) 2 (hACE2) coding sequence (lacking the last exon), and exons 6-7 and the poly(A) signal of the human K18 gene. The transgene integrated at a single site on chromosome 2 (99,209,508-99,220,724; mouse mm10). An ~11 kb duplication of the host genome (chr2:99,209,508-99,220,724) is present at both ends of the integrated transgene array. Currently, there are no genes annotated in this region. The transgene copy number of the hemizygous mouse is estimated to be 8 full copies (or 12-30 partial copies). Transgene expression is evident in airway epithelial cells (but not in alveolar epithelia), as well as in epithelia of other internal organs, including the liver, kidney, and gastrointestinal tract.