B6.Cg-Fcgrt^tm1Dcr Prkdc^scid Tg(FCGRT)32Dcr/DcrJ

Stock number: 018441
Product name: scid FcRn-/- hFcRn (32) Tg , HuPK™
Research areas: Cancer Research, Hematological Research, Immunology, Inflammation and Autoimmunity Research, Internal/Organ Research, Research Tools, Virology Research

Description

These scid FcRn-/- hFcRn (32) Tg mice express a human alpha chain FCGRT molecule in lieu of the endogenous mouse Fcgrt. The scid allele makes the mice immunodeficient, therefore allowing the ability to test potential immunogenic hIgGs and to perform xenograft studies in addition to evaluating the pharmocokinetics of human immunoglobulin and Fc-domain based therapeutics.

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Detailed description

These mFcRn-/- hFcRn (32) Tg mice are homozygous for the knockout mutation of the FcRn α-chain (Fcgrt^tm1Dcr) and express a human FcRn α-chain (FCGRT) transgene. By itself, the homozygous Fcgrt KO allele mice have low serum levels of IgG and albumin (Roopenian et al. J Immunol. 2003 Apr 1;170(7):3528-33; Chadhury et al. J Exp Med. 2003 Feb 3;197(3):315-22; Stein et al. 2012).

They fail to recycle IgG and albumin, and to transport IgG across the neonatal gut. By introducing the FCGRT transgene the albumin levels are restored to wild type, but the IgG levels remain low due to species-specific binding of IgG by human FCGRT. The transgenic founder line 32 provides a model to study serum half-life of human IgG (hIgG), with a good correlation to cynomolgus monkey and human. In addition, the model may be used to compare the serum half-life of antibodies as when screening FcRn binding variants (Petkova et al. 2006). When comparing the Tg32 model to Tg276 (see Stock No. 004919) overall longer half-lives have been observed, making it a better model for short-lived hIGs and Fc-fusion proteins. The humanized FcRn-/- hFcRn (32) Tg mice that are also homozygous for the Prkdc^scid allele produce no mature T cells or B cells, therefore allowing the ability to test potential immunogenic hIgGs and to perform xenograft studies in addition to evaluating the pharmocokinetics of human immunoglobulin and Fc-domain based therapeutics.

Development

These knockout/transgenic mice were generated in the laboratory of Dr. Derry Roopenian (The Jackson Laboratory) by crossing B6.Cg-Fcgrt^tm1Dcr Tg(FCGRT)32Dcr/DcrJ mice (Stock No. 014565) to B6.Cg-Fcgrt^tm1Dcr Prkdc^scid.

To generate the FcRn α-chain knock-out mice (Fcgrt^tm1Dcr; see also Stock No. 003982), a targeting vector was designed to replace 1588 nucleotide fragments (encoding promoter sequence 5' of the transcriptional start site, exon1, intron 2, and most of exon2) with a PGK-Neo^r cassette. The vector was electroporated into 129/SvJ-derived ESV/J-1182 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts. The resulting chimeric animals were crossed to C57BL/6J mice (Roopenian et al. J Immunol. 2003 Apr 1;170(7):3528-33).

To generate the hFcRn line 32 transgenic mice, a 33-Kb cosmid clone including the complete FCGRT gene (approximately 11kb as well as 10kb of 5' and 3' flanking sequences) was microinjected into fertilized C57BL/6J mouse eggs (Roopenian et al Methods Mol Biol. 2010;602:93-104). The transgene integrated 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.

Prkdc^scid occurred spontaneously in a colony of BALB/c-Igh^b (C.B-17) mice maintained at the Institute for Cancer Research in Philadelphia, PA. The mutation was transferred to the C57BL/6J background by an initial cross between C.B-17-Prkdc^scid/Prkdc^scid and C57BL/6J followed by sequential backcrossing of heterozygous animals of the F1 and male heterozygotes (identified by testcrossing) of subsequent generations to C57BL/6J. At the 10th backcross generation the mutation was made homozygous by brother-sister inbreeding.

Allele

Symbol: Prkdc^scid
Name: severe combined immunodeficiency
MGI accession ID: MGI:1857113
Generation method: Spontaneous
Synonyms: scid
Marker symbol: Prkdc
Marker name: protein kinase, DNA activated, catalytic polypeptide
Marker synonyms: DNAPDcs; DNAPK; DNA-PK; DNAPKc; DNA-PKC; DNA-PKcs; DNPK1; DOXNPH; dxnph; HYRC; HYRC1; IMD26; p350; S473K; slip; XRCC7
Chromosome: 16
Strain of origin: C.BKa-Igh^b/Icr
Site of expression: T and B lymphocytes.
Molecular note: A T-to-A transversion point mutation at a position corresponding to codon 4046 (codon 4095 in transcript ENSMUST00000023352.8) created a premature stop codon (p.Y4046*).

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.