B6.Cg-Tbx20^tm1.1Rph/J

Stock number: 024664
Product name: Tbx20^lacZ
Strain synonyms: Tbx20^-
Research areas: Cardiovascular Research, Developmental Biology Research, Internal/Organ Research, Research Tools

Description

These Tbx20^lacZ mutant mice have a lacZ sequence replacing exons 1-3 of the T-box 20 gene. This strain may be useful for visualizing cardiac progenitors and for studying congenital heart disease and adult cardiomyopathies.

Detailed description

Exons 1-3 of the Tbx20 gene have been replaced by a lacZ sequence in these Tbx20^lacZ mice. TBX20 is expressed in the heart and other regions including yolk sac, and is essential for lineage specification and morphogenesis of the developing heart. During development, Tbx20 is expressed in the cardiac crescent prior to heart tube formation, then in myocardium and endocardium of the looping heart. Mice that are heterozygous for this allele are viable and fertile. LacZ expression is evident in the cardiac crescent, and amniotic and yolk sac mesoderm at E7.5. From E7.5-10.5, lacZ is expressed in heart, yolk sac, brain, spinal cord, eye and allantois. Some expression is also apparent in the pharyngeal endoderm, endothelium of the dorsal aorta and associated sympathetic ganglia, vitelline and placental vessels, and adrenal medulla.

Complete embryonic lethality is seen in homozygotes by E10.5. Heart tube formation is retarded and abnormal from gestation. By E7.5, embryos show severe cardiac dysmorphogenesis and arrested yolk sac vascular remodeling. The primary ventricular chambers are small, looping is blocked, and there is a delay in closure of the foregut pocket at caudal levels.

Development

A targeting vector was designed to insert a single loxP site upstream of exon 1 and a loxP-flanked neomycin resistance (neo) cassette followed by a β-galactosidase (lacZ) sequence downstream of exon 3 of the T-box 20 (Tbx20) gene. The construct was electroporated into C57BL/6J-derived Bruce 4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts and resulting chimeric males were bred with C57BL/6J females. Offspring were bred with B6.C-Tg(CMV-cre)1Cgn/J mice (Stock No. 006054) to delete the neo cassette and the floxed exons. Resulting progeny contained multiple gene rearrangments; intact floxed-exons 1-3, intact floxed-neo cassette, or excision of exons 1-3 and the neo cassette. Resulting offspring, lacking exons 1-3 and the neo, were bred together to remove the cre-expressing transgene, and offspring were bred to C57BL/6J mice for at least 11 generations. Upon arrival, mice were bred to C57BL/6J inbred mice (Stock No. 000664) for at least one generation to establish the colony.

Allele

Symbol: Tbx20^tm1.1Rph
Name: targeted mutation 1.1, Richard P Harvey
MGI accession ID: MGI:3579836
Generation method: Targeted
Attributes: Reporter; Null/Knockout
Marker symbol: Tbx20
Marker name: T-box 20
Chromosome: 9
Strain of origin: B6.Cg-Thy1^a
Expressed genes: lacZ,beta-galactosidase,E. coli
Site of expression: LacZ expression in mice carrying this allele is seen in the cardiac crescent, and amniotic and yolk sac mesoderm at E7.5. From E7.5-10.5, lacZ is expressed in heart, yolk sac, brain, spinal cord, eye and allantois. Some expression is also apparent in the pharyngeal endoderm, endothelium of the dorsal aorta and associated sympathetic ganglia, vitelline and placental vessels, and adrenal medulla.
Molecular note: Cre-mediated recombination resulted in the excision of the coding sequence in exons 1-3, and the placement of a lacZ reporter gene into endogenous cis-regulatory elements. RT-PCR confirmed absence of exons 1-3 and preservation of exons 4-6.