B6.129X1(FVB)-Nkx2-1^tm2Shk/J

Stock number: 040315
Product name: T/ebp fl
Strain synonyms: Nkx2.1
Research areas: Developmental Biology Research, Endocrine Deficiency Research, Internal/Organ Research, Research Tools

Description

The T/ebp(fl/fl) allele has loxP sites flanking the common second coding exon of the Nkx2-1 gene. These mice may be useful for studying the organogenesis of the thyroid, lung, ventral forebrain, and pituitary.

Detailed description

The T/ebp(fl/fl) allele has loxP sites flanking the common second coding exon of the NK2 homeobox 1 (Nkx2-1) gene. Nkx2.1 encodes T/ebp (thyroid-specific enhancer-binding protein), a transcription factor known to control thyroid-specific gene transcription and lung epithelial cell morphogenesis and differentiation. It is essential for organogenesis of the thyroid, lung, ventral forebrain, and pituitary. The second coding exon encodes the homeodomain sequence. Homozygous mice are viable and fertile. When bred to mice that express tissue-specific Cre recombinase, resulting offspring will have the second coding exon deleted in the cre-expressing tissues.

When bred to TPO-cre mice (Stock No. 037095), with cre expression in thyrocytes, resulting T/ebp(fl/fl);TPO-Cre offspring lack T/ebp expression in many but not all thyrocytes at E16.5 and 1 month of age. As they age, they exhibit abnormal thyroid follicle morphology and have increased circulating thyroid-stimulating hormone levels. Specifically, T/ebp(fl/fl);TPO-Cre mice can be classified into two groups with different phenotypes: one having atrophic/degenerative thyroid follicles with frequent presence of adenomas and extremely high serum TSH levels, and the other having an altered thyroid structure with reduced numbers of extraordinary dilated follicles consisting of excessive numbers of follicular cells as compared with those usually found in the normal thyroid.

Of note, mice with a constitutive knock-out of the second coding exon are available as Stock No. 040314.

Development

A targeting vector was designed to insert a loxP site upstream of the common second coding exon of the NK2 homeobox 1 (Nkx2-1) gene (based on Ensembl canonical Transcript ENSMUST00000001536.9), and a loxP-flanked neomycin resistance (neo) cassette was inserted downstream of the second coding exon. The construct was electroporated into 129X1/SvJ-derived RW4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts and the resulting chimeric males were bred to C57BL/6 females. The resulting mice were bred to EIIa-Cre mice (Stock No. 003724) to remove the neo cassette. Resulting T/ebp(fl/fl) mice, lacking the neo cassette, were backcrossed at least 6 generations to C57BL/6J mice (Stock No. 000664) by the donating investigator. Upon arrival at The Jackson Laboratory, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes.

Allele

Symbol: Nkx2-1^tm2Shk
Name: targeted mutation 2, Shioko Kimura
MGI accession ID: MGI:3653645
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); No functional change
Synonyms: Nkx2-1^F; T/ebp(fl)
Marker symbol: Nkx2-1
Marker name: NK2 homeobox 1
Marker synonyms: BCH; BHC; NK-2; NKX2.1; NKX2A; NMTC1; T/EBP; TEBP; thyroid transcription factor-1; thyroid-specific enhancer-binding protein; tinman; TITF1; TTF1; Ttf-1
Chromosome: 12
Strain of origin: 129X1/SvJ
Molecular note: A loxP site was inserted into intron 1 and a loxP site flanked neomycin resistance gene cassette into intron 2. The neo was subsequently removed via Cre-mediated recombination.