STOCK Nkx2-1^{tm2.1(flpo)Zjh}/J

Stock number: 028577
Product name: Nkx2.1-ires-Flp
Research areas: Neurobiology Research, Research Tools

Description

Nkx2.1-ires-Flp knock-in mice have Flp Recombinase expression in medial-ganglionic eminence and the preoptic areas (MGE/POA), as directed by the endogenous NK2 homeobox 1 promoter. These mice are useful for studying the fate of progenitor cells at the MGE/POA intersection.

Detailed description

Nkx2.1-ires-Flp knock-in mice express Flp Recombinase from the endogenous NK2 homeobox 1 (Nkx2-1) promoter/enhancer elements. Nkx2.1 expressing cells are GABAergic neurons along the medial-ganglionic eminence and the preoptic areas (MGE-POA) in both the ventricular zone radial glia (RG) progenitors and subventricular zone intermediate progenitors (IP). Homozygous mice are viable and fertile. FLP is expressed in cells in MGE-derived neurons including parvalbumin (PV) and somatostatin (SST) neurons, with no expression in caudal-ganglionic eminence (CGE)-derived vasoactive intestinal polypeptide (VIP) neurons detected. When Nkx2.1-ires-Flp mice are bred with mice containing frt-flanked sequence(s), Flp-mediated recombination will result in deletion of the flanked sequence(s) in the Nkx2.1-expressing cells of the offspring.

These mice were bred to Ai65(RCFL-tdT)-neo mice (Stock No. 021875) (after removal of the loxP-flanked STOP codon by breeding with Nkx6-2-CreER^T2 mice (Stock No. 017536)) in order to study the fate of progenitor cells at the MGE/POA intersection. tdTomato-labeled MGE progenitors give rise to neurons in layers 1-3 show horizontally oriented morphology. L2/3 SST cells have Martinotti cell morphology with an ascending axon that arborizes in L1.

In contrast, when Ai65(RCFL-tdT)-neo mice were first bred with ER81-CreER mice (Stock No. 013048) many of the progenitors produce neurons in deep layers (layer 4-6), and are mostly multipolar cells with radiating axons in L5. They give rise to more PV than SST cells, and less than 10% of L2/3 putative Martinotti neurons cells.

Development

A targeting vector was designed to insert an internal ribosome entry site (IRES) fused to Flpo Recombinase gene (a codon-optimized FLPe gene modified for translation in mammalian cells and higher recombination efficiency in cells and in mice), followed by a loxP-flanked neo cassette, downstream of the stop codon of the NK2 homeobox 1 (Nkx2-1) gene. This construct was electroporated into (C57BL/6 x 129S4/SvJae)F1-derived V6.5 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts and chimeric mice were bred with B6.C-Tg(CMV-cre)1Cgn/J mice (Stock No. 006054) to remove the neo selection cassette. Resulting mice were bred to C57BL/6J mice to remove the Cre-expressing transgene, and offspring were subsequently bred together to create a homozygous colony of Nkx2.1-ires-Flp mice. 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 (Stock No. 000664).

Allele

Symbol: Nkx2-1^{tm2.1(flpo)Zjh}
Name: targeted mutation 2.1, Z Josh Huang
MGI accession ID: MGI:5700385
Generation method: Targeted
Attributes: Recombinase-expressing
Marker symbol: Nkx2-1
Marker name: NK2 homeobox 1
Chromosome: 12
Strain of origin: (C57BL/6 x 129S4/SvJae)F1
Expressed genes: FLP,FLP recombinase,Saccharomyces cerevisiae
Site of expression: Flp Recombinase is expressed in cells in medial-ganglionic eminence-derived neurons including parvalbumin and somatostatin neurons.
Molecular note: The targeting vector is designed to insert an internal ribosome entry site (IRES) fused to flpo recombinase gene (a codon-optimized FLPe gene modified for translation in mammalian cells and higher recombination efficiency in cells and in mice), followed by a loxP-flanked neo cassette, downstream of the stop codon of the gene. Cre-mediated recombination removed the floxed neo cassette.