STOCK Sst^{tm3.1(flpo)Zjh}/J

Stock number: 028579
Product name: Sst-ires-Flp
Research areas: Neurobiology Research, Research Tools

Description

Of note, the same Sst-ires-Flp allele will also be available on a C57BL/6J genetic background as Stock No. 031629.

Sst-ires-Flp knock-in mice (or SOM-IRES-Cre) have FLPo recombinase expression in GABAergic neurons derived from the medial-ganglionic eminence (MGE) - as directed by the endogenous somatostatin promoter. These mice are useful for studying the fate of progenitor cells at the SST/CR intersection.

Detailed description

Sst-ires-Flp knock-in mice express Flp Recombinase from the endogenous somatostatin (Sst) promoter/enhancer elements. SST expressing cells constitute half of the GABAergic neurons along the medial-ganglionic eminence and the preoptic areas (MGE-POA) and up to 30% all GABA neurons in many cortical areas. Homozygous mice are viable and fertile. FLP is detected in somatostatin positive neurons across layer 2 to 6, including dendritic inhibitory interneurons such as Martinotti cells and Oriens-Lacunosum-Moleculare (O-LM) cells. As such, when Sst-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 Sst-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 CR(calretinin)-ires-cre mice (Stock No. 010774) in order to study the fate of progenitor cells at the SST/CR intersection. tdTomato-labeled cells are enriched in layers 2 and 3 (L2/3), L5a, and L6 but are almost absent in L4. The L2/3 SST/CR cells have Martinotti cell morphology with an ascending axon that arborizes in L1 with fewer branches in L2/3. The L5 SST/CR neurons also have Martinotti cell morphology with ascending axons that invade layer 1. These neurons have adapting firing patterns.

Development

The Sst-ires-Flp knock-in allele (or SOM-IRES-Cre) was designed by Dr. Z. Josh Huang (Cold Spring Harbor Laboratory). A targeting vector was designed to insert an internal ribosome entry site (IRES) fused to the 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 somatostatin locus (Sst) on chromosome 16. 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. Chimeric animals were bred with B6.C-Tg(CMV-cre)1Cgn/J mice (Stock No. 006054) to generate the colony and remove the neo selection cassette. The resulting Sst-ires-Flp mice were bred to C57BL/6J mice to remove the Cre-expressing transgene, and then offspring were subsequently bred together to create a homozygous Sst-ires-Flp colony. 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: Sst^{tm3.1(flpo)Zjh}
Name: targeted mutation 3.1, Z Josh Huang
MGI accession ID: MGI:5700394
Generation method: Targeted
Attributes: Recombinase-expressing
Marker symbol: Sst
Marker name: somatostatin
Chromosome: 16
Strain of origin: (C57BL/6 x 129S4/SvJae)F1
Expressed genes: FLP,FLP recombinase,Saccharomyces cerevisiae
Site of expression: FLP Recombinase is detected in somatostatin positive 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.