B6.129S1(Cg)-Ascl3^{tm1.1(EGFP/cre)Ovi}/J

Stock number: 021794
Research areas: Research Tools

Description

In this targeted mutant strain, an EGFP-Cre knock-in ablates expression of the mouse Ascl3 achaete-scute complex homolog 3 (Drosophila) gene. Fluorescent labeling and Cre expression recapitulate endogenous Ascl3 expression, useful in studies of salivary gland development and maintenance.

Detailed description

Ascl3 (achaete-scute complex homolog 3 (Drosophila); also known as Sgn1) is a member of the mammalian achaete scute (Mash) gene family of transcription factors which have been implicated in cell fate specification and differentiation. In the mouse salivary gland, expression is restricted to a subset of duct cells which are progenitors of both acinar and ductal cell types and contribute to the maintenance of adult salivary glands. Studies of salivary gland development may enable functional restoration in patients with radiation-induced damage or autoimmune disease.

In this targeted mutant strain, an EGFP-Cre knock-in ablates expression of the mouse Ascl3 gene. Fluorescent labeling and Cre expression recapitulate endogenous Ascl3 expression. Characterization of the homozygous phenotype is ongoing, but heterozygous animals are born at predicted Mendelian frequencies and are indistinguishable in growth and fertility. Mutant mice show no signs of increased morbidity compared to their wild type littermates. Heterozygotes show no change in salivary gland function.

When crossed with a reporter strain carrying a floxed β-galactosidase (LacZ) gene under the control of the ubiquitously active Gt(ROSA)26Sor promoter (e.g. Stock No. 003474), non-fluorescent progeny of cells in which Cre has been expressed can be traced through lacZ staining. In these animals, acinar cells of the submandibular, sublingual, and parotid gland stain positive for lacZ, and fluorescent cells are limited to the progenitor cells in the ducts.

Development

A targeting vector was constructed to insert an EGFP-Cre recombinase fusion expression cassette combined with a 3' β-globin polyadenylation site and loxP-flanked PGK-neomycin cassette into exon 2, replacing the entire coding sequence. This mutation was generated in 129S1/Sv-Oca2⁺ Tyr⁺ Kitl⁺-derived CJ7 embryonic stem (ES) cells by homologous recombination. Resultant mice were backcrossed to C57BL/6J for at least 6 generations by the donating laboratory. Mice were subsequently crossed with a C57BL/6J background CMV-cre strain to excise the neo cassette.

Allele

Symbol: Ascl3^{tm1.1(EGFP/cre)Ovi}
Name: targeted mutation 1.1, Catherine E Ovitt
MGI accession ID: MGI:5520171
Generation method: Targeted
Attributes: Recombinase-expressing; Reporter; Null/Knockout
Marker symbol: Ascl3
Marker name: achaete-scute family bHLH transcription factor 3
Marker synonyms: bHLHa42; HASH3; ICRFP703B1614Q5.4; ICRFP703N2430Q5.4; Sgn1
Chromosome: 7
Strain of origin: 129S1/Sv-Oca2⁺ Tyr⁺ Kitl⁺
Expressed genes: cre,cre recombinase,bacteriophage P1; GFP,Green Fluorescent Protein,
Site of expression: Fluorescent labeling and Cre expression recapitulate endogenous Ascl3 expression which is restricted to a subset of duct cells that are progenitors of both acinar and ductal cell types and contribute to the maintenance of adult salivary glands.
Molecular note: A targeting vector was constructed to insert an EGFP-Cre recombinase fusion expression cassette with a 3' beta-globin polyadenylation site and loxP-flanked PGK-neomycin cassette into exon 2, replacing the entire coding sequence. Cre-mediated recombination removed the neomycin cassette.