C57BL/6-Tg(BEST1-cre)1Jdun/J

Stock number: 017557
Product name: Best1-cre
Research areas: Developmental Biology Research, Mouse/Human Gene Homologs, Research Tools, Sensorineural Research

Description

August 2022: The live colony had been found to produce some offspring with gray coat color. We are currently breeding black mice and will distribute black mice from breeding units that have not shown any unexpected coat colors. We investigated the genetic cause of this spontaneous, recessive coat color mutation and did not identify an associated mutation.

BEST1-Cre transgenic mice express Cre recombinase under the control of the human bestrophin 1 promoter. This strain represents an effective tool for generating retinal pigment epithelium (RPE) specific-targeted mutants that would be useful in studies of human retinopathies.

A tamoxifen-inducible BEST1-cre/ERT2 allele is also available as Stock No. 036292.

Detailed description

BEST1-Cre transgenic mice express Cre recombinase under the control of the human bestrophin 1 (BEST) promoter. Mosaic Cre recombinase expression (mRNA) is seen in 50-90% of retinal pigment epithelium (RPE) cells, with some expression seen in the testis. When crossed with a strain containing a loxP site-flanked sequence, Cre-mediated recombination results in deletion of the flanked sequence in RPE cells. Homozygotes are viable and fertile. This strain represents an effective tool for generating RPE specific-targeted mutants that would be useful in studies of human retinopathies.

See Development section for Coat Color Observations August 2022.

When bred to a strain expressing a floxed-Dicer1 gene (see Dicer1^tm1Bdh Stock No. 006366 for example), this mutant mouse strain may be useful for studying age-related macular degeneration.

Of note, a tamoxifen-inducible BEST1-cre/ERT2 allele is also available as Stock No. 036292 which does not exhibit the Cre toxicity in cells of the RPE which has been reported when using this constitutively active Cre.

Development

A transgenic construct containing cre coding sequence under the control of the human bestrophin 1 (BEST) promoter was introduced into C57BL/6NCrl donor oocytes. Resulting offspring, containing 20 copies of the transgene, were bred to and further maintained on a C57BL/6J background. The transgene inserted 58 kb upstream of Tmem108 on chromosome 9, the integration site contains a 120 bp deletion. Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6J (Stock No. 000664) for at least one generation to establish the colony.

In 2021, a 48 SNP (single nucleotide polymorphism) panel analysis, with 43 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. All of the markers are C57BL/6 allele-type, and all 5 that determine C57BL/6J from C57BL/6N were found to be C57BL/6J-derived.

Coat Color Observations August 2022: The live colony had been found to produce some offspring with gray coat color. We are currently breeding black mice and will distribute black mice from breeding units that have not shown any unexpected coat colors. We investigated the genetic cause of this spontaneous, recessive coat color mutation and did not identify an associated mutation.

Allele

Symbol: Tg(BEST1-cre)1Jdun
Name: transgene insertion 1, Joshua L Dunaief
MGI accession ID: MGI:4946605
Generation method: Transgenic
Attributes: Recombinase-expressing
Marker symbol: Tg(BEST1-cre)1Jdun
Marker name: transgene insertion 1, Joshua L Dunaief
Chromosome: 9
Strain of origin: C57BL/6
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: The BEST1-cre line with expression in the highest percentage of retinal pigment epithelium (RPE) cells displayed a patchy mosaic expression pattern, with 50% to 90% of RPE cells expressing cre.
Molecular note: A fragment of the human BEST1 promoter (nucleotides -585 to +38) drives cre recombinase cDNA, the SV40 t-antigen intron, and HSV-TK polyA in the construct. This was purified and microinjected into C57BL/6 zygotes. Six founders were generated with one F2 line that showed the highest percentage of cre immunoreactivity in the RPE was selected for further study. Expression of cre was mosaic, with 50-90% of RPE cells being labeled. This line has a transgene copy number of 20 determined by qPCR analysis (J:170522) or 5 copies (J:240920) inserted about 58 kb upstream of Tmem108 (chr9:103,722,073; NCBI37/mm9) with a 120 bp deletion at the transgene integration site.