B6.Cg-Tg(Syn1-cre)671Jxm/J

Stock number: 003966
Research areas: Neurobiology Research, Research Tools

Description

Specific cre expression in neuronal cells of these mice is controlled by the rat Synapsin I promoter. These mice may be useful when mated to floxed genes of interest in studies of neural development and disorders such as Neurofibromatosis type 1.
For Cre-lox experiments, researchers should assay all of the progeny to determine if germline deletion of the floxed allele has occurred. See Detailed Description for more information.

Detailed description

These transgenic mice express Cre recombinase under the direction of a synapsin promoter. The transgene integrated into chromosome 6, as detected by targeted locus amplification (TLA). Recombinase activity is detected in neuronal cells by embryonic day 12.5. Of note, transgene expression is active in the male germline (seminiferous tubules) and can result in germline recombination in progeny arising from a hemizygous transgenic male. Female germline expression may also be observed. See additional expression information below.

Although homozygotes are viable, lower than expected Mendelian ratios from hemizygous x hemizygous crosses are produced. Homozygotes are fertile, but litter size and pup size produced from breeding with homozygous animals are small, and most pups from homozygous matings do not survive to wean.

For Cre-lox experiments, researchers should assay all of the progeny to determine if germline deletion of the floxed allele has occurred.

Luo et al. 2020 Neuron 106:37 Table 1 shows germline recombination in offspring (F2) of Cre;floxed double mutant (F1) mice bred to floxed and/or wildtype mice. The authors also note that in general, the frequency of recombination in Cre;floxed double mutant germline cells appears to be considerably higher than in zygotes produced by breeding Cre mice to floxed mice. Further, this reports that Syn1-cre;floxed double mutant males bred to floxed females produced some offspring with germline deletion of the floxed allele [63%].

The Mouse Genome Informatics (MGI) information linked below suggests female germline expression may also be observed.

If the recombinase activity pattern of this allele is further characterized by the Genetic Resource Science group at The Jackson Laboratory, such findings will be reported on the Mouse Genome Informatics (MGI) Allele Detail entry. This same information may also be found searching the MGI Recombinase Activity and MGI Gene Expression + Recombinase Activity Comparison Matrix.

Development

A transgenic construct containing a 4 kb rat synapsin promoter directing expression of Cre recombinase was injected into fertilized B6;CBA mouse eggs. Founder line 671 animals were bred to wildtype C57BL/6NHsd mice. The transgene integrated into chromosome 6, as detected by targeted locus amplification (TLA). The mice were backcrossed to wildtype C57BL/6NHsd mice for at least 5 generations. Upon arrival at The Jackson Laboratory, the strain was bred to C57BL/6J (Stock No. 000664). As of November 2020, the live colony has been backcrossed 4 generations to C57BL/6J.

Allele

Symbol: Tg(Syn1-cre)671Jxm
Name: transgene insertion 671, Jamey Marth
MGI accession ID: MGI:2176055
Generation method: Transgenic
Attributes: Recombinase-expressing
Synonyms: cre^syn1; Syn-cre; Syn-Cre^tg; SynI-Cre
Marker symbol: Tg(Syn1-cre)671Jxm
Marker name: transgene insertion 671, Jamey Marth
Marker synonyms: Syn-cre; SynI-Cre
Chromosome: 6
Strain of origin: (C57BL/6 x CBA)F2
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: neuronal cells by embryonic day 12.5
Molecular note: This transgene expresses Cre recombinase under the control of a rat synapsin I promoter. Cre recombinase activity is detected in neuronal cells, including brain, spinal cord and DRGs, as early as E12.5, as well as in neurons in adult. Line 671 contains 10 copies of the transgene inserted into chromosome 6 over 1 Mb from the nearest gene (chr6:10,423,318; NCBI37/mm9) with a duplication of unknown size at the insertion site.
General note: Homozygous transgenic mice are viable, fertile, normal in size, and do not display any gross physical or behavioral abnormalities.