C57BL/6N-Aldh1a1^{tm1(cre/ERT2)Awar}/J

Stock number: 040634
Product name: Aldh1a1-CreER^T2
Research areas: Neurobiology Research, Research Tools

Description

Aldh1a1-CreER^T2 knock-in/knock-out mice express an inducible cre/ERT2 fusion gene under the control of the endogenous Aldh1a1 promoter. The insertion of the cre/ERT2 sequence abolishes Aldh1a1 expression. Following administration of tamoxifen, mice express Cre recombinase in midbrain dopamine (DA) neurons. These mice can be used to map projections of molecularly defined dopamine neuron subtypes and may also be combined with flp-frt lines for intersectional studies of sub-populations of DA neurons.

Detailed description

Aldh1a1-CreER^T2 knock-in/knock-out mice have a tamoxifen-inducible cre/ERT2 fusion gene, a WPRE fragment, and bGH pA, followed by an FRT-flanked neo cassette inserted in-frame with the ATG codon of the endogenous aldehyde dehydrogenase family 1, subfamily A1 (Aldh1a1) gene. The insertion of the cre/ERT2 sequence abolishes Aldh1a1 expression. Aldh1a1 encodes an enzyme expressed in midbrain dopamine (DA) neurons that is involved in alcohol and retinol metabolism. It is expressed by two distinct DA neuron subtypes: one located in the ventral tier of the substantia nigra pars compacta (SNc) and the other located largely in the interfascicular nucleus (IF) and ventral tegmental area (VTA; also known as the paranigral nucleus).

When these Aldh1a1-CreER^T2 mice are bred with mice containing loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination will result in deletion of floxed sequences in DA neurons in the midbrain. Mice that are homozygous for this knock-in allele are viable and fertile. No Cre activity is evident in these mice prior to tamoxifen administration.

The donating investigator bred these Aldh1a1-CreER^T2 mice to the tdTomato Cre reporter line, Ai65D (Stock No. 021875), which is a conditional allele designed with both an frt-flanked STOP cassette and a loxP-flanked STOP cassette preventing transcription of the tdTomato red fluorescent protein gene. Further breeding to Th-2A-Flpo mice creates a Aldh1a1-CreER^T2;Th-2A-Flpo;Ai65 mouse. Recombination by CreER^T2, after tamoxifen injection, results in the removal of the flanked STOP cassettes by FLP- and Cre-recombination, and tdTomato fluorescence is expected in only cells/tissues expressing both FLP recombinase and Cre recombinase. Specifically, tdTomato fluorescence is evident in projections to the dorsolateral caudate putamen (CP), nucleus accumbens (ACB) medial shell and lateral septum, but not the prefrontal cortex (PFC), in the Aldh1a1-CreER^T2;Th-2A-Flpo;Ai65 mouse. Also, in the CP, tdTomato shows enrichment in several µ opioid receptor (MOR)⁺ striosomes. Some fluorescence is also seen in cell populations outside the midbrain.

Development

The Aldh1a1-CreER^T2 targeting vector contains a cre/ERT2, a WPRE fragment, and bGH pA followed by an FRT-flanked neomycin resistance (neo) cassette. The vector was inserted into the aldehyde dehydrogenase family 1, subfamily A1 (Aldh1a1) gene in-frame with the endogenous ATG. The construct was electroporated into C57BL/6NTac-derived PRX-B6N embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts. The chimeric animals were crossed with C57BL/6NCrl females for germline transmission. The donating investigator reports the resulting Aldh1a1-CreER^T2 mice were backcrossed to C57BL/6NCrl for an unknown number of generations. Cryopreserved sperm was sent to The Jackson Laboratory. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6NJ oocytes (Stock No. 005304).

Allele

Symbol: Aldh1a1^{tm1(cre/ERT2)Awar}
Name: targeted mutation 1, Rajeshwar Awatramani
MGI accession ID: MGI:6726326
Generation method: Targeted
Attributes: Recombinase-expressing; Inducible
Synonyms: Aldh1a1-CreER^T2
Marker symbol: Aldh1a1
Marker name: aldehyde dehydrogenase family 1, subfamily A1
Marker synonyms: Ahd2; Ahd-2; ALDC; Aldh1; ALDH11; Aldh2; ALDH-E1; E1; HEL12; HEL-9; HEL-S-53e; PUMB1; Raldh1
Chromosome: 19
Strain of origin: C57BL/6NTac
Molecular note: By homologous recombination in ES cells, a CreERT2, a WPRE fragment, and bGH pA followed by FRT flanked neo cassette was inserted into the Aldh1a1 gene in-frame to the endogenous ATG.