Species: Mouse
Genes: SNCA
Modification: SNCA: Conditional Knock-out
Disease Relevance: Parkinson's Disease
Strain Name: B6(Cg)-Snca^tm1.1Vlb/J
Genetic Background: C57BL/6J
Availability: Available through The Jackson Laboratory, Stock #025636, Live.

Summary

Breeding these mice with various Cre-expressing transgenic mice allows for the depletion of α-synuclein in specific cell populations (Ninkina et al., 2015).

For example, these mice were bred to an “early deletor” line that expresses Cre recombinase embryonically using the CMV promoter (Ninkina et al., 2015). The deletion involved a 1,164–base pair fragment consisting of exon 2 and the adjacent intronic sequences of the mouse Snca gene. The resulting offspring had germline deletion of the floxed exon 2, and the gene targeting approach used to create these mice left behind minimal ectopic sequence, only a single loxP site. These homozygous SNCA^ΔfloxΔflox mice had no detectable α-synuclein protein in neuronal tissues. At 4 months of age, SNCA^ΔfloxΔflox mice had reduced tyrosine hydroxylase (TH) staining in the substantia nigra pars compacta (SNpc; Goloborshcheva et al., 2020).

Mouse lines carrying the modified Snca locus along with a Rosa26-stop-lacZ reporter cassette located in cis on chromosome 6 also have been developed (Roman et al., 2017). The reporter allows quick identification of cells with Snca inactivation.

In addition, Snca^flox mice have also been crossed to cell-specific Cre lines to explore outcomes of conditional deletion of Snca. For instance, in a cross with mice expressing a Cre recombinase under the phosphoenolpyruvate carboxykinase promoter (PEPCK Cre), Snca was knocked out of renal proximal tubular epithelial cells (Bozic et al., 2020). This knockout led to an acceleration of kidney fibrosis, based on gene expression outcomes, in a surgical model of fibrosis.

Others have crossed mice hemizygous for Cre-ERT2 recombinase driven by the neuro-specific enolase (NSE) promoter with mice that have a compound heterozygous mutation at the Snca allele (Snca^{floxΔneo/Δflox}; Ninkina et al., 2020). These mice had global expression of SNCA only until 6 or 12 months of age, at which point they were treated with tamoxifen to induce Cre expression and induce Snca KO specifically in neurons. In animals treated with tamoxifen at 6 months of age, striatal dopamine metabolism as measured by the concentration of dopamine and its metabolites, was not affected at 10, 14, or 18 months of age compared to vehicle-treated mice. However, if treated at 12 months of age, the striatal metabolites DOPAC and HVA were significantly reduced 6 months later, at 18 months of age, suggesting dopamine turnover may be compromised in the aging nervous system. The number of dopaminergic neurons in the SNpc was not affected in 18-month-old mice, regardless of whether they were injected with tamoxifen at 6 or 12 months. Locomotor activity (inverted grid test) was elevated in tamoxifen-treated mice when tested at 18 months of age, regardless of whether they received the tamoxifen exposure at 6 or 12 months of age.

Other studies have explored and found alterations in electroencephalogram coherence and oscillation in both the constitutive (SNCA^ΔfloxΔflox; Vorobyov et al., 2022) and time-dependent, neuron-specific (Snca^{flox/∆flox;NSE-Cre-ERT2/+}; Vorobyov et al., 2023) depletion models.

Modification Details

A targeting vector containing a FRT site-flanked neomysin cassette and a loxP site was inserted downstream of exon 2 (the first coding exon of Snca) and another loxP site was inserted upstream of exon 2. Flp-mediated recombination removed the FRT-flanked neo cassette, leaving exon 2 floxed. When bred to Cre-expressing mice, the resulting offspring have the first coding exon deleted in Cre-expressing tissues.

Related Strains

B6(Cg)-Sncatm1.2Vlb/J - These SncaΔflox knock-out mice constitutively lack the first coding exon (exon 2) of the Snca gene, but they do not carry the neo cassette, and thus are called a “clean KO.” Available through The Jackson Laboratory Stock# 028559.

B6.Cg-Sncatm1.1Vlb Gt(ROSA)26Sortm1Sho/J - This double mutant line carries the floxed Snca 1.1 allelle (from Stock# 025636) and the ROSA26-stop-lacZ reporter allele (from Stock #003504). The ROSA26-stop-lacZ reporter allele allows for the monitoring of Cre recombinase activity. The double mutant is available through The Jackson Laboratory Stock# 029855.

Phenotype Characterization

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References

Paper Citations

1. Ninkina N, Connor-Robson N, Ustyugov AA, Tarasova TV, Shelkovnikova TA, Buchman VL. A novel resource for studying function and dysfunction of α-synuclein: mouse lines for modulation of endogenous Snca gene expression. Sci Rep. 2015 Nov 13;5:16615. PubMed.
2. Goloborshcheva VV, Chaprov KD, Teterina EV, Ovchinnikov R, Buchman VL. Reduced complement of dopaminergic neurons in the substantia nigra pars compacta of mice with a constitutive "low footprint" genetic knockout of alpha-synuclein. Mol Brain. 2020 May 11;13(1):75. PubMed.
3. Roman AY, Limorenko G, Ustyugov AA, Tarasova TV, Lysikova EA, Buchman VL, Ninkina N. Generation of mouse lines with conditionally or constitutively inactivated Snca gene and Rosa26-stop-lacZ reporter located in cis on the mouse chromosome 6. Transgenic Res. 2017 Apr;26(2):301-307. Epub 2016 Nov 12 PubMed.
4. Bozic M, Caus M, Rodrigues-Diez RR, Pedraza N, Ruiz-Ortega M, Garí E, Gallel P, Panadés MJ, Martinez A, Fernández E, Valdivielso JM. Protective role of renal proximal tubular alpha-synuclein in the pathogenesis of kidney fibrosis. Nat Commun. 2020 Apr 23;11(1):1943. PubMed.
5. Ninkina N, Tarasova TV, Chaprov KD, Roman AY, Kukharsky MS, Kolik LG, Ovchinnikov R, Ustyugov AA, Durnev AD, Buchman VL. Alterations in the nigrostriatal system following conditional inactivation of α-synuclein in neurons of adult and aging mice. Neurobiol Aging. 2020 Jul;91:76-87. Epub 2020 Mar 5 PubMed.
6. Vorobyov V, Deev A, Sukhanova I, Morozova O, Oganesyan Z, Chaprov K, Buchman VL. Loss of the Synuclein Family Members Differentially Affects Baseline- and Apomorphine-Associated EEG Determinants in Single-, Double- and Triple-Knockout Mice. Biomedicines. 2022 Dec 4;10(12) PubMed.
7. Vorobyov V, Deev A, Morozova O, Oganesyan Z, Krayushkina AM, Ivanova TA, Chaprov K. Early Effects of Alpha-Synuclein Depletion by Pan-Neuronal Inactivation of Encoding Gene on Electroencephalogram Coherence between Different Brain Regions in Mice. Biomedicines. 2023 Dec 12;11(12) PubMed.

External Citations

1. The Jackson Laboratory Stock# 028559
2. The Jackson Laboratory, Stock #025636

Further Reading