The SYNGAP1lx-st conditional rescue knock-in allele has a loxP-flanked neo-STOP cassette upstream of exon 6 of the synaptic RasGAP (SynGAP) gene; resulting in disrupted expression of full-length SynGAP and expression of a truncated/inactive SynGAP protein. These mice allow Cre recombinase-inducible restoration of full-length SynGAP expression. SYNGAP1lx-st mice may be useful Cre-lox studies of synapse development (specifically in dendritic spine), cognitive and behavioral maturation, intellectual disability and autism spectrum disorder.
Gavin Rumbaugh, The Scripps Research Institute
Genetic Background | Generation |
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Allele Type | Gene Symbol | Gene Name |
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Targeted (Inserted expressed sequence, Humanized sequence) | Syngap1 | synaptic Ras GTPase activating protein 1 homolog (rat) |
Mutations that cause intellectual disability (ID) and autism spectrum disorder (ASD) are commonly found in genes that encode for synaptic proteins. Syngap1 encodes a synaptic RasGAP (SynGAP) that is largely localized to dendritic spines in neocortical pyramidal neurons, where it suppresses signaling pathways linked to NMDA receptor (NMDAR)-mediated synaptic plasticity and AMPA receptor (AMPAR) membrane insertion. Syngap1 has alternative transcriptional start sites and several alternatively spliced C-terminal exons that result in many possible SynGAP isoforms. Human SYNGAP1 haploinsufficiency results from a truncation of the full-length protein. Exon 7 contains the first common methionine present in the shortest splice variant.
The SYNGAP1lx-st allele has a loxP-flanked neo-STOP cassette upstream of exon 6 of the Syngap1 gene. Following cre-mediated recombination that removes the floxed region, SynGAP expression and function are fully recovered.
Prior to Cre recombinase exposure, mice heterozygous for the SYNGAP1lx-st allele express a SynGAP protein truncated after exon 5 (known to be an inactivate SynGAP protein), as well as diminished levels of functional SynGAP (from the wildtype allele). Therefore, the phenotype of heterozygotes (SYNGAP1lx-st/+) is the same as mice heterozygous for the global knockout allele, and both are a model of human SYNGAP1 haploinsufficiency - exhibiting normal synaptic transmission, modest defects in synaptic plasticity, enhanced synaptic function (accelerated rate of glutamatergic synapse maturation) during early neural development and profound cognitive and behavioral abnormalities. Specifically, heterozygous SynGAP-deficiency significantly disrupts excitatory/inhibitory (E/I) balance in the neural networks that support cognition and behavior. Abnormal behavioral phenotypes can be observing as early as 21 days of age with ~100% penetrance (although physiological abnormalities can be measured even earlier through other methods such as electrophysiological recordings). Furthermore, homozygotes (SYNGAP1lx-st/lx-st are phenotypically the same as global knockout homozygotes - exhibiting complete postnatal lethality between 2-5 days of age.
When SYNGAP1lx-st are bred to mice that express Cre recombinase, the resulting offspring may be useful in generating tissue-specific restoration of full-length SynGAP expression. For example, when SYNGAP1lx-st/+ mice are bred hemizygous for the CAGGCre-ERTM transgene (Stock No. 004682), the resulting animals allow widespread, tamoxifen-inducible SynGAP restoration. In those mice, complete restoration of SynGAP protein expression in adults had no detectable benefit on behavior or cognition - demonstrating that SYNGAP1 haploinsufficiency is a disorder of brain development.
The SYNGAP1 conditional rescue mice (SYNGAP1lx-st) was constructed by genOway S.A. (France) as a pay-for-service on behalf of Dr. Gavin Rumbaugh (The Scripps Research Institute).
The targeting vector was designed to insert a loxP-flanked STOP cassette (neomycin resistance gene and a series of stop codons) immediately downstream of exon 5 of the synaptic Ras GTPase activating protein 1 homolog (rat) locus (Syngap1) on chromosome 17.
The construct was electroporated into 129S2/SvPas-derived embryonic stem (ES) cells. Correctly targeted ES cells were identified and injected into recipient blastocysts. Chimeric males were bred to C57BL/6J for germline transmission.
The SYNGAP1lx-st colony was maintained on this mixed genetic background for several generations prior to sending males (with black or agouti coat color) to The Jackson Laboratory Repository in 2012.
Upon arrival, males were used to cryopreserve sperm. To establish a living mouse colony, an aliquot of the frozen sperm may be used to fertilize oocytes from C57BL/6J inbred females (Stock No. 000664).
Expressed Gene | Syngap1, synaptic Ras GTPase activating protein 1 homolog (rat), mouse, laboratory |
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Site of Expression |
Allele Name | targeted mutation 2, Genoway |
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Allele Type | Targeted (Inserted expressed sequence, Humanized sequence) |
Allele Synonym(s) | SYNGAP1lx-st |
Gene Symbol and Name | Syngap1, synaptic Ras GTPase activating protein 1 homolog (rat) |
Gene Synonym(s) | |
Expressed Gene | Syngap1, synaptic Ras GTPase activating protein 1 homolog (rat), mouse, laboratory |
Strain of Origin | 129S2/SvPas |
Chromosome | 17 |
Molecular Note | A floxed neo cassette was inserted into intron 5. Western blot analysis confirmed reduced protein expression in heterozygous samples. Cre-mediated recombination is required to remove the neo cassette and restore protein expression. |
Homozygous mice exhibit complete postnatal lethality between 2-5 days of age. Heterozygous mice develop profound cognitive and behavioral abnormalities grossly demonstrable ~21 days of age. The donating investigator breeds heterozygous mice to wildtype mice from the colony, using both sexes as the heterozygote.
When maintaining a live colony, at The Jackson Laboratory Repository, heterozygous mice may be bred to wildtype mice from the colony or to C57BL/6J inbred mice (Stock No. 000664).
When using the SYNGAP1lx-st (Cre-conditional rescue) mouse strain in a publication, please cite the originating article(s) and include JAX stock #029304 in your Materials and Methods section.
Facility Barrier Level Descriptions
Service/Product | Description | Price |
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Heterozygous or wildtype for Syngap1<tm2Geno> |
Frozen Mouse Embryo | B6;129S2-Syngap1<tm2Geno>/RumbJ Frozen Embryo | $2595.00 |
Frozen Mouse Embryo | B6;129S2-Syngap1<tm2Geno>/RumbJ Frozen Embryo | $2595.00 |
Frozen Mouse Embryo | B6;129S2-Syngap1<tm2Geno>/RumbJ Frozen Embryo | $3373.50 |
Frozen Mouse Embryo | B6;129S2-Syngap1<tm2Geno>/RumbJ Frozen Embryo | $3373.50 |
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