Homozygous PSD-93- knockout mice exhibit dysfunctional synaptic targeting of NMDARs and abnormal nociception. These mice may be useful in studying the MAGUK family of synaptic scaffolding proteins in synaptic function.
Roger A Nicoll, University of California, San Francisco
Synaptic α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) are the dominant glutamate receptor in the brain. A thick electron-dense material associated with the postsynaptic membrane, referred to as the postsynaptic density (PSD), imbeds glutamate receptors. The membrane-associated guanylate kinase (MAGUK) family of synaptic scaffolding proteins (PSD-93, PSD-95 and SAP102) is critical for proper synaptic function: PSD-MAGUK-specific regulation of AMPAR synaptic expression establishes and maintains glutamatergic synaptic transmission in the mammalian central nervous system. PSD-95 and PSD-93 are jointly required for normal synaptic expression of NMDARs. The role of PSD-MAGUK proteins in synaptic AMPAR targeting is developmentally regulated; SAP-102 is primarily responsible for AMPAR targeting/clustering in neonatal synapses, whereas PSD-95 and PSD-93 primarily anchor proteins in mature synapses.
The postsynaptic density-93 knockout allele (PSD-93-) has a neomycin resistance gene replacing the exon encoding the second PDZ domain. Homozygous mice (PSD-93-/- or Dlg2-/-) exhibit dysfunctional synaptic targeting of NMDARs and abnormal nociception. Other reported homozygous phenotypes include decreased adipose tissue and homeostasis/metabolism abnormalities.
Homozygous mice are viable and fertile. Heterozygous mice are viable and fertile with no reported abnormalities. Brain tissue from homozygous mice shows expression of PSD-93 RNA is highly reduced, and PSD-93 protein is undetectable.
The PSD-93- knockout allele was created by Dr. David S Bredt (University of California, San Francisco). A targeting vector was designed to have neomycin resistance gene replacing the exon encoding the second PDZ domain of the postsynaptic density-93 locus (PSD-93 or Dlg2) on chromosome 7. The construct was electroporated into SV129-derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts, and chimeric mice were bred with C57BL/6J for germline transmission. The resulting PSD-93- mice were maintained on a C57BL/6 genetic background and then sent to Dr. Roger A. Nicoll (University of California, San Francisco) in 2000. There, the PSD-93- colony was bred together for several generations and/or backcrossed to C57BL/6J mice for several generations, and then males with black coat color were sent to The Jackson Laboratory Repository in 2016 (see SNP notes below). Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
In 2016, a SNP (single nucleotide polymorphism) panel analysis, with 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 males sent to The Jackson Laboratory Repository. This revealed markers on 4 chromosomes that were not fixed for C57BL/6 allele-type (i.e., still segregating for 129S allele-type markers). In addition, 3 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating in some mice (note the allele-type for C57BL/6N and 129S are the same for these 5 markers). Collectively, these data suggest that the mice sent to The Jackson Laboratory Repository were incompletely backcrossed onto C57BL/6, and the C57BL/6 genetic background contributions may be a mix of C57BL/6J;C57BL/6N.
|Allele Name||targeted mutation 1, David S Bredt|
|Allele Type||Targeted (Hypomorph, Modified isoform(s))|
|Allele Synonym(s)||Dlg2deltaE9; PSD93-|
|Gene Symbol and Name||Dlg2, discs large MAGUK scaffold protein 2|
|Strain of Origin||129/Sv|
|Molecular Note||The exon encoding the second PDZ domain was replaced with a TK-neo cassette via homologous recombination. Northern blot analysis of brain RNA from homozygous mutant animals detected a faint mutant transcript of higher mobility, presumably an alternative splice product that skips the deleted exon. However, Western blot analysis of brain proteins using antibodies directed against a region N-terminal to the deleted exon did not detect protein product. |
Exon 9 is deleted. In knockout mice, the longer Dlg2gamma and DLG2alpha1 are not expressed in bone-marrow derived plasmacytoid dendritic cells. However, a shorter Dlg2n isoform is expressed in bone-marrow derived plasmacytoid dendritic cells and in brain (J:262606).
When maintaining a live colony, heterozygous mice may be bred together or to wildtype mice from the colony. Alternatively, homozygous mice may be bred together.
When using the PSD-93- mouse strain in a publication, please cite the originating article(s) and include JAX stock #028444 in your Materials and Methods section.