B6.129X1-Snap25^tm1Mcw/J

Stock number: 004863
Product name: SNAP-25 KO
Research areas: Cardiovascular Research, Developmental Biology Research, Neurobiology Research

Description

Homozygous Snap25 knock-out mice exhibit neonatal lethality. Late embryos lack spontaneous movement or sensorimotor reflexes, and abnormal innervation and muscle fiber development is observed.

Detailed description

Homozygous mutant mice die at birth from respiratory failure. At embryonic day 17.5 to 18.5 homozygous embryos appear smaller and do not display spontaneous movement or sensorimotor reflexes. Dilated vascular channels in subcutaneous tissues give the embryos an external blotchy appearance. No gene product (mRNA or protein) is detected by Northern or Western blot analysis of brain tissue from homozygous animals. Histological analysis of fetal diaphragm tissue reveals a dispersed pattern of innervation and fewer layers of muscle fibers. Thin, disarrayed intercostal and anterior chestwall muscles are also observed. Spontaneous miniature endplate potential (mEPP) activity is detected in the diaphragm phrenic nerve, but no evoked endplate potentials (EPP), evoked neurotransmitter release or muscle contraction is detected with stimulation of the neuromuscular junction (NMJ). Mutant NMJs exhibit larger endplate diameters and lower levels of acetylcholinesterase. Tetrodotoxin (TTX) resistant miniature excitatory postsynaptic currents (mEPSCs), but not evoked, action-potential dependent responses are detected from mutant central nervous system (CNS) synapses. Mice that are heterozygous for the targeted mutation are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. Thismutant mouse strain may be useful in studies of neuroexocytosis and neurotransmitter release in the developing nervous system.

Development

A targeting vector containing neomycin resistance and herpes simplex virus thymidine kinase genes was used to disrupt exons 5a and 5b and part of the downstream intron. The construct was electroporated into 129X1/SvJ derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts. The resulting chimeric animals were crossed to C57BL/6 mice, and then backcrossed to C57BL/6 for 7 generations (September 2003).

Allele

Symbol: Snap25^tm1Mcw
Name: targeted mutation 1, Michael C Wilson
MGI accession ID: MGI:2180178
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Snap25
Marker name: synaptosomal-associated protein 25
Chromosome: 2
Strain of origin: Not Specified
Molecular note: Exon 5a/b and part of the downstream intron were replaced with a PGK-neo cassette by homologous recombination. Western blot of brain proteins and RT-PCR analysis of total brain RNA from homozygous mutant embryos verified the absence of gene expression.