These mice carry a knockout allele of the Fxr2 (fragile X mental retardation, autosomal homolog 2) associated with a range of behavioral phenotypes.
David L Nelson, Baylor College of Medicine
Fxr2 (fragile X mental retardation, autosomal homolog 2) may play a role in the development of fragile X mental retardation syndrome and is crucial for dendritic maturation and network integration of new neurons.
Exon 7 of the mouse Fxr2 gene has been replaced with a neomycin cassette to create this knock-out allele. Western blot analysis of testis and brain tissue indicate that homozygous knockout mice do not express the protein.
Homozygotes develop normally, and are viable and fertile. They are hyperactive in open-field tests, impaired on rotarod tests, have reduced levels of repulse inhibition, display less contextual conditioned fear, are impaired at locating the hidden platform in the Morris water tank, and are less sensitive to heat stimulus. Fxr2 knockout mice display a shorter free-running period of locomotor activity in total darkness.
Exon 7 was replaced with a neomycin resistance cassette in reverse transcriptional orientation via homologous recombination in AB 129-derived embryonic stem (ES) cells. Resultant mice were backcrossed to C57BL/6J for more than 15 generations by the donating lab (see SNP results below).
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 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 rederived living colony at The Jackson Laboratory Repository. Four of the the 27 markers throughout the genome were segregating, suggesting an incomplete backcross. Also, 2 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6J ; C57BL/6N genetic background.
|Allele Name||targeted mutation 1, Ben Oostra|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||Fxr2 -|
|Gene Symbol and Name||Fxr2, fragile X mental retardation, autosomal homolog 2|
|Strain of Origin||129S7/SvEvBrd|
|Molecular Note||Exon 7 and surrounding intronic sequence was replaced with a neomycin selection cassette inserted by homologous recombination. Western blot analysis of testis and brain tissue, as well as immunohistochemical analysis, indicated an absence of protein in homozygous mutant mice.|
Heterozygotes and homozygotes are viable and fertile.
When using the Fxr2 KO mouse strain in a publication, please cite the originating article(s) and include JAX stock #029044 in your Materials and Methods section.