The Ndel1cko(IV) hypomorphic conditional knock-out allele (also called Ndel1cko or Ndel1hc) acts as a hypomorph before exposure to Cre recombinase, and can be converted to a null allele by cre-deletion of exon 4. These mice are useful in studying normal cortical neuronal migration, neurite outgrowth, and function of the microtubule organizing center in a dose-dependent manner.
Dr. Anthony Wynshaw-Boris, Case Western Reserve University, School of Medicine
The Ndel1cko(IV) hypomorphic conditional knock-out allele (also called Ndel1cko or Ndel1hc) has a loxP site upstream of Ndel1 exon 4, and a loxP-flanked PGK-neo cassette in Ndel1 intron 4.
Prior to Cre recombinase, presence of the PGK-neo gene in intron 4 reduces NDEL1 expression by ~30% compared to endogenous levels. Homozygous (Ndel1cko/cko) and heterozygous mice (Ndel1cko/+) are viable and fertile. Ndel1cko/cko mice exhibit isolated granular neuron defects (reduced outward nuclear migration and reduced neurite extension).
Subjecting the Ndel1cko(IV) allele to cre-mediated deletion of the entire floxed region results in a null allele (Ndel1ko) with no NDEL1 expression. Following germline deletion of exon 4, mice bred to be homozygous for the null allele (Ndel1ko/ko) die in the very early stages of embryogenesis. Mice with the compound heterozygous genotype (Ndel1cko/ko also called Ndel1hc/ko) exhibit ~20% reduced NDEL1 expression compared to endogenous levels, and mild neuronal migration defects (partial splitting and diffuse pyramidal cells in the CA3 and CA2 region of the hippocampus). Compared to wildtype mice, cortical slices from Ndel1hc/ko mice have ~30-35% of NDEL1 protein levels and reduced neuronal migration velocity characterized by diverse branched migration modes with multiple leading processes, suggesting defects in adhesion and/or polarity. The donating investigator reports they only observe cre-mediated deletion of the entire floxed exon4::PGK-neo (leaving only a single loxP site); they have never observed cre recombination that resulted in deletion of only the PGK-neo (leaving exon 4 floxed) or deletion of only exon 4 (leaving a floxed PGK-neo cassette).
Of note, the donating investigator reports they only observe cre-mediated deletion of the entire floxed exon4::PGK-neo (leaving only a single loxP site); they have never observed cre recombination that resulted in deletion of only the PGK-neo (leaving exon 4 floxed) or deletion of only exon 4 (leaving a floxed PGK-neo cassette).
In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. It should be noted that the phenotype of mice on a mixed 129S1/SvImJ;129S6/SvEvTac genetic background could vary from that originally described on a 129S6/SvEvTac genetic background. We may modify the strain description if necessary as published results become available.
The targeting vector was designed by Dr. Anthony Wynshaw-Boris (while at University of California San Diego) and Dr. Shinji Hirotsune (Osaka City University, Japan) to insert a loxP site upstream of exon 4, and a loxP-flanked PGK-neo cassette in intron 4 (loxP::exon 4::loxP::PGK-neo::loxP) of the nuclear distribution gene E-like homolog 1 (A. nidulans) gene (Ndel1) on chromosome 11.
The construct was electroporated into 129S6/SvEvTac-derived TC1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts. Chimeric males were bred with 129S6/SvEvTac females to generate mice heterozygous for the Ndel1cko(IV) hypomorphic conditional knock-out allele (also called Ndel1cko or Ndel1hc). The colony was maintained on the 129S6/SvEvTac genetic background (by breeding heterozygotes or homozygotes together) prior to sending agouti mice to The Jackson Laboratory Repository in 2015. Upon arrival, males were used to cryopreserve sperm. To establish our living mouse colony, an aliquot of the frozen sperm was used to fertilize oocytes from 129S1/SvImJ inbred females (Stock No. 002448).
|Allele Name||targeted mutation 2, Shinji Hirotsune|
|Allele Type||Targeted (Conditional ready (e.g. floxed), Hypomorph)|
|Allele Synonym(s)||Ndel1cko(IV); Ndel1cko|
|Gene Symbol and Name||Ndel1, nudE neurodevelopment protein 1 like 1|
|Strain of Origin||129S6/SvEvTac|
|Molecular Note||A targeting vector was designed to insert loxP sites to flank exon IV. A floxed neo was included in the vector. This allele acts as a hypomorph with expression suppressed to 30%.|
Heterozygous and homozygous mice are both viable and fertile. When maintaining a live colony, heterozygous mice may be bred together or to wildtype mice from the colony. Homozygous mice may also be bred together.
When using the Ndel1cko(IV) hypomorphic conditional knock-out mouse strain in a publication, please cite the originating article(s) and include JAX stock #026958 in your Materials and Methods section.