These ephrin A2/ephrin A5 double mutant mice may be useful in studies of retinocollicular mapping, axon topography, neuron projection, and modality-specific compartmentalization of visual, auditory, and somatosensory thalamic relay pathways.
David Feldhiem, University of California at Santa Cruz
Mice homozygous for both targeted mutations are viable, fertile, and normal in size. While the donating investigator reports that 10-20% of females homozygous at both loci neglect their litters, no such neglect is reported in the colonies at The Jackson Laboratory (Aug 2009). Double homozygous mice have no endogenous protein expression in inferior colliculus (IC) or superior colliculus (SC), and thus lack the concentration gradient created by the endogenous proteins across the midbrain in wildtype mice. Temporal and nasal retinal axon termination is severely altered: multiple ectopic aborizations in the SC indicate abnormalities in both anteroposterior and dorsoventral topography. Following surgical ablation of portions of the midbrain (including IC and SC), cross-modal innervation by retinal neurons is greater in double homozygous mutants compared to wildtype. Mice heterozygous at both loci are reported to have greater reproductive performance compared to double homozygous mice. Further, double heterozygotes have temporal (but not nasal) retinal axon aborization in the SC with diminished frequency and severity. These ephrin A2/ephrin A5 double mutant mice may be useful in studies of retinocollicular mapping, axon topography, neuron projection, and modality-specific compartmentalization of visual, auditory, and somatosensory thalamic relay pathways.
These mice harbor two targeted mutations; ephrin A2 and ephrin A5. For the ephrin A2 targeted mutation, a targeting vector was designed to insert a neomycin cassette in exon 2 after amino acid 66 (and just upstream of a cysteine repeat motif conserved throughout the ephrin family) of the Efna2 gene. The construct was electroporated into 129S6/SvEvTac-derived TC1 embryonic stem (ES) cells. Chimeric mice were bred with 129/SvEv mice. Mutant offspring were crossed to create homozygous mutant mice (Efna2-/-). The ephrin A5 targeted mutation was independently created by replacing the portion of Efna5 exon 2 encoding amino acids 42-129 with a PGK-neo cassette. The construct was electroporated into (129X1/SvJ x 129S1/Sv)F1-derived R1 ES cells. Chimeric mice were bred with C57BL/6 mice. Mutant offspring were crossed to Swiss Webster mice and then made homozygous for this mutation (Efna5-/-). Double mutant mice were obtained by crossing Efna2-/- in a 129/SvEv background with a Efna5-/- in a mixed background (Swiss-Webster, C57BL/6, 129). Upon arrival at The Jackson Laboratory, double mutant mice were bred with C57BL/6J for at least one generation to establish the colony.
|Allele Name||targeted mutation 1, Dennis D M O'Leary|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||A5-; eA5KO; ephrin-A5-|
|Gene Symbol and Name||Efna5, ephrin A5|
|Strain of Origin||(129X1/SvJ x 129S1/Sv)F1-Kitl+|
|Molecular Note||A neomycin selection cassette replaced sequence encoding amino acids 42 through 129 as well as a 5' splice acceptor. RT-PCR analysis showed an absence of transcript in homozygous mutant mice.|
|Allele Name||targeted mutation 1, John G Flanagan|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||A2-; ephrin-A2-|
|Gene Symbol and Name||Efna2, ephrin A2|
|Strain of Origin||129S6/SvEvTac|
|Molecular Note||A neomycin selection cassette, containing stop codons in all three reading frames, was inserted after the sequence encoding amino acid 66. The insertion was upstream of a conserved cysteine residue motif. RT-PCR analysis of midbrain RNA showed an absence of transcript in homozygous mutant embryos.|
When maintaining a live colony, mice that are homozygous for the Efna2tm1Jgf and heterozygous for the Efna5tm1Ddmo mutations are bred to mice that are heterozygous for the Efna2tm1Jgf and homozygous for the Efna5tm1Ddmo mutation. The donating investigator reports that 10-20% of females homozygous at both loci neglect their litters.
When using the STOCK Efna2tm1Jgf Efna5tm1Ddmo/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #005992 in your Materials and Methods section.