Mice homozygous for the Pitx2egl1 R115L point substitution on this C57BL/6J background provide a fully penetrant model for early-onset glaucoma, developing elevated intraocular pressure by five weeks of age, which subsequently becomes more severe. The size of the eye is similar to that of controls until 13 weeks of age when the eyes are larger. Image guided optical coherence tomography at three months of age shows enlargement of the anterior chamber and optic cupping, which presents as a ring-like feature around the optic nerve head by indirect ophthalmoscopy. Histology at 3 months of age shows optic head cupping, anterior synechia and a complete loss of the inner retinal layers. Functionally, at three months of age the rod a-wave is normal but there is a loss of rod b-waves and lower cone electroretinogram response. This ENU-induced mutation was mapped between D3Mit106 and D3Mit291 and found to be a single G to T transversion in Pitx2 exon 2 that changes amino acid 115 from arginine to leucine.
C57BL/6J males were treated with N-ethyl-N-nitrosourea and bred to C57BL/6J females and their male offspring were backcrossed to C57BL/6J females and their offspring were then backcrossed to their father to generate a population of mutants segregating for the recessive mutations of that N1 male. In that population a mouse was identified that had a shortened face and enlarged eyes. This mutant was backcrossed again to C57BL/6J and the shortened face phenotype bred away from the ocular phenotype, which was then maintained by sibling intercrossing to homozygosity. This strain reached sibling generation F32 in 2018.
|Allele Name||early-onset glaucoma 1|
|Allele Type||Chemically induced (ENU) (Not Specified)|
|Gene Symbol and Name||Pitx2, paired-like homeodomain transcription factor 2|
|Strain of Origin||C57BL/6J|
|Molecular Note||This ENU-induced G to T transversion at position 344 in exon 2 is predicted to cause the arginine at amino acid 115 to become a leucine.|