Interacting loci cause severe iris atrophy and glaucoma in DBA/2J mice

Area of Science:

• Ophthalmology
• Genetics
• Animal Models

Background:

• Glaucomas are a leading cause of blindness, often linked to elevated intraocular pressure (IOP) and retinal ganglion cell death.
• Anterior segment abnormalities, including pigment dispersion syndrome (PDS) and iris atrophy, are associated with some human glaucomas, but their causes are poorly understood.
• The DBA/2J mouse strain spontaneously develops glaucoma with anterior segment changes, serving as a relevant model.

Purpose of the Study:

• To identify genetic loci contributing to anterior segment abnormalities and glaucoma in the DBA/2J mouse model.
• To investigate the genetic relationship between iris pigment dispersion, iris stromal atrophy, and glaucoma development.
• To explore conserved synteny between mouse and human chromosomal regions associated with glaucoma and PDS.

Main Methods:

• Cross-breeding of DBA/2J mice with C57BL/6J mice to generate segregating populations.
• Quantitative trait locus (QTL) analysis to map genetic loci influencing anterior segment phenotypes.
• Phenotypic characterization of progeny for iris pigment dispersion and iris stromal atrophy.

Main Results:

• Two major quantitative trait loci (QTLs) were identified: 'ipd' on chromosome 6, associated with iris pigment dispersion, and 'isa' on chromosome 4, linked to iris stromal atrophy.
• The 'ipd' locus shows conserved synteny with human chromosome 7q, a region associated with PDS.
• Homozygosity for DBA/2J alleles at both 'ipd' and 'isa' loci resulted in earlier onset and more severe glaucoma-like phenotypes.

Conclusions:

• Genetic factors on mouse chromosomes 4 and 6 significantly influence the development of anterior segment abnormalities and glaucoma.
• The 'ipd' locus may harbor genes critical for iris pigment dispersion, with implications for understanding human PDS.
• The 'isa' locus, potentially involving the Tyrpl gene, contributes to iris atrophy and glaucoma severity, highlighting the role of pigment production in disease pathogenesis.