Because genetic approaches do not rely on previous assumptions, details about the mechanisms mediating development of the visual system and forebrain can be uncovered that might not be identifiable using other means. Genes involved in eye development. We are currently studying aniridia in humans and the Small eye trait in rodents. Individuals afflicted with this disease typically feature severe hypoplasia of the iris and may have associated defects including corneal opacification, cataracts, and hypoplasia of the ciliary body and retina. This combination of ocular defects results in poor visual acuity early in life and can lead to blindness.
Small eye is the mouse model for aniridia.
Aniridia and Small eye are caused by mutations in the PAX6 gene. PAX6, a paired-box transcription factor, is important for development of the eye, forebrain, and subsets of neurons within the brain and spinal cord. Homozygous mutations result in absence of the eyes and nose, loss of forebrain structures, disruption of axon tracts, abnormal neuronal migration, and misspecification of neurons. Although mutations in the PAX6 gene cause aniridia, there are cases in which the PAX6 gene is unaffected. We subsequently identified this gene in rodents, zebrafish, Drosophila , and C. elegans .