Abstract
BackgroundLittle is known about genetic factors affecting intraocular pressure (IOP) in mice and other mammals. The purpose of this study was to determine the IOPs of genetically distinct mouse strains, assess the effects of factors such as age, sex and time of day on IOP in specific strain backgrounds, and to assess the effects of specific candidate gene mutations on IOP.ResultsBased on over 30 studied mouse strains, average IOP ranges from approximately 10 to 20 mmHg. Gender does not typically affect IOP and aging results in an IOP decrease in some strains. Most tested strains exhibit a diurnal rhythm with IOP being the highest during the dark period of the day. Homozygosity for a null allele of the carbonic anhydrase II gene (Car2n) does not alter IOP while homozygosity for a mutation in the leptin receptor gene (Leprdb) that causes obesity and diabetes results in increased IOP. Albino C57BL/6J mice homozygous for a tyrosinase mutation (Tyrc-2J) have higher IOPs than their pigmented counterparts.ConclusionsGenetically distinct mouse strains housed in the same environment have a broad range of IOPs. These IOP differences are likely due to interstrain genetic differences that create a powerful resource for studying the regulation of IOP. Age, time of day, obesity and diabetes have effects on mouse IOP similar to those in humans and other species. Mutations in two of the assessed candidate genes (Lepr and Tyr) result in increased IOP. These studies demonstrate that mice are a practical and powerful experimental system to study the genetics of IOP regulation and disease processes that raise IOP to harmful levels.
Highlights
Little is known about genetic factors affecting intraocular pressure (IOP) in mice and other mammals
There is a wide range of IOP with strain BALB/cJ having one of the lowest average IOPs (11.1 ± 0.5 mmHg) and strain CBA/CaJ one of the highest IOPs (19.3 ± 0.3 mmHg)
IOP differences are reproducible and amenable to genetic analyses We report the IOPs of over 30 genetically different mouse strains that were housed in the same environmental conditions
Summary
Little is known about genetic factors affecting intraocular pressure (IOP) in mice and other mammals. Glaucoma involves retinal ganglion cell death and optic nerve damage that is often associated with elevated intraocular pressure (IOP) [1,2,3,4,5]. It is becoming increasingly clear that many forms of glaucoma have a genetic component [6,7], and much current research is focused on identifying chromosomal regions and genes that contribute to glaucoma [8,9,10]. Identifying such loci allows screening for individuals with an increased risk of developing glaucoma [11]. Mice are expected to be extremely helpful in characterizing genes and mechanisms that affect IOP or the susceptibility of the optic nerve and retina to glaucomatous damage [20]
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