Human Studies Of Poag

Linkage studies At least six loci for autosomal dominant POAG have been mapped through linkage studies, termed GLC1A-F, on chromosomes 1q23, 2cen-q13, 3q21-q24, 8q23, 10p15-p14, and 7q35-q36. A genome-wide scan in multiple small families from an Afro-Caribbean population provided significant evidence for linkage to regions on chromosomes 2q (but separate from the Mendelian POAG locus GLC2B and the infantile glaucoma locus GLC3A on chromosome 2) and 10p. Presumably, these represent loci for glaucoma risk factors common in the general population, as do the loci on chromosomes 2, 14, 17, and 19, identified by examining siblings in an American population of European descent. It is particularly important to note that few of these studies have been confirmed; especially the technically more difficult and laborious studies of POAG in the general population.

Association studies In addition to the identification of myocilin as a causative gene in glaucoma described earlier, which was carried out by linkage studies primarily in families with juvenile glaucoma and very elevated intraocular pressure, association studies have identified sequence changes in myocilin as a risk factor in a small percentage of POAG cases. Two additional genes have been shown to be involved in glaucoma by demonstrating an association between sequence changes in those genes and glaucoma in population studies. One of these genes is optineurin, for which the strongest associations have been obtained with normal tension glaucoma, but which also might be associated with POAG in some populations. A second is the OPA1 gene, which is known primarily as a cause of optic atrophy, but is also associated with normal tension glaucoma, though not with high tension primary open angle glaucoma in most studies. Association of both these genes with normal tension glaucoma suggests that

Figure 68.5 A. Diagram depicting the flow of aqueous humor from synthesis in the ciliary body to exit from the anterior chamber through the trabecular meshwork and Schlem's canal. B. Histological section showing an excavated optic cup in an individual with glaucoma. Courtesy of Dr. Chi Chao Chan, National Eye Institute, National Institutes of Health, from the collection of Dr. W. R. Green.

Figure 68.5 A. Diagram depicting the flow of aqueous humor from synthesis in the ciliary body to exit from the anterior chamber through the trabecular meshwork and Schlem's canal. B. Histological section showing an excavated optic cup in an individual with glaucoma. Courtesy of Dr. Chi Chao Chan, National Eye Institute, National Institutes of Health, from the collection of Dr. W. R. Green.

there may be some relationship between normal tension glaucoma and optic atrophy, and also emphasizes the importance of genetic changes that sensitize the retina and optic nerve to minor elevations of even normal intraocular pressure.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

Get My Free Ebook


Post a comment