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More than 100 genes have been mapped that cause inherited blinding diseases. The majority affect the outer layer of the retina, which is composed of photoreceptor cells and retinal pigment epithelium. Gene therapy is a potential means of correcting defects in specialized cellular structures that mediate phototransduction or visual pigment regeneration, as illustrated by a paper in this issue.
The extent of linkage disequilibrium critically determines the efficiency of strategies to identify genetic variants that predispose to human disease. New data indicate that the extent of disequilibrium is highly variable across the genome, and that differences in disequilibrium levels between isolated and mixed populations are modest.
Fetal nutrition depends on the placenta, and specifically, the branching of a layer of placental trophoblast cells that sits between the maternal blood and fetal blood vessels. The discovery that expression of the transcription factor Gcm1 in trophoblast stem cells regulates branching of this specialized epithelium offers new insights into a process whose pivotal features have been generally obscure.
