Abstract
Abstract: :
Purpose:Both retina and retina explants are excellent model systems to study neural development. Retina explant cultures have been used extensively for genetic, biochemical, and molecular biological studies of retina development. Although its morphological and differentiation features are similar to retinal development in vivo, it is unclear whether these two systems have similar gene expression profiles. To obtain this information and be more confident in the explants as a model system, we have carried out a serial of experiments comparing gene expression between retinas collected in vivo and in vitro. Methods:C57Bl/6 pregnant mice were used for these studies. Half of the animals from each litter were used for in vitro explant cultures and the other half maintained in vivo. For the explant culture groups, retinas were isolated at postnatal day 1 (PN1). After day 1, 3, 5, 7, 10, and 15 in culture, explanted retinas and the retinas of littermates were collected for RNA preparation. RNA from paired PN2, PN4, PN6, PN8, PN11, and PN16 time points were used for microarray experiments and analysis. Results:We first focused on the expression patterns of genes, including Rhodopsin, Sag, Prph2, Revrn, Rom1, Gng1, Rbp3, Pde6b, Pde6g, Guca1a, Abca4, Rpgrip1, Nrl, and Nr2e3, which are rod photoreceptor specific or enriched during retina development. At the early experimental times (from PN1 to PN4), the majority of the genes showed low expression levels, with only a minor tendency for reduced expression in explants compared with in vivo retina. Two transcription factors however, Nrl and Nr2e3, were significantly reduced during the first four days in culture. The low–point of reduced gene expression in explants is PN6 (after culture for 5 days), a time at which the majority of rod genes are starting to be expressed at this moment. After 7 days in culture, however, rod gene expression levels begin to approach those levels found in vivo. At PN8, especially, the expression levels of the two transcription factors, Nrl and Nr2e3, reach normal levels compared to in vivo retina. We also analyzed distinct sets of genes with higher or lower expression profiles at different developmental stages. Conclusions:This study provides fundamental information of gene expression during explant and natural retina development and also provides the basis for experimental design of retina developmental study in vitro. In general explant cultures undergo a short period of arrested development but then catch up and closely mimic many features of normal retinal development.
Keywords: gene microarray • retinal development • retinal culture