Abstract
Purpose: :
Activity is an important modulator of gene expression in neurons throughout the central nervous system. In particular, L-type voltage dependent calcium channels (VDCCs) are thought to play a key role in the modulation of gene expression that occurs during development and neuronal plasticity. During normal postnatal retinal development, spontaneous activity in the form of retinal waves is prominent until eye-opening (P11-P13), when waves cease. In Nyxnob (nob) mice, in which signaling is absent in depolarizing bipolar cells (DBCs), retinal waves and abnormal spontaneous activity are maintained into adulthood. This developmental defect is correlated both with abnormal visual responses of RGCs and an aberrant segregation of their axonal projections to the dorsal lateral geniculate nucleus. The purpose of this study was to examine the impact of abnormal activity in the nob retina on gene expression levels of L-type VDCCs subunits during postnatal development.
Methods: :
Three to five retinas were isolated from C57Bl/6J (WT) and nob mice at postnatal day (P): 1, 3, 5, 7, 13, 21, 26 and from adult mice. From these pooled samples, total RNA was isolated and cDNA was synthesized, using superscript III reverse transcriptase. We used real time PCR used to quantitatively assess the levels of expression of the three α1 and all four β subunits of L-type VDCCs (Cacn1f, Cacn1c and Cacn1d; and Cacnb1-4) present in retina as a function of postnatal development. We also measured the expression levels of Grm6 and Nyx, two genes expressed in DBCs.
Results: :
In WT retinas, expression of all genes, except Cacnb3, peaked at eye opening (P11-13), correlating with the peak of retinal synapse maturation. In nob retina, the expression of Grm6 was similar to WT. In contrast, the expression of all VDCC subunits was depressed in nob retina at every time point compared to WT.
Keywords: gene/expression • photoreceptors • retina