Abstract
We investigated the time course of the expression of several activity-dependent genes evoked by visual inputs in the primary visual cortex (V1) in adult marmosets. In order to examine the rapid time course of activity-dependent gene expression, marmosets were first monocularly inactivated by tetrodotoxin (TTX), kept in darkness for two days, and then exposed to various length of light stimulation. Activity-dependent genes including HTR1B, HTR2A, whose activity-dependency were previously reported by us, and well-known immediate early genes (IEGs), c-FOS, ZIF268, and ARC, were examined by in situ hybridization. Using this system, first, we demonstrated the ocular dominance type of gene expression pattern in V1 under this condition. IEGs were expressed in columnar patterns throughout layers II–VI of all the tested monocular marmosets. Second, we showed the regulation of HTR1B and HTR2A expressions by retinal spontaneous activity, because HTR1B and HTR2A mRNA expressions sustained a certain level regardless of visual stimulation and were inhibited by a blockade of the retinal activity with TTX. Third, IEGs dynamically changed its laminar distribution from half an hour to several hours upon a stimulus onset with the unique time course for each gene. The expression patterns of these genes were different in neurons of each layer as well. These results suggest that the regulation of each neuron in the primary visual cortex of marmosets is subjected to different regulation upon the change of activities from retina. It should be related to a highly differentiated laminar structure of marmoset visual systems, reflecting the functions of the activity-dependent gene expression in marmoset V1.
Highlights
The primary visual cortex (V1) of primates is estimated to occupy more than 30% of the cerebral cortex (Collins et al, 2012)
OF THE RESULTS In this study, we carried out a series of monocular visual stimulation experiments using adult marmosets to investigate the time course of a group of activity-dependent genes in V1
The first conclusion from the series of experiments was that all activity-dependent genes clearly revealed the ocular dominance type of expression pattern in monocular stimulated marmoset V1
Summary
The primary visual cortex (V1) of primates is estimated to occupy more than 30% of the cerebral cortex (Collins et al, 2012). We previously showed that the expression of a group of genes, such as OCC1 (FSTL1), 5-hydroxytryptamine (serotonin) receptor 1B and 2A (HTR1B and HTR2A, respectively), Testican-1, and Testican-2, are highly enriched in the thalamorecipient layers of V1 of adult macaques (Tochitani et al, 2001; Takahata et al, 2009; Watakabe et al, 2009). Their V1enriched expression patterns were conserved in several species of primate but not in ferrets and mice (Takahata et al, 2008, 2012), suggesting that there are primate-specific mechanisms for expression of these genes. Whereas this experiment revealed the requirement for retinal activity in gene expression in V1, it has not been clear how the incoming visual inputs induce the expression of these genes
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