Monocular enucleation profoundly reduces secretogranin II expression in adult mouse visual cortex

Secretogranin II (ScgII), a member of the chromogranin family, is almost exclusively found in large dense core vesicles of a wide variety of endocrine and neuronal tissues, being stored together with many different neurotransmitters, peptide hormones and neuropeptides. In the brain ScgII is almost completely processed to secretoneurin, a peptide involved in neurite outgrowth, neuroprotection and neuronal plasticity. Furthermore, correlations with neurotransmitter release and a variety of neurological diseases were reported. In this study we examined possible changes in ScgII mRNA expression in the visual system of adult mice after removal of one eye. Mice were monocularly deprived of vision and sacrificed 1 day or 1, 3, 5 and 7 weeks after enucleation. Starting 1 day after the deprivation, a marked decrease of ScgII was visible in the contralateral visual cortex. Recovery initiated in the lateral supragranular visual cortex after 5 weeks of enucleation, but was far from complete in the 7 week animals, especially in the monocularly driven medial cortex. By comparison with the immediate early gene zif268, it was proven that ScgII cannot be categorized as an activity marker, but more likely plays a role in visual system plasticity by modulating a range of neurotransmitters and neuropeptides.