Expression and Distribution of Mesencephalic Astrocyte-Derived Neurotrophic Factor in the Retina and Optic Nerve

Abstract

Mesencephalic astrocyte-derived neurotrophic factor (MANF), otherwise named Arginine-Rich, Mutated in Early-stage Tumors (ARMET), is a secretory endoplasmic reticulum stress (ERS) protein that is widely expressed in mammalian tissues. To date, little is known about the distribution and expression of MANF in the retina and optic nerve (ON). Therefore, we studied the expression and distribution of MANF in the ON and retina by real-time PCR, immunofluorescence staining and western blotting. Results from rat and mouse were highly consistent in the retina. MANF was detected in both tissues in rat, wherein it was principally localized to the ganglion cell layer (GCL), followed by the inner nuclear layer (INL). The MANF protein levels in the rat retina were 3.33-fold higher than in the rat ON. Additionally, MANF was robustly expressed by retinal ganglion cells (RGCs) in the human retina. In human ON, MANF was partially co-localized with glial fibrillary acidic protein (GFAP), suggesting that it was not restricted to astrocytes. In vitro studies confirmed that MANF could be robustly expressed in RGCs and was found principally within the cytoplasm. Hypoxia can stimulate up-regulation by of MANF expression over time, suggesting that MANF may play a vital role in the functional regulation of RGCs both in health and disease. We believe that the present study improves our understanding of the distribution and expression of MANF in the retina and ON and could help in further analysis of its interact and correlate with the relevant ophthalmic diseases.

Identification of Mesencephalic Astrocyte-Derived Neurotrophic Factor as a Novel Neuroprotective Factor for Retinal Ganglion Cells

“…As we have previously described Gao et al (2017) , immunofluorescence staining shows that MANF is predominantly localized in the ganglion cell layer and inner nuclear layer in both rat and human retinas ( Figures 1A,B ). To determine if the MANF expression in the ganglion cell layer was specific to the RGCs, primary cultured RGCs were used for in vitro validation.…”

“…Recently, studies conducted at the University of Helsinki demonstrated that the concentration of MANF is increased in the serum in children with type 1 diabetes, which indicated that MANF may be used as a potential therapeutic protein for diabetes ( Galli et al, 2016 ). Furthermore, our recent studies showed that MANF could be robustly expressed in RGCs and that hypoxia can stimulate the up-regulation of MANF expression over time, which suggested that MANF may play a vital role in the functional regulation of RGCs in both health and disease ( Gao et al, 2017 ).…”

Functional analysis of mesencephalic astrocyte‐derived neurotrophic factor in retinal ganglion cells under oxidative stress

“…Recently, MANF has been implicated in several nervous system disorders 17,22 . Furthermore, several reports have determined that MANF promotes optic nerve survival and plays a role in ophthalmic diseases 23‐25 . In this study, we have shown that MANF might play an important role in extension of neurites and cell death in RGCs.…”

“…Recent reports have indicated that MANF protects dopaminergic neurons and other cell types in animal models of Parkinson's disease, Alzheimer's disease and brain ataxia 17,22 . Although several reports have shown that MANF is associated with optic nerve survival and ophthalmic diseases, 23‐25 little is known about the neuroprotective function of MANF for RGC survival in glaucoma.…”

Neuroprotective and reparative effects of endoplasmic reticulum luminal proteins – mesencephalic astrocyte-derived neurotrophic factor and cerebral dopamine neurotrophic factor

“…MANF is expressed in the human retina and optic nerve (35), and it protects retinal ganglia cells from hypoxia and apoptotic injury in vitro and in vivo (36). MANF in D. melanogaster (DmMANF) was also found to be expressed in the fly visual system neurons and glia, and its removal caused degeneration of glial cells (37).…”