Distribution of Cytoglobin in the Mouse Brain.

Stefan Reuss,Thomas Hankeln,Ursula Disque-Kaiser,Sylvia Wystub,Thorsten Burmester

doi:10.3389/fnana.2016.00047

Abstract

Cytoglobin (Cygb) is a vertebrate globin with so far poorly defined function. It is expressed in the fibroblast cell-lineage but has also been found in neurons. Here we provide, using immunohistochemistry, a detailed study on the distribution of Cygb in the mouse brain. While Cygb is a cytoplasmic protein in active cells of the supportive tissue, in neurons it is located in the cytoplasm and the nucleus. We found the expression of Cygb in all brain regions, although only a fraction of the neurons was Cygb-positive. Signals were of different intensity ranging from faint to very intense. Telencephalic neurons in all laminae of the cerebral cortex (CCo), in the olfactory bulb (in particular periglomerular cells), in the hippocampal formation (strongly stained pyramidal cells with long processes), basal ganglia (scattered multipolar neurons in the dorsal striatum, dorsal and ventral pallidum (VP)), and in the amygdala (neurons with unlabeled processes) were labeled by the antibody. In the diencephalon, we observed Cygb-positive neurons of moderate intensity in various nuclei of the dorsal thalamus, in the hypothalamus, metathalamus (geniculate nuclei), epithalamus with strong labeling of habenular nucleus neurons and no labeling of pineal cells, and in the ventral thalamus. Tegmental neurons stood out by strongly stained somata with long processes in, e.g., the laterodorsal nucleus. In the tectum, faintly labeled neurons and fibers were detected in the superior colliculus (SC). The cerebellum exhibited unlabeled Purkinje-neurons but signs of strong afferent cortical innervation. Neurons in the gray matter of the spinal cord showed moderate immunofluorescence. Peripheral ganglia were not labeled by the antibody. The Meynert-fascicle and the olfactory and optic nerves/tracts were the only Cygb-immunoreactive (Cygb-IR) fiber systems. Notably, we found a remarkable level of colocalization of Cygb and neuronal nitric oxide (NO)-synthase in neurons, which supports a functional association.

Highlights

The globin family comprises small porphyrin-containing proteins that reversibly bind O2 by means of an iron (Fe2+) ion of the heme prosthetic group (Weber and Vinogradov, 2001; Wittenberg and Wittenberg, 2003; Burmester and Hankeln, 2014)
Cygb was initially identified as Stellate cell activation-associated protein’’ (STAP) in the mammalian liver (Kawada et al, 2001), but later studies showed a much broader distribution in many different tissues (Asahina et al, 2002; Burmester et al, 2002; Trent and Hargrove, 2002)
Most previous analyses focused on the cellular localization and the function of Cygb in cells of the supportive tissues, leading to the conclusion that modulated Cygb-expression is associated with diseases such as fibrosis or cancer (He et al, 2011; Oleksiewicz et al, 2013; Kawada, 2015; Thuy Le et al, 2015)

Summary

Introduction

The globin family comprises small porphyrin-containing proteins that reversibly bind O2 by means of an iron (Fe2+) ion of the heme prosthetic group (Weber and Vinogradov, 2001; Wittenberg and Wittenberg, 2003; Burmester and Hankeln, 2014). Cygb was first identified in hepatic stellate cells, where it showed enhanced expression in fibrosis, and was named ‘‘Stellate cell activation-associated protein’’ (STAP; Kawada et al, 2001; Asahina et al, 2002). This hemeprotein is expressed in a broad range of tissues and has, received the official designation ‘‘Cygb’’ (Burmester et al, 2002; Schmidt et al, 2004). More detailed studies indicated an exclusively cytoplasmic localization of Cygb in fibroblasts and related cell types such as chondroblasts and osteoblasts (Nakatani et al, 2004; Schmidt et al, 2004)

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Conclusion