Hsp25 and Hsc70 Expression in Retina of trkB Transgenic Mice and Their Wild–Type Controls

Abstract

Abstract: : Purpose: Cells and tissues are constantly exposed to acute and chronic environmental stress which may lead to alterations in protein structure and functions. In order to adapt to the prevailing conditions, evolutionarily highly conserved heat shock proteins (Hsps) are expressed. Hsps function as molecular chaperones. They, thus, normalize homeostatic conditions in response to different kinds of chemical and physical stresses. In addition, Hsps regulate growth and development processes. Brain derived neurotrophic factor (BDNF) has been suggested to support the survival of retinal cells. In the present study, we investigated whether 1) the overexpression of the dominant–negative truncated splice variant of BDNF receptor trkB (trkB.T1 mice), and, in contrast, 2) the overexpression of the full–length trkB receptor (trkB.TK+ mice), affect the expression of the 25 kDa heat shock protein (Hsp25) and the 70 kDa heat shock cognate protein (Hsc70) in the mouse retina. Methods: TrkB.T1, trkB.TK+ mice and their wild–type controls were sacrificed, eyes were enucleated, embedded into paraffin and cut into 5 µm sections. Sections were stained for haematoxylin/eosin and immunostained for Hsp25 and Hsc70 using 3,3'–diaminobenzidine as a chromogen. The analysis was done using light microscopy. Results: The microscopical structure of transgenic mice and their wild–type controls was identical as was also the immunohistochemical localization of Hsp25 and Hsc70. The Hsp25 immunostaining was observed in the inner plexiform (IPL), outer plexiform (OPL), outer nuclear (ONL) layers and photoreceptor cells (REC). Furthermore, the strongest Hsp25 expression was seen in the retinal pigmentepithelial layer (RPE). The inner nuclear layer (INL) was only weakly stained. The Hsc70 immunostaining was moderate in the retinal ganglion cells and IPL, but the OPL and RPE were strongly stained. In contrast, ONL, INL and REC were almost unstained for Hsc70. Cells located in the INL were immunopositive both for Hsp25 and Hsc70. Conclusions: Changes in the trkB receptor expression do not affect the microscopical structure or immunostaining patterns of Hsp25 and Hsc70 in the mouse retina.

Keywords: transgenics/knock-outs • chaperones • comparative anatomy