Differential expression of beta-amyloid precursor and Bcl-2 proto-oncogene proteins in the developing dog retina

Hyperphosphorylation of tau protein by calpain regulation in retina of Alzheimer's disease transgenic mouse

Aim to investigate phosphorylated tau expression and its pathogenic mechanism in eye of Alzheimer's disease (AD) transgenic mice. Levels of tau, phosphorylated tau and other related factors (p35/p25, Cyclin-dependent kinase 5 (Cdk5), calpain) were observed by western blot. β-Amyloid (Aβ) plaques and neuron-fibrillary tangles (NFTs) in APP/PS1 double transgenic mice were detected by immuno-histochemistry. We found that hyper-expression of phosphorylated tau was detected in retina, and only a few or no expressed in optic nerve, cornea and lens of transgenic mice. Increased senile plaques (Aβ) and NFTs were observed in transgenic mice accompanying with increased tau phosphorylation. The increased tau phosphorylation was associated with a significant increase in production of p35 and p25, and up-regulation of calpain. In conclusion, phosphorylated tau level was highly expressed in retina of AD transgenic mice. The pathogenic mechanism of AD was triggered by accelerating tau pathology via calpain-mediated tau hyper-phosphorylation in retina of an AD mice model.

APP involvement in retinogenesis of mice

Very few studies have examined expression and function of amyloid precursor protein (APP) in the retina. We showed that APP mRNA and protein are expressed according to the different waves of retinal differentiation. Depletion of App led to an absence of amacrine cells, a 50% increase in the number of horizontal cells and alteration of the synapses. The retinas of adult APP(-/-) mice showed only half as many glycinergic amacrine cells as wild-type retinas. We identified Ptf1a, which plays a role in controlling both amacrine and horizontal cell fates, as a downstream effector of APP. The observation of a similar phenotype in sorLA knockout mice, a major regulator of APP processing, suggests that regulation of APP functions via sorLA controls the determination of amacrine and horizontal cell fate. These findings provide novel insights that indicate that APP plays an important role in retinal differentiation.

Expression of Bcl-2 during the development of rabbit retina

AIM

Programmed cell death or apoptosis plays an important role in retinal development. Bcl-2 is one of the genes whose endproducts regulate apoptosis. This study has examined the expression of Bcl-2 during the development of rabbit retina.

METHOD

Bcl-2 was detected by immunohistochemistry in developing rabbit retinas from embryonic day (E) 15, 22, 26, 29 and postnatal day (PN) 0, 3, 7, 15 and adults.

RESULTS

Faint immunoreactivity in the anuclear layer was observed at E 15, which increased in E 19. Immunoreactivity in certain radially aligned neuroepithelial cells/immature Müller cells could be recognized at E 22 and it progressively increased until in mature Müller cells radial processes were immunoreactive beyond the outer plexiform layer in PN 15 retinas. Immunoreactivity was already present in the optic nerve at E 15 but it decreased with increasing age until it disappeared at the time of birth.

CONCLUSIONS

Observations suggest that Bcl-2 is transiently expressed by ganglion cell axons during embryonic development. Detection of Bcl-2 immunoreactivity in the endfeet and proximal processes of radially aligned neuroepithelial cells/immature Müller cells early during the development, and its persistence in the endfeet and much of radial processes of Müller cells in adult life suggest that these cells possibly play a role in the development of the retinal ganglion cells, and also in the maintenance of the retinal neurons in the adults.