Abstract
Purpose: :
To study the developmental expression of ZBED4 in retina. Recently, we reported on the characterization of ZBED4 mRNA and its encoded protein, which in adult human retina is expressed in cones and Muller cell endfeet. As a first step to determine the role of ZBED4 in retina, we followed its expression and quantified its level throughout the mouse life. We also compared the localization of ZBED4 in mouse retina with that in rat, cow, chicken and human retinas.
Methods: :
Expression was determined by Northern and Western blotting of retinal mRNAs and proteins, respectively, and by immunostaining of retinal sections. Antibodies used were against ZBED4, proliferating cell nuclear antigen (PCNA), glutamine synthase, vimentin, and BRN3a. Quantitative real-time RT-PCR was carried out to measure ZBED4 mRNA levels at different developmental times.
Results: :
In contrast with humans, mice and rats have two ZBED4 transcripts that only differ in the presence of one additional non-coding exon. In the adult mouse, highest expression of ZBED4 mRNA is detected in thymus, with lower levels in retina. Interestingly, mouse embryos also have high levels of ZBED4 mRNA. QPCR showed a decrease in the relative amount of retinal ZBED4 mRNA from embryonic levels to P4 and P12, followed by a gradual increase that reaches its maximum at P40 and remains the same thereafter. Also in contrast with the ZBED4 localization in cones of human, cow and chicken retinas, the majority of ZBED4 in adult mouse and rat retinas is found in the endfeet of Muller cells and in their processes. Developmentally, ZBED4 is first seen at both the outer and vitreal borders of the retina and it extends throughout the retina by E18 and P0. Between P6 and P9 ZBED4's expression becomes more localized to the inner retina, and from then until P30 it is reduced to the innermost layer. ZBED4 co-localizes with Muller cells but not with other cell types in mouse retina.
Conclusions: :
The patterns of spatial and temporal expression suggest a possible role for ZBED4 in retinal morphogenesis.
Keywords: gene/expression • microscopy: light/fluorescence/immunohistochemistry • Muller cells