Abstract
Purpose: :
In the Nuc1 spontaneous mutant rat, an unusual feature is the failure of the normal programmed loss of nuclei from lens fiber cells. We have utilized the mutant to investigate the possible role of PKD and Bit1, as anoikis effectors, in normal lens denucleation process.
Methods: :
Immunofluorescence staining was performed on frozen sections of both wildtype (wt) and Nuc1 rat lenses. Various stages examined include embryonic (E) day 19, postnatal (P) day 3 and 10.
Results: :
At E19, both wt and Nuc1 lenses show a similar expression pattern for PKD. The cells in the bow region of the lens and fiber cells at the center of the lens were positive with no expression of PKD detected in the lens epithelium. At P3, wt lenses lost PKD expression in the central fiber cells with weak expression remaining at the equator. A similar pattern was observed at P 10, with further decrease in staining at the equator. In contrast, in Nuc1 homozygous lenses the staining at P3 and P10 was similar to that observed in E19 lenses. Bit1 was expressed both in fiber cells and epithelium at E19. In wt, Bit1 decreased in fiber cells after birth similar to PKD. In contrast, there was no apparent decrease in fiber expression in the Nuc1 lens at P3-P10.
Conclusions: :
Programmed removal of nuclei from the lens fiber cells is thought to occur by a process similar to apoptosis. Anoikis mediated by PKD and Bit1 is apoptosis induced by loss of cell attachment to the extracellular matrix. Our present studies indicate that PKD and Bit1 expression is lost from wt lens fibers during development along with the loss of cell nuclei. In Nuc1 homozygous lens fibers, where nuclei are retained, PKD and Bit1 continue to be expressed after birth. We provide novel evidence that anoikis regulated by PKD and Bit1 may be involved in lens denucleation.
Keywords: apoptosis/cell death • development • immunohistochemistry