Abstract
Purpose :
Cap2 encodes a cytoskeletal protein involved in the regulation of actin. Here, we applied iSyTE (integrated Systems Tool for Eye gene discovery)–which in the past has identified several cataract-linked genes–to predict Cap2 as a key factor in the lens. iSyTE analysis indicates that Cap2 is highly expressed in the lens from embryonic stages through adulthood, becoming lens-enriched from lens vesicle stage at mouse embryonic (E) day 11.5. Interestingly, iSyTE also shows that Cap2 is mis-expressed in mice exhibiting lens defects and/or cataract that are deficient for lens-regulatory genes such as Pax6, Notch2 and Hsf4. Further, the Cvekl lab has identified Cap2 as a positively controlled direct target of Pax6 in lens cells. Thus, we sought to investigate the role of Cap2 in the lens.
Methods :
To examine the significance of Cap2 in the lens, Cap2 germline targeted knockout (Cap2-/-) mice were generated in C57/BL6 background. Lens tissue was examined by histological analysis using hematoxylin and eosin staining. Scanning electron microscopy was used to examine, at high-resolution, the cellular morphology of the lens. Staining of lens tissue sections by Wheat germ agglutinin (WGA) and Phalloidin was performed to evaluate cell morphology and F-actin distribution of lens cells.
Results :
Histological analysis demonstrated that Cap2-/- mice have smaller lens compared to control at age 3 months. Scanning electron microscopy revealed altered fiber cell morphology in 3 month old Cap2-/- mouse lens. Phalloidin staining revealed abnormal distribution of F-actin in Cap2-/- lens fiber cells. Specifically, compared to control, F-actin appeared abnormally abundant near the short sides of the hexagons of Cap2-/- lens fiber cells that had undergone nuclear degradation. In agreement with these findings, WGA staining showed abnormal lens fiber cell morphology in Cap2-/- mice. Specifically, the broad-side of the hexagonal fiber cells were significantly longer in Cap2-/- mice.
Conclusions :
These data identify Cap2 as a new factor involved in the control of F-actin distribution in post-nuclear degradation lens fiber cells. Taken in the context of our other new findings that Tdrd7-/- mice exhibit morphological abnormalities specifically in fiber cells that have undergone nuclear degradation, these new data suggests that distinct mechanisms involving factors such as Cap2 and Tdrd7 function in the control of cellular morphology in lens fiber cell differentiation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.