Role of the executioner caspases during lens development

Area of Science:

• Ophthalmology
• Cell Biology
• Molecular Biology

Background:

• Cell death pathways are implicated in lens organelle degradation.
• Executioner caspases (caspase-3, -6, -7) are central to apoptosis.
• Their specific roles in lens fiber cell differentiation and organelle loss are unclear.

Purpose of the Study:

• To investigate the direct role of executioner caspases in mouse lens fiber cell differentiation and organelle degradation.
• To determine the expression and activity of caspases -3, -6, and -7 in the developing lens.

Main Methods:

• Real-time RT-PCR and Western blot analysis to detect caspase mRNA and protein.
• Assays for endogenous caspase proteolytic activity.
• Analysis of lenses from caspase-deficient mice (knock-outs) and double knock-outs.
• Confocal microscopy to map lens organelle distribution.

Main Results:

• Caspase-3, -6, and -7 transcripts were found in lens fiber cells; caspase-6 and -7 proteins were detected. Caspase-3 activity was present, but not for -6 or -7.
• Caspase-3 deficient lenses showed anterior cataracts; other knock-outs were grossly normal.
• No significant difference in the organelle-free zone (OFZ) was observed in single or double knock-out lenses.
• Staurosporine induced caspase-3 and -6 activity.

Conclusions:

• Executioner caspases are not required for lens organelle removal during fiber cell differentiation.
• Caspase-3 activity appears necessary for maintaining lens transparency, independent of organelle degradation.
• Further investigation into caspase-3's specific function in lens clarity is warranted.