Dysregulation of Autophagy Occurs During Congenital Cataract Development in βA3ΔG91 Mice.

PURPOSE: To examine lens phenotypic characteristics in βA3ΔG91 mice and determine if βA3ΔG91 affects autophagy in the lens.

METHODS: We generated a βA3ΔG91 mouse model using CRISPR/Cas9 methodology. Comparative phenotypic and biochemical characterizations of lenses from postnatal day 0 (P0), P15, and 1-month-old βA3ΔG91 and wild-type (WT) mice were performed. The methodologies used included non-invasive slit-lamp examination, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blot, and immunohistochemical (IHC) analyses to determine the levels of autophagy-related genes and proteins. Transmission electron microscopy (TEM) analysis of lenses was performed to assess organelle degradation and the presence of autophagic vesicles. TUNEL staining was used to determine apoptosis in the lens.

RESULTS: Relative to WT lenses, 1-month-old βA3ΔG91 mice developed congenital nuclear cataract and microphthalmia and showed an early loss of endoplasmic reticulum (ER) in the cortex and attenuation of nuclei degradation. This observation was confirmed by TEM analysis, as was the presence of autophagic vesicles in βA3ΔG91 lenses. Comparative IHC and RT-qPCR analyses showed relatively higher levels of autophagy markers (ubiquitinated proteins and p62, LC3, and LAMP2 proteins) in βA3ΔG91 lenses compared to WT lenses. Additionally, βA3ΔG91 lenses showed relatively greater numbers of apoptotic cells and higher levels of cleaved caspase-3 and caspase-9.

CONCLUSIONS: The deletion of G91 in βA3ΔG91 mice leads to higher levels of expression of autophagy-related proteins and their transcripts relative to WT lenses. Taken together, G91 deletion in βA3/A1-crystallin is associated with autophagy disruption, attenuation of nuclei degradation, and cellular apoptosis in the lens, which might be congenital cataract causative factors.