Comparative proteomics in captive giant pandas to identify proteins involved in age-related cataract formation

Abstract 20% of the aged giant pandas in captivity have developed cataracts that impair their quality of life. Hardness and curvature of the panda's lens make it difficult to replicate in vitro. Therefore, early prediction will be the most effective way to prevent the occurrence of cataract in giant pandas. We carried out a quantitative proteomics analysis of 10 giant pandas to identify proteins differing in abundance between healthy and cataract-bearing animals. We identified almost 150 proteins exceeding our threshold for differential expression, most of which were associated with GO categories suggesting extracellular localization. The most significant differential abundance was associated with components of the proteasome and other proteins with a role in proteolysis or its regulation, most of which were depleted in pandas with cataracts. Other modulated proteins included components of the extracellular matrix or cytoskeleton, as well as associated signaling proteins and regulators, but we did not find any differentially expressed transcription factors. These results indicate that the formation of cataracts involves a complex network of signaling inside and outside lens cells to drive a stress response mainly at the protein level as a means to address the accumulation of protein aggregates triggered by oxidative damage. The modulated proteins also suggests that it should be possible to predict the onset of cataracts in captive pandas by taking blood samples and testing them for the presence or absence of particular protein markers.