The α-crystallin small heat shock proteins contribute to the transparency and refractive properties of the vertebrate eye lens and prevent the protein aggregation that would otherwise produce lens cataracts, the leading cause of human blindness. There are conflicting data in the literature as to what role the α-crystallins may play in early lens development. In this study, we used CRISPR gene editing to produce zebrafish lines with mutations in each of the three a-crystallin genes (cryaa, cryaba and cryabb) to prevent protein production. The absence of each α-crystallin protein was analyzed by mass spectrometry, and lens phenotypes were assessed with differential interference contrast microscopy and histology. Loss of αA-crystallin produced a variety of lens defects with varying severity in larval lenses at 3 and 4 dpf but little substantial change in normal fiber cell denucleation. Loss of αBa-crystallin produced no substantial lens defects. Our cryabb mutant produced a truncated aBb-crystallin protein and showed no substantial change in lens development. Mutation of each α-crystallin gene did not alter the mRNA levels of the remaining two, suggesting a lack of genetic compensation. These data suggest that αA-crystallin plays some role in lens development, but the range of phenotype severity in null mutants indicates its loss simply increases the chance for defects and that the protein is not essential. Our finding that cryaba and cryabb mutants lack noticeable lens defects is congruent with insubstantial transcript levels for these genes in lens epithelial and fiber cells through five days of development. Future experiments can explore the molecular mechanisms leading to lens defects in cryaa null mutants and the impact of αA-crystallin loss during zebrafish lens aging.

This dataset includes micrographs of the gross anatomy of PTU-treated zebrafish larvae and differential interference contrast microscopy of their eyes showing the lens. Included are sets of images at 3 and 4 days post fertilization of wild type fish, mutants for three α-crystallin genes (cryaa, cryaba and cryabb) and crispants for cryaa. All larvae were imaged at 45X total magnification and eyes at 200X total magnification. Also included are images of stage micrometers photographed at each magnification. These micrometer images were used to measure total larval length and lens diameter for all images.

These images were used to analyze lens size versus body length and to quantify the presence of lens defects, found in figures 4 and 5 in the linked manuscript. Three data seta do not contain images of larvae and were only used to quantify presence of lens defects: “112221 cryaa 3 dpf”, “102620 crispants 3 dpf” and “121421 crispants 4 dpf”. Quantified data and R scripts used to analyze these images can be found in the following GitHub repository: github.com/masonfromohio/alpha-crystallin-CRISPR-Rscripts

All image files are found as TIFF files and can be opened in any image viewer or editor. Larval length and eye lens diameters were measured using ImageJ and analyzed with R. The R scripts used to analyze these images can be found in the following GitHub repository: github.com/masonfromohio/alpha-crystallin-CRISPR-Rscripts