Biology subjects

Kaye, T.

Publications and source records attributed to Kaye, T..

3 recordsLinked to original sources

bioRxiv2024

Loss of αBa-crystallin, but not αA-crystallin, increases age-related cataract in the zebrafish lens

The vertebrate eye lens is an unusual organ in that most of its cells lack nuclei and the ability to replace aging protein. The small heat shock protein -crystallins evolved to become key components of this lens, possibly because of their ability to prevent aggregation of aging protein that would otherwise lead to lens opacity. Most vertebrates express two -crystallins, A- and B-crystallin, and mutations in each are linked to human cataract. In a mouse knockout model only the loss of A-crystallin led to early-stage lens cataract. We have used the zebrafish as a model system to investigate the role of -crystallins during lens development. Interestingly, while zebrafish express one lens-specific A-crystallin gene (cryaa), they express two B-crystallin genes, with one evolving lens specificity (cryaba) and the other retaining the broad expression of its mammalian ortholog (cryabb). In this study we used individual mutant zebrafish lines for all three -crystallin genes to determine the impact of their loss on age-related cataract. Surprisingly, unlike mouse knockout models, we found that the loss of the Ba-crystallin gene cryaba led to an increase in lens opacity compared to cryaa null fish at 24 months of age. Loss of A-crystallin did not increase the prevalence of cataract. We also used single cell RNA-Seq and RT-qPCR data to show a shift in the lens expression of zebrafish -crystallins between 5 and 10 days post fertilization (dpf), with 5 and 6 dpf lenses expressing cryaa almost exclusively, and expression of cryaba and cryabb becoming more prominent after 10 dpf. These data show that cryaa is the primary -crystallin during early lens development, while the protective role for cryaba becomes more important during lens aging. This study is the first to quantify cataract prevalence in wild-type zebrafish, showing that lens opacities develop in approximately 25% of fish by 18 months of age. None of the three -crystallin mutants showed a compensatory increase in the expression of the remaining two crystallins, or in the abundant {beta}B1-crystallin. Overall, these findings indicate an ontogenetic shift in the functional importance of individual -crystallins during zebrafish lens development. Our finding that the lens-specific zebrafish Ba-crystallin plays the leading role in preventing age-related cataract adds a new twist to our understanding of vertebrate lens evolution.

developmental biology↗

bioRxiv2021

Effects of α-crystallin gene knockout on zebrafish lens development

The -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 -crystallins may play in early lens development. In this study, we used CRISPR gene editing to produce zebrafish lines with null mutations for each of the three -crystallin genes (cryaa, cryaba and cryabb). The absence of normal protein was confirmed by mass spectrometry, and lens phenotypes were assessed with differential interference contrast microscopy and histology. Loss of A-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 either Ba- or full-length Bb-crystallin produced no substantial lens defects. Mutation of each -crystallin gene did not alter the mRNA levels of the remaining two, suggesting a lack of genetic compensation. These data confirm a developmental role for A-crystallin in lens development, but the range of phenotype severity suggests that 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 in lens epithelial and fiber cells. Future experiments can explore the molecular consequences of cryaa mutation and causes of lens defects in this null mutant, as well as the roles of other genes in lens development and function.

developmental biology↗

bioRxiv2018

Population extinctions driven by climate change, population size, and time since observation may make rare species databases inaccurate

Loss of biological diversity through population extinctions is a global phenomenon that threatens many ecosystems. Managers often rely on databases of rare species locations to plan land use actions and conserve at-risk taxa, so it is crucial that the information they contain is accurate and dependable. However, climate change, small population sizes, and long gaps between surveys may be leading to undetected extinctions of many populations. We used repeated survey records for a rare but widespread orchid, Cypripedium fasciculatum (clustered ladys slipper), to model population extinction risk based on elevation, population size, and time between observations. Population size was negatively associated with extinction, while elevation and time between observations interacted such that low elevation populations were most vulnerable to extinction, but only over larger time spans. We interpret population losses at low elevations as a potential signal of climate change impacts. We used this model to estimate the probability of persistence of populations across California and Oregon, and found that 31%-56% of the 2415 populations reported in databases from this region are likely extinct. Managers should be aware that the number of populations of rare species in their databases is potentially an overestimate, and consider resurveying these populations to document their presence and condition, with priority given to older reports of small populations, especially those at low elevations or in other areas with high climate vulnerability.

ecology↗