The genetics of outer segment morphogenesis in zebrafish

A method for isolation of cone photoreceptors from adult zebrafish retinae

Background

Cone photoreceptors are specialised sensory retinal neurons responsible for photopic vision, colour perception and visual acuity. Retinal degenerative diseases are a heterogeneous group of eye diseases in which the most severe vision loss typically arises from cone photoreceptor dysfunction or degeneration. Establishing a method to purify cone photoreceptors from retinal tissue can accelerate the identification of key molecular determinants that underlie cone photoreceptor development, survival and function. The work herein describes a new method to purify enhanced green fluorescent protein (EGFP)-labelled cone photoreceptors from adult retina of Tg(3.2gnat2:EGFP) zebrafish.

Results

Methods for dissecting adult zebrafish retinae, cell dissociation, cell sorting, RNA isolation and RNA quality control were optimised. The dissociation protocol, carried out with ~30 retinae from adult zebrafish, yielded approximately 6 × 10⁶ cells. Flow cytometry cell sorting subsequently distinguished 1 × 10⁶ EGFP⁺ cells and 4 × 10⁶ EGFP⁻ cells. Electropherograms confirmed downstream isolation of high-quality RNA with RNA integrity number (RIN) >7.6 and RNA concentration >5.7 ng/µl obtained from both populations. Reverse Transcriptase-PCR confirmed that the EGFP-positive cell populations express known genetic markers of cone photoreceptors that were not expressed in the EGFP-negative cell population whereas a rod opsin amplicon was only detected in the EGFP-negative retinal cell population.

Conclusions

This work describes a valuable adult zebrafish cone photoreceptor isolation methodology enabling future identification of cone photoreceptor-enriched genes, proteins and signalling networks responsible for their development, survival and function. In addition, this advancement facilitates the identification of novel candidate genes for inherited human blindness.

SiO2 nanoparticles change colour preference and cause Parkinson's-like behaviour in zebrafish

With advances in the development of various disciplines, there is a need to decipher bio-behavioural mechanisms via interdisciplinary means. Here, we present an interdisciplinary study of the role of silica nanoparticles (SiO2-NPs) in disturbing the neural behaviours of zebrafish and a possible physiological mechanism for this phenomenon. We used adult zebrafish as an animal model to evaluate the roles of size (15-nm and 50-nm) and concentration (300 μg/mL and 1000 μg/mL) in SiO2-NP neurotoxicity via behavioural and physiological analyses. With the aid of video tracking and data mining, we detected changes in behavioural phenotypes. We found that compared with 50-nm nanosilica, 15-nm SiO2-NPs produced greater significant changes in advanced cognitive neurobehavioural patterns (colour preference) and caused potentially Parkinson's disease-like behaviour. Analyses at the tissue, cell and molecular levels corroborated the behavioural results, demonstrating that nanosilica acted on the retina and dopaminergic (DA) neurons to change colour preference and to cause potentially Parkinson's disease-like behaviour.