ELISA based quantification of Pax6 expression in the developing Zebrafish embryos

The generation and characterization of a transgenic zebrafish line with lens-specific Cre expression

Purpose

Danio rerio zebrafish constitute a popular model for studying lens development and congenital cataracts. However, the specific deletion of a gene with a Cre/LoxP system in the zebrafish lens is unavailable because of the lack of a lens-Cre-transgenic zebrafish. This study aimed to generate a transgenic zebrafish line in which Cre recombinase was specifically expressed in the lens.

Methods

The pTol2 cryaa:Cre-polyA-cryaa:EGFP (enhanced green fluorescent protein) plasmid was constructed and co-injected with Tol2-transposase into one-to-two-cell-stage wild-type (WT) zebrafish embryos. Whole-mount in situ hybridization (ISH), tissue section, hematoxylin and eosin staining, a Western blot, a split-lamp observation, and a grid transmission assay were used to analyze the Cre expression, lens structure, and lens transparency of the transgenic zebrafish.

Results

In this study, we generated a transgenic zebrafish line, zTg(cryaa:Cre-cryaa:EGFP), in which Cre recombinase and EGFP were driven by the lens-specific cryaa promoter. zTg(cryaa:Cre-cryaa:EGFP) began to express Cre and EGFP specifically in the lens at the 22 hpf stage, and this ectopic Cre could efficiently and specifically delete the red fluorescent protein (RFP) signal from the lens when zTg(cryaa:Cre-cryaa:EGFP) embryos were injected with the loxP-flanked RFP plasmid. The overexpression of Cre and EGFP did not impair zebrafish development or lens transparency. Accordingly, this zTg(cryaa:Cre-cryaa:EGFP) zebrafish line is a useful tool for gene editing, specifically with zebrafish lenses.

Conclusions

We established a zTg(cryaa:Cre-cryaa:EGFP) zebrafish line that can specifically express an active Cre recombinase in lens tissues. This transgenic zebrafish line can be used as a tool to specifically manipulate a gene in zebrafish lenses.

Daphnia magna Multigeneration Exposure to Carbendazim: Gene Transcription Responses

The world population is experiencing colossal growth and thus demand for food, leading to an increase in the use of pesticides. Persistent pesticide contamination, such as carbendazim, remains a pressing environmental concern, with potentially long-term impacts on aquatic ecosystems. In the present study, Daphnia magna was exposed to carbendazim (5 µg L-1) for 12 generations, with the aim of assessing gene transcription alterations induced by carbendazim (using a D. magna custom microarray). The results showed that carbendazim caused changes in genes involved in the response to stress, DNA replication/repair, neurotransmission, ATP production, and lipid and carbohydrate metabolism at concentrations already found in the environment. These outcomes support the results of previous studies, in which carbendazim induced genotoxic effects and reproduction impairment (increasing the number of aborted eggs with the decreasing number of neonates produced). The exposure of daphnids to carbendazim did not cause a stable change in gene transcription between generations, with more genes being differentially expressed in the F0 generation than in the F12 generation. This could show some possible daphnid acclimation after 12 generations and is aligned with previous multigenerational studies where few ecotoxicological effects at the individual and populational levels and other subcellular level effects (e.g., biochemical biomarkers) were found.

Medaka (Oryzias latipes) Olpax6.2 acquires maternal inheritance and germ cells expression, but was functionally degenerated in the eye

Gene duplication provides raw material for the evolution of genetic and phenotypic complexity. It has remained a long-standing mystery how duplicated genes evolve into new genes by neofunctionalization via the acquisition of new expression and/or activity and simultaneous loss of the old expression and activity. Fishes have many gene duplicates from whole genome duplication, making them excellent for studying the evolution of gene duplicates. In the fish medaka (Oryzias latipes), an ancestral pax6 gene has given rise to Olpax6.1 and Olpax6.2. Here we report that medaka Olpax6.2 is evolving towards neofunctionalization. A chromosomal syntenic analysis indicated that Olpax6.1 and Olpax6.2 are structurally co-homologous to the single pax6 in other organisms. Interestingly, Olpax6.2 maintains all conserved coding exons but loses the non-coding exons of Olpax6.1, and has 4 promoters versus 8 in Olpax6.1. RT-PCR revealed that Olpax6.2 maintained expression in the brain eye, pancreas as Olpax6.1. Surprisingly, Olpax6.2 also exhibited maternal inheritance and gonadal expression by RT-PCR, in situ hybridization and RNA transcriptome analysis. The expression and distribution of Olpax6.2 is not different from Olpax6.1 in the adult brain, eye and pancreas, but exhibited overlapping and distinct expression in early embryogenesis. We show that ovarian Olpax6.2 expression occurs in female germ cells. Olpax6.2 knockout showed no obvious defect in eye development, while Olpax6.1 F0 mutant have severe defects in eye development. Thus, Olpax6.2 has acquired maternal inheritance and germ cell expression, but was functionally degenerated in the eye, making this gene as an excellent model to study the neofunctionalization of duplicated genes.

Real-time imaging and developmental biochemistry analysis during embryogenesis of Caridina pseudogracilirostris

This paper reports on the real-time imaging and developmental biochemistry of the freshwater caridean shrimp, Caridina pseudogracilirostris. The complete time-lapse development of a single embryo was recorded in an artificial mold, developed in our lab, and imaged under a stereomicroscope. It took 8 days to complete the 5 stages of embryonic development (1 cleavage stage, 2 gastrulation stage, 3 nauplius stage, 4 prehatching embryo, and 5 zoea stages). As the decapod eggs are enriched with dense yolk, biochemical determination of the major components was made to evaluate the yolk utilization during embryogenesis. The concentration of protein, lipid, and carbohydrate declined drastically from Stage I (cleavage) to Stage IV (Zoea), reflecting sustained yolk utilization during embryogenesis. The increase in the size of the embryo correlates with changes in water content. Lipids, being the principal organic substrate, changes in the fatty acid (FA) composition of embryos during development were determined by GC. The FA composition was observed within the range of 25%-60.87% for saturated, 22.57%-56.45% for monounsaturated, and 5.64%-18.51% for total polyunsaturated FAs. The essential polyunsaturated fatty acid were higher in Stages I, IV, and V, suggesting a major role in embryogenesis. The cellular proliferation and organogenesis as visualized in the real-time imaging correlate well with the biochemical variations observed in C. pseudogracilirostris.

Zebrafish: an emerging real-time model system to study Alzheimer's disease and neurospecific drug discovery

Zebrafish (Danio rerio) is emerging as an increasingly successful model for translational research on human neurological disorders. In this review, we appraise the high degree of neurological and behavioural resemblance of zebrafish with humans. It is highly validated as a powerful vertebrate model for investigating human neurodegenerative diseases. The neuroanatomic and neurochemical pathways of zebrafish brain exhibit a profound resemblance with the human brain. Physiological, emotional and social behavioural pattern similarities between them have also been well established. Interestingly, zebrafish models have been used successfully to simulate the pathology of Alzheimer’s disease (AD) as well as Tauopathy. Their relatively simple nervous system and the optical transparency of the embryos permit real-time neurological imaging. Here, we further elaborate on the use of recent real-time imaging techniques to obtain vital insights into the neurodegeneration that occurs in AD. Zebrafish is adeptly suitable for Ca²⁺ imaging, which provides a better understanding of neuronal activity and axonal dystrophy in a non-invasive manner. Three-dimensional imaging in zebrafish is a rapidly evolving technique, which allows the visualisation of the whole organism for an elaborate in vivo functional and neurophysiological analysis in disease condition. Suitability to high-throughput screening and similarity with humans makes zebrafish an excellent model for screening neurospecific compounds. Thus, the zebrafish model can be pivotal in bridging the gap from the bench to the bedside. This fish is becoming an increasingly successful model to understand AD with further scope for investigation in neurodevelopment and neurodegeneration, which promises exciting research opportunities in the future.

Zebrafish: A Premier Vertebrate Model for Biomedical Research in Indian Scenario

The zebrafish (Danio rerio) is a versatile model organism that has been used in biomedical research for several decades to study a wide range of biological phenomena. There are many technical advantages of using zebrafish over other vertebrate models. They are readily available, hardy, easy, and inexpensive to maintain in the laboratory, have a short life cycle, and have excellent fecundity. Due to its optical clarity and reproducible capabilities, it has become one of the predominant models of human genetic diseases. Zebrafish research has made rapid strides in the United States and Europe, but in India the field is at an early stage and many researchers still remain unaware of the full research potential of this tiny fish. The zebrafish model system was introduced into India in the early 2000s. Up to now, more than 200 scientific referred articles have been published by Indian researchers. This review gives an overview of the current state of knowledge for zebrafish research in India, with the aim of promoting wider utilization of zebrafish for high level biological studies.