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Published on: April 26, 2017
Developmental Delay and Male-Biased Sex Ratio in esr2b Knockout Zebrafish
Wei Peng1,2, Yunsheng Zhang1,2, Bolan Song1,2
1College of Life and Environmental Sciences, Hunan University of Arts and Science, Changde 415000, China.
Abstract:
The estrogen receptor signaling pathway plays an important role in vertebrate embryonic development and sexual differentiation. There are four major estrogen receptors in zebrafish: esr1, esr2a, esr2b and gper. However, the specific role of different estrogen receptors in zebrafish is not clear. To investigate the role of esr2b in zebrafish development and reproduction, this study utilized TALENs technology to generate an esr2b knockout homozygous zebrafish line. The number of eggs laid by esr2b knockout female zebrafish did not differ significantly from that of wild zebrafish. The embryonic development process of wild-type and esr2b knockout zebrafish was observed, revealing a significant developmental delay in the esr2b knockout zebrafish. Additionally, mortality rates were significantly higher in esr2b knockout zebrafish than in their wild-type counterparts at 24 hpf. The reciprocal cross experiment between esr2b knockout zebrafish and wild-type zebrafish revealed that the absence of esr2b resulted in a decline in the quality of zebrafish oocytes, while having no impact on sperm cells. The knockout of esr2b also led to an abnormal sex ratio in the adult zebrafish population, with a female-to-male ratio of approximately 1:7. The quantitative PCR (qPCR) and in situ hybridization results demonstrated a significant downregulation of cyp19ab1b expression in esr2b knockout embryos compared to wild-type embryos throughout development (at 2 dpf, 3 dpf and 4 dpf). Additionally, the estrogen-mediated induction expression of cyp19ab1b was attenuated, while the estradiol-induced upregulated expression of vtg1 was disrupted. These results suggest that esr2b is involved in regulating zebrafish oocyte development and sex differentiation.
Insights
Estrogen receptor esr2b is crucial for zebrafish development and reproduction. Its absence causes developmental delays, higher mortality, and skewed sex ratios, impacting oocyte quality and gene expression.
Area of Science:
- Developmental Biology
- Endocrinology
- Genetics
Background:
- Estrogen receptor signaling is vital for vertebrate embryonic development and sexual differentiation.
- Four major estrogen receptors (esr1, esr2a, esr2b, gper) exist in zebrafish, but their specific roles are unclear.
- The function of estrogen receptor beta 2 (esr2b) in zebrafish development and reproduction requires further investigation.
Purpose of the Study:
- To investigate the specific role of the estrogen receptor esr2b in zebrafish development and reproduction.
- To generate and characterize an esr2b knockout zebrafish model.
Main Methods:
- Utilized TALENs technology to create homozygous esr2b knockout zebrafish.
- Observed embryonic development and measured egg production in knockout and wild-type zebrafish.
- Conducted reciprocal cross experiments and analyzed sex ratios in adult populations.
- Performed quantitative PCR (qPCR) and in situ hybridization to assess gene expression (cyp19ab1b, vtg1).
Main Results:
- esr2b knockout zebrafish exhibited significant developmental delays and increased mortality rates at 24 hours post-fertilization (hpf).
- Female knockout zebrafish showed no difference in egg laying, but oocyte quality declined, while sperm quality remained unaffected.
- The adult knockout population displayed an abnormal sex ratio (approximately 1:7 female to male).
- Expression of cyp19ab1b was significantly downregulated in knockout embryos, and estrogen-mediated induction of cyp19ab1b and estradiol-induced expression of vtg1 were disrupted.
Conclusions:
- Estrogen receptor esr2b plays a critical role in regulating zebrafish embryonic development and survival.
- esr2b is essential for maintaining oocyte quality and influences sex differentiation in zebrafish.
- The findings highlight esr2b's involvement in key developmental and reproductive processes through regulation of specific gene expressions.
