Cellular responses to ionizing radiation change quickly over time during early development in zebrafish

Area of Science:

• Developmental Biology
• Radiation Biology
• Molecular Biology

Background:

• Animal cells respond to environmental factors like ionizing radiation.
• Cellular responses to radiation during early embryonic development are not well understood.
• DNA repair is crucial for cell survival after radiation damage.

Purpose of the Study:

• To analyze the effects of ionizing radiation on zebrafish embryos.
• To investigate the timing of cellular responses to radiation during early development.
• To identify key regulatory factors in the embryonic response to genotoxins.

Main Methods:

• Irradiation of zebrafish embryos at different developmental stages.
• Analysis of γH2AX foci formation and cell cycle arrest.
• Quantification of P21/WAF1 protein accumulation and p21 mRNA levels.

Main Results:

• Radiation-induced γH2AX foci and cell cycle arrest were observed starting at the gastrula stage.
• Maternal DNA repair gene transcripts were present before gastrulation.
• P21/WAF1 protein accumulation began around 6 hours post-fertilization, despite earlier p21 mRNA upregulation by radiation.
• Cellular responses at 2-4 hours post-fertilization did not overcome P21 protein accumulation.

Conclusions:

• Zebrafish embryos exhibit a delayed cellular response to ionizing radiation, with key events like γH2AX foci formation and cell cycle arrest occurring later in development.
• P21/WAF1 protein stabilization is a critical factor in mediating the cellular response to genotoxins during early zebrafish embryogenesis.
• The regulation of P21/WAF1 protein stability plays a significant role in the ability of early embryonic cells to respond to DNA damage.