Toxicity of perfluorooctanoic acid on zebrafish early embryonic development determined by single-cell RNA sequencing.

The perfluorooctanoic acid (PFOA) poses a high risk for aquatic organisms. Nevertheless, the current toxicity studies rarely report how PFOA affects different cell populations during the embryonic development of fish. Here, the zebrafish embryos at 2-30 hpf were exposed to 1-100 μg/L PFOA. The heartbeat and locomotor behavior were significantly decreased after ≥ 25 μg/L PFOA exposure. The single-cell RNA sequencing showed that PFOA exposure influenced nine cell populations, including heart cells, hatching gland cells, macrophages, lens cells, ionocytes, melanoblasts, optic cup cells, periderm cells, and differentiating neurons cells. Among them, heart cells were the most affected cell population. Functions of cardiac muscle contraction, actin cytoskeleton and oxygen binding were significantly changed in the heart cells, which were involved in the altered expressions of tnni2a.4, acta1a, atp1a1a.2, mylpfa, and so on. Besides, the changes of apoptotic process, innate immune response, and translation in lens cells, hatching gland cells, macrophages and ionocytes should also be of concern. Our study indicates that 2-30 hpf of embryonic development is the sensitivity window for the PFOA exposure. Identification of the target cell population provides clear information of the toxic endpoint of PFOA, which sheds new light on the risk assessment of PFOA on aquatic organisms.