BDE-99 Disrupts the Photoreceptor Patterning of Zebrafish Larvaevia Transcription Factor six7

Proper visual function is essential for collectingenvironmental information and supporting the decision-making inthe central nervous system and is therefore tightly associated withwildlife survival and human health. Polybrominated diphenyl ethers(PBDEs) were reported to impair zebrafish vision development,and thyroid hormone (TH) signaling was suspected as the maincontributor. In this study, a pentabrominated PBDE, BDE-99, waschosen to further explore the action mechanism of PBDEs on thedisruption of zebrafish color vision. The results showed that BDE-99 could impair multiple photoreceptors in the retina and disturbthe behavior guided by the color vision of zebrafish larvae at 120 hpost-fertilization. Although the resulting alteration in photoreceptorpatterning highly resembled the effects of 3,3 ',5-triiodo-L-thyroine, introducing the antagonist for TH receptors was unable to fullyrecover the alteration, which suggested the involvement of other potential regulatory factors. By modulating the expression ofsix7,akey inducer of middle-wavelength opsins, we demonstrated thatsix7, not THs, dominated the photoreceptor patterning in thedisruption of BDE-99. Our work promoted the understanding of the regulatory role ofsix7in the process of photoreceptorpatterning and proposed a novel mechanism for the visual toxicity of PBDEs.