L-thyroxine Inhibits Homeostasis Maintenance of Melanocytes in Zebrafish Embryos
QIAN Luwei, XU Jingjin, HAN Qize, KANG Yunsi*
TH (thyroid hormone) is essential for maintaining the proper development of the body. Although excessive thyroid hormone has been found to inhibit the proliferation of melanocytes and promote the development of xanthophores in adult zebrafish, it remains unclear whether thyroid hormone is involved in the development of pigment cells during early embryonic stages in zebrafish. This study aimed to investigate this matter and revealed that L-thyroxine treatment causes abnormal melanin pigmentation in zebrafish embryos. By treating zebrafish embryos at different stages, this work demonstrated that L-thyroxine played a crucial role in the homeostasis, but not the differentiation, of melanocytes—which differed from the role it plays in adult zebrafish. Live imaging and histological analysis showed that L-thyroxine treatments affected melanosome formation and eventually led to melanocyte apoptosis. Notably, the inhibition of melanosome formation was specific to melanocytes, as L-thyroxine treatment did not affect the development of melanosomes in retinal pigment epithelium cells. Overall, this work sheds light on the physiological function of thyroid hormone during early embryonic stages and provides further insights into skin pigment determination in zebrafish.
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