Expression Patterns of Three Estrogen Receptor Genes During Zebrafish Development: Evidence for High Expression in Neuromasts

This study analyzed the expression patterns of three estrogen receptor genes (esr1, esr2a, and esr2b) in zebrafish during development using whole-mount in situ hybridization. High levels of esr2a and esr2b of maternal origin were observed in early embryos, with all three genes showing similar spatio-temporal expression patterns post mid-blastula transition. By 24 hours postfertilization (hpf), esr2a and esr2b were highly expressed in the epidermis, pectoral fin buds, hatching gland, and developing brain, while esr1 was expressed at lower levels. From 60 hpf, esr2a was abundant in mature primary neuromasts, and by 3 days postfertilization (dpf), both esr2a and esr2b were significantly expressed in all mature primary neuromasts. Histological sections revealed high esr2a levels in mechanoreceptive hair cells and supporting cells, even after neomycin-induced hair cell death. From 6 dpf onward, esr2a and esr2b were robustly co-expressed in primary neuromasts, branchial arches, pectoral fins, and anal papilla, with slight esr1 expression.