The ndrg2 gene is conserved across multiple species and highly expressed in early developmental otic vesicles and neuromasts in posterior lateral line (pLL). (A) Amino acid sequence alignment of zebrafish (Danio rerio) ndrg2 (marked with a red star), human ndrg2 and homologous genes in several mammalian animals. (B) The established phylogenetic tree utilizing Neighbor-Joining method and MEGA software (version 6.0) containing zebrafish ndrg2 (marked with a red star), human ndrg2 and its orthologs in other species. (C–E) Expression profiles of ndrg2 mRNA examined via whole-mount in situ hybridization (WISH) with the lateral view in zebrafish embryos at 24, 48 and 72 hpf, respectively. The positive signals of ndrg2 mRNA were focused on the otic vesicle (marked with red dashed box) and neuromasts in pLL (marked with red arrowheads) during early embryo development. A schematic of the inner ear structure in zebrafish was shown in (D). UO, utricular otolith; SO, saccular otolith; UM, utricular macula; SM, saccular macula; AC, anterior crista; LC, lateral crista; PC, posterior crista. (C’,D’,E’) Magnified images of the positive signals in otic vesicle with lateral view in zebrafish at 24, 48 and 72 hpf, respectively. (C’’) A dorsal view of otic vesicles in zebrafish at 24 hpf. (D’’,E’’) Enlarged images of the positive signals in neuromasts in pLL (marked with red arrowheads) with lateral view in zebrafish at 48 and 72 hpf, respectively.
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