The N-terminal domain of gastrulation brain homeobox 2 (Gbx2) is required for iridophore specification in zebrafish

Abstract

Although body color pattern formation by pigment cells plays critical roles in animals, pigment cell specification has not yet been fully elucidated. In zebrafish, there are three chromatophores: melanophore, iridophore, and xanthophore, that are derived from neural crest cells (NCCs). A recent study has reported the differentially expressed genes between melanophores and iridophores. Based on transcriptome data, we identified that Gbx2 is required for iridophore specification during development. In support of this, iridophore formation is suppressed by gbx2 knockdown by morpholino antisense oligonucleotide, at 72 h post fertilization (hpf) in zebrafish. Moreover, gbx2 is expressed in sox10-expressing NCCs and guanine crystal plates-containing iridophores during development at 24 and 48 hpf, respectively. In gbx2 knockdown zebrafish embryos, apoptosis of sox10-expressing NCCs was detected at 24 hpf without any effect on the formation of melanophores and xanthophores at 48 hpf. We further observed that the N-terminal domain of Gbx2 is able to rescue the iridophore formation defect caused by gbx2 knockdown. Our study provides insights into the requirement of N-terminal domain of Gbx2 for iridophore specification in zebrafish.

Epigenetic dynamics shaping melanophore and iridophore cell fate in zebrafish

“…Recently, the knockdown of gbx2 through morpholino experiments has been shown to diminish iridophore count in zebrafish larvae [ 24 ]. However, whether the alx TFs are necessary for iridophore cell fate is currently unknown.…”

“…Using motif enrichment results from iridophore-specific DMRs, DARs, and DMARs, we curated a list of previously known transcription factors related to iridophore development ( sox10 [ 10 ], foxd3 [ 9 , 22 ], tfec [ 23 ], and gbx2 [ 24 ] ). In murine model, Ets1 has been shown to be essential for Sox10 expression for proper melanocyte development [ 77 ].…”

“…The gene regulatory network for iridophore differentiation is underexplored. However, sox10 [ 10 ], foxd3 [ 9 , 22 ], tfec [ 23 ], and gbx2 [ 24 ] transcription factors have been implicated in iridophore cell fate.…”

Harnessing Hue: Advances and Applications of Fish Skin Pigmentation Genetics in Aquaculture

“…The knockdown of edn3b results in a significant reduction in iridophore numbers by 48hpf [78], and the knockout of its receptor, ednrba, in adult zebrafish leads to decreased iridophore numbers and defects in stripe patterns [79]. Furthermore, other transcription factors like gbx2, alx4a, and mpv17, which encode various regulatory proteins, contribute to the specialization of iridophores, although the specifics of their downstream regulatory mechanisms remain to be fully elucidated [80][81][82].…”