sox2 and sox3 cooperate to regulate otic/epibranchial placode induction in zebrafish

Abstract

Expression of sox3 is one of the earliest markers of Fgf-dependent otic/epibranchial placode induction. We report here that sox2 is also expressed in the early otic/epibranchial placode in zebrafish. To address functions of sox2 and sox3, we generated knockouts and heat shock-inducible transgenes. Mutant analysis, and low-level misexpression, showed that sox2 and sox3 act redundantly to establish a full complement of otic/epibranchial cells. Disruption of pax8, another early regulator, caused similar placodal deficiencies to sox3 mutants or pax8-sox3 double mutants, suggesting that sox3 and pax8 operate in the same pathway. High-level misexpression of sox2 or sox3 during early stages cell-autonomously blocked placode induction, whereas misexpression several hours later could not reverse placodal differentiation. In an assay for ectopic placode-induction, we previously showed that misexpression of fgf8 induces a high level of ectopic sox3, but not pax8. Partial knockdown of sox3 significantly enhanced ectopic induction of pax8, whereas full knockdown of sox3 inhibited this process. Together these findings show that sox2 and sox3 are together required for proper otic induction, but the level of expression must be tightly regulated to avoid suppression of differentiation and maintenance of pluripotency.

Sox2 and Sox3 are essential for development and regeneration of the zebrafish lateral line

“…Further, sox2/sox3 double mutants showed a stronger reduction in the number of hair 472 cells (P<0.0001; Figure 5 F,N). In addition, some of the sox2 single and sox2/sox3 double 473 mutants also show a short body axis and an upward curled tail, as we have previously shown 474 (Gou et al 2018a). These data indicate that both sox2 and sox3 genes are important for 475 protoneuromast formation and timing of pro-neuromast deposition during migration of the 476 primordium, as well as to reach the correct number of hair cells within neuromasts.…”

“…Using immunofluorescence, we observed the expression of Sox2 and Sox3 proteins in most 572 cells of the migratory primordium, interneuromastic cells, pre-and pro-neuromasts, and 573 neuromasts of the anterior and posterior lateral line systems, suggesting that both genes are 574 required for proper early lateral line development, as is the case in the zebrafish otic placode 575 (Gou et al, 2018a). In mature neuromasts, some Sox2+ and Sox3+ cells were also proliferating, 576…”

Notch signalling regulates epibranchial placode patterning and segregation

“…We next addressed the question of how the pool of Pax2 + PPA progenitors may segregate into three discrete epibranchial placodes as well as interplacodal pharyngeal ectodermal cells. We first investigated the spatiotemporal patterning of the epibranchial placodes from E8.5 to E9.5 using a series of placodal and pharyngeal markers including Eya1 and Six1 ( placodal progenitor markers); Neurog2 (the earliest pre-neural marker in epibranchial placode; Fode et al, 1998); Sox2 (essential for epibranchial neural competence; Gou et al, 2018;Tripathi et al, 2009); Irx5 (expressed in PPA; Feijoo et al, 2009;Glavic et al, 2004); vestigial-like2 (Vgll2) (expressed in the pharyngeal region; Chen et al, 2017;Johnson et al, 2011); Fgf3; and the FGF downstream target Etv5 (essential for pharyngeal morphogenesis) (Urness et al, 2011).…”

Hcfc1a regulates neural precursor proliferation and asxl1 expression in the developing brain.

“…We tested this possibility by creating a transgenic zebrafish expressing human HCFC1 under the control of the heat shock promoter for the hsp701 gene. The efficacy of the hsp701 promoter in zebrafish has been widely established in previous studies (28,(39)(40)(41)(42)(43). We activated expression of HCFC1 by performing a heat shock as described in the methods section for a period of 5 days.…”