Dlx3b/4b is required for early-born but not later-forming sensory hair cells during zebrafish inner ear development

摘要: ABSTRACT Morpholino-mediated knockdown has shown that the homeodomain transcription factors Dlx3b and Dlx4b are essential for proper induction of otic-epibranchial progenitor domain (OEPD), as well subsequent formation sensory hair cells in developing zebrafish inner ear. However, increasing use reverse genetic approaches revealed poor correlation between morpholino-induced mutant phenotypes. Using CRISPR/Cas9-mediated mutagenesis, we generated a defined deletion eliminating entire open reading frames dlx3b dlx4b (dlx3b/4b) investigated potential phenotypic difference mutants morpholino-mediated knockdown. Consistent with previous findings obtained by Dlx4b, dlx3b/4b display compromised otic induction, development smaller vesicles an elimination all indications specification when combined loss foxi1, second known OEPD competence factor zebrafish. Furthermore, sensorigenesis is also affected mutants. find only early-born (tether cells), seed anchor otoliths, affected. Later-forming present, indicating two genetically distinct pathways control later-forming cells. Finally, impairment cell embryos reverses common temporal sequence neuronal zebrafish, resembling order amniotes; Neurog1 expression before Atoh1 expression. We conclude Dlx3b/4b-dependent pathway been either acquired newly fish lineage or lost other vertebrate species during evolution, events early ear remarkably similar amniotes absence this pathway.