Abstract
The tunicate
Ciona robusta
is an emerging model system to study the evolution of the nervous system. Due to their small embryos and compact genomes, tunicates, like
Ciona robusta
, have great potential to comprehend genetic circuitry underlying cell specific gene repertoire, among different neuronal cells. Their simple larvae possess a sensory vesicle comprising two pigmented sensory organs, the ocellus and the otolith. We focused here on
Klhl21/30
, a gene belonging to
Kelch
family, that, in
Ciona robusta
, starts to be expressed in pigmented cell precursors, becoming specifically maintained in the otolith precursor during embryogenesis. Evolutionary analyses demonstrated the conservation of
Klhl21/30
in all the chordates.
Cis
-regulatory analyses and CRISPR/Cas9 mutagenesis of potential upstream factors, revealed that
Klhl21/30
expression is controlled by the combined action of three transcription factors, Mitf, Dmrt, and Msx, which are downstream of FGF signaling. The central role of Mitf is consistent with its function as a fundamental regulator of vertebrate pigment cell development. Moreover, our results unraveled a new function for Dmrt and Msx as transcriptional co-activators in the context of the
Ciona
otolith.