A transcription factor network dictates neuronal cell fate decisions in the zebrafish dorsal diencephalon
The zebrafish epithalamus, which includes the dorsal habenular nuclei and pineal complex, displays robust molecular and anatomical asymmetries. The full elaboration of molecular and anatomical differences between the left and right dorsal habenular nuclei depends on the formation of a left-sided parapineal organ. This work has yielded significant insights into the role of Tbx2b during parapineal development using both the candidate gene approach as well as the non-biased, transcriptome analysis approach. Through the candidate approach, it was determined that Tbx2b acts in a permissive manner during parapineal specification, but it is necessary for proper parapineal migration. Further, the inhibitory roles of Flh and Nr2e3 during formation of parapineal neurons have been characterized. Using RNA-sequencing to perform differential expression analysis between wild-type and tbx2b-deficient pineal complex cells has yielded many targets that are downstream of Tbx2b. Together, these studies also provided a novel insight into a potential genetic interaction system between Tbx2b and Nr2e3 during cone versus rod photoreceptor differentiation.