sox1a_ka705Tg whole genome sequencing

The transcription factors sox1a and sox1b label a neuronal subtype in the developing spinal cord of zebrafish embryos. Analysis and mapping of sox1a/b gene expression revealed that both genes are necessary for the specification of a new V2 interneuron subtype, which we call V2s. A transgenic line created by Tol2-transgenesis to test a regulatory element of an unrelated gene, reliably labelled these V2s neurons. This led us to analyse this line in more detail. The eGFP expression of the transgene fully recapitulated sox1a expression throughout embryonic development. WGS revealed then that the transgene integrated into the 5´-UTR of the sox1a gene, indicating that it is under the control of the endogenous sox1a promoter. Subsequent analysis showed that the eGFP expression is not related to the initially used regulatory element, thus it is a gene trap line for the sox1a gene. With the help of this line we were able to show that V2s neurons grow long ipsilateral descending axonal projections and they are inhibitory interneurons. Unilateral ablation of V2s interneurons causes a delay in touch-provoked zebrafish escape behaviour, suggesting that V2s interneurons are involved in locomotion.