SCN1A and epilepsy: To mimic the genetic architecture of DS in human patients as best possible, the animal model should display a 50% haploinsufficiency of SCN1A. Zebrafish likely carry two orthologues for the human SCN1A gene; Scn1Laa and Scn1Lab. While the expression of these genes does not overlap at embryonic- but only at larval stages [19, 20], they have a shared functional role in epilepsy [21].