In vivo allele-specific enhancer function of HCNR 617 in zebrafish. (A) Results of the zebrafish enhancer screen with the expression domains for the protective and risk allele in orange and purple, respectively. (B) Representative embryos of the F1 generation with the protective ([A] adenine) and the risk allele ([G] = guanine) construct of HCNR 617 showed an allele-specific difference in reporter EGFP expression in the neural tube. The protective allele of HCNR 617 drove EGFP expression in the retina, fore-, mid-, and hindbrain and spinal cord. The risk allele significantly reduced the expression almost to background levels (bar represents 250 µm). (C) Boxplot (left) The risk allele reduced the fluorescence intensity to 70% compared to the protective allele (100%) (Wilcoxon rank sum test, P = 0.08; EGFP-brain signal measured, nprotective = 5, nrisk = 5). The bar chart (right) represents the percentage of all EGFP-positive founders in the respective area (y-axis) with respect to the protective (orange) and risk (purple) allele of HCNR 617. The risk allele leads either to a significant reduction or a complete loss of the EGFP signal.
