Muq synergistically reinforces (A) human RARα in vitro and (B) zebrafish RARα in vitro. Relative luciferase units in response to 0.1, 1, and 10 µM of Muq. Retinoic acid (RA) at 0.001 µM was used as an hRARα and a zRARα agonist positive control. The activity of the vehicle control was set at 1 and the relative luciferase activities obtained for each control and concentration tested are presented as a fold induction with respect to the vehicle control. Statistical analysis was performed by comparing each concentration of Muq and that of RA to the vehicle control using the Student’s t-test. The analyses were performed using GraphPad Prism 7 software. Statistically significant differences were accepted when the p-value was at least ≤0.05. Data are expressed as means ± SEM, (n = 9) for human RARα and (n = 3) for zebrafish RARα. * p  ≤  0.05. (C) Muq behaves as a weak RARα agonist and enhances RA signaling in zebrafish. Embryos carrying the 12XRARE-ef1a:EGFP transgene at 48 hpf that were treated from 24 hpf with (C,D) DMSO, (E,F) 10 μM Muq, (G,H) 0.5 μM RA, and (I,J) 0.5 μM RA + 10 μM Muq. Embryos in C, E, G, and I are the same as D, F, H, and J. Red arrows in G and I indicate smaller eyes. Black arrows in G and I indicate shortened tail. White arrow indicates E-GFP from the transgene in the anterior spinal cord. For this study, 25 embryos per condition were examined.