Table 7. Changes in RA metabolism enzyme-related mRNA levels in response to RA and EDN3.

	Comparison of relative mean mRNA levels
	(p value)
Target gene:	Raldh2		Cyp26a1
	3d	14d	3d	14d
RA- vs. RA+ (EDN3-)	1.0 vs. 0.117	1.0 vs. 4.748	1.0 vs. 846.015	1.0 vs. 1.682
	(p=0.003)	(p=0.007)	(p<0.001)
RA- vs. RA+ (EDN3+)	0.391 vs. 0.072	0.619 vs. 0.257	0.325 vs. 98.403	0.139 vs. 6.461
				(p<0.001)
EDN3- vs. EDN3+ (RA-)	1.0 vs. 0.391	1.0 vs. 0.619	1.0 vs. 0.325	1.0 vs. 0.139
	(p=0.024)
EDN3- vs. EDN3+ (RA+)	0.117 vs. 0.072	4.748 vs. 0.257	846.015 vs. 98.403	1.682 vs. 6.461
		(p=0.003)	(p<0.001)	(p=0.004)
Interaction present?	No	Yes (p=0.023)	Yes (p<0.001)	Yes (p=0.01)

This table summarizes the effects of RA and EDN3 on the gene expression in ENS precursor cultures after 3 and 14 days. Immunoselected cells were cultured in the presence of RA, EDN3, RA with EDN3, or neither compound. When EDN3 was absent, the EDN signaling inhibitor BQ-788 was added to inhibit endogenous EDNRB signaling. Relative mRNA levels were measured by quantitative RT-PCR. Levels are normalized to β-actin and the - RA/- EDN3 condition was standardized to a value of 1. Relative mRNA levels were compared between the groups. A two way ANOVA was employed to identify the contribution of each compound to changes in the proportion of proliferating cells. Significant changes (p<0.05) are in bold. Abbreviations: 3d = 3-day culture; 14d = 14-day culture; EDN3 = endothelin-3; RA = Retinoic acid;