Table 6. Changes in RA receptor-related mRNA levels in response to RA and EDN3.

	Comparison of relative mean mRNA levels
	(p value)
Target gene:	Rara		Rarb		Rarg
	3d	14d	3d	14d	3d	14d
RA- vs. RA+ (EDN3-)	1.0 vs. 0.953	1.0 vs. 1.124	1.0 vs. 9.005	1.0 vs. 183.758	1.0 vs. 1.4	1.0 vs. 0.854
			(p<0.001)	(p=0.002)	(p=0.005)
RA- vs. RA+ (EDN3+)	0.846 vs. 1.028	1.315 vs. 0.751	0.438 vs. 7.406	1.589 vs. 222.325	0.817 vs. 0.995	1.320 vs. 1.031
			(p=0.001)	(p<0.001)
EDN3- vs. EDN3+ (RA-)	1.0 vs. 0.846	1.0 vs. 1.315	1.0 vs. 0.438	1.0 vs. 1.589	1.0 vs. 0.817	1.0 vs. 1.32
EDN3- vs. EDN3+ (RA+)	0.953 vs. 1.028	1.124 vs. 0.751	9.005 vs. 7.406	183.758 vs. 222.325	1.4 vs. 0.995	0.854 vs. 1.031
			(p=0.023)		(p=0.005)
Interaction present?	No	No	No	No	No	No

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;