Table 3.

Pharyngeal arch artery defects in mutant E10.5 embryos

Genetic background	n	PAA	Abnormal	Unilateral	Bilateral	Bilateral defects
						Present	Hypo/Int/Abs	Absent
B6-Pax9–/– a	20	1	11 (55%)	1	10	9	1	0
		2	8 (40%)	3	5	4	1	0
		3	15 (75%)	3	12	–	8	4
		4	20 (100%)	1	19	–	3	16
CD1-Pax9–/–	9	1	7 (78%)	1	6	6	0	0
		2	8 (89%) *	1	7	7	0	0
		3	8 (89%)	0	8	–	3	5
		4	9 (100%)	0	9	–	0	9
CD1-Pax9–/–;Msx1+/–	16	1	8 (50%)	0	8	8	0	0
		2	8 (50%)	0	8	8	0	0
		3	4 (25%) **	0	4	–	3	1
		4	16 (100%)	0	16	–	6*	10

Embryos were collected at E10.5 and assessed for pharyngeal arch artery (PAA) defects by intracardiac ink injection

**p < 0.005, *p < 0.05 (Fisher’s exact test for associations)

^aData for Pax9^–/– embryos on a C57Bl/6J (B6) genetic background have been published [3]. For Pax9^–/– embryos, each left and right PAA 1–4 was scored as having a unilateral or bilateral defect, and the bilateral defects categorised as either present, a combination of hypoplastic, interrupted and/or absent (Hypo/Int/Abs), and bilaterally absent. All control B6-Pax9^+/+ (n = 18) and CD1-Pax9^+/+ (n = 12) embryos were normal. CD1-Pax9^+/+;Msx1^–/– (n = 6) and CD1-Pax9^+/–;Msx1^–/– (n = 7) embryos were normal. The increase in abnormal 2nd PAAs in CD1-Pax9^–/– compared with B6-Pax9^–/– embryos is significant. The decrease in 3rd PAA defects, and the increase in hypoplastic 4th PAA defects, in CD1-Pax9^–/–;Msx1^+/– compared with CD1-Pax9^–/– embryos is significant