Analysis of cardiovascular anomalies in the Hoxa3 and Pax-3 homozygous null mutant mice.

Hoxa 3基因在第三咽弓和咽囊中表达，并且除了胸腺、甲状旁腺和颈动脉体之外，第三弓动脉的发育也需要Hoxa 3基因。我们对Hoxa 3纯合子突变小鼠颈动脉系统畸形与野生型和杂合子同窝小鼠进行了统计学分析。在Hoxa 3纯合子中，在E10.5观察到第三弓动脉，但在E11.5退化。因此，颈总动脉，第三弓动脉的衍生物在无效突变体中缺失或非常短。大动脉的图尼卡中膜是由外胚间充质神经嵴细胞形成的。为了评估第三弓动脉退化的原因，将Hoxa 3杂合子小鼠与连接蛋白43-lacZ转基因小鼠杂交，其中神经嵴细胞由β-半乳糖苷酶表达指定。神经嵴细胞正常迁移到第三咽弓，并包围弓动脉的无效突变体以及野生型。应用<165>激光捕获显微切割和实时荧光定量PCR方法，对E10.5Hoxa3基因缺失突变体第三弓状动脉中与胚胎血管或弓状动脉发育有关的VEGF_（1）及其受体（酪氨酸激酶Flt-1和Flk-1）、内皮素ET-1和dHand的表达进行了分析。无效<165>突变体中VEGF mRNA几乎完全缺失，ET-1 mRNA表达明显降低。突变体中Flk-1 mRNA表达下调，而Flt-1 mRNA表达上调。Hoxa 3基因可能调控VEGF和ET-1系统在第三弓动脉发育中的作用。

Hoxa3 gene is expressed in the third pharyngeal arch and pouch and is required for development of the third arch artery in addition to the thymus, parathyroid land and carotid body. We statistically analyzed malformations of the carotid artery system in Hoxa3 homozygous mutant mice, in comparison with wild-type and heterozygous littermates. In the Hoxa3 homozygotes, the third arch artery was observed at E 10.5 but degenerated at E 11.5. Therefore the common carotid artery, the derivative of the third arch artery was absent or very short in the null mutants. The tunica media of great arteries derived from the arch arteries is formed by the ectomesenchymal neural crest cells. To assess the cause of the third arch artery regression, the Hoxa3 heterozygous mice were crossed with the connexin43-lacZ transgenic mice in which neural crest cells are specified by β-galactosidase expression. The neural crest cells normally migrated into the third pharyngeal arch and surrounded the arch artery in the null mutants as well as wild types. The expressions of VEGF_<165>, its receptors (tyrosine kinases Flt-1 and Flk-1), endothelin ET-1 and dHand which are responsible for development of embryonic blood vessels or arch arteries, were analyzed in the third arch artery of the E 10.5 Hoxa3 null mutants, in comparison with wild types, by the laser capture microdissection and real-time PCR methods. VEGF_<165> mRNA was almost lost and ET-1 mRNA was markedly reduced in the null mutants. Flk-1 mRNA expression was down-regulated whereas Flt-1 mRNA was up-regulated in the mutants. The Hoxa3 gene may ragulate the pathways of both VEGF and ET-1 systems for the third arch artery development.