Boorman Clive J, Shimeld Sebastian M
School of Animal and Microbial Sciences, The University of Reading, Whiteknights, UK.
Dev Genes Evol. 2002 Aug;212(7):349-53. doi: 10.1007/s00427-002-0249-9. Epub 2002 Jun 15.
The Pitx homeobox gene family has important roles in vertebrate pituitary, eye, branchial arch, hindlimb and brain development, as well as a key function in regulating left-right asymmetry. Here we report the isolation of a Pitx gene, PitxA, from two lamprey species, Lampetra planeri and Petromyzon marinus. Molecular phylogenetics show PitxA is most closely related to the Pitx1 and Pitx2 genes of jawed vertebrates, however resolution in the trees is insufficient to determine if PitxA is orthologous to a specific jawed vertebrate gene. In situ hybridisation studies show lamprey PitxA is expressed in the developing nasohypohyseal system and stomodeal ectoderm from early development through to early ammocoette larvae. PitxA expression was also detected in several areas of the developing brain, in the developing optic system, in pharyngeal endoderm and endostyle and in the lateral somite. These results show some key aspects of Pitx gene expression in gnathostomes are primitive for all living vertebrates.
Pitx同源框基因家族在脊椎动物的垂体、眼睛、鳃弓、后肢和大脑发育中发挥着重要作用，并且在调节左右不对称方面具有关键功能。在此，我们报告了从两种七鳃鳗物种，即溪七鳃鳗（Lampetra planeri）和海七鳃鳗（Petromyzon marinus）中分离出一个Pitx基因，即PitxA。分子系统发育学表明，PitxA与有颌脊椎动物的Pitx1和Pitx2基因关系最为密切，然而，系统发育树中的分辨率不足以确定PitxA是否与特定的有颌脊椎动物基因是直系同源的。原位杂交研究表明，七鳃鳗PitxA在从早期发育到早期沙隐虫幼虫阶段的发育中的鼻垂体系统和口凹外胚层中表达。在发育中的大脑的几个区域、发育中的视觉系统、咽内胚层和内柱以及外侧体节中也检测到了PitxA的表达。这些结果表明，有颌类动物中Pitx基因表达的一些关键方面对于所有现存脊椎动物来说都是原始的。
