Kullander K, Carlson B, Hallböök F
Department of Developmental Neuroscience, Box 587, Biomedical Center, Uppsala University, S-751 23 Uppsala, Sweden.
J Mol Evol. 1997 Sep;45(3):311-21. doi: 10.1007/pl00006235.
We have investigated the phylogenetic relationships of monotremes and marsupials using nucleotide sequence data from the neurotrophins; nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3). The study included species representing monotremes, Australasian marsupials and placentals, as well as species representing birds, reptiles, and fish. PCR was used to amplify fragments encoding parts of the neurotrophin genes from echidna, platypus, and eight marsupials from four different orders. Phylogenetic trees were generated using parsimony analysis, and support for the different tree structures was evaluated by bootstrapping. The analysis was performed with NGF, BDNF, or NT-3 sequence data used individually as well as with the three neurotrophins in a combined matrix, thereby simultaneously considering phylogenetic information from three separate genes. The results showed that the monotreme neurotrophin sequences associate to either therian or bird neurotrophin sequences and suggests that the monotremes are not necessarily related closer to therians than to birds. Furthermore, the results confirmed the present classification of four Australasian marsupial orders based on morphological characters, and suggested a phylogenetic relationship where Dasyuromorphia is related closest to Peramelemorphia followed by Notoryctemorphia and Diprotodontia. These studies show that sequence data from neurotrophins are well suited for phylogenetic analysis of mammals and that neurotrophins can resolve basal relationships in the evolutionary tree.
我们利用神经营养因子（神经生长因子（NGF）、脑源性神经营养因子（BDNF）和神经营养因子-3（NT-3））的核苷酸序列数据，研究了单孔目动物和有袋目动物的系统发育关系。该研究涵盖了代表单孔目动物、澳大利亚有袋目动物和胎盘类动物的物种，以及代表鸟类、爬行动物和鱼类的物种。采用聚合酶链反应（PCR）从针鼹、鸭嘴兽以及来自四个不同目别的八种有袋目动物中扩增编码神经营养因子基因部分片段。利用简约分析生成系统发育树，并通过自展法评估不同树形结构的支持度。分析分别使用NGF、BDNF或NT-3序列数据进行，同时也使用这三种神经营养因子的组合矩阵进行，从而同时考虑来自三个独立基因的系统发育信息。结果表明，单孔目动物的神经营养因子序列与有胎盘类动物或鸟类的神经营养因子序列相关联，这表明单孔目动物与有胎盘类动物的关系不一定比与鸟类的关系更近。此外，结果证实了目前基于形态特征对四个澳大利亚有袋目目别的分类，并表明了一种系统发育关系，即袋鼬目与袋狸目关系最密切，其次是袋鼹目和双门齿目。这些研究表明，神经营养因子的序列数据非常适合用于哺乳动物的系统发育分析，并且神经营养因子能够解析进化树中的基础关系。
