Evolution of sodium channels predates the origin of nervous systems in animals
Evolution of sodium channels predates the origin of nervous systems in animals
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DOI：
10.1073/pnas.1106363108
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发表时间：
2011-05-31
影响因子：
11.1
通讯作者：
Zakon, Harold H.
中科院分区：
文献类型：
--
作者：
Liebeskind, Benjamin J.;Hillis, David M.;Zakon, Harold H.
电压依赖性钠通道被认为是从神经系统起源的钙通道进化而来的。对单细胞领鞭毛虫（动物的姐妹群）基因组的搜索确定了一个与动物钠通道同源的基因，并且在钙和钠通道之间具有假定的离子选择性过滤器中间体。对各种各样的动物基因组（包括每个基础谱系的代表）的分析表明，在大多数谱系中保留了相似的同源物。其中之一，Placozoa，没有神经系统。我们克隆和测序的完整choanoflagellate通道和部分的两个板块动物通道的mRNA，显示它们的表达。系统发育分析将这些通道的基因与其他已知的钠通道聚类。从这个hepatogeny，我们推断祖先的离子选择性过滤器的状态，并表明，这种状态已被保留在choanoflagellate和placozoan通道。我们还确定了关键的基因重复和损失，并显示收敛的氨基酸替换在重要的点沿着动物谱系。
Voltage-dependent sodium channels are believed to have evolved from calcium channels at the origin of the nervous system. A search of the genome of a single-celled choanoflagellate (the sister group of animals) identified a gene that is homologous to animal sodium channels and has a putative ion selectivity filter intermediate between calcium and sodium channels. Searches of a wide variety of animal genomes, including representatives of each basal lineage, revealed that similar homologs were retained in most lineages. One of these, the Placozoa, does not possess a nervous system. We cloned and sequenced the full choanoflagellate channel and parts of two placozoan channels from mRNA, showing that they are expressed. Phylogenetic analysis clusters the genes for these channels with other known sodium channels. From this phylogeny we infer ancestral states of the ion selectivity filter and show that this state has been retained in the choanoflagellate and placozoan channels. We also identify key gene duplications and losses and show convergent amino acid replacements at important points along the animal lineage.