据普渡大学教育网站2006年9月14日报道，一种喜阴的啮齿动物有可能揭示人类基因和进化的神秘性。普渡大学研究显示，一种类似老鼠的啮齿类动物野鼠不仅是进化最快的哺乳动物，而且还包含有许多挑战当前科学理解中令人费解的遗传特性。
“没有人特别研究过野鼠，”森林和自然资源系副教授，其研究发表在本月《遗传》杂志上的J•安德鲁•代物第说，“但是当涉及到遗传这方面的时候，野鼠应受到更多的关注。”小啮齿动物经常被误认为是老鼠，除了有较短的尾巴和泡泡眼外，其余与老鼠长得都很像。野鼠生活范围遍布整个北半球，经常被认为是农业害虫，因为它们以绿色素菜为食。但是野鼠是包含许多奇怪特性的“进化中的谜”，代物第说道。了解了造成这些特性的原因就能更好地了解出现在人类遗传和遗传障碍上的相似现象，同时对基因治疗也有积极的意义，他说。
这项研究对象包括野鼠类Mocrotus中的60个种类，野鼠类已经进化了有50万年到200万年了。这意味着在创造不同物种方面，野鼠的进化速度比脊椎动物的平均进化速度快60－100倍。在类里面，野鼠的染色体的数量17—64不等。代物第说这是个不寻常的发现，因为在单个类中的同种物体染色体数通常是相同的。存在于野鼠中的其他不寻常遗传特性：
•在一种物种中，X染色体，两个决定性别的染色体（另一个是Y染色体）之一，包含了整个基因组的20%。通常性别染色体中包含更少的遗传信息。
•在另一种物种中，雌性体内包含大比例的Y（雄）染色体。
•在还有一种物种中，雌性和雄性体的染色体数量不同，这点在动物体内是极不寻常的。
一个 “有悖常理的古怪” 结论是：虽然基因存在差异，但是所有的野鼠长得都很相似，代物第的前研究生和该研究的合著者代波•瑞特说。“所有的野鼠看起来都很相似，甚至许多种是完全分辨不出差异，”
在一种特别的情况，代物第甚至是在近距离观察分析了它们的头盖骨结构的情况下都不能辨别两个种类的不同；只有通过基因测试才能够揭示它们的区别。
然而，野鼠却是很简单就能认出同伴。“我没有发现不同种类的野鼠进行交配。”瑞特说，“我们不知道它们是如何做到这点的，但是气味和行为举止可能起作用了。”
代物第说，“野鼠是一种能够用于研究许多可能影响人类自然现象的模型系统。”
他的研究强调线粒体基因组，是一组包含在负责产生能量（线粒体）的细胞间隔处的DNA。瑞特额外工作的一部分是探究野鼠线粒体DNA把自己植入到细胞核DNA中的独特能力。中心染色体组，就像被知道的那样，包含大多数的细胞DNA，主要作用是控制细胞功能及其发展。
“在这个领域，代波的工作可能对关于基因的基本科学知识产生潜在影响，比如那些被运用到基因疗法中的传送机制方面的基本科学知识。”代物第说。
在这个相对较新的理论里，治疗包括将基因植入患者的细胞中，为了对抗一些像血友病之类的疾病。然而，将特定基因植入到“正确”位置上或者期望它发挥作用的位置上通常是困难的。对野鼠奇特行为的普遍性现象，以及这种行为的发生方式地更好了解，可能对人类遗传研究具有重要的意义。
代物第的研究获国家科学基金和美国农业部支助。代物第希望以后可以继续他关于野鼠基因的研究。
英文原文:
Rodent's bizarre traits deepen mystery of genetics, evolution
Vole
Download photo
Purdue University research has shown that the vole, a mouselike rodent, is not only the fastest evolving mammal, but also harbors a number of puzzling genetic traits that challenge current scientific understanding.
"Nobody has posters of voles on their wall," said J. Andrew DeWoody, associate professor of genetics in the Department of Forestry and Natural Resources, whose study appears this month in the journal Genetica. "But when it comes down to it, voles deserve more attention."
Small rodents often confused for mice, except with shorter tails and beady eyes, voles live throughout the Northern Hemisphere and are often considered agricultural pests because they eat vegetation. Nevertheless, voles are an "evolutionary enigma" with many bizarre traits, DeWoody said. Understanding the basis for these traits could lead to better understanding of the same phenomena in human genetics and genetic disorders, and could have implications for gene therapy, he said.
The study focuses on 60 species within the vole genus Microtus, which has evolved in the last 500,000 to 2 million years. This means voles are evolving 60-100 times faster than the average vertebrate in terms of creating different species. Within the genus (the level of taxonomic classification above species), the number of chromosomes in voles ranges from 17-64. DeWoody said that this is an unusual finding, since species within a single genus often have the same chromosome number.
Among the vole's other bizarre genetic traits:
•In one species, the X chromosome, one of the two sex-determining chromosomes (the other being the Y), contains about 20 percent of the entire genome. Sex chromosomes normally contain much less genetic information.
•In another species, females possess large portions of the Y (male) chromosome.
•In yet another species, males and females have different chromosome numbers, which is uncommon in animals.
A final "counterintuitive oddity" is that despite genetic variation, all voles look alike, said DeWoody's former graduate student and study co-author Deb Triant.
"All voles look very similar, and many species are completely indistinguishable," DeWoody said.
In one particular instance, DeWoody was unable to differentiate between two species even after close examination and analysis of their cranial structure; only genetic tests could reveal the difference.
Nevertheless, voles are perfectly adept at recognizing those of their own species.
"I have seen absolutely no evidence of mating between different species," Triant said. "We don't know how they do this, but scent and behavior probably play a role."
DeWoody said, "The vole is a great a model system that could be used to study lots of natural phenomena that could impact humans."
His research focuses on the mitochondrial genome, the set of DNA within the cellular compartment responsible for generating energy (the mitochondria). Some of Triant's additional work explores the unique ability of vole's mitochondrial DNA to insert itself within DNA in the cell nucleus. The nuclear genome, as it is known, contains the vast majority of a cell's DNA and is responsible for controlling cellular function and development.
"Deb's work in this area could potentially have some basic science impact on gene delivery mechanisms, such as those used in gene therapy," DeWoody said.
In this relatively new therapy, treatment involves the insertion of a gene into human patients' cells in order to counter some illness or disease like hemophilia. However, it is often difficult to insert the desired gene in the "correct" location, or a location where it does what it is supposed to do. A better understanding of the unusual prevalence of this activity in voles, and the manner in which it happens, could have important human implications.
DeWoody's research was funded by the National Science Foundation and the U.S. Department of Agriculture. DeWoody hopes to continue his work on vole genetics at some point in the future.
