Mechanism of an Evolutionary Change in Development

在进化过程中，人们对发育变化是如何产生的知之甚少。为了解决这个问题，杰弗里博士利用了一个独特的模型系统，该系统由具有不同发育形式的密切相关的海鞘物种组成。海鞘是一种简单的动物，具有许多与脊椎动物相同的发育特征，包括脊索（脊柱的进化前身）、背中枢神经系统和尾巴。大多数海鞘发育上述特征，然而，少数物种在进化过程中失去了这一特性。这个实验室研究的两个物种中，一个具有脊椎动物的特征，而另一个则失去了这些特征。值得注意的是，当这两个物种杂交时，缺乏脊椎动物特征的物种恢复了它们的特征，这表明后者失去了发育调节基因的功能。这一结果开启了鉴定参与调节脊椎动物特征发育和进化的基因的可能性。在此之前，该实验室使用了一种减法程序，即从一个物种的克隆基因中减去另一个物种的克隆基因的RNA产物，以识别这些调节基因。Jeffery小组发现的一种基因被称为manx，因为它是尾巴发育所必需的（例如，manx猫没有尾巴）。manx基因产生一种调节蛋白，可能控制其他基因的活性。这项提议将得到资助，以获得更多关于manx基因如何控制海鞘尾部形成的信息，并确定由manx控制的其他基因在脊椎动物特征的发展中发挥作用。通过这些程序，他们将确定与脊索、尾巴和中枢神经系统发育有关的其他基因。所获得的信息有望帮助理解在高等动物的发展和进化过程中身体计划是如何产生的。****

Jeffrey, William IBN #9417799 Little is known about how changes in development arise during evolution. To address this problem, Dr. Jeffrey capitalizes on a unique model system consisting of closely-related species of ascidians with different forms of development. Ascidians are simple animals with many of the same developmental features as vertebrates, including a notochord (the evolutionary precursor of the vertebral column), a dorsal central nervous system, and a tail. Most ascidians develop the features described above, however, a few species have lost this property during evolution. One of the two species studied by this laboratory has vertebrate-like features, whereas the other has lost them. Remarkably, when these two species are hybridized, the species lacking vertebrate-like features recovers them, suggesting that the function of developmental regulatory genes has been lost in the latter species. This result opens the possibility of identifying genes involved in regulating development and evolution of the vertebrate-like features. Previously this laboratory has used a subtractive procedure in which the RNA products of cloned genes from one species were subtracted from those of another species to identify these regulatory genes. One of the genes the Jeffery group has identified is called manx because it is required for development of the tail (e.g. Manx cats lack a tail). The manx gene produces a regulatory protein that is likely to control the activity of other genes. This proposal will be funded in order to obtain more information on how the manx gene controls tail formation in ascidians and to identify the other genes controlled by manx that play a role in development of vertebrate-like features. Using these procedures, they will identify additional genes involved in development of the notochord, tail, and central nervous system. The information obtained is expected to help understand how the body plan is generated during the developm ent and evolution of higher animals.****