Integrating systems biology and transgenic technologies to unlock the secrets of Sertoli cell development and function

睾丸的功能是产生生殖细胞（精子）和制造雄激素（睾酮）。这些行动对于正常的男性生育力、男性行为和一般成年男性的健康至关重要。该项目旨在了解睾丸中不同组成细胞类型如何相互作用，以确保睾丸正常发育和功能。这些信息将与先前发表的数据相结合，以创建睾丸如何工作的计算机模型，该模型将使科学家能够测试睾丸功能的新场景和假设。睾丸主要由一系列小管（生精小管）组成，精子在其中发育，由一组称为支持细胞的细胞支持。曲细精管被另一种称为管周肌样细胞的细胞包围，这种细胞被认为有助于精子发育。雄激素是由间质细胞分泌的，它们位于生精小管之间。众所周知，睾丸的早期形成取决于支持细胞。它们首先发育，然后促进其他细胞类型的后续分化。然而，尚不清楚的是，支持细胞对成年后睾丸发育和整体功能的重要性。换句话说，我们不知道支持细胞是否协调整个睾丸功能，或者只是在小管内起作用以维持精子发育。这一点很重要，因为它是我们理解睾丸生物学的基础，睾丸的正常发育对成年生育能力和正常成年健康至关重要。对于旨在检查特定细胞类型的整体功能的研究，最有效的方法是破坏该细胞，看看成年人器官发育或器官功能会发生什么。直到最近，只有使用细胞特异性毒素才有可能，而且这些毒素只存在于极少数细胞类型中。然而，小鼠转基因技术的最新发展现在意味着几乎任何细胞类型都可以被靶向。新技术依赖于啮齿动物对白喉毒素的不敏感性，白喉毒素对人类可能是致命的。在人类中，白喉毒素与细胞表面的一种受体（称为白喉毒素受体或DTR）结合，使部分白喉毒素分子进入细胞并破坏细胞。小鼠通常缺乏这种DTR，但使用转基因技术，现在可以创造出在特定细胞类型上具有DTR的小鼠。这使得这些细胞对白喉毒素的毒性作用敏感。我们现在已经制造了一系列在支持细胞上具有DTR的小鼠。初步实验表明，当我们将白喉毒素注射到这些小鼠体内时，它会很快杀死支持细胞，但不会对小鼠造成其他损害。我们现在要做的是找出当我们杀死部分或全部支持细胞时，睾丸中其他类型的细胞会发生什么。此外，由于我们可以选择何时注射白喉毒素，我们可以发现支持细胞的功能是否随着动物的发育而变化。例如，成年动物中的支持细胞死亡对肾小管周围肌样细胞的影响是否与新生动物中的细胞死亡相同？这项工作和以前研究的数据将在我们的建模程序（Biolayout Express 3D，见www.biolayout.org）中汇集在一起，以创建睾丸内细胞和分子如何相互作用以促进正确睾丸功能的计算机模型。这些计算机和小鼠模型将使我们能够确定支持细胞与睾丸中其他细胞类型相互作用的复杂方式，以及它们如何促进睾丸生长并确保成年男性的生育力和健康。

The testes function to produce germ cells (sperm) and to make androgens (testosterone). These actions are essential for normal male fertility, male behaviour and for general adult male wellbeing. This project is designed to find out how the different component cell types in the testis interact to ensure that the testes develop and function normally. This information will be combined with previously published data to create a computer model of how the testis works and this model will be made available to allow scientists to test novel scenarios and hypotheses of testis function. The testes are composed largely of an array of small tubules (the seminiferous tubules) in which the sperm develop supported by a group of cells called the Sertoli cells. The seminiferous tubules are surrounded by another cell type called the peritubular myoid cells which are thought to help sperm development. Androgens are secreted by the Leydig cells and these are found lying in between the seminiferous tubules. Early formation of the testis is known to be dependent upon the Sertoli cells. They develop first and then act to promote the subsequent differentiation of other cell types. What is much less clear, however, is how important the Sertoli cells are for later testis development and for overall function in the adult. In other words, we don't know if the Sertoli cells orchestrate overall testicular function or just act within the tubules to maintain sperm development. This is important because it is fundamental to our understanding of testis biology and normal development of the testis is essential for adult fertility and normal adult health.For studies designed to examine the overall function of a particular cell type the most effective approach is to destroy that cell and see what happens to organ development or organ function in the adult. Until recently that was only possible using cell-specific toxins and these only existed for a very small number of cell types. Recent developments in mouse transgenics, however, now mean that almost any cell type can be targeted. The new techniques depend upon rodent insensitivity to the effects of diphtheria toxin which can be lethal in the human. In humans, diphtheria toxin binds to a receptor present on the cell surface (called the diphtheria toxin receptor or DTR) allowing part of the diphtheria toxin molecule to enter the cell and destroy it. Mice normally lack this DTR but using transgenics it is now possible to create mice that have the DTR on specific cell types. This then makes those cells sensitive to the toxic effects of diphtheria toxin. We have now made a line of mice that have the DTR on the Sertoli cells. Preliminary experiments have shown that when we inject diphtheria toxin into these mice it very quickly kills the Sertoli cells but does no other damage to the mouse. What we now propose to do is find out what happens to the other cell types in the testis when we kill some or all of the Sertoli cells. In addition, because we can choose when to inject the diphtheria toxin we can find out whether the function of the Sertoli cell changes as the animal develops. For example, will Sertoli cell death in the adult animal have the same effect on the peritubular myoid cells as cell death in the newborn? Data from this work and from previous studies will be brought together within our modelling programme (Biolayout Express 3D, see www.biolayout.org) to create a computer model of how the cells and molecules within the testis interact to promote correct testis function. Together these computer and mouse models will allow us to determine the complex ways in which the Sertoli cell interacts with other cell types in the testis and how they act to promote testis growth and ensure fertility and wellbeing in the adult male.