Investigating the sexually dimorphic neural circuit in Drosophila melanogaster using behavioural genetics and structural biology

“我们的大脑是如何控制我们的行为的？”从希波克拉底时代起就一直是人类的好奇。试图解开这个谜团仍然是一项艰巨的任务，因为人类的大脑由近1000亿个神经元组成，连接着100万亿个神经元。我们如何理解这样一个复杂的系统是如何运作的？为了帮助我们深入了解我们的大脑是如何工作的，我们把常见的果蝇作为一个模型系统。苍蝇的神经系统只有大约10万个神经元，要简单得多。学习简单网络的基础，如苍蝇的大脑，将提供与更大网络运行相关的基本知识。 动物与生俱来的某些本能确保了它们的生存和繁殖成功。由于本能是与生俱来的，它给了我们一个机会，利用遗传工具来操纵神经系统，以了解神经系统是如何发挥作用来引发行为的。在果蝇身上，求偶是一种特定性别的复杂本能行为。雄性进行一系列的求偶仪式(定位、轻拍、唱歌、舔、交配)，而雌性则决定是逃跑还是放慢速度，允许交配。雄性求爱行为需要使用所有感官(即视觉、嗅觉和味觉)，并需要一个决定过程来触发马达输出来执行求偶仪式，雄性求爱行为由一个名为无果(FEU)电路的神经网络控制。FU环路由神经系统中的~2000个神经元组成。虽然这个回路的神经元组织是可用的，但每个神经元在求爱行为中是如何发挥作用的还没有完全弄清楚。FRU回路是性别特有的，因为一些神经元在雌性中不存在，一些在两性中都存在，但具有不同的形态，其他的可能在雄性和雌性中具有不同的功能。FRU基因产物的男性形式(FRUM)是负责FRU回路发育的关键蛋白质。最近，人们发现Frum与两种蛋白质因子(HDAC1和HP1a)一起工作，以微调至少两个电路小区域的性别属性。目前尚不清楚同样的蛋白质因素是否也会影响FRU回路的其他性别特定区域。 凭借我在结构生物学和行为遗传学方面的独特培训，以及我以前工作中产生的允许将基因靶向到FRU回路的一小部分的试剂，我将能够从三个方向继续我的研究计划：1)这些FRU神经元的子集在求爱中扮演什么角色？2)与FRUM相关的哪些因素会影响该回路不同性别特定区域的发育？3)FRUM如何与其结合伙伴在三维空间中相互作用，导致行为和形态结果。在我的五年计划中，我将专注于三个短期目标：1)确定在求爱过程中处理视觉感觉的FRU神经元；2)评估HDAC1和HP1a在我们先前工作中分离的一小群FRU神经元特定性别发育中的作用；以及3)在体外研究FRUM与HDAC1和HP1a的不同结合特性。 我的研究项目的意义在于将整体论和简化论方法结合起来理解FRU电路的功能和发展的新颖性。从这种结合的方法中发展出来的独特见解将有益于天生行为的神经生物学领域。由这笔赠款资助的HQP将成为广泛的非常技术性的实验方法方面的专家，确保他们在加拿大和国际科学劳动力中的竞争力。这一多学科的研究计划可以带来新的技术，可以用来研究动物的行为。

“How does our brain govern how we behave?” has been a curiosity of mankind since the time of Hippocrates. Attempting to solve this mystery is still a monumental task as the human brain consists of close to 100 billion neurons making 100 trillion connections. How do we make sense of how such a complicated system works? To help us gain some insight into how our brain works, we turn to the common fruit fly as a model system. With only ~100,000 neurons, the fly nervous system is much simpler. Learning the underpinnings of a simple network such as a fly’s brain will provide the fundamental knowledge relevant to the operation of a larger network. Animals are born with certain instincts that ensure their survival and reproductive success. Since instincts are hard-wired, it gives us an opportunity to use genetic tools to manipulate the nervous system in order to understand how the nervous system functions to elicit a behaviour. In flies, courtship is a sex-specific complex instinctive behaviour. Males perform a series of courtship rituals (orientation, tapping, singing, licking, copulation) while females decide whether to run away or slow down and allow copulation. Requiring the use of all senses (i.e., vision, smell, and taste) and a decision process that triggers a motor output to perform the courtship rituals, male courtship behaviour is controlled by a neural network called the fruitless (fru) circuit. The fru circuit consists of ~2000 neurons in the nervous system. While the neuronal organization of this circuit is available, how each neuron functions in the context of courtship behaviour has not been fully worked out. The fru circuit is gender-specific in that some neurons are absent in females, some are present in both sexes but have different morphology, and others may have different functions in males and females. The male-form of the fru gene product (FruM) is the key protein that is responsible for the development of the fru circuit. Recently, it was discovered that FruM works with two protein factors (HDAC1 and HP1a) to fine-tune the gender property of at least two small regions of the circuit. It is not known whether the same protein factors affect other gender-specific regions of the fru circuit as well. With my unique training both in structural biology and behavioural genetics and reagents generated from my previous work that permits gene targeting to a small subsets of the fru circuit, I will be able to pursue my research program in three directions: 1) what role do these subsets of fru neurons play in courtship? 2) What factors associate with FruM to influence the development of different gender-specific regions of the circuit? 3) How does FruM interact with its binding partners in three-dimensional space to cause behavioural and morphological outcomes. In my five-year proposal, I will focus on three short-term objectives: 1) to identify fru neurons that process visual senses during courtship; 2) to evaluate the role of HDAC1 and HP1a in the gender-specific development of a small group of fru neurons isolated in our previous work; and 3) to investigate the different binding property of FruM to HDAC1 and HP1a in vitro. The significance of my research program is in the novelty of combining holistic and reductionist approaches to understand the functioning and development of the fru circuit. The unique insights developed from this combined approach will benefit the field of neurobiology of innate behaviour. The HQPs funded by this grant will become experts in a wide range of very technical experimental approaches, ensuring their competitiveness in the Canadian and international scientific workforce. The multidisciplinary research program can lead to new techniques that can be used to study animal behaviour.