如何创造出100亿多个细胞，而每个细胞的职责又都不同？人类的大脑可以自然而然做到这一点。瑞典Linkping大学的研究人员现在已经向解决这个谜题迈出了第一步。
神经科学助理教授Mattias Alenius说：“了解神经元多样化的机制，以及是如何让它们拥有多样性是必要的，以便在未来能培养神经细胞和更换神经细胞。他已将最新研究成果发表在本期PLoS Biology期刊上。
Alenius和实验和临床医学部的研究小组从一个较小的角度寻求对这一关键问题的答案：果蝇的嗅觉系统。
我们不起眼的果蝇的嗅觉系统包含1200个嗅觉神经元（人类有600万个），共分为34组。每个神经元小组对一套特殊的气味起反应，因为每个神经元小组中所有的神经元只使用果蝇嗅觉中的一个受体。总之，受体提供果蝇辨别数以千计气味的能力：一个嗅觉受体，一组神经元，既简单又复杂。
Alenius和他的同事们首先通过研究果蝇的753个基因调控基因，又称为转录因子。他们已经鉴定确定了七个转录因子，它们对建立嗅觉系统中所有34个神经元组都是必须的。一个惊人的发现是大多数转录因子能同时执行两项任务：它们在激活感受气味的受体表达时，而在同一时间能关闭同一细胞中其它的气味受体。
Alenius解释说：“这研究对将来非常有帮助，如果你想制造和培养构成我们大脑的成千上万个神经细胞群之一的话。（生物谷：Bioon）
doi:10.1371/journal.pbio.1001280
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Combinatorial Activation and Repression by Seven Transcription Factors Specify Drosophila Odorant Receptor Expression
Shadi Jafari1, Liza Alkhori1, Alexander Schleiffer2, Anna Brochtrup3, Thomas Hummel3, Mattias Alenius1*
The mechanism that specifies olfactory sensory neurons to express only one odorant receptor (OR) from a large repertoire is critical for odor discrimination but poorly understood. Here, we describe the first comprehensive analysis of OR expression regulation in Drosophila. A systematic, RNAi-mediated knock down of most of the predicted transcription factors identified an essential function of acj6, E93, Fer1, onecut, sim, xbp1, and zf30c in the regulation of more than 30 ORs. These regulatory factors are differentially expressed in antennal sensory neuron classes and specifically required for the adult expression of ORs. A systematic analysis reveals not only that combinations of these seven factors are necessary for receptor gene expression but also a prominent role for transcriptional repression in preventing ectopic receptor expression. Such regulation is supported by bioinformatics and OR promoter analyses, which uncovered a common promoter structure with distal repressive and proximal activating regions. Thus, our data provide insight into how combinatorial activation and repression can allow a small number of transcription factors to specify a large repertoire of neuron classes in the olfactory system.
