Bai Lei, Goldman Aaron L, Carlson John R
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA.
J Neurosci. 2009 Oct 14;29(41):12940-7. doi: 10.1523/JNEUROSCI.3525-09.2009.
Little is known about how individual olfactory receptor neurons (ORNs) select, from among many odor receptor genes, which genes to express. Abnormal chemosensory jump 6 (Acj6) is a POU domain transcription factor essential for the specification of ORN identity and odor receptor (Or) gene expression in the Drosophila maxillary palp, one of the two adult olfactory organs. However, the mechanism by which Acj6 functions in this process has not been investigated. Here, we systematically examine the role of Acj6 in the maxillary palp and in a major subset of antennal ORNs. We define an Acj6 binding site by a reiterative in vitro selection process. The site is found upstream of Or genes regulated by Acj6, and Acj6 binds to the site in Or promoters. Mutational analysis shows that the site is essential for Or regulation in vivo. Surprisingly, a novel ORN class in acj6 adults is found to arise from ectopic expression of a larval Or gene, which is repressed in wild type via an Acj6 binding site. Thus, Acj6 acts directly in the process of receptor gene choice; it plays a dual role, positive and negative, in the logic of the process, and acts in partitioning the larval and adult receptor repertoires.
关于单个嗅觉受体神经元（ORN）如何从众多气味受体基因中选择要表达的基因，目前所知甚少。异常化学感应跳跃6（Acj6）是一种POU结构域转录因子，对于果蝇成虫的两个嗅觉器官之一——上颌触须中ORN身份的确定和气味受体（Or）基因的表达至关重要。然而，Acj6在这一过程中的作用机制尚未得到研究。在此，我们系统地研究了Acj6在上颌触须和触角ORN的一个主要亚群中的作用。我们通过反复的体外筛选过程确定了一个Acj6结合位点。该位点位于受Acj6调控的Or基因上游，且Acj6能与Or启动子中的该位点结合。突变分析表明，该位点对于体内Or基因的调控至关重要。令人惊讶的是，在acj6突变体成虫中发现了一类新的ORN，它源自一个幼虫Or基因的异位表达，而该基因在野生型中通过一个Acj6结合位点被抑制。因此，Acj6直接参与受体基因选择过程；它在这一过程的逻辑中发挥着正负双重作用，并在划分幼虫和成虫受体库中起作用。
