Institute of Medical Biology, 8A Biomedical Grove, Singapore 138648.
Neural Dev. 2011 Oct 14;6:34. doi: 10.1186/1749-8104-6-34.
The dopaminergic (DA) neurons present in the central brain of the Drosophila larva are spatially arranged in stereotyped groups that define clusters of bilaterally symmetrical neurons. These clusters have been classified according to anatomical criteria (position of the cell bodies within the cortex and/or projection pattern of the axonal tracts). However, information pertaining to the developmental biology, such as lineage relationship of clustered DA neurons and differential cell subtype-specific molecular markers and mechanisms of differentiation and/or survival, is currently not available.
Using MARCM and twin-spot MARCM techniques together with anti-tyrosine hydroxylase immunoreactivity, we have analyzed the larval central brain DA neurons from a developmental point of view and determined their time of birth, their maturation into a DA neurotransmitter phenotype as well as their lineage relationships. In addition, we have found that the homeodomain containing transcription factor Orthodenticle (Otd) is present in a cluster of clonally related DA neurons in both the larval and adult brain. Taking advantage of the otd hypomorphic mutation ocelliless (oc) and the oc2-Gal4 reporter line, we have studied the involvement of orthodenticle (otd) in the survival and/or cell fate specification of these post-mitotic neurons.
Our findings provide evidence of the presence of seven neuroblast lineages responsible for the generation of the larval central brain DA neurons during embryogenesis. otd is expressed in a defined group of clonally related DA neurons from first instar larvae to adulthood, making it possible to establish an identity relationship between the larval DL2a and the adult PPL2 DA clusters. This poses otd as a lineage-specific and differential marker of a subset of clonally related DA neurons. Finally, we show that otd is required in those DA neurons for their survival.
果蝇幼虫中枢神经系统中的多巴胺能（DA）神经元呈空间排列，形成具有双侧对称性的神经元簇。这些簇根据解剖学标准（细胞体在皮层中的位置和/或轴突束的投射模式）进行分类。然而，目前尚无关于发育生物学的信息，例如簇状 DA 神经元的谱系关系、细胞亚型特异性分子标记以及分化和/或存活的差异机制。
我们使用 MARCM 和双点 MARCM 技术以及抗酪氨酸羟化酶免疫反应，从发育的角度分析了幼虫中枢神经系统中的 DA 神经元，确定了它们的出生时间、成熟为 DA 神经递质表型的时间，以及它们的谱系关系。此外，我们发现同源域转录因子 Orthodenticle（Otd）存在于幼虫和成虫大脑中一簇克隆相关的 DA 神经元中。利用 otd 功能减弱突变体 ocelliless（oc）和 oc2-Gal4 报告线，我们研究了 orthodenticle（otd）在这些有丝分裂后神经元的存活和/或细胞命运特化中的作用。
我们的研究结果提供了证据，证明有七个神经母细胞谱系负责胚胎发生过程中幼虫中枢神经系统 DA 神经元的产生。otd 在第一龄幼虫到成年的克隆相关 DA 神经元中表达，使得幼虫 DL2a 和成年 PPL2 DA 簇之间有可能建立身份关系。这使得 otd 成为克隆相关 DA 神经元亚群的谱系特异性和差异标记物。最后，我们表明 otd 是这些 DA 神经元存活所必需的。
