Diverse types of neurons must be specified in the developing brain to form the functional neural circuits that are necessary for the execution of daily tasks. Here, we describe the participation of Forkhead box class O (FOXO) in cell fate specification of a small subset of Drosophila ventral olfactory projection neurons (vPNs). Using the two-color labeling system, twin-spot MARCM, we determined the temporal birth order of each vPN type, and this characterization served as a foundation to investigate regulators of cell fate specification. Flies deficient for chinmo, a known temporal cell fate regulator, exhibited a partial loss of vPNs, suggesting that the gene plays a complex role in specifying vPN cell fate and is not the only regulator of this process. Interestingly, loss of foxo function resulted in the precocious appearance of late-born vPNs in place of early-born vPNs, whereas overexpression of constitutively active FOXO caused late-born vPNs to take on a morphology reminiscent of earlier born vPNs. Taken together, these data suggest that FOXO temporally regulates vPN cell fate specification. The comprehensive identification of molecules that regulate neuronal fate specification promises to provide a better understanding of the mechanisms governing the formation of functional brain tissue.

必须在发育中的大脑中指定不同类型的神经元，以形成执行日常任务所需的功能性神经回路。在这里，我们描述了果蝇腹侧嗅觉投射神经元（vPNs）的小子集的细胞命运规范中的前叉箱类O（FOXO）的参与。使用双色MARCM双色标记系统，我们确定了每种vPN类型的时间出生顺序，并且该表征为研究细胞命运规范的调节剂奠定了基础。缺乏chinmo（一种已知的时间性细胞命运调节因子）的苍蝇表现出vPN的部分缺失，表明该基因在指定vPN细胞命运方面起着复杂的作用，而不是该过程的唯一调节因子。有趣的是，损失foxo功能导致早产vPN代替早产vPN的早熟外观，而组成型活性FOXO的过度表达导致晚产vPN呈现出让人想起早产vPN的形态。综上所述，这些数据表明FOXO在时间上调节vPN细胞命运规范。调节神经元命运规范的分子的全面鉴定有望对控制功能性脑组织形成的机制提供更好的理解。