Helfrich-Förster C
Botanisches Institut, Tübingen, Germany.
J Comp Physiol A. 1998 Apr;182(4):435-53. doi: 10.1007/s003590050192.
Mutations at the disconnected (disco) locus of Drosophila melanogaster disrupt neural cell patterning in the visual system, leading to the loss of many optic lobe neurons. Drosophila's presumptive circadian pacemaker neurons--the dorsal and ventral lateral neurons--are usually among the missing cells, and most disco flies are behaviorally arrhythmic. In this study, I show that ventral lateral neurons (LNvs) are occasionally present and provoke robust circadian rhythmicity in disco mutants. Of 357 individual disco flies four animals with robust circadian rhythmicity were found. All four retained LNvs together with terminals in the superior protocerebrum. Residual or bi-circadian rhythmicity was found in about 20% of all flies; the remaining flies were completely arrhythmic. One of the flies with residual rhythmicity and two of the arrhythmic flies also had some LNvs stained. However, these flies lacked the LNv fibers in the superior protocerebrum. The results suggest that the presence of single LNvs is sufficient to provoke robust circadian rhythmicity in locomotor activity if the LNv terminals reach the superior protocerebrum. The presence of residual or bi-circadian rhythmicity in 20% of the flies without LNvs indicates that also other cells contribute to the rhythmic control of locomotor activity.
果蝇黑腹果蝇不连续（disco）位点的突变会破坏视觉系统中的神经细胞模式，导致许多视叶神经元缺失。果蝇假定的昼夜节律起搏器神经元——背侧和腹侧外侧神经元——通常是缺失的细胞之一，大多数disco果蝇在行为上表现为无节律。在这项研究中，我表明腹侧外侧神经元（LNvs）偶尔会出现，并在disco突变体中引发强烈的昼夜节律。在357只个体disco果蝇中，发现了4只具有强烈昼夜节律的果蝇。这4只果蝇都保留了LNvs以及原脑上部的终端。在所有果蝇中，约20%发现有残余或双昼夜节律；其余果蝇完全无节律。其中一只具有残余节律的果蝇和两只无节律的果蝇也有一些LNvs被染色。然而，这些果蝇在原脑上部缺乏LNv纤维。结果表明，如果LNv终端到达原脑上部，单个LNvs的存在足以在运动活动中引发强烈的昼夜节律。20%没有LNvs的果蝇中存在残余或双昼夜节律，这表明其他细胞也有助于运动活动的节律控制。
