Lateral neurons

Cermakian I have a general question. In the Drosophila system can we really talk about peripheral and central oscillators, or should we consider the lateral neurons as one clock among many other clocks that are fairly independent ... 

Hardin I think the lateral neurons are one clock, the antennae are another clock, the legs are yet another, and so on. At least from the evidence here, they appear to be independent. 

Sehgal I disagree. We found that there is a clock in the prothoracic gland that controls eclosion and the lateral neurons are required for the cycling of the prothoracic gland. There are some clocks in Drosophila that are not autonomous. 

Hardin In the antenna, the oscillator is sufficient for driving that rhythm. It doesn t seem to be affected by the lack of lateral neurons. 

Stanewsky I would hke to return to the question of peripheral versus central oscillators. There is a difference between the lateral neuron clock and the peripheral oscillators. The only rhythm known to persist in flies is the behavioural rhythm, which is driven by the lateral neurons. Whatever other tissue you look at, per and tim expression dampens fast in constant darkness. Do you know anything about the antennal rhythms ... 

Weit It seems that what we have heard about is damped and sustained oscillations, but we haven t yet heard anything telling us whether there are damped or sustained oscillators. So far, very few of these assays have employed single-cell studies. It is conceivable that the main difference between the SCN and other tissues, or between lateral neurons and other tissues, is that those are coupled together by synaptic coupling. 

Kay It is like flies. Their lateral neuron rhythms will damp 99% of the signal in the peripheral tissues. If you take those flies from the topcount luminescence assay and put them in locomotor and DD, you will see that their locomotor rhythms are still fine. It is not just a culture effect that you see damping of these rhythms. 

Young In flies, with behaviour lasting as long as it does, I remember rumours of someone looking at oscillations in lateral neurons specifically. We are making assumptions about how lateral neurons work, but does anyone have data on lateral neurons after 10 days in DD, for example, to show that they really do cycle ... 

The molecular assays in Clk"mAic2As bom fide rhythms with a predominant effect on circadian rhythm amplitude and no more than a modest effect on phase or period. With circadian per and tim enhancers, we observed reduced enhancer activity and a reduced cycling amplitude in a Clk" background, consistent with the role of Clk in regulating these enhancers. Nonetheless, the phase of oscillating bioluminescence is similar to that of wild-type flies. The presence of molecular rhythms contrasts with the absence of detectable behavioural rhythms. We favour the notion that this reflects a level or amplitude reduction below a critical threshold for behavioural rhythmicity. The absence of anticipation of light—dark transitions makes it very unlikely that an effect restricted to the lateral neurons — the absence of the neuropeptide PDF, for example — is primarily responsible for the behavioural phenotypes. This is also because LD behavioural rhythms are largely normal in flies devoid of PDF or the pacemaker lateral neurons (Renn et al 1999). However, we cannot exclude the possibility of selective effects of Clk" on other behaviourally relevant neurons. 

Roshash That is correct. The point here is that expression in the lateral neurons (by other people s experiments) is insufficient. So there is nothing weird about that Clk result. What hadn t been done before is the crj rescue, which is much better. My guess would be that if we use per or tim, we would get the same result. 

Kosbash This was the first thing we tried and they are both lethal. And we don t get any aberrant behaviour with pdfgal4 or crygal4, which both over-express in those lateral neurons. 

While the abundance of DBT does not oscillate, the subcellular localization of DBT does change throughout the circadian day (Fig. 2). In Drosophila, the subcellular distribution of DBT in the lateral neurons of the brain and in photoreceptor cells of the eye largely follows the changing localization of PER (Kloss et al 2001). In mammals, the pattern of CKl accumulation is also under circadian control the kinase appears to associate initially with mPER and mCRY in the cytoplasm, but it is also found in nuclear complexes and may regulate their movement to the nucleus (Lee et al 2001). 

Kaj We are looking at this now in the lateral neurons (LNs). As you might suspect, we can still see some cycling protein activity there. Slowpoke does look to me like it is providing some necessary function for gating or rhythmically guiding activity. 

These neurons know where to go because of a series of remarkable chemical signals, different from neurotransmitters, called adhesion molecules (Table 1—4). First, glial cells form a cellular matrix. Neurons can trace glial fibers like a trail through the brain to their destinations. Later, neurons can follow the axons of other neurons... 

Davies, A. and Lumsden, A. (1983) Influence of NGF on developing dorso-medial and ventro-lateral neurons of chick and mouse trigeminal ganglia. Int. J. Dev. Neurosci. 1 171-177. 

Fig. 2.3 Olfactory pathways in the antennal lobe. Axons from pheromome sense cells terminate in the macroglomerulus whereas axons from other olfactory cells project to numerous ordinary glomeruli . Second-order cell bodies are located in the medial and lateral neuronal clusters of the antennal lobe. Axons from output neurons in these clusters form the tractus olfactorio globularis, which project to the calyces and lateral lobe of protocerebrum. The diagram is modified after Boeckh and Boeckh (1979) who found that second-order neurons in Antherea sp., responding to pheromones, were located exclusively in the medial clusters. However, in Manduca sexta, Matsumoto and Hildebrand, have revealed that output neurons with dendritic arborizations in the macroglomerulus are located in both clusters.

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