XB-ART-51690Sci Rep September 21, 2015; 5 17893.
Ca-α1T, a fly T-type Ca2+ channel, negatively modulates sleep.
Mammalian T-type Ca(2+) channels are encoded by three separate genes (Cav3.1, 3.2, 3.3). These channels are reported to be sleep stabilizers important in the generation of the delta rhythms of deep sleep, but controversy remains. The identification of precise physiological functions for the T-type channels has been hindered, at least in part, by the potential for compensation between the products of these three genes and a lack of specific pharmacological inhibitors. Invertebrates have only one T-type channel gene, but its functions are even less well-studied. We cloned Ca-α1T, the only Cav3 channel gene in Drosophila melanogaster, expressed it in Xenopus oocytes and HEK-293 cells, and confirmed it passes typical T-type currents. Voltage-clamp analysis revealed the biophysical properties of Ca-α1T show mixed similarity, sometimes falling closer to Cav3.1, sometimes to Cav3.2, and sometimes to Cav3.3. We found Ca-α1T is broadly expressed across the adult fly brain in a pattern vaguely reminiscent of mammalian T-type channels. In addition, flies lacking Ca-α1T show an abnormal increase in sleep duration most pronounced during subjective day under continuous dark conditions despite normal oscillations of the circadian clock. Thus, our study suggests invertebrate T-type Ca(2+) channels promote wakefulness rather than stabilizing sleep.
PubMed ID: 26647714
PMC ID: PMC4673464
Article link: Sci Rep
Genes referenced: cacna1g cacna1h cacna1i cav3.1 cav3.2 clock cnga1 gnl3 igf2bp3
Article Images: [+] show captions
|Figure 2. GFP::Ca-α1T expression in the adult brain.(a) Gene targeting and GFP::Ca-α1T generation strategy. Ca-α1T coding exons are red. (b) Adult brain expression of GFP::Ca-α1T (green) divided into maximal intensity projections of confocal stacks from the anterior (b1), middle (b2), and posterior (b3) brain. (c–h) GFP::Ca-α1T expression in specific neuropils whose location corresponds to the boxed areas in (b). (c) Expression in the antennal lobes (AL) and subesophageal ganglia (SOG). (d) Expression in the mushroom body (MB) lobes (α, β, and α’). (e) Expression in the fan-shaped body (FB), ellipsoid body (EB), and noduli (NO) of the central complex. (f) Expression in the (f1) anterior and (f2) posterior mushroom body (MB) peduncles. (g) Expression in the protocerebral bridge (PB) of the central complex. (h) Expression in the mushroom body (MB) calyx. Neuropils are counter-stained with the nc82 antibody (α-Bruchpilot, magenta).|