DrosophilaABC transporter mutantswhite,brownandscarlethave altered contents and distribution of biogenic amines in the brain

Abstract

SUMMARYMonoamines such as dopamine, histamine and serotonin (5-HT) are widely distributed throughout the brain of the fruit fly Drosophila melanogaster, where many of their actions have been investigated. For example, histamine is released from photoreceptor synapses in the lamina neuropile of the visual system. Mutations of the genes white, an important eye pigmentation marker in fly genetics that encodes an ABC transporter, and its binding partner brown, cause neural phenotypes not readily reconciled solely with actions in eye pigmentation. We find that flies mutant for these genes, and another binding partner, scarlet, have about half the wild-type amount of histamine in the head, as well as reduced 5-HT and dopamine. These differences parallel reductions in immunoreactivity to the corresponding biogenic amines. They also correlate with the amine content of fractions after differential centrifugation of head homogenates. Thus, most of the amine is found in the vesicle-rich fraction of wild-type head homogenates, whereas it is found in the supernatant fractions from white, brown and scarlet flies. White co-expresses in lamina epithelial glia with Ebony, which conjugates histamine to β-alanine. Histamine is then released when the conjugate is hydrolyzed in photoreceptors, by Tan. Mutant white ameliorates the effects of tan on head histamine whereas it exacerbates the effects of ebony. Our results are consistent with the proposal that histamine uptake by the epithelial glia may be white dependent. Behavioral abnormalities in white, brown and scarlet mutants could arise because aminergic neurons in the Drosophila brain have reduced amine for release.

Drosophila Vesicular Monoamine Transporter Mutants Can Adapt to Reduced or Eliminated Vesicular Stores of Dopamine and Serotonin

“…DVMAT protein was not detected in the homozygous dVMAT P1 (P/P) mutant, dVMAT Since the w gene also has been reported recently to alter monoamine levels in the fly Sitaraman et al 2008), and some of our experiments were performed in a w background, we compared the dopamine and serotonin contents of w 1118 CS 10 vs. CS adult fly heads. Our data show no significant effect of w on either dopamine or serotonin levels and overall lower monoamine levels in CS heads as compared to both Sitaraman et al (2008) and Borycz et al (2008).…”

The ABCs of Eye Color inTribolium castaneum: Orthologs of theDrosophila white,scarlet, andbrownGenes

“…st mutants have also been shown to have altered learning capabilities (Diegelmann et al 2006), while both st and bw mutants show altered anesthetic responses (Campbell and Nash 2001). The most likely explanation for these phenomena is that biogenic amines are altered in amount and subcellular location in all three mutant types (Borycz et al 2008), probably as a result of altered cellular import of the tryptophan-and guanine-derived precursors of these amines. Thus, the neurological functions of W, St, and Bw are not unlike their pigmentation roles.…”

“…While this conclusion has also been supported by an apparent lack of a Tribolium bw ortholog, bw orthologs have been identified in other species that also lack pteridine eye pigments (Tatematsu et al 2011;Wang et al 2013). Furthermore, Bw is known in Drosophila to play a role in other tissues (Campbell and Nash 2001;Borycz et al 2008), so it would not be surprising for the Tribolium lineage to have maintained an ortholog of this gene. To distinguish a bw ortholog from other ABC transporters in the Tribolium genome, a motif unique to pigment transporters was required.…”

Phototactic personality in fruit flies and its suppression by serotonin and white

“…4F). Indeed, white mutants have diminished concentrations of the neurotransmitters serotonin, dopamine, and histamine (13,14) and concomitant behavioral phenotypes affecting courtship (15), spatial learning (16), and olfactory learning (17). To further investigate the role of white, we assayed the mutants brown, scarlet, and cinnabar (which encodes an enzyme in the xanthommatin synthesis pathway downstream of Scarlet but not in the serotonin synthesis pathway).…”