skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Comparative exploration of mammalian deafness gene homologues in the Drosophila auditory organ shows genetic correlation between insect and vertebrate hearing
Johnston’s organ, theDrosophilaauditory organ, is anatomically very different from the mammalian organ of Corti. However, recent evidence indicates significant cellular and molecular similarities exist between vertebrate and invertebrate hearing, suggesting thatDrosophilamay be a useful platform to determine the function of the many mammalian deafness genes whose underlying biological mechanisms are poorly characterized. Our goal was a comprehensive screen of all known orthologues of mammalian deafness genes in the fruit fly to better understand conservation of hearing mechanisms between the insect and the fly and ultimately gain insight into human hereditary deafness. We used bioinformatic comparisons to screen previously reported human and mouse deafness genes and found that 156 of them have orthologues inDrosophila melanogaster. We used fluorescent imaging of T2A-GAL4 gene trap and GFP or YFP fluorescent protein trap lines for 54 of theDrosophilagenes and found 38 to be expressed in different cell types in Johnston’s organ. We phenotypically characterized the function of strong loss-of-function mutants in three genes expressed in Johnston’s organ (Cad99C,Msp-300, andKoi) using a courtship assay and electrophysiological recordings of sound-evoked potentials.Cad99CandKoiwere found to have significant courtship defects. However, when we tested these genes for electrophysiological defects in hearing response, we did not see a significant difference suggesting the courtship defects were not caused by hearing deficiencies. Furthermore, we used a UAS/RNAi approach to test the function of seven genes and found two additional genes,CG5921andMyo10a, that gave a statistically significant delay in courtship but not in sound-evoked potentials. Our results suggest that many mammalian deafness genes haveDrosophilahomologues expressed in the Johnston’s organ, but that their requirement for hearing may not necessarily be the same as in mammals.  more » « less
Award ID(s):
2037828
PAR ID:
10497165
Author(s) / Creator(s):
; ; ; ; ; ; ;
Editor(s):
Mahdieh, Nejat
Publisher / Repository:
Public Library of Science
Date Published:
Journal Name:
PLOS ONE
Volume:
19
Issue:
2
ISSN:
1932-6203
Page Range / eLocation ID:
e0297846
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. The Lim1 transcription factor is required in Drosophila for patterning the eye-antennal disk. At the adult stage, Lim1 is strongly expressed in Johnston’s Organ (JO) neurons, the antennal auditory organ. Using RNAi-mediated knockdown of Lim1 using a strong neuronal driver, we find a significant reduction in electrophysiological responses to auditory stimuli, recorded from the antennal nerve. This reduction can be accounted for by Lim1 knockdown in the auditory subset of JO neurons, with no effect of knockdown in JO neuron subsets associated with wind or gravity detection. Conversely, Lim1 knockdown in JO sense organ precursors had no effect on hearing. Mosaic animals with antennal clones of the Lim1E9 null mutation showed morphological defects in the antenna, and significant auditory electrophysiological defects. Our results are consistent with two distinct functions for Lim1 in the antenna, including an early patterning function in the eye-antennal disk, and a later neural differentiation function in the JO neurons. 
    more » « less
  2. Abstract Flies have an open circulatory system and their Blood Brain Barrier (BBB) surrounds the brain like a tight cap. The fly BBB consists of two layers of glial cells. The outer layer is formed by the Perineurial Glia (PG). The inner BBB layer consists of the Subperineurial Glia (SPG) that form the tight barrier that, like its mammalian counterpart, acts both as a diffusion and a xenobiotic transport barrier. Underneath the SPG lie the neuronal cell bodies. The Drosophila BBB shows the same barrier properties as the mammalian barrier and profiling of Drosophila BBB cells has shown a high degree of molecular conservation. We have previously shown that the Drosophila BBB plays a sex-specific role in regulating behavior. Conditional adult feminization of SPG cells in otherwise normal males leads to significantly reduced courtship. In agreement with this, in a microarray screen of isolated SPG cells, we identified a number of male-enriched transcripts. One of them encodes the dopamine-2 like receptor (D2R). We have found that conditional knockdown of D2R in adult male Drosophila SPG decreases courtship. Likewise, D2R mutant males have courtship defects. They can be rescued by expression of wildtype D2R in the SPG cells of mature adult males, demonstrating a physiological requirement for the receptor in these cells for courtship control4. The D2R receptor is highly conserved. It has been found that it can act via biased signaling (through G protein or b-arrestin) in mammals. We have previously found that signaling through Gao and arrestin in the BBB is required for proper male courtship. Although D2R is best known for signaling through cAMP, we have not found a requirement for cAMP/PKA signaling for courtship. To investigate the signaling pathways downstream of D2R that are responsible for courtship control we have mutagenized D2R proteins and examined their ability to rescue D2R mutants. Based on Peterson et al. we designed proteins capable of G-protein or arrestin biased signaling, respectively, and tested their ability to rescue the courtship defects of D2R mutants. Our data suggest that D2R signaling through b-arrestin is a major mediator of BBB courtship control. 
    more » « less
  3. Abstract The blood brain barrier (BBB) has the essential function to protect the brain from potentially hazardous molecules while also enabling controlled selective uptake. How these processes and signaling inside BBB cells control neuronal function is an intense area of interest. Signaling in the adultDrosophilaBBB is required for normal male courtship behavior and relies on male‐specific molecules in the BBB. Here we show that the dopamine receptorD2Ris expressed in the BBB and is required in mature males for normal mating behavior. Conditional adult male knockdown ofD2Rin BBB cells causes courtship defects. The courtship defects observed in geneticD2Rmutants can be rescued by expression of normalD2Rspecifically in the BBB of adult males.DrosophilaBBB cells are glial cells. Our findings thus identify a specific glial function for theDR2receptor and dopamine signaling in the regulation of a complex behavior. 
    more » « less
  4. IntroductionCilia biogenesis relies on intraflagellar transport (IFT), a conserved transport mechanism which functions bi-directionally to bring protein complexes to the growing ciliary tip and recycle signaling and transport proteins between the cilium and cell body. InDrosophila, anterograde IFT is critical for assembly of sensory cilia in the neurons of both chordotonal (ch) organs, which have relatively long ciliary axonemes, and external sensory (es) organs, which have short axonemal segments with microtubules in distal sensory segments forming non-axonemal bundles. We previously isolated thebeethoven(btv) mutant in a mutagenesis screen for auditory mutants. Although manybtvmutant flies are deaf, some retain a small residual auditory function as determined both by behavior and by auditory electrophysiology. ResultsHere we molecularly characterize thebtvgene and demonstrate that it encodes the IFT-associated dynein-2 heavy chain Dync2h1. We also describe morphological changes in Johnston’s organ as flies age to 30 days, and we find that morphological and electrophysiological phenotypes in this ch organ ofbtvmutants become more severe with age. We show that NompB protein, encoding the conserved IFT88 protein, an IFT complex B component, fails to be cleared from chordotonal cilia inbtvmutants, instead accumulating in the distorted cilia. In macrochaete bristles, a class of es organ,btvmutants show a 50% reduction in mechanoreceptor potentials. DiscussionThus, thebtv-encoded Dync2h1 functions as the retrograde IFT motor in the assembly of long ciliary axonemes in ch organs and is also important for normal function of the short ciliary axonemes in es organs. 
    more » « less
  5. Abstract The fruit flyDrosophila melanogasterhas provided important insights into how sensory information is transduced by transient receptor potential (TRP) channels in the peripheral nervous system (PNS). However, TRP channels alone have not been able to completely model mechanosensitive transduction in mechanoreceptive chordotonal neurons (CNs). Here, we show that, in addition to TRP channels, the sole voltage-gated sodium channel (NaV) inDrosophila, Para, is localized to the dendrites of CNs. Para is localized to the distal tip of the dendrites in all CNs, from embryos to adults, and is colocalized with the mechanosensitive TRP channels No mechanoreceptor potential C (NompC) and Inactive/Nanchung (Iav/Nan). Para localization also demarcates spike initiation zones (SIZs) in axons and the dendritic localization of Para is indicative of a likely dendritic SIZ in fly CNs. Para is not present in the dendrites of other peripheral sensory neurons. In both multipolar and bipolar neurons in the PNS, Para is present in a proximal region of the axon, comparable to the axonal initial segment (AIS) in vertebrates, 40–60 μm from the soma in multipolar neurons and 20–40 μm in bipolar neurons. Whole-cell reduction ofparaexpression using RNAi in CNs of the adult Johnston’s organ (JO) severely affects sound-evoked potentials (SEPs). However, the duality of Para localization in the CN dendrites and axons identifies a need to develop resources to study compartment-specific roles of proteins that will enable us to better understand Para’s role in mechanosensitive transduction. 
    more » « less