Increased activity of Diaphanous homolog 3 (DIAPH3)/diaphanous causes hearing defects in humans with auditory neuropathy and in Drosophila.

Auditory neuropathy is a rare form of deafness characterized by an absent or abnormal auditory brainstem response with preservation of outer hair cell function. We have identified Diaphanous homolog 3 (DIAPH3) as the gene responsible for autosomal dominant nonsyndromic auditory neuropathy (AUNA1), which we previously mapped to chromosome 13q21-q24. Genotyping of additional family members narrowed the interval to an 11-Mb, 3.

Unique transgenic animal model for hereditary hearing loss.

Objectives: This study capitalizes on the unique molecular and developmental similarities between the auditory organs of Drosophila and mammals, to investigate genes implicated in human syndromic and nonsyndromic hearing loss in a genetically tractable experimental animal model, the fruit fly Drosophila.

Methods: The Drosophila counterparts of 3 human deafness genes (DIAPH1/DFNA1, ESPN/DFNB36, and TMHS/DF-NB67) were identified by sequence similarity. An electrophysiological assay was used to record sound-evoked potentials in response to an acoustic stimulus, the Drosophila courtship song.

Distinct functional domains of neurofibromatosis type 1 regulate immediate versus long-term memory formation.

Neurofibromatosis type 1 (NF1) is a dominant genetic disorder that causes tumors of the peripheral nervous system. In addition, >40% of afflicted children have learning difficulties. The NF1 protein contains a highly conserved GTPase-activating protein domain that inhibits Ras activity, and the C-terminal region regulates cAMP levels via G-protein-dependent activation of adenylyl cyclase.

Effect of neurofibromatosis type I mutations on a novel pathway for adenylyl cyclase activation requiring neurofibromin and Ras.

Neurofibromatosis type I (NFI) is a common genetic disorder that causes nervous system tumors, and learning and memory defects in humans, and animal models. We identify a novel growth factor stimulated adenylyl cyclase (AC) pathway in the Drosophila brain, which is disrupted by mutations in the epidermal growth factor receptor (EGFR), neurofibromin (NF1) and Ras, but not Galpha(s). This is the first demonstration in a metazoan that a receptor tyrosine kinase (RTK) pathway, acting independently of the heterotrimeric G-protein subunit Galpha(s), can activate AC.

Stereotyped odor-evoked activity in the mushroom body of Drosophila revealed by green fluorescent protein-based Ca2+ imaging.

To study the representation of olfactory information in higher brain centers, we expressed a green fluorescent protein-based Ca2+ sensor, G-CaMP, in the Drosophila mushroom body (MB). Using two-photon microscopy, we imaged odor-evoked G-CaMP fluorescence transients in MB neurons [Kenyon cells (KCs)] with single-cell resolution. Odors produced large fluorescence transients in a subset of KC somata and in restricted regions of the calyx, the neuropil of the MB.

Notch signaling in Drosophila long-term memory formation.

Notch (N) is a cell surface receptor that mediates an evolutionarily ancient signaling pathway to control an extraordinarily broad spectrum of cell fates and developmental processes. To gain insights into the functions of N signaling in the adult brain, we examined the involvement of N in Drosophila olfactory learning and memory. Long-term memory (LTM) was disrupted by blocking N signaling in conditional mutants or by acutely induced expression of a dominant-negative N transgene.

Neurofibromin regulates G protein-stimulated adenylyl cyclase activity.

Neurofibromatosis type 1 (NF1) is a dominant genetic disorder characterized by multiple benign and malignant nervous system tumors, and by learning defects in 45% of children with NF1 mutations. Studies of neurofibromin, the protein encoded by NF1, have focused on its functions in tumorigenesis and regulation of Ras activity; however, Drosophila NF1 regulates both Ras and cyclic AMP (cAMP) pathways. Expression of a human NF1 transgene rescued cAMP-related phenotypes in NF1 mutant flies (small body size and G protein-stimulated adenylyl cyclase (AC) activity defects), and neuropeptide- and G protein-stimulated AC activity were lower in Nf1-/- as compared to Nf1+/- mouse brains, demonstrating that neurofibromin regulates AC activity in both mammals and flies.