In this review, I describe recent progress toward understanding the developmental genetics governing formation of the Drosophila auditory apparatus. The Drosophila auditory organ, Johnston's organ, is housed in the antenna. Intriguingly, key genes needed for specification or function of auditory cell types in the Drosophila antenna also are required for normal development or function of the vertebrate ear. These genes include distal-less, spalt and spalt-related, atonal, crinkled, nanchung and inactive, and prestin, and their vertebrate counterparts Dlx, spalt-like (sall), atonal homolog (ath), myosin VIIA, TRPV, and prestin, respectively. In addition, Drosophila auditory neurons recently were shown to serve actuating as well as transducing roles, much like their hair cell counterparts of the vertebrate cochlea. The emerging genetic and physiologic parallels have come as something of a surprise, because conventional wisdom holds that vertebrate and invertebrate hearing organs have separate evolutionary origins. The new findings raise the possibility that auditory organs are more ancient than previously thought and indicate that Drosophila is likely to be a powerful model system in which to gain insights regarding the etiologies of human deafness disorders. Developmental Dynamics 232:550 -558, 2005.

Hearing is a specialized mechanosensory modality that is refined during evolution to meet the particular requirements of different organisms. In the fruitfly, Drosophila, hearing is mediated by Johnston's organ, a large chordotonal organ in the antenna that is exquisitely sensitive to the near-field acoustic signal of courtship songs generated by male wing vibration. We summarize recent progress in understanding the molecular genetic determinants of Johnston's organ development and discuss surprising differences from other chordotonal organs that likely facilitate hearing. We outline novel discoveries of active processes that generate motion of the antenna for acute sensitivity to the stimulus. Finally, we discuss further research directions that would probe remaining questions in understanding Johnston's organ development, function and evolution.

Drosophila melanogaster provides a powerful genetic model system in which to investigate the molecular mechanisms underlying neurodegenerative diseases. In this review, we discuss recent progress in Drosophila modeling Alzheimer’s Disease, Parkinson’s Disease, Amyotrophic Lateral Sclerosis (ALS), Huntington’s Disease, Ataxia Telangiectasia, and neurodegeneration related to mitochondrial dysfunction or traumatic brain injury. We close by discussing recent progress using Drosophila models of neural regeneration and how these are likely to provide critical insights into future treatments for neurodegenerative disorders.

Mutations in SALL1, the human homolog of the Drosophila spalt gene, result in Townes-Brocks' syndrome, which is characterized by hand͞foot, anogenital, renal, and ear anomalies, including sensorineural deafness. spalt genes encode zinc finger transcription factors that are found in animals as diverse as worms, insects, and vertebrates. Here, we examine the effect of losing both of the spalt genes, spalt and spalt-related, in the fruit fly Drosophila melanogaster, and report defects similar to those in humans with Townes-Brocks' syndrome. Loss of both spalt and spalt-related function in flies yields morphological defects in the testes, genitalia, and the antenna. Furthermore, spalt͞spalt-related mutant antennae show severe reductions in Johnston's organ, the major auditory organ in Drosophila. Electrophysiological analyses confirm that spalt͞spalt-related mutant flies are deaf. These commonalities suggest that there is functional conservation for spalt genes between vertebrates and insects.Distal-less ͉ homothorax ͉ atonal ͉ chordotonal organ ͉ split hand͞split foot malformation T ownes-Brocks' syndrome (TBS) is an autosomal dominant disorder that maps to the SALL1 locus at 16q12.1 (1). SALL1 is one of three known vertebrate homologs of Drosophila spalt (sal) (2, 3). The mutations in SALL1 that result in TBS typically lead to a premature stop codon after the first zinc finger (1, 4-7). Although the clinical manifestations of TBS are variable, Ϸ85% of patients with TBS exhibit hand͞foot, anogenital, renal, and ear anomalies, including sensorineural deafness (8-13). TBS is estimated to occur in 1:250,000 liveborn (14), but may be misdiagnosed because its defects overlap with those of other genetic diseases (7,11,15,16). Consistent with TBS phenotypes, human SALL1 expression has been detected in the brain, heart, ureteric bud, and developing tubules of the kidney, testes, and ovary (2, 17). In mice, sal genes are expressed in brain, testes, ovaries, kidneys, limb buds, heart, inner ear, and the lens of the eye (18,19).spalt genes have been identified in a variety of vertebrates and invertebrates (2,3,18,(20)(21)(22)(23)(24)(25)(26)(27)(28). In Drosophila, there are two adjacent spalt genes, spalt (sal) and spalt-related (salr). These genes use shared regulatory regions and are expressed in similar patterns throughout development. Early studies of sal single mutants indicated that sal is required for the development of the embryonic terminalia, tracheal system, and wings (20,(29)(30)(31)(32). Mutations in sal result in partial transformations of the posterior head and anterior tail toward trunk identity (20). sal functions during tracheal development both to restrict the positions of the initial placodes and in directed migration of dorsal trunk cells (30). At larval stages, Dpp-activated sal expression in the wing pouch is activated in response to graded levels of Dpp to properly position wing pattern elements (29,31,33).More recent studies of Drosophila lacking the function of both sal and salr indicate that there ...