TAR DNA-binding protein 43 (TDP-43) is genetically and functionally linked to amyotrophic lateral sclerosis (ALS) and regulates transcription, splicing, and transport of thousands of RNA targets that function in diverse cellular pathways. In ALS, pathologically altered TDP-43 is believed to lead to disease by toxic gain-of-function effects on RNA metabolism, as well as by sequestering endogenous TDP-43 and causing its loss of function. However, it is unclear which of the numerous cellular processes disrupted downstream of TDP-43 dysfunction lead to neurodegeneration. Here we found that both loss and gain of function of TDP-43 in Drosophila cause a reduction of synaptic growth–promoting bone morphogenic protein (BMP) signaling at the neuromuscular junction (NMJ). Further, we observed a shift of BMP receptors from early to recycling endosomes and increased mobility of BMP receptor–containing compartments at the NMJ. Inhibition of the recycling endosome GTPase Rab11 partially rescued TDP-43–induced defects in BMP receptor dynamics and distribution and suppressed BMP signaling, synaptic growth, and larval crawling defects. Our results indicate that defects in receptor traffic lead to neuronal dysfunction downstream of TDP-43 misregulation and that rerouting receptor traffic may be a viable strategy for rescuing neurological impairment.

As in human infant speech development, vocal imitation in songbirds involves sensory acquisition and memorization of adult-produced vocal signals, followed by a protracted phase of vocal motor prac...

Neurons acquire their molecular, neurochemical, and connectional features during development as a result of complex regulatory mechanisms. Here, we show that a ubiquitous, multifunctional protein cofactor, Chip, plays a critical role in a set of neurons inDrosophilathat control the well described posteclosion behavior. Newly eclosed flies normally expand their wings and display tanning and hardening of their cuticle. Using multiple approaches to interfere with Chip function, we find that these processes do not occur without normal activity of this protein. Furthermore, we identified the nature of the deficit to be an absence of Bursicon in the hemolymph of newly eclosed flies, whereas the responsivity to Bursicon in these flies remains normal. Chip interacts with transcription factors of the LIM-HD (LIM-homeodomain) family, and we identified one member, dIslet, as a potential partner of Chip in this process. Our findings provide the first evidence of transcriptional mechanisms involved in the development of the neuronal circuit that regulates posteclosion behavior inDrosophila.

Background/Objectives: Fabry disease is an X-linked disorder caused by lysosomal accumulation of glycosphingolipids due to the deficiency of α-Galactosidase (α-GAL), which leads to pathology in multiple organ systems. The standard of care is enzyme replacement therapy (ERT) with recombinant native α-GAL protein. Shortcomings of the native α-GAL include low stability, a short circulating half-life, and inadequate uptake by affected tissues that limits the efficacy of ERT and could potentially reduce AAV gene therapy (GT) benefits. Cross-correction by secreted α-GAL is essential for liver-targeted as well as ubiquitous AAV GT due to poor transduction and/or short half-life of some of the significantly affected cell types. Methods: To overcome potential limitations of AAV GT delivering native α-GAL, we used an engineered GLA transgene product to improve enzyme stability and reduce predicted immunogenicity. Results: The stabilized α-GAL variant, Eng-C, had an extended circulatory half-life, allowing for enhanced distribution and efficient uptake by target organs. AAV gene therapy with Eng-C demonstrated significantly greater substrate reduction in the severe Fabry G3Stg/GlaKO mouse model across all affected tissues. Efficacy of the Eng-C AVV GT was equal to or greater than the efficacy of the higher doses of the AAV GT with native α-GAL. Furthermore, this study is the first to demonstrate that the pre-existing pathology in some tissues in G3Stg/GlaKO mice can be reversed with efficient treatment. Conclusions: Our findings demonstrate that an AAV-based gene therapy expressing an engineered α-GAL with improved stability and lower immunogenicity could be effective at lower doses than other AAV GTs, potentially offering lower safety risks typically associated with high AAV vector doses.

Early infantile epileptic encephalopathy (EIEE)–associated mutations in MUNC18-1 cause Munc18-1 misfolding and cellular aggregation. In this issue, Chai et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201512016) find that Munc18-1 is a molecular chaperone for α-synuclein and that aggregated Munc18-1 EIEE-causing mutants promote α-synuclein aggregation.