The brain is a DJ using neuropeptides as sensory crossfaders

Sensory loss induces cross-modal plasticity, often resulting in altered performance in remaining sensory modalities. Whereas much is known about the macroscopic mechanisms underlying cross-modal plasticity, only scant information exists about its cellular and molecular underpinnings. We found that Caenorhabditis elegans nematodes deprived of a sense of body touch exhibit various changes in behavior, associated with other unimpaired senses. We focused on one such behavioral alteration, enhanced odor sensation, and sought to reveal the neuronal and molecular mechanisms that translate mechanosensory loss into improved olfactory acuity. To this end, we analyzed in mechanosensory mutants food-dependent locomotion patterns that are associated with olfactory responses and found changes that are consistent with enhanced olfaction. The altered locomotion could be reversed in adults by optogenetic stimulation of the touch receptor (mechanosensory) neurons. Furthermore, we revealed that the enhanced odor response is related to a strengthening of inhibitory AWC→AIY synaptic transmission in the olfactory circuit. Consistently, inserting in this circuit an engineered electrical synapse that diminishes AWC inhibition of AIY counteracted the locomotion changes in touch-deficient mutants. We found that this cross-modal signaling between the mechanosensory and olfactory circuits is mediated by neuropeptides, one of which we identified as FLP-20. Our results indicate that under normal function, ongoing touch receptor neuron activation evokes FLP-20 release, suppressing synaptic communication and thus dampening odor sensation. In contrast, in the absence of mechanosensory input, FLP-20 signaling is reduced, synaptic suppression is released, and this enables enhanced olfactory acuity; these changes are long lasting and do not represent ongoing modulation, as revealed by optogenetic experiments. Our work adds to a growing literature on the roles of neuropeptides in cross-modal signaling, by showing how activity-dependent neuropeptide signaling leads to specific cross-modal plastic changes in neural circuit connectivity, enhancing sensory performance.status: publishe

The HLH-6 Transcription Factor Regulates C. elegans Pharyngeal Gland Development and Function

The Caenorhabditis elegans pharynx (or foregut) functions as a pump that draws in food (bacteria) from the environment. While the “organ identity factor” PHA-4 is critical for formation of the C. elegans pharynx as a whole, little is known about the specification of distinct cell types within the pharynx. Here, we use a combination of bioinformatics, molecular biology, and genetics to identify a helix-loop-helix transcription factor (HLH-6) as a critical regulator of pharyngeal gland development. HLH-6 is required for expression of a number of gland-specific genes, acting through a discrete cis-regulatory element named PGM1 (Pharyngeal Gland Motif 1). hlh-6 mutants exhibit a frequent loss of a subset of glands, while the remaining glands have impaired activity, indicating a role for hlh-6 in both gland development and function. Interestingly, hlh-6 mutants are also feeding defective, ascribing a biological function for the glands. Pharyngeal pumping in hlh-6 mutants is normal, but hlh-6 mutants lack expression of a class of mucin-related proteins that are normally secreted by pharyngeal glands and line the pharyngeal cuticle. An interesting possibility is that one function of pharyngeal glands is to secrete a pharyngeal lining that ensures efficient transport of food along the pharyngeal lumen

A randomized clinical trial comparing fixed vs pro-re-nata dosing of Ozurdex in refractory diabetic macular oedema (OZDRY study)

OBJECTIVE: To compare the clinical effectiveness and safety of 5-monthly fixed dosing vs pro-re-nata (PRN) Ozurdex treatment in patients with refractory diabetic macular oedema (DMO). DESIGN: Prospective, multicentre, randomized active-controlled non-inferiority clinical trial. PARTICIPANTS: Participants were 100 patients who attended Medical Retina Clinics for management of centre-involving refractory DMO. INTERVENTIONS: Participants were randomized 1 : 1 to either 5-monthly fixed dosing or optical coherence tomography (OCT)-guided PRN regimen of Ozurdex therapy for DMO. Data were collected on best-corrected visual acuity (BCVA), patient-reported outcome measures (PROM), macular thickness and morphology, diabetic retinopathy status, number of injections and adverse events from baseline for a period of 12 months. MAIN OUTCOME MEASURES: The primary outcome was the difference between arms in change in BCVA from baseline to 12 months. The prespecified non-inferiority margin was five ETDRS letters. Key secondary outcomes included change in PROM scores, change in macular thickness, change in retinopathy and macular morphology, and safety profile. RESULTS: The mean change in BCVA was +1.48 (SD 14.8) in the fixed arm vs −0.17 (SD 13.1) in the PRN arm, with adjusted effect estimate +0.97, 90% confidence interval (−4.01, +5.95), P=0.02 (per protocol analysis). The conclusions of the ITT analysis were primarily supportive, −0.34 (−5.49, 4.81) P=0.07, but sensitive to an alternative assumption on missing data, +0.28 (−4.72, 5.27) P=0.04. CONCLUSIONS: The mean change in BCVA with 5-monthly fixed dosing of Ozurdex was non-inferior to OCT-guided PRN Ozurdex therapy for refractory DMO based on a per protocol analysis