Basal autophagy is required for promoting dendritic terminal branching in Drosophila sensory neurons.

Dendrites function as the primary sites for synaptic input and integration with impairments in dendritic arborization being associated with dysfunctional neuronal circuitry. Post-mitotic neurons require high levels of basal autophagy to clear cytotoxic materials and autophagic dysfunction under native or cellular stress conditions has been linked to neuronal cell death as well as axo-dendritic degeneration. However, relatively little is known regarding the developmental role of basal autophagy in directing aspects of dendritic arborization or the mechanisms by which the autophagic machinery may be transcriptionally regulated to promote dendritic diversification. We demonstrate that autophagy-related (Atg) genes are positively regulated by the homeodomain transcription factor Cut, and that basal autophagy functions as a downstream effector pathway for Cut-mediated dendritic terminal branching in Drosophila multidendritic (md) sensory neurons. Further, loss of function analyses implicate Atg genes in promoting cell type-specific dendritic arborization and terminal branching, while gain of function studies suggest that excessive autophagy leads to dramatic reductions in dendritic complexity. We demonstrate that the Atg1 initiator kinase interacts with the dual leucine zipper kinase (DLK) pathway by negatively regulating the E3 ubiquitin ligase Highwire and positively regulating the MAPKKK Wallenda. Finally, autophagic induction partially rescues dendritic atrophy defects observed in a model of polyglutamine toxicity. Collectively, these studies implicate transcriptional control of basal autophagy in directing dendritic terminal branching and demonstrate the importance of homeostatic control of autophagic levels for dendritic arbor complexity under native or cellular stress conditions.

Assessment of a Dedicated Transplant Low Clearance Clinic and Patient Outcomes on Dialysis After Renal Allograft Loss at 2 UK Transplant Centers.

BACKGROUND: Low clearance transplant clinics (LCTCs) are recommended for the management of recipients with a failing kidney transplant (RFKT) but data to support their use is limited. We conducted a retrospective study to assess management of RFKT at 2 transplant centers, 1 with a LCTC (center A) and 1 without (center B). METHODS: Patients who transitioned to an alternative form of renal replacement therapy (RRT) between January 1, 2012, and November 30, 2016, were included. Patients with graft failure within a year of transplantation or due to an unpredictable acute event were excluded. Clinical data were collected after review of medical records. RESULTS: One hundred seventy-nine patients (age, 48.6 ± 13.4 years, 99 [55.3%] male, and mean transplant duration 10.3 ± 7.8 years) were included. RRT counseling occurred in 79 (91%) and 68 (74%) patients at centers A and B (P = 0.003), at median 135 (61-319) and 133 (69-260) days before dialysis after graft loss (P = 0.92). Sixty-one (34.1%) patients were waitlisted for retransplantation; 18 (32.7%) nonwaitlisted patients were still undergoing workup at center A compared with 37 (58.7%) at center B (P = 0.028). Preemptive retransplantation occurred in 4 (4.6%) and 5 (5.4%) patients at centers A and B (P = 0.35). At 1 year after initiation of dialysis after graft loss, 11 (15.3%) and 11 (17.2%) patients were retransplanted (P = 0.12), and mortality was 6.6% overall. CONCLUSIONS: A dedicated LCTC improved RRT counseling and transplant work-up but did not lead to improved rates of retransplantation. Earlier consideration of retransplantation in LCTCs is required to improve RFKT outcomes.

Dendritic Cytoskeletal Architecture Is Modulated by Combinatorial Transcriptional Regulation in Drosophila melanogaster.

Transcription factors (TFs) have emerged as essential cell autonomous mediators of subtype specific dendritogenesis; however, the downstream effectors of these TFs remain largely unknown, as are the cellular events that TFs control to direct morphological change. As dendritic morphology is largely dictated by the organization of the actin and microtubule (MT) cytoskeletons, elucidating TF-mediated cytoskeletal regulatory programs is key to understanding molecular control of diverse dendritic morphologies. Previous studies in Drosophila melanogaster have demonstrated that the conserved TFs Cut and Knot exert combinatorial control over aspects of dendritic cytoskeleton development, promoting actin and MT-based arbor morphology, respectively. To investigate transcriptional targets of Cut and/or Knot regulation, we conducted systematic neurogenomic studies, coupled with in vivo genetic screens utilizing multi-fluor cytoskeletal and membrane marker reporters. These analyses identified a host of putative Cut and/or Knot effector molecules, and a subset of these putative TF targets converge on modulating dendritic cytoskeletal architecture, which are grouped into three major phenotypic categories, based upon neuromorphometric analyses: complexity enhancer, complexity shifter, and complexity suppressor. Complexity enhancer genes normally function to promote higher order dendritic growth and branching with variable effects on MT stabilization and F-actin organization, whereas complexity shifter and complexity suppressor genes normally function in regulating proximal-distal branching distribution or in restricting higher order branching complexity, respectively, with spatially restricted impacts on the dendritic cytoskeleton. Collectively, we implicate novel genes and cellular programs by which TFs distinctly and combinatorially govern dendritogenesis via cytoskeletal modulation.

Axon targeting of the alpha 7 nicotinic receptor in developing hippocampal neurons by Gprin1 regulates growth.

Cholinergic signaling plays an important role in regulating the growth and regeneration of axons in the nervous system. The α7 nicotinic receptor (α7) can drive synaptic development and plasticity in the hippocampus. Here, we show that activation of α7 significantly reduces axon growth in hippocampal neurons by coupling to G protein-regulated inducer of neurite outgrowth 1 (Gprin1), which targets it to the growth cone. Knockdown of Gprin1 expression using RNAi is found sufficient to abolish the localization and calcium signaling of α7 at the growth cone. In addition, an α7/Gprin1 interaction appears intimately linked to a Gαo, growth-associated protein 43, and CDC42 cytoskeletal regulatory pathway within the developing axon. These findings demonstrate that α7 regulates axon growth in hippocampal neurons, thereby likely contributing to synaptic formation in the developing brain.