title: Genetic analysis reveals that amyloid precursor protein and death receptor 6 function in the same pathway to control axonal pruning independent of β-secretase.
abstract: In the developing brain, initial neuronal projections are formed through extensive growth and branching of developing axons, but many branches are later pruned to sculpt the mature pattern of connections. Despite its widespread occurrence, the mechanisms controlling pruning remain incompletely characterized. Based on pharmacological and biochemical analysis in vitro and initial genetic analysis in vivo, prior studies implicated a pathway involving binding of the Amyloid Precursor Protein (APP) to Death Receptor 6 (DR6) and activation of a downstream caspase cascade in axonal pruning. Here, we further test their involvement in pruning in vivo and their mechanism of action through extensive genetic and biochemical analysis. Genetic deletion of DR6 was previously shown to impair pruning of retinal axons in vivo. We show that genetic deletion of APP similarly impairs pruning of retinal axons in vivo and provide evidence that APP and DR6 act cell autonomously and in the same pathway to control pruning. Prior analysis had suggested that β-secretase cleavage of APP and binding of an N-terminal fragment of APP to DR6 is required for their actions, but further genetic and biochemical analysis reveals that β-secretase activity is not required and that high-affinity binding to DR6 requires a more C-terminal portion of the APP ectodomain. These results provide direct support for the model that APP and DR6 function cell autonomously and in the same pathway to control pruning in vivo and raise the possibility of alternate mechanisms for how APP and DR6 control pruning.
authors.affiliation: Laboratory of Brain Development and Repair, The Rockefeller University, New York, New York 10065, Department of Biomedical Imaging, Department of Neuroscience, Department of Biochemical and Cellular Pharmacology, and Department of Protein Chemistry, Genentech Inc., South San Francisco, California 94080, and Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, California 92037.
authors.forename: Olav
authors.initials: O
authors.lastname: Olsen
authors.forename: Dara Y
authors.initials: DY
authors.lastname: Kallop
authors.forename: Todd
authors.initials: T
authors.lastname: McLaughlin
authors.forename: Sarah
authors.initials: S
authors.lastname: Huntwork-Rodriguez
authors.forename: Zhuhao
authors.initials: Z
authors.lastname: Wu
authors.forename: Cynthia D
authors.initials: CD
authors.lastname: Duggan
authors.forename: David J
authors.initials: DJ
authors.lastname: Simon
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Lu
authors.forename: Courtney
authors.initials: C
authors.lastname: Easley-Neal
authors.forename: Kentaro
authors.initials: K
authors.lastname: Takeda
authors.forename: Philip E
authors.initials: PE
authors.lastname: Hass
authors.forename: Alexander
authors.initials: A
authors.lastname: Jaworski
authors.forename: Dennis D M
authors.initials: DD
authors.lastname: O'Leary
authors.forename: Robby M
authors.initials: RM
authors.lastname: Weimer
authors.forename: Marc
authors.initials: M
authors.lastname: Tessier-Lavigne
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000502:physiology*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics*; D000818:Animals; D030801:Animals, Genetically Modified; D001369:Axons / Q000502:physiology*; D002452:Cell Count; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D051379:Mice; D009410:Nerve Degeneration / Q000235:genetics / Q000473:pathology; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics*; D012165:Retinal Ganglion Cells / Q000502:physiology; D011984:Sensory Receptor Cells / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D016564:Amyloid beta-Protein Precursor; D034741:RNA, Small Interfering; D018124:Receptors, Tumor Necrosis Factor; C114109:TNFRSF21 protein, human; D053829:Amyloid Precursor Protein Secretases
keywords: degeneration; pruning