title: Axonal wiring in neural development: Target-independent mechanisms help to establish precision and complexity.
abstract: The connectivity patterns of many neural circuits are highly ordered and often impressively complex. The intricate order and complexity of neuronal wiring remain not only a challenge for questions related to circuit functions but also for our understanding of how they develop with such an apparent precision. The chemotropic guidance of the growing axon by target-derived cues represents a central paradigm for how neurons get connected with the correct target cells. However, many studies reveal a remarkable variety of important target-independent wiring mechanisms. These mechanisms include axonal sorting, axonal tiling, growth cone polarization, as well as cell-intrinsic mechanisms underlying growth cone sprouting, and neurite branching. Our review focuses on target independent wiring mechanisms and in particular on recent progress emerging from studies on three different sensory systems: olfactory, visual, and somatosensory. We discuss molecular mechanisms that operate during axon-axon interactions or constitute axon-intrinsic functions and outline how they complement the well-known target-dependent wiring mechanisms.
authors.affiliation: Neuronal Wiring Laboratory, VIB, Leuven, Belgium.|Department of Oncology, School of Medicine, University of Leuven, Leuven, Belgium.
authors.forename: Milan
authors.initials: M
authors.lastname: Petrovic
authors.affiliation: Neuronal Wiring Laboratory, VIB, Leuven, Belgium.|Department of Oncology, School of Medicine, University of Leuven, Leuven, Belgium.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schmucker
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D020439:Growth Cones / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000378:metabolism; D012903:Smell / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology
chemical_list: D011956:Receptors, Cell Surface
keywords: axon guidance; axon-axon interactions; axonal branching; axonal tiling; cell recognition molecules; chemoaffinity; neural development; sensory maps; target-independent wiring