title: Non-Cell-Autonomous Regulation of Retrograde Motoneuronal Axonal Transport in an SBMA Mouse Model.
abstract: Defects in axonal transport are seen in motoneuronal diseases, but how that impairment comes about is not well understood. In spinal bulbar muscular atrophy (SBMA), a disorder linked to a CAG/polyglutamine repeat expansion in the androgen receptor (AR) gene, the disease-causing AR disrupts axonal transport by acting in both a cell-autonomous fashion in the motoneurons themselves, and in a non-cell-autonomous fashion in muscle. The non-cell-autonomous mechanism is suggested by data from a unique "myogenic" transgenic (TG) mouse model in which an AR transgene expressed exclusively in skeletal muscle fibers triggers an androgen-dependent SBMA phenotype, including defects in retrograde transport. However, motoneurons in this TG model retain the endogenous AR gene, leaving open the possibility that impairments in transport in this model also depend on ARs in the motoneurons themselves. To test whether non-cell-autonomous mechanisms alone can perturb retrograde transport, we generated male TG mice in which the endogenous AR allele has the testicular feminization mutation (Tfm) and, consequently, is nonfunctional. Males carrying the Tfm allele alone show no deficits in motor function or axonal transport, with or without testosterone treatment. However, when Tfm males carrying the myogenic transgene (Tfm/TG) are treated with testosterone, they develop impaired motor function and defects in retrograde transport, having fewer retrogradely labeled motoneurons and deficits in endosomal flux based on time-lapse video microscopy of living axons. These findings demonstrate that non-cell-autonomous disease mechanisms originating in muscle are sufficient to induce defects in retrograde transport in motoneurons.
authors: Neuroscience Program , Michigan State University , East Lansing, Michigan 48824-1115.
authors: Katherine
authors: K
authors: Halievski
authors: Neuroscience Program , Michigan State University , East Lansing, Michigan 48824-1115.
authors: Michael Q
authors: MQ
authors: Kemp
authors: Neuroscience Program , Michigan State University , East Lansing, Michigan 48824-1115.
authors: S Marc
authors: SM
authors: Breedlove
authors: Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1115; Department of Integrative Biology, Michigan State University, East Lansing, Michigan 48824-1115.
authors: Kyle E
authors: KE
authors: Miller
authors: Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1115; Department of Physiology, Michigan State University, East Lansing, Michigan 48824-1115.
authors: Cynthia L
authors: CL
authors: Jordan
mesh_terms: D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D004195:Disease Models, Animal; D011992:Endosomes / Q000378:metabolism / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009043:Motor Activity / Q000502:physiology; D009046:Motor Neurons / Q000378:metabolism* / Q000473:pathology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D020966:Muscular Disorders, Atrophic / Q000378:metabolism* / Q000473:pathology; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism; D012584:Sciatic Nerve / Q000378:metabolism / Q000473:pathology; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology; D013739:Testosterone / Q000008:administration & dosage / Q000378:metabolism
chemical_list: D011944:Receptors, Androgen; D013739:Testosterone
keywords: Kennedy’s disease; androgen; androgen receptor; neuromuscular disease; skeletal muscle; testicular feminization mutation