title: Igf1 gene disruption results in reduced brain size, CNS hypomyelination, and loss of hippocampal granule and striatal parvalbumin-containing neurons.
abstract: Homozygous Igf1-/- mice at 2 months of age had reduced brain weights, with reductions evenly affecting all major brain areas. The gross morphology of the CNS was normal, but the size of white matter structures in brain and spinal cord was strongly reduced, owing to decreased numbers of axons and oligodendrocytes. Myelinated axons were more strongly reduced in number than unmyelinated axons. The volume of the dentate gyrus granule cell layer was reduced in excess of the decrease in brain weight. Among populations of calcium-binding protein-containing neurons, there was a selective reduction in the number of striatal parvalbumin-containing cells. Numbers of mesencephalic dopaminergic neurons, striatal and basal forebrain cholinergic neurons, and spinal cord motoneurons were unaffected. Cerebellar morphology was unaltered. Our findings suggest cell type- and region-specific functions for IGF-I and emphasize prominent roles in axon growth and maturation in CNS myelination.
authors.affiliation: Department of Neuroscience, Genentech, Incorporated, South San Francisco, California 94080, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: Beck
authors.forename: L
authors.initials: L
authors.lastname: Powell-Braxton
authors.forename: H R
authors.initials: HR
authors.lastname: Widmer
authors.forename: J
authors.initials: J
authors.lastname: Valverde
authors.forename: F
authors.initials: F
authors.lastname: Hefti
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D001921:Brain / Q000254:growth & development* / Q000502:physiology / Q000648:ultrastructure; D064032:Calbindin 2; D064026:Calbindins; D002452:Cell Count; D003342:Corpus Striatum / Q000166:cytology*; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D006624:Hippocampus / Q000166:cytology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D009186:Myelin Sheath / Q000502:physiology*; D009474:Neurons / Q000166:cytology; D009929:Organ Size; D010320:Parvalbumins / Q000378:metabolism*; D064030:S100 Calcium Binding Protein G / Q000032:analysis; D013116:Spinal Cord / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D064032:Calbindin 2; D064026:Calbindins; D005904:Glial Fibrillary Acidic Protein; D010320:Parvalbumins; D064030:S100 Calcium Binding Protein G; D007334:Insulin-Like Growth Factor I