title: MRI evidence of white matter damage in a mouse model of Nijmegen breakage syndrome.
abstract: Nijmegen breakage syndrome (NBS) is a genomic instability disease caused by hypomorphic mutations in the NBS1 gene encoding the Nbs1 (nibrin) protein. Nbs1 is a component of the Mre11/Rad50/Nbs1 (MRN) complex that acts as a sensor of double strand breaks (DSBs) in the DNA and is critical for proper activation of the broad cellular response to DSBs. Conditional disruption of the murine ortholog of NBS1, Nbn, in the CNS of mice was previously reported to cause microcephaly, severe cerebellar atrophy and ataxia. In this study we used MRI to study the brain morphology and organization of Nbn deleted mice. Using conventional T(2)-weighted magnetic resonance, we found that the brains of the mutant mice (Nbs1-CNS-del) were significantly smaller than those of the wild-type animals, with marked mal-development of the cerebellum. Region of interest analysis of the T(2) maps revealed significant T(2) increase in the areas of white matter (corpus callosum, internal capsule and midbrain), with minor changes, if any, in gray matter. Diffusion tensor imaging (DTI) data confirmed that fractional anisotropy values were significantly reduced in these areas, mainly due to increased radial diffusivity (water diffusion perpendicular to neuronal fibers). Biochemical analysis showed low and dispersed staining for MBP and GalC in Nbs1-CNS-del brains, indicating defects in myelin formation and oligodendrocyte development. Myelin index and protein levels were significantly reduced in these brains. Our results point to a novel function of Nbs1 in the development and organization of the white matter.
authors.affiliation: Department of Neurobiochemistry, George S Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel. asafyan@zahav.net.il
authors.forename: Yaniv
authors.initials: Y
authors.lastname: Assaf
authors.forename: Ronit
authors.initials: R
authors.lastname: Galron
authors.forename: Itai
authors.initials: I
authors.lastname: Shapira
authors.forename: Anat
authors.initials: A
authors.lastname: Nitzan
authors.forename: Tamar
authors.initials: T
authors.lastname: Blumenfeld-Katzir
authors.forename: Arieh S
authors.initials: AS
authors.lastname: Solomon
authors.forename: Vered
authors.initials: V
authors.lastname: Holdengreber
authors.forename: Zhao-Qi
authors.initials: ZQ
authors.lastname: Wang
authors.forename: Yosef
authors.initials: Y
authors.lastname: Shiloh
authors.forename: Ari
authors.initials: A
authors.lastname: Barzilai
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000473:pathology*; D018797:Cell Cycle Proteins / Q000235:genetics; D043171:Chromosomal Instability / Q000235:genetics*; D004249:DNA Damage; D002658:Developmental Disabilities / Q000473:pathology*; D004195:Disease Models, Animal; D005145:Face / Q000002:abnormalities*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D007231:Infant, Newborn; D008607:Intellectual Disability / Q000235:genetics / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D051379:Mice; D008810:Mice, Inbred C57BL; D008831:Microcephaly / Q000235:genetics* / Q000473:pathology*; D008854:Microscopy, Electron; D009186:Myelin Sheath / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics; D009836:Oligodendroglia / Q000473:pathology; D013577:Syndrome
chemical_list: D018797:Cell Cycle Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins