title: Late degeneration of nigro-striatal neurons in ATM-/- mice.
abstract: The generation of an Atm -/- mouse model of the human ataxia-telangiectasia (AT) opened new avenues toward a better understanding of the molecular and cellular basis of AT. We have recently reported that 5-month-old Atm-/- mice exhibit severe loss of tyrosine hydroxylase-positive, dopaminergic nigro-striatal neurons, down to 26% of age-matched controls. In the present study we analyzed development of the dopaminergic cell loss in the context of the nigro-striatal system. We found that dopaminergic neurons are formed normally in the Atm-/- mouse, and degenerate during the first few months of life; there was no difference between 1-month-old Atm-/- and control mice in the number of dopaminergic cells that were retrogradely labeled by an injection of fluorescent tracer into the striatum. On the other hand, a dramatic reduction in the number of labeled cells was found in 5-month-old Atm-/- mice. This cell loss was significant in areas A9 and A10 but not in area A9-I. These findings indicate that midbrain dopaminergic neurons in Atm-/- mice initially send normal axons to the striatum, only to degenerate later in life. In addition, an age-dependent as well as topographic, medial-to-lateral loss of GAD, met-enkephaline and substance-P immunopositive cells was found in the striatum of the Atm-/- mice. This phenomenon was significant only in the 5-month-old Atm-/- mice (3 months after the beginning of detectable dopaminergic cell loss). In both the striatum and the substantia nigra, the apparent cell loss was accompanied by gliosis. In addition, alpha-synuclein immunopositive bodies were observed in the cortex, striatum and substantia nigra of these mice. The present data indicate that Atm-/- mice exhibit a progressive, age-dependent, reduction in dopaminergic cells of the substantia nigra, followed by a reduction in projection neurons of the striatum. Thus, the Atm-/- mouse may model the extrapyramidal motor deficits seen in AT patients.
authors.affiliation: Department of Neurobiology, The Weizmann Institute, Rehovot 76100, Israel.
authors.forename: R
authors.initials: R
authors.lastname: Eilam
authors.forename: Y
authors.initials: Y
authors.lastname: Peter
authors.forename: Y
authors.initials: Y
authors.lastname: Groner
authors.forename: M
authors.initials: M
authors.lastname: Segal
mesh_terms: D000367:Age Factors; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002452:Cell Count / Q000379:methods; D018797:Cell Cycle Proteins; D003342:Corpus Striatum / Q000378:metabolism / Q000473:pathology*; D004268:DNA-Binding Proteins; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009410:Nerve Degeneration / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency* / Q000235:genetics; D013378:Substantia Nigra / Q000378:metabolism / Q000473:pathology*; D025521:Tumor Suppressor Proteins
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases