title: Decrease in striatal enkephalin mRNA in mouse models of Huntington's disease.
abstract: Huntington's disease is a devastating progressive neurodegenerative illness characterized by massive neuronal loss in the striatum. It is caused by the presence of an expanded CAG repeat in the gene encoding huntingtin, a protein of unknown function. We have examined the expression of neurotransmitters and other antigens present in striatal neurons with immunohistochemistry, and the level of expression of mRNAs encoding enkephalin, substance P, and glutamic acid decarboxylases with quantitative in situ hybridization histochemistry, in the striatum of two mouse models of Huntington's disease: transgenic animals expressing exon 1 of the human huntingtin gene with 144 CAG repeats and "knock-in" mice containing a chimeric mouse/human exon 1 with 71 or 94 CAG repeats inserted by homologous targeting. Although the transgenic (but not the knock-in) mice were previously shown to display prominent huntingtin- and ubiquitin-containing nuclear inclusions in striatal neurons, in situ nick translation followed by emulsion autoradiography did not reveal any DNA damage in striatum or cortex in these mice. Immunolabeling for calbindin D 28K, enkephalin, substance P, glutamic acid decarboxylases (M(r) 65,000 or 67,000, GAD65 and GAD67), somatostatin, choline acetyltransferase, parvalbumin, and glial fibrillary acidic protein were remarkably similar in transgenic, knock-in, and wild-type mice. Both transgenic and knock-in mice, however, showed a marked decrease in the level of expression of enkephalin mRNA in striatal neurons without significant decreases in mRNAs encoding substance P, GAD65, or GAD67. The data indicate that decreased expression of enkephalin mRNA may be an early sign of neuronal dysfunction due to the Huntington's disease mutation.
authors.affiliation: Department of Neurology and Mental Retardation Center, University of California at Los Angeles School of Medicine, Los Angeles, California 90095, USA.
authors.forename: L
authors.initials: L
authors.lastname: Menalled
authors.forename: H
authors.initials: H
authors.lastname: Zanjani
authors.forename: L
authors.initials: L
authors.lastname: MacKenzie
authors.forename: A
authors.initials: A
authors.lastname: Koppel
authors.forename: E
authors.initials: E
authors.lastname: Carpenter
authors.forename: S
authors.initials: S
authors.lastname: Zeitlin
authors.forename: M F
authors.initials: MF
authors.lastname: Chesselet
mesh_terms: D000818:Animals; D015415:Biomarkers; D064026:Calbindins; D002540:Cerebral Cortex / Q000378:metabolism; D003342:Corpus Striatum / Q000166:cytology / Q000378:metabolism*; D004249:DNA Damage / Q000235:genetics; D004195:Disease Models, Animal; D004745:Enkephalins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005968:Glutamate Decarboxylase / Q000096:biosynthesis / Q000235:genetics; D006720:Homozygote; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics* / Q000378:metabolism*; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008818:Mice, Neurologic Mutants; D009043:Motor Activity / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics; D009474:Neurons / Q000166:cytology / Q000201:enzymology; D009687:Nuclear Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism*; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis; D013373:Substance P / Q000096:biosynthesis / Q000235:genetics; D018911:Trinucleotide Repeats / Q000235:genetics
chemical_list: D015415:Biomarkers; D064026:Calbindins; D004745:Enkephalins; C506812:Htt protein, mouse; D000071058:Huntingtin Protein; D007527:Isoenzymes; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; D013373:Substance P; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; C401141:glutamate decarboxylase 2