Brain Glyceraldehyde-3-Phosphate Dehydrogenase Activity in Human Trinucleotide Repeat Disorders

ORIGINAL CONTRIBUTION Brain Glyceraldehyde-3-Phosphate Dehydrogenase Activity in Human Trinucleotide Repeat Disorders

Stephen J. Kish, PhD; Iscia Lopes-Cendes, MD, PhD; Mark Guttman, MD; Yoshiaki Furukawa, MD; Massimo Pandolfo, MD; Guy A. Rouleau, MD, PhD; Brian M. Ross, PhD; Martha Nance, MD; Lawrence Schut, MD; Lee Ang, MD; Linda DiStefano, BSc

Background: Although the abnormal gene products re- (Huntington disease, spinocerebellar ataxia 1 [SCA1], sponsible for several hereditary neurodegenerative dis- SCA2, and SCA3–Machado-Joseph disease), in brains of orders caused by repeat CAG trinucleotides have been patients with Friedreich ataxia (a GAA repeat disorder) identified, the mechanism by which the proteins con- and Alzheimer disease, and in brains of matched containing the expanded polyglutamine domains cause cell trol subjects. death is unknown. The observation that several of the mutant proteins interact in vitro with the key glycolytic Results: Brain GAPDH activity was normal in all groups enzyme glyceraldehyde-3-phosphate dehydrogenase with the exception of a slight but statistically significant (GAPDH) suggests that interaction between the dif- region-specific reduction in the patients with Hunting- ferent gene products and GAPDH might damage brain ton disease (caudate nucleus, −12%) and Alzheimer dis- neurons. ease (temporal cortex, −19%).

Objective: To measure the activity of GAPDH in post- Conclusion: The presence of the polyglutamine- mortem brain of patients with CAG repeat disorders. containing proteins in CAG repeat disorders does not result in substantial irreversible inactivation or in in- Patients and Methods: Activity of GAPDH was mea- creased activity of GAPDH in human brain. sured in morphologically affected and unaffected brain areas of patients with 4 different CAG repeat disorders Arch Neurol. 1998;55:1299-1304

O DATE, at least 7 autoso- DRPLA (atrophin) interact, at least in vitro, mal-dominant neurodegen- with the enzyme glyceraldehyde-3- erative disorders are known phosphate dehydrogenase (GAPDH).3,4 to be caused by CAG ex- This enzyme is a glycolytic enzyme re- pansions in the coding re- sponsible for the conversion of D-glycer- Tgions of the genes. These include spinobul- aldehyde-3-phosphate to 1,3-diphospho- From the Human bar muscular atrophy, Huntington disease glycerate. As the in vitro data indicate that Neurochemical Pathology (HD), spinocerebellar ataxia type 1 the binding between at least 1 of the mu- Laboratory, Center for (SCA1), SCA2, SCA3–Machado-Joseph tant proteins (ataxin 1) and GAPDH is un- Addiction and Mental Health, disease (MJD), SCA6, SCA7, and denta- expectedly strong for a protein-protein in- Toronto, Ontario (Drs Kish, torubropallidoluysian (DRPLA) atro- teraction, being dissociated only by high Guttman, Furukawa, and Ross 1,2 and Ms DiStefano); phy. The mechanism by which the (Ͼ1-mol/L sodium chloride) salt washes, Departamento de Gene´tica proteins containing the expanded poly- the possibility exists that the abnormal pro- Me´dica, Universidade Estadual glutamine domains cause cell death is un- teins might cause irreversible degrada- de Campinas, Campinas, Brazil known. Recently, much attention has been tion of the enzyme.4 (Dr Lopes-Cendes); Centre de devoted to the possibility that the abnor- As a key enzyme of glycolysis, Recherche Louis-Charles mal proteins might cause death of neu- GAPDH plays an important role in en- Simard (Dr Pandolfo) and rons through protein-protein interac- ergy metabolism. In principle, therefore, Montreal General Hospital tions, with the disease-specific regional the interaction between GAPDH and the Research Institute (Dr Rouleau), specificity conferred by selective vulner- polyglutamine-containing proteins might Montreal, Quebec; ability of different cells or, perhaps, a spe- lead to decreased energy stores, which the Department of Neurology, University of Minnesota, cific brain-regional pattern of the inter- could trigger a degenerative process in sus- Minneapolis (Drs Nance and acting protein. In this regard, the protein ceptible cells. Interestingly, however, a Schut); and the Department of products of the genes for HD (hunting- separate body of experimental data sug- Pathology, Sunnybrook tin), SCA1 (ataxin-1), spinobulbar mus- gests a competing scenario, namely, that Hospital, Toronto (Dr Ang). cular atrophy (androgen receptor), and overexpression of GAPDH might play a

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©1998 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 PATIENTS AND METHODS METHODS For the neurochemical analyses, cerebral cortical subdivi- PATIENTS sions were excised according to Brodmann classification, with the caudate nucleus (intermediate portion of slice 4) and Brains were obtained from groups of patients with the 4 nucleus lateralis of the thalamus dissected as described by Kish CAG repeat and 2 non-CAG repeat neurodegenerative et al15 and in the atlas of Riley,16 respectively. disorders. At autopsy, half of each brain and, for most of The GAPDH activity (measured in the forward reac- the patients with SCA, half of each spinal cord was fixed tion) was determined using minor modifications of a spec- in formalin for neuropathological analysis, whereas the trophotometric procedure,17 which used brain homog- other half was frozen at −80°C until neurochemical enates that had been sonicated (2 ϫ 15 strokes) in 50-mmol/L analysis. The diagnosis in patients with SCA1, SCA2, tris(hydroxymethyl)aminoethane phosphate (pH 7.5), 0.32- SCA3-MJD, and HD was based on presence of character- mol/L sucrose, 1.0-mmol/L sodium EDTA acid, 1.0-mmol/L istic clinical features (for SCA, imbalance, limb ataxia, dithiothreitol, and 0.5% Triton X-100. The incubation mix- dysarthria, and dysphagia; for HD, involuntary move- ture contained 135-mmol/L tris(hydroxymethyl) ments, including chorea), positive family history indicat- aminoethane acetate, 0.14-mmol/L oxidized nicotinamide- ing autosomal dominant inheritance, and, at autopsy, adenine dinucleotide (NAD+), 17-mmol/L disodium arsenate, neuropathological evidence of moderate to severe cell 3.3-mmol/L cysteine, 0.25 mg of tissue wet weight, and 1.5- loss in the spinocerebellar system (for SCA, cerebellum, mmol/L glyceraldehyde-3-phosphate in a total volume of 3.0 lower brainstem, and spinal cord) or basal ganglia (for mL. The assay conditions were optimized for human brain HD, caudate, putamen, and globus pallidus). Polymerase to ensure that the concentrations of glyceraldehyde-3- chain reaction analysis of genomic DNA isolated from phosphate and NAD+ were at maximally stimulating levels. the brains confirmed the expanded CAG repeat size in Changes in absorbance at 340 nm, corresponding to the re- the affected allele in all of the patients (range, SCA1, 54- duction of NAD+, were determined using a spectrophotom- 72; SCA2, 39-44; SCA3-MJD, 69-80; HD, 39-59). All eter (Hitachi model U-2000, Tokyo, Japan) at 30°C. Boiled patients with FA fulfilled the diagnostic criteria for FA,11 tissue homogenates, which gave values identical to those of including onset of ataxia and deep tendon areflexia in samples employing buffer in place of glyceraldehyde-3- lower limbs before the age of 17 years and severe degen- phosphate or homogenate, were used as blanks. eration of the posterior columns, lateral corticospinal tract, and posterior spinocerebellar tract. The PCR STATISTICAL ANALYSES analysis of genomic DNA from the brains of the patients with FA confirmed the expanded GAA repeats in all To establish whether activity of GAPDH was heterogeneously samples. All patients with AD had clinical evidence of distributed among different brain areas, a 1-way analysis of dementia and, at neuropathological examination, an variance (ANOVA) at the .05 criterion level was employed. abundance of neuritic plaques and neurofibrillary To determine the relationship between age and postmortem tangles in neocortex and hippocampus in the absence of interval (interval between death and freezing of the brain) on any other degenerative process. All of the neurological enzyme activity, Pearson correlation coefficients were com- diseases were end-stage in their courses. Some neuro- puted. Possible differences between brain GAPDH activity in pathological information on some of the patients with patient vs control groups were assessed using 1-way ANOVA SCA1,12 FA,13 and AD14 has been published previously. followed by the Tukey test if ANOVA was significant at .05 Brain was also obtained at autopsy from 60 control sub- criterionwhencomparisonsweremadebetweenacontrolgroup jects aged 1 day to 92 years, who died without evidence and multiple disease conditions in which the same brain ar- of neurological or psychiatric disease or brain neuro- eas were examined (controls vs patients with SCA1, SCA2, pathological abnormality. Table 1 and Table 2 show SCA3-MJD, and FA). For other comparisons involving dif- the ages, sex, and suspected cause of death for the con- ferent brain areas between a control group and a single dis- trol and patient subjects, respectively, with the number ease state (HD and AD), the Student 2-tailed t test was em- of CAG repeats for the patients with HD and SCA shown ployed. The null hypothesis was that there would be no ef- in Table 2. fect of disease condition on enzyme activity.

role in cell death mechanisms. In this regard, cerebellar subjects to determine whether the susceptibility of dif- granule cells undergoing apoptotic cell death show in- ferent brain areas to neurodegeneration in the various creased protein levels of GAPDH, with the neuronal death CAG repeat disorders might be related to regional dif- inhibited by treatment with a GAPDH antisense oligo- ferences in enzyme activity. To assess the possible nucleotide.5-7 As increased protein levels of GAPDH do influence of disease state on enzyme levels, we then not appear to be associated with elevated enzyme activ- measured the total activity of the enzyme in homog- ity in the in vitro cell death model,7 a nonglycolytic role enates of degenerating and morphologically normal of GAPDH might be involved in the neuronal apoptotic brain areas of patients with 4 different neurodegenera- process.8 tive disorders caused by expansions of CAG repeats, As a first step toward understanding the possible namely HD, SCA1, SCA2, and SCA3-MJD, and in involvement of GAPDH in CAG repeat disorders, we matched control subjects. As disease controls, we measured the total activity of the enzyme in a sam- included a group of patients with Friedreich ataxia pling of cortical and subcortical brain areas of normal (FA), an autosomal recessive disorder caused by an

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©1998 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 Table 1. Subject Characteristics and Suspected Table 2. Subject Characteristics and Suspected Cause of Death of Control Subjects Cause of Death of Patients*

Subject No./ Subject No./ CAG Repeat Sex/Age Cause of Death Sex/Age, y Cause of Death Number 1/F/1 d Birth asphyxia Huntington Disease 2/F/9 d Congestive heart disease 61/M/71 Bronchopneumonia 40 3/F/24 d Asphyxia 62/F/62 Bronchopneumonia 39 4/M/1 mo Electrolyte abnormality 63/F/73 Unknown 40 5/M/2 mo Congestive heart disease 64/M/29 Bronchopneumonia 59 6/M/2 mo Congestive cardiomyopathy 65/F/56 Bronchopneumonia 45 with endocardial fibroelastosis 66/F/56 Bronchopneumonia 46 7/F/3 mo Myocarditis 67/F/63 Bronchopneumonia 43 8/F/4 mo Sudden death, sepsis 68/F/74 Chronic infections, 38 9/M/6 mo Sudden unexplained death, coarctation obstructive lung disease 10/M/6 mo Bronchopneumonia, pulmonary hemosiderosis 69/M/51 Bronchopneumonia 48 11/M/6 mo Myocarditis 70/F/56 Unknown 43 12/F/8 mo Dehydration SCA 1 13/F/9 mo Asphyxia 71/M/41 Bronchopneumonia 59 14/F/10 mo Drowning 72/M/48 Bronchopneumonia 57 15/F/10 mo Drowning 73/M/22 Bronchopneumonia 72 16/M/1 y Asphyxia 74/F/38 Bronchopneumonia 57 17/M/1 y Gastrointestinal tract disturbance 75/M/45 Bronchopneumonia 56 18/F/11⁄2 y Blunt abdominal trauma 76/F/46 Bronchopneumonia 54 19/F/13⁄4 y Accidental asphyxia 77/F/57 Bronchopneumonia 54 20/F/2 y Abdominal trauma 78/F/53 Bronchopneumonia 54 21/M/2 y Unexpected death 79/M/37 Bronchopneumonia 57 22/M/21⁄2 y Small-bowel obstruction SCA 2 23/M/31⁄2 y Trauma 80/M/55 Bronchopneumonia 42 24/F/5 y Drowning 81/M/49 Bronchopneumonia 40 25/M/5 y Suffocation 82/F/66 Bronchopneumonia 40 26/F/8 y Renal failure 83/M/70 Bronchopneumonia 40 27/F/11 y Congenital heart disease, intraoperative death 84/F/34 Pulmonary congestion 44 28/M/13 y Accidental gunshot wound to the heart 85/F/65 Bronchopneumonia 39 29/F/14 y Perforated intestine SCA 3-MJD 30/M/17 y Chest trauma 86/F/58 Bronchopneumonia 75 31/M/19 y Accidental gunshot wound to left ventricle 87/F/63 Bronchopneumonia 74 32/M/24 y Multiple injuries, accidental 88/F/27 Bronchopneumonia 80 33/F/28 y Intra-abdominal hemorrhage 89/M/63 Congestive cardiomyopathy 69 34/M/28 y Accidental drowning 90/M/56 Bronchopneumonia 73 35/M/30 y Leukemia 91/M/43 Unknown 78 36/M/31 y Massive cardiomegaly due to 92/M/62 Unknown 71 hypertrophic cardiomyopathy 93/F/44 Unknown 77 37/M/36 y Compressional asphyxia 94/M/46 Unknown 75 38/M/38 y Acute and chronic myocardial infarction 39/M/40 y Hypertensive cardiovascular disease Friedreich Ataxia 40/M/40 y Myocardial infarction 95/M/37 Coronary artery thrombosis . . . 41/M/44 y Exsanguination 96/M/28 Unknown . . . 42/M/48 y Cardiomyopathy 97/M/34 Congestive cardiac failure ... 43/M/48 y Atherosclerotic cardiovascular disease and bronchopneumonia 44/M/52 y Sepsis following surgery 98/M/31 Unknown . . . 45/F/56 y Adenocarcinoma of pancreas, pulmonary embolus 99/F/22 Bronchopneumonia . . . 46/M/59 y Atherosclerotic cardiovascular disease 100/M/22 Unknown . . . 47/F/60 y Massive bronchial hemorrhage 101/F/25 Bronchopneumonia . . . 48/F/64 y Cardiac arrest, pulmonary emboli Alzheimer Disease 49/M/68 y Chronic obstructive pulmonary disease 102/M/70 Acute coronary insufficiency . . . with pulmonary atherosclerosis 103/M/75 Bronchopneumonia . . . 50/F/70 y Myocardial infarction 104/F/72 Colostomy surgery . . . 51/M/72 y Complicated coronary atherosclerosis, 105/M/71 Bronchopneumonia . . . apical septa, myocardial infarction 106/M/76 Septicemia . . . 52/M/74 y Myocardial infarction 107/M/76 Unknown . . . 53/M/75 y Sepsis 108/F/70 Bronchopneumonia . . . 54/F/77 y Congestive heart failure, myocardial infarction 109/M/76 Unknown . . . 55/F/80 y Atheroembolization and ischemic colitis 110/M/63 Unknown . . . 56/F/82 y Cardiopulmonary arrest 111/M/63 Arteriosclerosis of basal cerebral ... 57/F/83 y Myocardial infarction arteries with stenosis of middle 58/M/87 y Diffuse interstitial pulmonary disease cerebral artery trifurcation 59/F/89 y Congestive heart disease 60/F/92 y Pulmonary emboli *SCA indicates spinocerebellar ataxia; MJD, Machado-Joseph disease; and ellipses, not applicable.

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2.5 2.5

2.0

2.0 1.5 mol/min per Milligram of Protein µ 1.0 1.5 mol/min per Milligram of Protein

0.5 µ

GAPDH Activity, GAPDH Activity, 1.0 0.0 10 21 17 7b CC WM PUT PI PE NL Brain Area GAPDH Activity, GAPDH Activity, Figure 1. Cortical and subcortical activity of glyceraldehyde-3-phosphate 0.5 dehydrogenase (GAPDH) in postmortem brain of neurologically normal subjects. Values represent mean ± SE of 5 subjects (age, 40 ± 3 years). Numbers indicate Brodmann cerebral cortical areas 10 (frontal cortex), 21 (temporal cortex), 17 (occipital cortex), and 7b (parietal cortex); CC, cerebellar cortex; WM, white matter taken dorsal to head of the caudate; 01530 45 60 75 90 PUT, putamen; PI and PE, internal and external globus pallidus, respectively; Age, y and NL, nucleus thalamus lateralis. Figure 2. Influence of age on activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in postmortem occipital cortex of 60 neurologically intronic GAA triplet expansion,9 and a group of normal subjects aged from 1 day to 92 years. patients with Alzheimer disease (AD), a disorder in which decreased brain GAPDH activity has previously entire age range (Figure 2) and from 1 day to 8 months been reported.10 (r = 0.83; PϽ.001; n = 13).

RESULTS GAPDH IN ABNORMAL HUMAN BRAIN

GAPDH IN HEALTHY HUMAN BRAIN As shown in Table 3, no statistically significant differences in brain GAPDH activity were observed between The GAPDH activity in the human brain was linear with the patients with SCA1, SCA2, SCA3-MJD, and FA as com- respect to enzyme protein level and time across the range pared with the control group. For the patients with HD, used. As expected,18 enzyme activity was inhibited by io- a slight but statistically significant reduction in enzyme doacetic acid (50% inhibition at approximately 150 activity was observed in caudate nucleus (−12%; PϽ.001), µmol/L; n = 3, parietal cortex). The Km (Michaelis- whereas in the AD group, GAPDH activity was de- Menten constant) (mean of 3 determinations in control creased by 19% in the temporal cortex (PϽ.02). No sta- parietal cortex) for glyceraldehyde-3-phosphate and NAD+ tistically significant correlations (Spearman rank) were were 101 and 6.4 µmol/L, respectively. Regression analy- observed between number of CAG repeats and GAPDH ses revealed no statistically significant influence of post- activity in any of the 4 CAG repeat disorders in any brain mortem interval on brain GAPDH activity for the con- region examined (PϾ.05). trol or patient groups (PϾ.05). An ANOVA revealed a heterogeneous (PϽ.001) dis- COMMENT tribution of GAPDH activity among the different brain areas of normal controls (mean age, 40 years) (Figure 1). Our major finding is that GAPDH activity is normal or However, with the exception of the white matter (taken near normal in brains of patients with 4 different CAG dorsal to the caudate nucleus), in which enzyme levels repeat disorders. were modestly lower than in gray matter areas, activity To determine whether the brain regional pattern of of the enzyme was similar in all examined cortical and cell loss in different trinucleotide repeat disorders might subcortical brain areas. be related to differences in amount of GAPDH, we ex- To examine the influence of age on GAPDH activ- amined the regional distribution of GAPDH activity in ity, enzyme levels were determined in occipital cortex of cortical and subcortical areas of the normal human brain. a total of 60 normal controls aged from 1 day to 92 years. However, activity of GAPDH was similar in all gray mat- As shown in Figure 2, substantial levels of GAPDH were ter brain regions examined, including regions affected (for present in occipital cortex during the perinatal period, HD, putamen and globus pallidus; for SCA disorders, cer- with a moderate (approximately 60%) increase in activ- ebellar cortex) and relatively unaffected (cerebral cor- ity to about 8 months of age. This was followed by a slight tex, thalamus) by neuronal loss in the CAG repeat dis- increase in activity throughout childhood and adult- orders. Our human brain data are consistent with those hood. Regression analysis revealed a statistically signifi- of Mizuno and Ohta,19 who reported a lack of heteroge- cant age-related increase in enzyme activity across the neity of GAPDH activity among different brain areas of

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©1998 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 Table 3. Subject Characteristics and Activity of GAPDH in Postmortem Brain of Patients With Trinucleotide Repeat Disorders and Alzheimer Disease*

GAPDH Activity†

No. of Postmortem Nucleus Lateralis Group Subjects Age, y Interval, h Frontal Cortex Parietal Cortex Cerebellar Cortex Thalamus Control 17 42 ± 4 13 ± 2 1.72 ± 0.04 1.76 ± 0.04 1.64 ± 0.04 1.83 ± 0.05 SCA1 9 43 ± 3 9 ± 2 1.94 ± 0.03 1.96 ± 0.02 1.75 ± 0.04 2.03 ± 0.04 SCA2 6 57 ± 6 12 ± 2 1.87 ± 0.11 1.93 ± 0.10 1.71 ± 0.09 2.10 ± 0.05 SCA3-MJD 9 51 ± 4 9 ± 3 1.88 ± 0.11 1.88 ± 0.15 1.75 ± 0.08 1.91 ± 0.14 FA 7 28 ± 2 8 ± 3 1.62 ± 0.09 1.77 ± 0.06 1.71 ± 0.05 1.71 ± 0.17

Temporal Cortex Occipital Cortex Caudate Nucleus Control 10 60 ± 5 11 ± 2 . . . 1.89 ± 0.05 2.14 ± 0.04 HD 10 59 ± 4 10 ± 2 . . . 1.77 ± 0.03 1.89 ± 0.05‡

Control 10 67 ± 3 11 ± 2 2.02 ± 0.03 1.96 ± 0.05 . . . AD 10 71 ± 2 11 ± 3 1.64 ± 0.14§ 1.64 ± 0.17 . . .

*GAPDH indicates glyceraldehyde-3-phosphate dehydrogenase; SCA, spinocerebellar ataxia; MJD, Machado-Joseph disease; FA, Friedreich ataxia; HD, Huntington disease; AD, Alzheimer disease; and ellipses, not analyzed. Unless otherwise indicated, data are given as mean ± SEM. No statistically significant differences were observed for age or postmortem interval among the SCA1, SCA2, SCA3-MJD, FA, and respective control groups (1-way analysis of variance [ANOVA], PϾ.05) or among the HD, AD, and respective control groups (Student 2-tailed t test, PϾ.05). No statistically significant differences in brain GAPDH activity were observed among the SCA1, SCA2, SCA3-MJD, FA, and respective control groups (1-way ANOVA). †Represented as micromoles per minute per milligram of protein. ‡PϽ.001, Student 2-tailed t test. §PϽ.02, Student 2-tailed t test.

the rat and little difference between brain enzyme activ- Two scenarios have been suggested regarding the ity in adult vs aged rats. These findings in mammalian possible nature of the involvement of GAPDH and the brain suggest that susceptibility of different brain areas CAG expansion. First, the interaction between polyglu- to neuronal degeneration is unlikely to be explained by tamine-containing proteins and GAPDH results in re- regional differences in total GAPDH levels. duced activity of this energy-metabolizing enzyme and, We found that activity of GAPDH, measured under consequently, cell death in susceptible brain areas due conditions that would assess maximal amount of the to decreased energy stores.3,4 Second, the abnormal pro- active enzyme, was normal in the brain of patients with tein-GAPDH interaction leads to overexpression of the the 4 different CAG repeat disorders, with the excep- enzyme and consequent cell death by apoptosis,5-8 a form tion of a slight (12%) reduction, in the HD group, of of cell death reported to occur in brain of patients with enzyme activity in the caudate nucleus, a brain region HD23-25 and SCA1.26 The abnormal gene products in SCA1, affected by severe neuronal loss. In the case of HD, our SCA3-MJD, and HD are widely distributed throughout finding of only slightly decreased brain GAPDH activity the brain, being present in normal and degenerating brain is generally consistent with the results of a recent inves- regions.27-29 However, we found that activity of GAPDH, tigation in which normal levels of the enzyme were which can bind, at least in vitro, to several of these mu- found in the brain (cortical and subcortical areas) of tant proteins,3,4 was normal or near normal in morpho- patients with HD (who had not undergone assessment logically affected and unaffected brain regions in the 4 for CAG repeat number).20 The difference between the CAG repeat disorders. Thus, we conclude, on the basis results of this and our own studies might be due to dif- of our postmortem brain findings, that the presence of ferent methods of GAPDH measurement (enzyme activ- the mutant proteins in CAG trinucleotide repeat disor- ity restricted to subcellular fraction assessed by reverse ders does not result in any substantial, irreversible loss enzyme reaction in the other study20; total enzyme of GAPDH protein or overexpression of GAPDH (as activity in brain homogenates assessed by forward reac- inferred by activity levels measured under maximal sub- tion in our investigation) or due to differences in strate conditions) consequent to the polyglutamine patient severity of illness in both studies. In agreement protein-GAPDH interaction. We emphasize, however, with an early investigation,10 activity of GAPDH was that these data do not at all exclude the possibility that slightly (−19%) reduced in the temporal cortex of the glutamine-repeat proteins might reversibly inhibit patients with AD. The modest reduction of brain GAPDH activity in vivo and thereby lead to cell death, GAPDH activity restricted to abnormal areas in HD or that the abnormal proteins could result in function- and AD is consistent with the possibility that GAPDH ally significant changes in protein levels of the enzyme, might be irreversibly damaged in some disease-specific perhaps in specific subcellular or neuronal compart- neurodegenerative processes (eg, by associated oxida- ments, which are not reflected in altered total activity of tive processes21,22) or that the enzyme has some slight GAPDH. The molecular mechanism by which CAG preferential localization to neurons degenerated in gene expansions cause neurodegenerative disease both conditions. requires further investigation.

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©1998 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/01/2021 Accepted for publication February 25, 1998. SCA-1-linked olivopontocerebellar atrophy define a unique phenotype. Acta Neu- This study was supported by grant 26034 from the Na- ropathol (Berl). 1995;90:572-581. 13. Mastrogiacomo F, LaMarche J, Dozic S, et al. Immunoreactive levels of ␣- tional Institute of Neurological Disorders and Stroke, Na- ketoglutarate dehydrogenase subunits in Friedreich’s ataxia and spinocerebellar tional Institutes of Health, Bethesda, Md (Dr Kish). ataxia type 1. Neurodegeneration. 1996;5:27-33. Some postmortem brain tissue was received from the 14. Mastrogiacomo F, Bergeron C, Kish SJ. Brain ␣-ketoglutarate dehydrogenase Tissue Donation Program of the National Ataxia Founda- complex activity in Alzheimer’s disease. J Neurochem. 1993;61:2007-2014. 15. Kish SJ, Shannak K, Hornykiewicz O. Uneven pattern of dopamine loss in the tion, Wayzata, Minn, and the Canadian Brain Tissue Bank, striatum of patients with idiopathic Parkinson’s disease. N Engl J Med. 1988; Toronto, Ontario. 318:867-880. Reprints: Stephen J. Kish, PhD, Human Neurochemi- 16. Riley HA. An Atlas of the Basal Ganglia, Brainstem and Spinal Cord. New York, cal Pathology Laboratory, Clarke Institute of Psychiatry, NY: Hafner; 1960. 250 College St, Toronto, Ontario, Canada M5T 1R8 (e- 17. Vyas I, Lowndes HE, Howland RD. Inhibition of glyceraldehyde-3-phosphate dehydrogenase in tissues of the rat by acrylamide and related compounds. Neu- mail: [email protected]). rotoxicology. 1985;6:123-132. 18. Sabri MI, Ochs S. Inhibition of glyceraldehyde-3-phosphate dehydrogenase in REFERENCES mammalian nerve by iodoacetic acid. J Neurochem. 1971;18:1509-1514. 19. Mizuno Y, Ohta K. Regional distributions of thiobarbituric acid-reactive products, activities of enzymes regulating the metabolism of oxygen free radicals, 1. Zhuchenko 0, Bailey J, Bonnen P, et al. Autosomal dominant cerebellar ataxia and some of the related enzymes in adult and aged rat brain. J Neurochem. 1986;

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Images In Neurology

We are pleased to announce the addition of a new feature, Images in Neurology, to the ARCHIVES. For this section we invite your submission of interesting images of patients, tissue biopsy samples, and radiographic images, including magnetic reso- nance imaging, positron emission tomography, and x-ray scans, etc. With your image, please send a brief summary (300 words or less) describing its uniqueness and importance. Also, indicate the magnification and stain where appropriate. Both black-and-white and color images (at no charge to the author) are welcome. Submissions should be sent in triplicate to: Roger N. Rosenberg, MD, Editor, Archives of Neurology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75235-9108.

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