Human Molecular Genetics, 2000, Vol. 9, No. 5 779-785
© 2000 Oxford University Press
Repeat instability and motor incoordination in mice with a targeted expanded CAG repeat in the Sca1 locus
1Department of Molecular and Human Genetics, 2Department of Pediatrics, 3Department of Pathology and 4Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA and 5Institute for Human Genetics, University of Minnesota, Minneapolis, MN, USA
Received 23 November 1999; Revised and Accepted 12 January 2000.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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To elucidate the pathophysiology of spinocerebellar ataxia type 1 (SCA1) and to evaluate repeat length instability in the context of the mouse Sca1 gene, we generated knock-in mice by inserting an expanded tract of 78 CAG repeats into the mouse Sca1 locus. Mice heterozygous for the CAG expansion show intergenerational repeat instability (+2 to –6) at a much higher frequency in maternal transmission than in paternal transmission. The majority of changes transmitted through the female germline were small contractions, as in humans, whereas small expansions occurred more frequently in paternal transmission. The frequency of intergenerational changes was age dependent for both paternal and maternal transmissions. Mice homozygous for mutant ataxin-1 on a C57BL/6J–129/SvEv mixed background performed significantly less well on the rotating rod than did wild-type littermates at 9 months of age, although they were not ataxic by cage behavior. Histological examination of brain tissue from mutant mice up to 18 months of age revealed none of the neuropathological changes observed in other transgenic models overexpressing expanded polyglutamine tracts. These data suggest that, even with 78 glutamines, prolonged exposure to mutant ataxin-1 at endogenous levels is necessary to produce a neurological phenotype reminiscent of human SCA1. Pathogenesis is thus a function of polyglutamine length, protein levels and duration of neuronal exposure to the mutant protein.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited late-onset neurodegenerative disorder characterized by progressive ataxia, dysarthria and swallowing difficulties (1). The onset of SCA1 clinical symptoms occurs usually in the third or fourth decade of life, although juvenile cases have been observed (2). The disease worsens progressively over 10–15 years, leading eventually to death due to bulbar dysfunction. Neuropathologically, SCA1 is characterized by selective degeneration of cerebellar Purkinje cells and neurons of the inferior olive and brainstem.
The mutation underlying SCA1 is an expansion of a CAG trinucleotide repeat, encoding a polyglutamine tract in the open reading frame of the SCA1 transcript (3). In the normal population, the repeat is polymorphic, with allele sizes ranging from 6 to 44 CAG units, and it is interrupted by at least one CAT triplet. Conversely, SCA1 chromosomes carry uninterrupted CAG tracts ranging in size from 40 to 83 repeat units (4,5). Although alleles in the normal size range are relatively stable on germline transmission, expanded alleles change size in the majority of the parent-to-offspring transmissions (4,5). This results in an earlier manifestation of the clinical symptoms in subsequent generations of SCA1 families, a phenomenon known as anticipation. There is an inverse correlation between the size of the expanded alleles and age of disease onset (3).
The SCA1 gene encodes a 100 kDa protein of unknown function termed ataxin-1, and is widely expressed in the central nervous system and peripheral tissues (6). Immunohisto- chemical studies showed that ataxin-1 localizes predominantly to the nucleus of neuronal cells and in the cytoplasm of other cell types (7). In SCA1 patients, ataxin-1 accumulates in single ubiquitin-positive nuclear inclusions which are present in affected neurons (8). Transgenic mice overexpressing an expanded human SCA1 cDNA under the control of the Purkinje cell-specific promoter, Pcp2, have been generated to gain insight into the pathogenesis of the SCA1 mutation (9,10). One of these transgenic lines, named B05, overexpresses mutant ataxin-1 mRNA at ~50–100 times endogenous levels, only in Purkinje cells. These mice develop neuropathological changes limited to Purkinje cells and begin to show an ataxic phenotype at ~12 weeks of age (9,11). As in brain tissue from SCA1 patients, expanded ataxin-1 shows an altered distribution in the Purkinje cell nuclei of B05 mice where it forms ubiquitin-positive inclusions (8).
In order to study the effects of the expression of a mutant form of ataxin-1 under the control of its own promoter, we designed a knock-in strategy aimed to insert an expanded CAG trinucleotide repeat into the mouse Sca1 locus. These mice would allow study of the effects of the pathogenicity of mutant ataxin-1 when expressed at endogenous levels in a spatial and temporal pattern that parallels the human condition. Also, introducing the expansion into the genomic locus might provide insight into the repeat instability. Here we describe the generation of the Sca1 knock-in mice that carry 78 CAG repeats in the Sca1 locus, and their phenotypic and neuropathological analyses.
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RESULTS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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The Sca178Q allele is expressed in the brain of knock-in mice
An expanded CAG repeat tract (78Q) was targeted into the Sca1 locus using homologous recombination in embryonic stem (ES) cells. Two types of ES cell were targeted: wild-type cells and those whose Sca1 gene had been replaced by a hypoxanthine phosphoribosyl transferase (HPRT) cassette, as detailed in Figure 1 and Materials and Methods. The latter ES cells yielded a high targeting efficiency, with 50% correctly targeted; after Cre recombination excised the neo cassette, chimeric mice were generated by microinjection of two independent targeted ES clones in C57BL/6J blastocysts and were mated to wild-type C57BL/6J or 129/SvEv females. Germline transmission of the Sca178Q allele in the offspring from these matings was confirmed by genomic Southern blot analysis using mouse tail DNA (Fig. 2A). Crosses between F1 mice carrying the Sca178Q allele produced heterozygous, wild-type and homozygous Sca178Q/Sca178Q offspring in the expected proportions. Mice were generated from both types of ES cell and were identical in phenotype (see below).
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To verify that the insertion of the expanded CAG repeat in the coding region of the Sca1 gene resulted in a functional allele, we checked for the expression of expanded ataxin-1 in brain extracts from mice carrying the Sca178Q allele. Polyclonal antibody 11750 (7), raised against the C-terminal portion of human ataxin-1, was used for western blot analysis on brain homogenates from chimeric, Sca178Q/Sca12Q heterozygous and wild-type mice, as well as on lymphoblast extracts from an SCA1 patient carrying an expanded allele of 82 CAG repeats. In mice carrying the Sca178Q allele, an immunoreactive band above the 130 kDa molecular weight standard is present in addition to a 100 kDa band corresponding to the wild-type ataxin-1. A band of similar mobility is detected in the SCA1 patient lymphoblasts but not in the brain of a wild-type mouse (Fig. 2B). Accordingly, in brain extracts of Sca178Q/Sca178Q homozygous mice, only the expanded ataxin-1 is present (data not shown). Analogous results were obtained by using a different antibody (11NQ) directed against the N-terminal portion of the human protein (8) (data not shown). These data demonstrate that the Sca178Q allele is translated into a full-length peptide.
Stability of the Sca178Q allele in intergenerational transmissions
We have investigated intergenerational CAG repeat instability in Sca178Q/Sca12Q knock-in mice of 129/SvEv pure background by comparing the length of the repeat tract in each mother or father with that observed in their progeny. In results obtained from 200 progeny (109 from paternal and 91 from maternal transmissions), the mutation rate per transmission of the CAG expansion allele was 9.2% (10 transmissions) for the male germline and 69.2% (63 transmissions) for the female germline, respectively, suggesting that maternal transmissions of the mutated allele were much more unstable than the paternal transmissions. The majority of changes in the size of the repeat transmitted through the female germline were small contractions up to six repeats in length, whereas small expansions and contractions of CAG repeats were observed in 5.5 and 3.7% per descendant, respectively, in paternally inherited alleles. The mean changes in the sizes of CAG repeats per generation were –0.02 ± 0.06 and –1.57 ± 0.16 in male and female trans- missions, respectively. To investigate parental age effect on the frequency and magnitude of instability, we compared intergenerational repeat size change among six (for maternal transmission) and seven (for paternal transmission) subgroups according to parental ages at mating (Fig. 3). In paternal transmission, the frequency of expansion per descendant increased with advancing age of the transmitting parent (from 0 to 20%). There was a significant correlation between the intergenerational changes and the paternal age (P < 0.01). The parental age effect on repeat instability was even more evident in maternal transmissions, where the contraction rate per descendant increased from 42 to 100%. Comparing the changes in repeat size revealed an increase in the magnitude of CAG tract contraction with increasing age of the mother (P < 0.0001).
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Phenotypic analyses of mice carrying the Sca178Q allele
Neither heterozygous nor homozygous knock-in mice showed any gross abnormalities compared with their wild-type littermates, nor did they display ataxic behavior (by observation of cage activity) up to 18 months of age. To detect subtle motor coordination impairment, homozygous knock-in mice with mixed genetic background were tested on the accelerating rod apparatus (Rotarod) at 3, 6 and 9 months of age (Fig. 4). At 3 months of age, Sca178Q/Sca178Q mice of mixed background did not differ significantly in Rotarod performance from their wild-type littermates; the 6-month-old homozygous animals performed slightly less well on the Rotarod than their wild-type littermates at all the trials except for the initial trial on the first day of the experiment (Fig. 4A and B). At 9 months of age (Fig. 4C), the Rotarod performance of Sca178Q/Sca178Q mice was significantly below that of the control group (P < 0.05 by ANOVA with repeated measures). Thus, although aged Sca178Q/Sca178Q mice do not display an ataxic phenotype, they do develop a subtle motor incoordination.
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Interestingly, seven 9-month-old Sca178Q/Sca178Q mice of pure 129/SvEv background performed as well as their wild-type littermates on the Rotarod (data not shown). The data suggest that genetic background affects neuronal sensitivity to the mutant ataxin-1.
Neuropathological analyses of knock-in mice
To investigate possible neuropathological changes associated with the expression of mutant ataxin-1 protein, we compared cerebellar and brainstem sections from Sca1 knock-in mice with brain sections from wild-type littermates. Hematoxylin and eosin and cresyl violet (Nissl) stains revealed no gliosis or neuronal loss in cerebellum or brainstem in those mice up to 18 months of age.
To determine whether the expression of the Sca178Q allele results in accumulation of expanded ataxin-1 in ubiquitin-positive intranuclear inclusions as observed in SCA1 individuals and transgenic mice (8), brain sections of knock-in and wild-type mice were stained immunohistochemically using the 11NQ antibody. Sca178Q/Sca12Q mice were analyzed at 5, 10 and 18 months of age, and Sca178Q/Sca178Q at 6, 9, 15 and 18 months of age, along with age-matched wild-type littermates. At all ages analyzed, immunostaining of both Sca178Q/Sca12Q and Sca178Q/Sca178Q mice showed no neuronal intranuclear inclusions (NIs) in Purkinje cells nor in other neuronal types affected in human SCA1. Antibody 11750 revealed no abnormal staining in the brain of an Sca178Q/Sca178Q mouse at 18 months of age. Brain sections from Sca178Q/Sca178Q mice were also stained with ubiquitin antibodies. These antibodies failed to detect any NIs in the Purkinje cells and brainstem neurons of knock-in homozygotes, staining the nuclei homogeneously (data not shown).
One Sca178Q/Sca178Q mutant and one wild-type littermate were used for electron microscopic analysis to examine whether homozygous knock-in mice develop any ultrastructural changes in Purkinje cells. The nuclear structure of these cells was similar in mutant and wild-type brains. Cytoplasmic vacuoles, the first morphological abnormality to appear in Purkinje cells of B05 ataxin-1 transgenic mice (11), were not observed in mutant Purkinje cell somata (data not shown).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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We created Sca178Q knock-in mice that express an expanded allele of ataxin-1 at levels comparable to the endogenous wild-type protein in the same spatial and temporal expression pattern seen in human SCA1 patients. These mutant mice showed intergenerational instability of the CAG repeat expansion. Neither heterozygous nor homozygous Sca178Q mice were ataxic, nor did they show any overt neurological phenotype up to 18 months of age. Sca178Q/Sca178Q mice of C57BL/6J–129/SvEv mixed genetic background performed poorly on the Rotarod at 9 months of age, although none of the neuropathological changes reported for other mouse mutants overexpressing expanded polyglutamine tracts were observed in their brains. These results suggest that the mutant ataxin-1 protein with 78 polyglutamines, expressed at endogenous levels, is not sufficient to cause any detectable pathological changes during the short life span of a mouse, but can cause motor incoordination in a strain-dependent manner.
Numerous lines of transgenic or knock-in mice carrying CAG repeat expansions have been created to reproduce inter- generational repeat instability. Among these are SCA1 cDNA CAG82 transgenic mice (12), Hdh4/Q80 knock-in mice (13), HdhQ18-Q111 knock-in mice (14), huntingtin exon 1 transgenic mice (CAG113–156) (15), androgen receptor yeast artificial chromosome (YAC) transgenic mice (CAG45) (16) and DRPLA YAC transgenic mice (CAG76–78) (17). Similarly to the findings in these other studies, we found that the direction of repeat instability is biased toward small contractions in maternal transmission whereas small expansions are observed more frequently in paternal transmissions in Sca178Q/Sca12Q mice. These results are consistent with the notion that the mechanism underlying gametic mosaicism may be distinct in females and males. Notably, the female germline mutation rates of Sca178Q/Sca12Q mice were similar to SCA1 cDNA CAG82 D02 mice and appear to be higher than those of Hdh4/Q80 knock-in mice and DRPLA YAC transgenic mice (CAG76–78) (~27%) (13,17). In addition, maternal age has comparable effects on CAG contractions, both in Sca178Q/Sca12Q and D02 mice. These observations suggest that, although the mechanistic basis for repeat contractions is still unclear, the rate and magnitude of intergenerational instability in female transmission is dependent not only on the length of the CAG repeat itself, but also on the cis-acting sequence that is present near or adjacent to the CAG repeat; the flanking DNA sequences at some distance from the CAG repeat appear not to be a major determinant for the repeat contraction in female transmission.
Sca178Q/Sca12Q mice mirror a key feature of genetic instability observed in human SCA1 patients. Both in patients and mice, expansions happen more frequently through paternal trans- missions than maternal transmission, whereas a decrease in repeat number is observed more frequently in maternal trans- mission. This suggests that Sca178Q/Sca12Q mice share, at least in part, the common fundamental machinery for genetic instability with human patients, and therefore might provide a tool for elucidating the mechanism underlying genetic instability in human patients. The rate and magnitude of genetic instability in paternally transmitted SCA1 patients are higher than in the Sca178Q/Sca12Q mice, and large intergenerational expansions such as those found in juvenile human patients did not occur in the mice. A similar discrepancy between human polyglutamine disease and its mouse model was shown for DRPLA (17), and these differences could be due to the different reproductive life spans; the mean increase in the repeat size per spermatogenesis cycle was comparable in both the human patients and DRPLA YAC transgenic mice (17). Interestingly, as maternal age increased in our mice, the magnitude of the repeat change increased significantly (10-fold between 10 and 30 weeks of age)—much as transmission by older human parents is more likely to result in a change in repeat size.
Why do the Sca178Q knock-in mice fail to develop any clear neuropathological changes? It is now established that overexpression of full-length mutant proteins that are associated with polyglutamine diseases can induce neurodegeneration in mice. B05 transgenic mice overexpress mutant ataxin-1 with 82 polyglutamines in Purkinje cells and develop an ataxic phenotype with characteristic neuropathological changes that include cytoplasmic vacuoles and loss of dendritic arborization (11). Additional transgenic lines using the same promoter but at lower expression levels develop this phenotype only much later in life, and only when homozygous (10, and unpublished data). Moreover, a transgenic mouse line harboring a mutant ataxin-1 transgene with 82 CAG repeats under the control of the neuron-specific enolase promoter expresses approximately twice the endogenous levels of mutant protein (in homozygosity) and does not manifest neurodegeneration during its normal life span (H.T. Orr, unpublished data). Mice overexpressing full-length huntingtin with 89 CAG repeats develop progressive striatal neurodegeneration (18). In contrast to these models, our knock-in mice, expressing the mutant proteins with similar repeat sizes but at levels comparable with the endogenous proteins, do not show an overt neurodegenerative phenotype mirroring the human disease. This is also the case with knock-in mice carrying 72–80 CAG repeats at the murine Hdh locus (13). In human SCA1 patients, expansions similar to our Sca1 knock-in allele are associated with juvenile onset of the clinical symptoms; one patient carrying an 82 CAG repeat developed initial symptoms at 4 years of age (3), but the presence of neuropathological changes at this initial stage of the disease is still unknown. These data suggest that in these knock-in mouse models, the amount of time that a neuron is exposed to the mutant proteins might not be sufficient for them to manifest neuronal degeneration. A larger amount of the mutant ataxin-1 might be required for mice to develop symptoms in their shorter life span. Alternatively, a longer polyglutamine tract within ataxin-1 could induce neuronal degeneration at endogenous levels. There is a clear inverse correlation between the age of onset and CAG repeat size in SCA1 (19). Mice carrying 146 polyglutamine repeats in the Hprt locus developed NIs in the absence of neurodegeneration (20). An Sca1 knock-in mouse with very large CAG repeats might develop a more overt ataxic phenotype and display neuropathological changes at a younger age. (We are testing this hypothesis by targeting 154 repeats into the mouse locus.) Another factor that may influence the development of the ataxia phenotype in B05 transgenics is the protein context (B05 mice express human ataxin-1). It is possible that mouse ataxin-1 is less pathogenic than its human counterpart. It is unlikely that the timing of transgene expression is a factor, since endogenous Sca1 is turned on during embryogenesis, whereas the SCA1 transgene in B05 mice is turned on postnatally (10).
One intriguing feature of our knock-in mice is the impaired motor coordination observed in aged animals on a C57BL/6J–129/SvEv mixed background. This behavioral phenotype was not associated with apparent neurodegeneration and therefore might be attributable to some neuronal dysfunction. It is unclear whether this phenotype is the early manifestation of the disease that occurs in humans or is unrelated to SCA1. Nevertheless, the first sign of difficulty in human patients is often the perception of slight motor incoordination during the course of performing highly complex motor tasks, which leads us to believe that the motor incoordination in mice mirrors the early symptoms of the human disease. Interestingly, Hdh knock-in mice displayed impaired long-term potentiation and increased aggressiveness in the absence of neurodegeneration (13,21). These observations suggest that subtle neuronal dysfunction may precede neuropathological changes in polyglutamine diseases, and further investigations of the mechanism of these changes might be helpful for disclosing initial events in the process of progression of polyglutamine diseases. A body of evidence suggests that genetic background affects neuropathological and behavioral phenotype in transgenic animal models of neurodegenerative diseases. It is well known that genetic background profoundly modifies Alzheimer’s disease-related phenotypes such as amyloid plaque formation in transgenic mice overexpressing mutant amyloid precursor protein (22). B05 ataxin-1 transgenic mice on an FVB/N–129/SvEv background showed disease ~4 weeks later than B05 mice on an FVB/N pure background (H. Orr, unpublished data). Our results are consistent with these observations. Identification of modifier genes may prove useful in therapeutic intervention or disease prevention.
In conclusion, the Sca178Q knock-in mice showed intergenerational repeat instability and impaired motor coordination that is dependent on genetic background, but revealed no detectable neuropathological changes. Age seems to be a factor in both instability and motor impairment. These mice may be useful for searching for factors that enhance disease-related phenotype. Recently, the possibility has been raised that protein misfolding caused by polyglutamine expansion and proteolytic cleavage by the ubiquitin–proteasome pathway might be involved in the pathogenesis of SCA1 (23,24). At present, several spontaneous or gene-targeted mutant mice that are deficient in specific molecules involved in this pathway are available. Analyses of double mutant animals such as Sca1 knock-in–Ube3a ubiquitin ligase knock-out mice (25) will provide a good tool for testing this hypothesis.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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Targeting an expanded CAG allele into the Sca1 locus and generating mice carrying the Sca178Q allele
All Sca1 fragments used for the construct assembly were derived from a
phage clone isolated from a 129/SvEv genomic library and subcloned in pBluescript KS+ plasmid vector (Stratagene, La Jolla, CA). The mouse homolog of the SCA1 gene shares a high degree of homology with its human counterpart, but contains only two CAG units in its coding region (26). A PCR-generated MscI–HincII fragment was amplified from an SCA1 cDNA clone carrying a repeat of 83 CAG units using the two oligonucleotides shown in Figure 1B (10) and inserted into a BamHI–XhoI fragment containing the 5'-most portion of the Sca1 coding region. Only two additional amino acid changes were introduced by this insertion (Fig. 1A). The entire exon 8 sequence was reconstituted by inserting this BamHI–XhoI clone into an XbaI–ApaI genomic fragment spanning the intronic sequence at the 5' and 3' portions of the coding region. Subsequently, 4.7 kb EcoRV–BamHI and 3.2 kb ApaI–BamHI genomic fragments spanning intronic sequences at the 5' and 3' ends, respectively, were ligated to the expanded exon 8. The selectable markers cassette was inserted into a KpnI site situated ~0.8 kb from the 5' intron–exon boundary. The entire exon 8 in the final construct was checked for sequence accuracy. Propagation of the expanded allele in a bacterial plasmid vector reduced the repeat size to 78 CAG units in the final construct. Homologous recombination in ES cells inserted the chimeric Sca1–SCA1 exon 8 with 78 CAG repeats and a cassette carrying the neomycin resistance gene (neo) and the thymidine kinase gene (Tk) flanked by two loxP sites (27) into the 5' region of exon 8 (Fig. 1B). Correct targeting of the Sca178Q allele in ES cells was confirmed by Southern blot analysis. To prevent potential interference of the selectable cassette with the transcription of the knock-in allele, the neo and Tk markers were removed from the targeted locus by Cre-mediated recom- bination between the flanking loxP sites (Fig. 1B) (13). ES cell clone SCA1-KI-66-A1 was injected into blastocysts to produce chimeric mice as described previously (28).
Size determination of the Sca178Q allele
Genomic DNA was isolated from tails taken at 3 weeks of age. Primers 5'repU (5'-AACATGGGCAGTCTGACG-3') and 3'repL (5'-AGCCCTGCTGAGGTGCTG-3') flanking the repeat were used to determine the repeat length. Approximately 100 ng of mouse genomic DNA was used in a 15 µl reaction tube that contained 1 µM each primer, 10% dimethylsulfoxide, 250 µM each dNTP, 2 µCi of [
-32P]dCTP, 1.25 mM MgCl2, 50 mM KCl, 10 mM Tris–HCl pH 8.3 and 0.5 U of Taq DNA polymerase. Cycling conditions were as follows: 94°C for 3 min followed by 32 cycles of denaturing at 94°C for 1 min, annealing at 60°C for 1 min, extension at 72°C for 1 min and final extension at 72°C for 7 min. A 5 µl aliquot of the PCR was mixed with 2 µl of formamide containing loading dye, denatured, run on a 6% polyacrylamide sequencing gel and visualized by autoradiography. The size of the CAG repeat tract was determined by comparison with an M13 DNA sequencing ladder.
Statistical analysis
Statistical analyses were performed using the StatView v5.0 for Macintosh (SAS Institute, Cary, NC). Spearman rank correlation analysis was used to determine the correlation between the intergenerational changes and parental ages.
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ACKNOWLEDGEMENTS |
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We thank R. Paylor for help with the behavioral analyses, P. Wang, Q. Guo and B. Antalffy for expert technical assistance, and V. Brandt for a critical reading of the manuscript. This work is supported by a grant from the National Institutes of Health (NS27699) and by cores from the Mental Retardation Research Center at Baylor College of Medicine. H.Y.Z. is an Investigator and K.W. is a Postdoctoral Research Associate with the Howard Hughes Medical Institute.
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FOOTNOTES |
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+ These authors contributed equally to this work
§ To whom correspondence should be addressed. Tel: +1 713 798 6523; Fax: +1 713 798 8728; Email: hzoghbi@bcm.tmc.edu
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REFERENCES |
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1 Zoghbi, H.Y. and Orr, H.T. (1995) Spinocerebellar ataxia type 1. Semin. Cell Biol., 6, 29–35.[Web of Science][Medline]
2 Zoghbi, H.Y., Pollack, M.S., Lyons, L.A., Ferrell, R.E., Daiger, S.P. and Beaudet, A.L. (1988) Spinocerebellar ataxia: variable age of onset and linkage to human leukocyte antigen in a large kindred. Ann. Neurol., 23, 580–584.[Web of Science][Medline]
3 Orr, H.T., Chung, M.Y., Banfi, S., Kwiatkowski Jr, T.J., Servadio, A., Beaudet, A.L., McCall, A.E., Duvick, L.A., Ranum, L.P. and Zoghbi, H.Y. (1993) Expansion of an unstable trinucleotide CAG repeat in spinocerebellar ataxia type1. Nature Genet., 4, 221–226.[Web of Science][Medline]
4 Chung, M.Y., Ranum, L.P., Duvick, L.A., Servadio, A., Zoghbi, H.Y. and Orr, H.T. (1993) Evidence for a mechanism predisposing to intergenerational CAG repeat instability in spinocerebellar ataxia type I. Nature Genet., 5, 254–258.[Web of Science][Medline]
5 Ranum, L.P., Chung, M.Y., Banfi, S., Bryer, A., Schut, L.J., Ramesar, R., Duvick, L.A., McCall, A., Subramony, S.H., Goldfarb, L. et al. (1994) Molecular and clinical correlations in spinocerebellar ataxia type I: evidence for familial effects on the age at onset. Am. J. Hum. Genet., 55, 244–252.[Web of Science][Medline]
6 Banfi, S., Servadio, A., Chung, M.Y., Kwiatkowski Jr, T.J., McCall, A.E., Duvick, L.A., Shen, Y., Roth, E.J., Orr, H.T. and Zoghbi, H.Y. (1994) Identification and characterization of the gene causing type 1 spinocerebellar ataxia. Nature Genet., 7, 513–520.[Web of Science][Medline]
7 Servadio, A., Koshy, B., Armstrong, D., Antalffy, B., Orr, H.T. and Zoghbi, H.Y. (1995) Expression analysis of the ataxin-1 protein in tissues from normal and spinocerebellar ataxia type 1 individuals. Nature Genet., 10, 94–98.[Web of Science][Medline]
8 Skinner, P.J., Koshy, B.T., Cummings, C.J., Klement, I.A., Helin, K., Servadio, A., Zoghbi, H.Y. and Orr, H.T. (1997) Ataxin-1 with an expanded glutamine tract alters nuclear matrix-associated structures. Nature, 389, 971–974.[Medline]
9 Burright, E.N., Orr, H.T. and Clark, H.B. (1997) Mouse models of human CAG repeat disorders. Brain Pathol., 7, 965–977.[Web of Science][Medline]
10 Burright, E.N., Clark, H.B., Servadio, A., Matilla, T., Feddersen, R.M., Yunis, W.S., Duvick, L.A., Zoghbi, H.Y. and Orr, H.T. (1995) SCA1 transgenic mice: a model for neurodegeneration caused by an expanded CAG trinucleotide repeat. Cell, 82, 937–948.[Web of Science][Medline]
11 Clark, H.B., Burright, E.N., Yunis, W.S., Larson, S., Wilcox, C., Hartman, B., Matilla, A., Zoghbi, H.Y. and Orr, H.T. (1997) Purkinje cell expression of a mutant allele of SCA1 in transgenic mice leads to disparate effects on motor behaviors, followed by a progressive cerebellar dysfunction and histological alterations. J. Neurosci., 17, 7385–7395.
12 Kaytor, M.D., Burright, E.N., Duvick, L.A., Zoghbi, H.Y. and Orr, H.T. (1997) Increased trinucleotide repeat instability with advanced maternal age. Hum. Mol. Genet., 6, 2135–2159.
13 Shelbourne, P.F., Killeen, N., Hevner, R.F., Johnston, H.M., Tecott, L., Lewandoski, M., Ennis, M., Ramirez, L., Li, Z., Iannicola, C. et al. (1999) A Huntington’s disease CAG expansion at the murine Hdh locus is unstable and associated with behavioural abnormalities in mice. Hum. Mol. Genet., 8, 763–774.
14 Wheeler, V.C., Auerbach, W., White, J.K., Srinidhi, J., Auerbach, A., Ryan, A., Duyao, M.P., Vrbanac, V., Weaver, M., Gusella, J.F. et al. (1999) Length-dependent gametic CAG repeat instability in the Huntington’s disease knock-in mouse. Hum. Mol. Genet., 8, 115–122.
15 Mangiarini, L., Sathasivam, K., Mahal, A., Mott, R., Seller, M. and Bates, G.P. (1997) Instability of highly expanded CAG repeats in mice transgenic for the Huntington’s disease mutation. Nature Genet., 15, 197–200.[Web of Science][Medline]
16 La Spada, A.R., Peterson, K.R., Meadows, S.A., McClain, M.E., Jeng, G., Chmelar, R.S., Haugen, H.A., Chen, K., Singer, M.J., Moore, D. et al. (1998) Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability. Hum. Mol. Genet., 7, 959–967.
17 Sato, T., Oyake, M., Nakamura, K., Nakao, K., Fukusima, Y., Onodera, O., Igarashi, S., Takano, H., Kikugawa, K., Ishida, Y. et al. (1999) Transgenic mice harboring a full-length human mutant DRPLA gene exhibit age-dependent intergenerational and somatic instabilities of CAG repeats comparable with those in DRPLA patients. Hum. Mol. Genet., 8, 99–106.
18 Reddy, P.H., Williams, M., Charles, V., Garrett, L., Pike-Buchanan, L., Whetsell Jr, W.O., Miller, G. and Tagle, D.A. (1998) Behavioural abnormalities and selective neuronal loss in HD transgenic mice expressing mutated full-length HD cDNA. Nature Genet., 20, 198–202.[Web of Science][Medline]
19 Zoghbi, H.Y. (1995) Spinocerebellar ataxia type 1. Clin. Neurosci., 3, 5–11.[Web of Science][Medline]
20 Ordway, J.M., Tallaksen-Greene, S., Gutekunst, C.A., Bernstein, E.M., Cearley, J.A., Wiener, H.W., Dure, L.S.T., Lindsey, R., Hersch, S.M., Jope, R.S. et al. (1997) Ectopically expressed CAG repeats cause intranuclear inclusions and a progressive late onset neurological phenotype in the mouse. Cell, 91, 753–763.[Web of Science][Medline]
21 Usdin, M.T., Shelbourne, P.F., Myers, R.M. and Madison, D.V. (1999) Impaired synaptic plasticity in mice carrying the Huntington’s disease mutation. Hum. Mol. Genet., 8, 839–846.
22 Carlson, G.A., Borchelt, D.R., Dake, A., Turner, S., Danielson, V., Coffin, J.D., Eckman, C., Meiners, J., Nilsen, S.P., Youkin, S.G. and Hsiao, K.K. (1997) Genetic modification of the phenotypes produced by amyloid precursor protein overexpression in transgenic mice. Hum. Mol. Genet., 6, 1951–1959.
23 Cummings, C.J., Orr, H.T. and Zoghbi, H.Y. (1999) Progress in pathogenesis studies of spinocerebellar ataxia type 1. Phil. Trans. R. Soc. Lond. B Biol. Sci., 354, 1079–1081.
24 Zoghbi, H.Y. and Orr, H.T. (1999) Polyglutamine diseases: protein cleavage and aggregation. Curr. Opin. Neurobiol., 5, 566–570.
25 Jiang, Y.H., Armstrong, D., Albrecht, U., Atkins, C.M., Noebels, J.L., Eichele, G., Sweatt, J.D. and Beaudet, A.L. (1998) Mutation of the Angelman ubiquitin ligase in mice causes increased cytoplasmic p53 and deficits of contextual learning and long-term potentiation. Neuron, 21, 799–811.[Web of Science][Medline]
26 Banfi, S., Servadio, A., Chung, M., Capozzoli, F., Duvick, L.A., Elde, R., Zoghbi, H.Y. and Orr, H.T. (1996) Cloning and developmental expression analysis of the murine homolog of the spinocerebellar ataxia type 1 gene (Sca1). Hum. Mol. Genet., 5, 33–40.
27 Abuin, A. and Bradley, A. (1996) Recycling selectable markers in mouse embryonic stem cells. Mol. Cell. Biol., 16, 1851–1856.[Abstract]
28 Matilla, A., Roberson, E.D., Banfi, S., Morales, J., Armstrong, D.L., Burright, E.N., Orr, H.T., Sweatt, J.D., Zoghbi, H.Y. and Matzuk, M.M. (1998) Mice lacking ataxin-1 display learning deficits and decreased hippocampal paired-pulse facilitation. J. Neurosci., 18, 5508–5516.
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