Huntington's disease (HD) is associated with the expansion of a CAG trinucleotide repeat in a novel gene. We have assessed 360 HD individuals from 259 unrelated families and found a highly significant correlation (r = 0.70, p = 10(-7)) between the age of onset and the repeat length, which accounts for approximately 50% of the variation in the age of onset. Significant associations were also found between repeat length and age of death and onset of other clinical features. Sib pair and parent-child analysis revealed that the CAG repeat demonstrates only mild instability. Affected HD siblings had significant correlations for trinucleotide expansion (r = 0.66, p < 0.001) which was not apparent for affected parent-child pairs.

CAG trinucleotide expansion is the molecular basis of Huntington's disease worldwide and is a highly sensitive and specific marker for inheritance of the disease mutation.

Huntington disease is associated with an unstable and expanded (CAG) trinucleotide repeat. We have analysed the CAG expansion in different tissues from 12 affected individuals. All tissues examined were found to display some repeat mosaicism, with the greatest levels detected in brain and sperm. Regions within the brain showing most obvious neuropathology, such as the basal ganglia and the cerebral cortex, displayed the greatest mosaicism, whereas the cerebellar cortex, which is seldom involved, displayed the lowest degree of CAG instability. In two cases of childhood onset disease we detected differences of 8 and 13 trinucleotides between the cerebellum and other regions of the brain. Our results provide evidence for tissue specific instability of the CAG repeat, with the largest CAG repeat lengths in affected regions of the brain.

This study of allelic association using three intra- and two extragenic markers within 150 kb of the Huntington disease (HD) mutation has provided evidence for linkage disequilibrium for four of five markers. Haplotype analysis of 67 HD families using markers in strong linkage disequilibrium with HD identified two haplotypes underlying 77.6% of HD chromosomes. Normal chromosomes with these two haplotypes had a mean number of CAG repeats significantly larger than and an altered distribution of CAG repeats compared with other normal chromosomes. Furthermore, haplotype analysis of five new mutation families reveals that HD has arisen on these same two chromosomal haplotypes. These findings suggest that HD arises more frequently on chromosomes with specific DNA haplotypes and higher CAG repeat lengths. We then studied CAG and CCG repeat lengths in the HD gene on 896 control chromosomes from different ancestries to determine whether the markedly reduced frequency of HD in Finland, Japan, China and African Blacks is associated with an altered frequency of DNA haplotypes and subsequently lower CAG lengths on control chromosomes compared to populations of Western European descent. The results show a highly significant inverse relationship between CAG and CCG repeat lengths. In populations with lowered prevalence rates of HD, CAG repeat lengths are smaller and the distribution of CCG alleles is markedly different from Western European populations. These findings suggest that, in addition to European emigration, new mutations make a contribution to geographical variation of prevalence rates and is consistent with a multistep model of HD developing from normal chromosomes with higher CAG repeat lengths.

Mutations in the receptor expression enhancing protein 1 (REEP1) have recently been reported to cause autosomal dominant hereditary spastic paraplegia (HSP) type SPG31. In a large collaborative effort, we screened a sample of 535 unrelated HSP patients for REEP1 mutations and copy number variations. We identified 13 novel and 2 known REEP1 mutations in 16 familial and sporadic patients by direct sequencing analysis. Twelve out of 16 mutations were small insertions, deletions or splice site mutations. These changes would result in shifts of the open-reading-frame followed by premature termination of translation and haploinsufficiency. Interestingly, we identified two disease associated variations in the 3'-UTR of REEP1 that fell into highly conserved micro RNA binding sites. Copy number variation analysis in a subset of 133 HSP index patients revealed a large duplication of REEP1 that involved exons 2-7 in an Irish family. Clinically most SPG31 patients present with a pure spastic paraplegia; rare complicating features were restricted to symptoms or signs of peripheral nerve involvement. Interestingly, the distribution of age at onset suggested a bimodal pattern with the appearance of initial symptoms of disease either before the age of 20 years or after the age of 30 years. The overall mutation rate in our clinically heterogeneous sample was 3.0%; however, in the sub-sample of pure HSP REEP1 mutations accounted for 8.2% of all patients. These results firmly establish REEP1 as a relatively frequent autosomal dominant HSP gene for which genetic testing is warranted. We also establish haploinsufficiency as the main molecular genetic mechanism in SPG31, which should initiate and guide functional studies on REEP1 with a focus on loss-of-function mechanisms. Our results should be valid as a reference for mutation frequency, spectrum of REEP1 mutations, and clinical phenotypes associated with SPG31.

Cerebral amyloid angiopathy is caused by deposition of the amyloid β protein in the cerebral vasculature. In analogy to previous observations in Alzheimer disease, we hypothesized that analysis of amyloid β40 and β42 proteins in the cerebrospinal fluid might serve as a molecular biomarker. We observed strongly decreased cerebrospinal fluid amyloid β40 (p < 0.01 vs controls or Alzheimer disease) and amyloid β42 concentrations (p < 0.001 vs controls and p < 0.05 vs Alzheimer disease) in cerebral amyloid angiopathy patients. The combination of amyloid β42 and total tau discriminated cerebral amyloid angiopathy from controls, with an area under the receiver operator curve of 0.98. Our data are consistent with neuropathological evidence that amyloid β40 as well as amyloid β42 protein are selectively trapped in the cerebral vasculature from interstitial fluid drainage pathways that otherwise transport amyloid β proteins toward the cerebrospinal fluid.

Background and Purpose-Cerebral autoregulation may become impaired after stroke. To provide a review of the nature and extent of any autoregulation impairment after stroke and its course over time, a technique allowing repeated bedside measurements with good temporal resolution is required. Transcranial Doppler (TCD) in combination with continuous blood pressure measurements allows noninvasive continuous bedside investigation with high temporal resolution of the dynamic and the steady-state components of cerebral autoregulation. Therefore, this review focuses on all TCD studies on cerebral autoregulation in the setting of documented ischemic stroke. Methods-PubMed and EMBASE were searched for studies of stroke, autoregulation, and TCD. Studies were either acute phase (Ͻ96 hours after index stroke) or chronic phase (Ͼ96 hours after index stroke) autoregulation studies. Quality of studies was studied in a standardized fashion. Results-Twenty-three studies met the inclusion criteria. General agreement existed on cerebral autoregulation being impaired, even after minor stroke. Bilateral impairment of autoregulation was documented, particularly after lacunar stroke. Studies showed progressive deterioration of cerebral autoregulation in the first 5 days after stroke and recovery over the next 3 months. Impaired cerebral autoregulation as assessed by TCD was related to neurological deterioration, the necessity for decompressive surgery, and poor outcome. Synthesis of the data of various studies was, however, limited by studies not meeting key methodological criteria for observational studies. Conclusions-TCD

Falls are common in patients with Huntington's disease, but the incidence, falling circumstances and contributing factors have never been examined. We recorded falls in 45 early to midstage Huntington's disease patients, both retrospectively (12 months) and prospectively (3 months). Fall rates were related to relevant baseline measures, including the Unified Huntington's Disease Rating Scale (UHDRS) and quantitative measures of balance (using angular velocity sensors) and gait (using a pressure-sensitive walkway). Balance and gait measures were compared between patients and 27 healthy age-matched controls. Twenty-seven patients (60%) reported two or more falls in the previous year and were classified as fallers. During prospective follow-up 40% reported at least one fall. A high proportion of falls (72.5%) caused minor injuries. Compared to nonfallers, fallers showed significantly higher scores for chorea, bradykinesia and aggression, as well as lower cognitive scores. Compared to controls, Huntington patients had a decreased gait velocity (1.15 m/s versus 1.45 m/s, P < 0.001) and a decreased stride length (1.29 m versus 1.52 m, P < 0.001). These abnormalities were all significantly greater in fallers compared to nonfallers. In addition, fallers had an increased stride length variability and a significantly greater trunk sway in medio-lateral direction compared to nonfallers. We conclude that falls are common in Huntington's disease. Contributing factors include a combination of "motor" deficits (mainly gait bradykinesia, stride variability and chorea, leading to excessive trunk sway), as well as cognitive decline and perhaps behavioral changes. These factors should be considered as future targets for therapies that aim to reduce falls in Huntington's disease.