Forecasting individual progression trajectories in Huntington disease enables more powered clinical trials.

Variability in neurodegenerative disease progression poses great challenges for the evaluation of potential treatments. Identifying the persons who will experience significant progression in the short term is key for the implementation of trials with smaller sample sizes. We apply here disease course mapping to forecast biomarker progression for individual carriers of the pathological CAG repeat expansions responsible for Huntington disease. We used data from two longitudinal studies (TRACK-HD and TRACK-ON) to synchronize temporal progression of 15 clinical and imaging biomarkers from 290 participants with Huntington disease. We used then the resulting HD COURSE MAP to forecast clinical endpoints from the baseline data of 11,510 participants from ENROLL-HD, an external validation cohort. We used such forecasts to select participants at risk for progression and compute the power of trials for such an enriched population. HD COURSE MAP forecasts biomarkers 5 years after the baseline measures with a maximum mean absolute error of 10 points for the total motor score and 2.15 for the total functional capacity. This allowed reducing sample sizes in trial up to 50% including participants with a higher risk for progression ensuring a more homogeneous group of participants.

8OHdG is not a biomarker for Huntington disease state or progression.

OBJECTIVE: To evaluate plasma 8-hydroxy-deoxy-guanosine (8OHdG) levels as a potential biomarker of premanifest and early Huntington disease (HD). METHODS: Personnel from 2 independent laboratories quantified 8OHdG in blinded longitudinal plasma samples taken 24 months apart from 160 TRACK-HD participants, as well as samples containing control plasma with added ("spiked") 8OHdG. One laboratory used a liquid chromatography-electrochemical array (LCECA) assay, and the other used liquid chromatography-mass spectrometry (LCMS). RESULTS: The LCMS assay was more accurate than the LCECA assay for measurements of "spiked" 8OHdG levels in plasma. Neither assay demonstrated cross-sectional differences in plasma 8OHdG among controls, premanifest HD, and early symptomatic HD. Similarly, neither assay showed longitudinal changes in any disease group over 24 months. CONCLUSIONS: Plasma concentration of 8OHdG is not a biomarker of disease state or progression in HD. We recommend that future putative biomarker studies use blinded sample analysis, standard curves, independent analytical methods, and strict quality control of sample collection and storage.

Comprehensive behavioral testing in the R6/2 mouse model of Huntington's disease shows no benefit from CoQ10 or minocycline.

Previous studies of the effects of coenzyme Q10 and minocycline on mouse models of Huntington's disease have produced conflicting results regarding their efficacy in behavioral tests. Using our recently published best practices for husbandry and testing for mouse models of Huntington's disease, we report that neither coenzyme Q10 nor minocycline had significant beneficial effects on measures of motor function, general health (open field, rotarod, grip strength, rearing-climbing, body weight and survival) in the R6/2 mouse model. The higher doses of minocycline, on the contrary, reduced survival. We were thus unable to confirm the previously reported benefits for these two drugs, and we discuss potential reasons for these discrepancies, such as the effects of husbandry and nutrition.

Biological and clinical manifestations of Huntington's disease in the longitudinal TRACK-HD study: cross-sectional analysis of baseline data.

BACKGROUND: Huntington's disease (HD) is an autosomal dominant, fully penetrant, neurodegenerative disease that most commonly affects adults in mid-life. Our aim was to identify sensitive and reliable biomarkers in premanifest carriers of mutated HTT and in individuals with early HD that could provide essential methodology for the assessment of therapeutic interventions. METHODS: This multicentre study uses an extensive battery of novel assessments, including multi-site 3T MRI, clinical, cognitive, quantitative motor, oculomotor, and neuropsychiatric measures. Blinded analyses were done on the baseline cross-sectional data from 366 individuals: 123 controls, 120 premanifest (pre-HD) individuals, and 123 patients with early HD. FINDINGS: The first participant was enrolled in January, 2008, and all assessments were completed by August, 2008. Cross-sectional analyses identified significant changes in whole-brain volume, regional grey and white matter differences, impairment in a range of voluntary neurophysiological motor, and oculomotor tasks, and cognitive and neuropsychiatric dysfunction in premanifest HD gene carriers with normal motor scores through to early clinical stage 2 disease. INTERPRETATION: We show the feasibility of rapid data acquisition and the use of multi-site 3T MRI and neurophysiological motor measures in a large multicentre study. Our results provide evidence for quantifiable biological and clinical alterations in HTT expansion carriers compared with age-matched controls. Many parameters differ from age-matched controls in a graded fashion and show changes of increasing magnitude across our cohort, who range from about 16 years from predicted disease diagnosis to early HD. These findings might help to define novel quantifiable endpoints and methods for rapid and reliable data acquisition, which could aid the design of therapeutic trials.

A cell-based screen for drugs to treat Huntington's disease.

We have developed a medium-throughput cell-based assay to screen drugs for Huntington's disease (HD). The assay measures the ability of drugs to protect cultured neuronal (PC12) cells from death caused by an expanded polyglutamine (poly Q) form of huntingtin exon 1. Using this assay, we have blindly screened a library of 1040 compounds compiled by the NINDS: the NIH Custom Collection (NCC). Each compound was tested at five concentrations for its ability to protect cells against huntingtin-induced cell death as well as for its toxicity. Of the compounds tested, 18 prevented cell death completely, and 51 partially. Some of these also exhibited toxicity at higher doses. The majority of drugs (81%) were ineffective. Caspase inhibitors and cannabinoids showed reproducible protection in our assay. We believe these compounds, and others in our hit list, are appealing candidates for further investigation. Additionally, this assay is amenable to scaling up to screen additional compounds for treating Huntington's disease.

Cerebellar Purkinje cell loss in aging Hu-Bcl-2 transgenic mice.

The number of cerebellar Purkinje cells is increased by over 40% in young transgenic mice that overexpress a human Bcl-2 transgene (Hu-Bcl-2). To determine whether the Bcl-2-mediated rescue of Purkinje cells persists through life, the numbers of Purkinje cells were estimated in 6-, 12-, 18-, and 24-month-old Hu-Bcl-2 transgenic mice and age-matched controls. In addition, the expression of four markers for Purkinje cell differentiation, calbindin (CaBP), the 67-kDa isoform of glutamic acid decarboxylase (GAD67), gamma-aminobutyric acid transaminase (GABA-T), and the NMDA-R1 receptor subtype (NMDA-NR1) was analyzed in 6-month-old Hu-Bcl-2 transgenics and controls to determine whether overexpression of Bcl-2 and rescue from naturally occurring cell death affects the normal differentiation of Purkinje cells. The estimates of Purkinje cell numbers showed that the number of Purkinje cells in the Hu-Bcl-2 transgenics declines after 6 months to approach wild-type values by 18 months. Although the exogenous human BCL-2 is still expressed in Purkinje cells at 24 months, the expression levels of human BCL-2 appear to decline significantly after 6 months, suggesting that survival of the supernumary Purkinje cells depends on the sustained overexpression of Bcl-2. All the Purkinje cells in the Hu-Bcl-2 transgenic mice appeared to express normal levels of the differentiation markers analyzed so there was no evidence for a class of Purkinje cells that do not differentiate normally when rescued from naturally occurring cell death.

Teaching old drugs new tricks. Meeting of the Neurodegeneration Drug Screening Consortium, 7-8 April 2002, Washington, DC, USA.

Meeting of the Neurodegeneration Drug Screening Consortium, held on 7-8 April 2002, Washington, DC, USA.

Genetically engineered GABA-producing cells demonstrate anticonvulsant effects and long-term transgene expression when transplanted into the central piriform cortex of rats.

Local application of GABA-potentiating agents can prevent or reduce the development and maintenance of behavioral seizures induced by limbic kindling in rats. Microinjection and lesion studies suggest that the transition zone between anterior and posterior piriform cortex (PC), termed here central PC, is a potential target for transplantation of GABA-producing cells. In the present study, we transplanted conditionally immortalized mouse cortical neurons, engineered with the GABA-synthesizing enzyme GAD(65), to the central PC of rats. Suspensions of 1.5 x 10(5) cells in 1 microl were transplanted bilaterally. Control animals received transplantation of beta-galactosidase (beta-gal)-expressing cells. All rats were subsequently kindled through a chronically implanted electrode placed in the basolateral amygdala. The pre- and postkindling threshold currents for eliciting behavioral seizures were determined before and after kindling. We found the prekindling partial seizure threshold to be significantly increased by about 200% in the rats that received the GABA-producing cells compared to rats receiving beta-gal-producing transplants. After kindling, the seizure threshold tended to be higher by 100% in rats that received GABA-producing cells, although the difference from controls was not statistically significant. GABA-producing transplants had no significant effect on the rate of amygdala kindling, but the latency to the first generalized seizure during kindling was significantly increased in animals receiving GABA-producing cells. The transplanted cells showed long-term GAD(65) expression as verified immunohistologically after termination of the experiments. The findings substantiate and extend previous findings that the central PC is part of the anatomical substrate that facilitates propagation from partial to generalized seizures. The data demonstrate that genetically engineered cells have the potential to raise seizure thresholds when transplanted to the central PC.

Use-dependent modulation of inhibitory capacity in the feline lumbar spinal cord.

The ability to perform stepping and standing can be reacquired after complete thoracic spinal cord transection in adult cats with appropriate, repetitive training. We now compare GAD(67)A levels in the spinal cord of cats that were trained to step or stand. We confirmed that a complete spinal cord transection at approximately T12 increases glutamic acid decarboxylase (GAD)(67) in both the dorsal and ventral horns of L5-L7. We now show that step training decreases these levels toward control. Kinematic analyses show that this downward modulation is correlated inversely with stepping ability. Compared with intact cats, spinal cord-transected cats had increased punctate GAD(67) immunoreactivity around neurons in lamina IX at cord segments L5-L7. Compared with spinal nontrained cats, those trained to stand on both hindlimbs had more GAD(67) puncta bilaterally in a subset of lamina IX neurons. In cats trained to stand unilaterally, this elevated staining pattern was limited to the trained side and extended for at least 4 mm in the L6 and L7 segments. The location of this asymmetric GAD(67) staining corresponded to the motor columns of primary knee flexors, which are minimally active during standing, perhaps because of extensor-activated inhibitory interneuron projections. The responsiveness to only a few days of motor training, as well as the GABA-synthesizing potential in the spinal cord, persists for at least 25 months after the spinal cord injury. This modulation is specific to the motor task that is performed repetitively and is closely linked to the ability of the animal to perform a specific motor task.