Background: Huntington's Disease (HD) is a progressive neurodegenerative disorder with a single causal mutation in the Huntingtin (HTT) gene. MicroRNAs (miRNAs) have recently been implicated as epigenetic regulators of neurological disorders, however, their role in HD pathogenesis is not well defined. Here we study transgenic HD monkeys (HD monkeys) to examine miRNA dysregulation in a primate model of the disease.Results: In this report, 11 miRNAs were found to be significantly associated (P value < 0.05) with HD in the frontal cortex of the HD monkeys. We further focused on one of those candidates, miR-128a, due to the corresponding disruption in humans and mice with HD as well as its intriguing lists of gene targets. miR-128a was downregulated in our HD monkey model by the time of birth. We then confirmed that miR-128a was also downregulated in the brains of pre-symptomatic and post-symptomatic HD patients. Additionally, our studies confirmed a panel of canonical HD signaling genes regulated by miR-128a, including HTT and Huntingtin Interaction Protein 1 (HIP1).Conclusion: Our studies found that miR-128a may play a critical role in HD and could be a viable candidate as a therapeutic or biomarker of the disease.

BACKGROUND:A two-year longitudinal study composed of morphometric MRI measures and cognitive behavioral evaluation was performed on a transgenic Huntington's disease (HD) monkey. rHD1, a transgenic HD monkey expressing exon 1 of the human gene encoding huntingtin (HTT) with 29 CAG repeats regulated by a human polyubiquitin C promoter was used together with four age-matched wild-type control monkeys. This is the first study on a primate model of human HD based on longitudinal clinical measurements.RESULTS:Changes in striatal and hippocampal volumes in rHD1 were observed with progressive impairment in motor functions and cognitive decline, including deficits in learning stimulus-reward associations, recognition memory and spatial memory. The results demonstrate a progressive cognitive decline and morphometric changes in the striatum and hippocampus in a transgenic HD monkey.CONCLUSIONS:This is the first study on a primate model of human HD based on longitudinal clinical measurements. While this study is based a single HD monkey, an ongoing longitudinal study with additional HD monkeys will be important for the confirmation of our findings. A nonhuman primate model of HD could complement other animal models of HD to better understand the pathogenesis of HD and future development of diagnostics and therapeutics through longitudinal assessment.

Huntington's disease (HD) is a dominant neurodegenerative disorder caused by the expansion of glutamine residues in the N-terminal region of the huntingtin (HTT) protein. The disease results in progressive neuronal loss, leading to motor, cognitive, and psychiatric impairment. Here, we report the establishment of neural progenitor cell (NPC) lines derived from induced pluripotent stem cells (iPSCs) of transgenic HD monkeys. Upon differentiation to neurons, HD neural cells develop cellular features of HD, including the formation of nuclear inclusions and oligomeric mutant HTT (mHTT) aggregates, as well as increased apoptosis. These phenotypes are rescued by genetic suppression of HTT and pharmacological treatment, demonstrating the ability of our HD cell model to respond to therapeutic treatment. The development and reversal of HD-associated phenotypes in neural cells from HD monkeys provides a unique nonhuman primate (NHP) model for exploring HD pathogenesis and evaluating therapeutics that could be assessed further in HD monkeys.

Background: Huntington's Disease (HD) is a progressive neurodegenerative disorder caused by an expansion in the polyglutamine (polyQ) region of the Huntingtin (HTT) gene. The clinical features of HD are characterized by cognitive, psychological, and motor deficits. Molecular instability, a core component in neurological disease progression, can be comprehensively evaluated through longitudinal transcriptomic profiling. Development of animal models amenable to longitudinal examination enables distinct disease-associated mechanisms to be identified.Results: Here we report the first longitudinal study of transgenic monkeys with genomic integration of various lengths of the human HTT gene and a range of polyQ repeats. With this unique group of transgenic HD nonhuman primates (HD monkeys), we profiled over 47,000 transcripts from peripheral blood collected over a 2 year timespan from HD monkeys and age-matched wild-type control monkeys.Conclusions: Messenger RNAs with expression patterns which diverged with disease progression in the HD monkeys considerably facilitated our search for transcripts with diagnostic or therapeutic potential in the blood of human HD patients, opening up a new avenue for clinical investigation.