Temporal Characterization of Behavioral and Hippocampal Dysfunction in the YAC128 Mouse Model of Huntington’s Disease

Anxiety, memory, and social impairments in the YAC128 mouse model of Huntington's disease

BACKGROUND

Huntington's disease (HD) is an autosomal dominant hereditary disorder, caused by an expansion of polyglutamine in the huntingtin protein. HD is characterized by a progressive decline in motor functions. This decline includes involuntary movements (chorea) and the worsening of controlled motions caused mainly by neuronal dysfunction in the striatum. In addition to the deterioration of motor symptoms, HD patients also suffer from cognitive changes, mood swings, apathy, depression, outbursts of anger, psychosis, and social withdrawal.

OBJECTIVE

A comprehensive examination of cognitive, affective, and social changes in the HD mouse model is required for the development of combined therapy for both motor and non-motor deficits in HD.

METHODS

The behavioral tests for anxiety, memory, and social traits were used in this study.

RESULTS

YAC128 HD transgenic mice exhibited anxiolytic behavior in the novel brightly illuminated environment of the open field and light-dark place preference tests. Moreover, YAC128 HD mice also suffered from a decline in their recognition memory during the novel object recognition test. YAC128 HD mice demonstrated reduced exploration interest during the open field with a non-social target as well as during the first day of the three-chamber social test. Social interaction was also impaired in YAC128 HD mice as it was shown in the social interaction with resident intruder test.

CONCLUSIONS

YAC128 HD mouse model may be used as a model system to test the possible treatments for both motor and non-motor symptoms including memory loss, agitation and social withdrawal.

Pathomechanisms of behavioral abnormalities in Huntington disease: an update

Huntington disease (HD), a devastating autosomal-dominant neurodegenerative disease caused by an expanded CAG trinucleotide repeat, is clinically characterized by a triad of symptoms including involuntary motions, behavior problems and cognitive deficits. Behavioral symptoms with anxiety, irritability, obsessive-compulsive behaviors, apathy and other neuropsychiatric symptoms, occurring in over 50% of HD patients are important features of this disease and contribute to impairment of quality of life, but their pathophysiology is poorly understood. Behavior problems, more frequent than depression, can be manifest before obvious motor symptoms and occur across all HD stages, usually correlated with duration of illness. While specific neuropathological data are missing, the relations between gene expression and behavior have been elucidated in transgenic models of HD. Disruption of interneuronal communications, with involvement of prefronto-striato-thalamic networks and hippocampal dysfunctions produce deficits in multiple behavioral domains. These changes that have been confirmed by multistructural neuroimaging studies are due to a causal cascade linking molecular pathologies (glutamate-mediated excitotoxicity, mitochondrial dysfunctions inducing multiple biochemical and structural alterations) and deficits in multiple behavioral domains. The disruption of large-scale connectivities may explain the variability of behavior profiles and is useful in understanding the biological backgrounds of functional decline in HD. Such findings offer new avenues for targeted treatments in terms of minimizing neurobehavioral impairment in HD.

Emerging Evidence of Golgi Stress Signaling for Neuropathies

The Golgi apparatus is an intracellular organelle that modifies cargo, which is transported extracellularly through the nucleus, endoplasmic reticulum, and plasma membrane in order. First, the general function of the Golgi is reviewed and, then, Golgi stress signaling is discussed. In addition to the six main Golgi signaling pathways, two pathways that have been increasingly reported in recent years are described in this review. The focus then shifts to neurological disorders, examining Golgi stress reported in major neurological disorders, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. The review also encompasses findings related to other diseases, including hypomyelinating leukodystrophy, frontotemporal spectrum disorder/amyotrophic lateral sclerosis, microcephaly, Wilson's disease, and prion disease. Most of these neurological disorders cause Golgi fragmentation and Golgi stress. As a result, strong signals may act to induce apoptosis.

A Novel Huntington's Disease Assessment Platform to Support Future Drug Discovery and Development

Huntington's disease (HD) is a lethal neurodegenerative disorder without efficient therapeutic options. The inefficient translation from preclinical and clinical research into clinical use is mainly attributed to the lack of (i) understanding of disease initiation, progression, and involved molecular mechanisms; (ii) knowledge of the possible HD target space and general data awareness; (iii) detailed characterizations of available disease models; (iv) better suitable models; and (v) reliable and sensitive biomarkers. To generate robust HD-like symptoms in a mouse model, the neomycin resistance cassette was excised from zQ175 mice, generating a new line: zQ175^Δneo. We entirely describe the dynamics of behavioral, neuropathological, and immunohistological changes from 15-57 weeks of age. Specifically, zQ175^Δneo mice showed early astrogliosis from 15 weeks; growth retardation, body weight loss, and anxiety-like behaviors from 29 weeks; motor deficits and reduced muscular strength from 36 weeks; and finally slight microgliosis at 57 weeks of age. Additionally, we collected the entire bioactivity network of small-molecule HD modulators in a multitarget dataset (HD_MDS). Hereby, we uncovered 358 unique compounds addressing over 80 different pharmacological targets and pathways. Our data will support future drug discovery approaches and may serve as useful assessment platform for drug discovery and development against HD.