Mutation Screening And Functional MRI Researches On Huntington Disease And Associated Diseases

Huntington disease（HD）is an autosomal dominant neurodegeneration disease,and HTT is the causative gene.The three primary clinical manifestations are chorea,cognitive disorder and psychological and behavioral abnormalities.Chorea is usually the onset symptom of typical HD patients.With the combination of chorea and positive family history,it is not difficult to diagnose.However,in some HD patients with atypical manifestations,the onset symptoms could be walking unstably,bradykinesia,recognition decline,and some patients might not develop chorea for long time.The patients with atypical manifestations could be diagnosed as leukodystrophies,hereditary ataxia,hereditary spastic paraplegia,and so on.Genetic test is of great importance for accurate diagnosis.There is no disease modifying therapy available for HD,and new drugs are still in clinical trials.As for accurately assessing the effect of these treatment,appropriate biomarkers are essential.Compared with the insensitive clinical scales and invasive detection of mutant HTT protein,the image biomarkers from magnetic resonance imaging（MRI）are more sensitive,more convenient,more secure and noninvasive.Compared with 3T and other MRI with lower field strength,7T MRI possesses higher solution,signal noise ratio,contrast and sensitivity,which is in favor of identifying image biomarkers in early stage.Therefore,we screened HTT gene for all patients first.If positive,patients would undergo a 7T resting state functional MRI scan,and we analyzed the image data to identify biomarkers.If negative,patients would undergo whole exome sequencing（WES）,and we dug out the pathogenic variants and did necessary functional experiment to end up with accurate diagnosis.Section Ⅰ: Genetic diagnosis of Huntington disease and associated diseasesObjective: To diagnose genetically for patients with HD and associated diseases.Methods: Firstly,screen HTT in 58 patients with movement disorder,cognitive disorder,and/or mental abnormality,and 45 asymptomatic individuals with positive HD family history.For those who were negative in HTT test,WES was completed.For the variants with uncertain significance,we performed cell experiments to further determine their pathogenicity.Results: We made definite diagnosis in 30 symptomatic and 21 presymptomatic HD patients,and 8 leukodystropies patients in whom we identified 3 novel variants,including c.2654₂654+3del within CSF1 R,a nonsense variant c.1321C>T,and a missense variant c.166G>C within GALC.c.2654₂654+3del within CSF1 R causes abnormal splicing.EIF2B3 c.22A>T and c.1037T>C enhanced the phosphorylation level of e IF2α and the expression of green fluorescent protein mediated by the 5’untranslated region of ATF4.In addition,we analyzed their clinical feature and found new phenotype.Conclusions: Our results have deepened the understanding of clinical manifestations in HD and leukodystropies,and expanded their spectrum of pathogenic variants and clinical features.Section Ⅱ: Image biomarkers research on HD patients and prediction of disease progression on presymtomatic HD individualsObjective: Analyze 7T resting state functional MRI biomarker on HD patients by mass-univariate approaches.Predict CAP in presymtomatic HD individuals（p HD）by multivariate pattern analysis of Re Ho.Methods: A total of 51 HD patients and 34 healthy controls were scanned by a 7T MRI scanner.Through data-driven analysis,we located the brain areas with abnormal function,and defined these areas as seeds to conduct seed-based functional connectivity analysis further.Subsequently,we employed multivariates pattern analysis to predict CAP of p HD by Re Ho.Results: ReHo of pHD in right postcentral gyrus,right inferior frontal gyrus,right middle temporal gyrus and right precentral gyrus was negatively related to CAP.In p HD,the FC significantly strengthened between the seed in right postcentral gyrus and left middle temporal gyrus,left middle occipital gyrus,left median cingulate and paracingulate gyri,left precentral gyrus,left middle frontal gyrus,left dorsolateral superior frontal gyrus,and bilateral supplementary motor area,between the seed in right middle temporal gyrus and right superior temporal gyrus,right median cingulate and paracingulate gyri,right precentral gyrus and right supplementary motor areas.Moreover,when we selected the Re Ho in the ROIs as input and applied the kernel ridge regression,the predictive CAP that was significantly and strongly correlated with real CAP.Conclusions: We firstly used 7T resting state MRI to investigate image biomarkers in HD patients.We firstly found that in the aspect of reflecting disease progression,Re Ho showed higher sensitivity in the presymtomatic stage,and Re Ho in the areas correlated with CAP could effectively predict the CAP in a new p HD individual.In addition,the strengthened FC within sensorimotor network,and among sensorimotor network,default mode network and attention network might be associated with the maintenance of normal function in motor and cognition.