Genetic Analysis of Chinese Patients with Early-Onset Dementia Using Next-Generation Sequencing.

OBJECTIVE: Early-onset dementia (EOD) is a relatively uncommon form of dementia that afflicts people before age 65. Only a few studies analyzing the genetics of EOD have been performed in the Chinese Han population. Diagnosing EOD remains a challenge due to the diverse genetic and clinical heterogeneity of these diseases. The aim of this study was to investigate the genetic spectrum and clinical features of Chinese patients with EOD. MATERIALS AND METHODS: A total of 49 EOD patients were recruited. Targeted next-generation (NGS) analyses were performed to screen for all of the known genes associated with dementia. Possible pathogenic variants were confirmed by performing Sanger sequencing. The genetic spectrum and clinical features of the EOD patients were analyzed. RESULTS: Seven previously reported pathogenic variants (p.I213T and p.W165C in PSEN1; p.D678N in APP; c.1349_1352del in TBK1; p.P301L and p.R406W in MAPT; p.R110C in NOTCH3) and two novel variants of uncertain significance (p.P436L in PSEN2; c.239-11G>A in TARDBP) were identified. CONCLUSION: Our study demonstrated the genetic spectrum and clinical features of EOD patients, and it reveals that genetic testing of known causal genes in EOD patients can help to make a precise diagnosis.

Identification of novel senataxin mutations in Chinese patients with autosomal recessive cerebellar ataxias by targeted next-generation sequencing.

BACKGROUND: Autosomal recessive cerebellar ataxias (ARCA) are a group of neurodegenerative disorders characterized by early onset of gait impairment, disturbed limb coordination, dysarthria, and eye movement abnormalities, most likely due to the degeneration of cerebellum, brainstem, and spinal cord. Despite of the rarity, ARCA are both clinically and genetically heterogeneous. To date, more than 30 culprit genes have been identified in ARCA. Unraveling the specific causative mutation in cases with ARCA remains challenging so far. METHODS: Three ARCA pedigrees of Chinese ancestry were recruited. Clinical features were evaluated and peripheral blood was collected after obtaining the written inform. Laboratory examinations, brain MRI, and EMG were performed for all the affected individuals. Genomic DNA was extracted, followed by the screening of GAA repeat expansion in FXN gene to exclude Friedreich's ataxia. Targeted next-generation sequencing combining Sanger sequencing was performed in each proband of these families. RESULTS: Compound heterozygous mutations, c.3190G > T (p.E1064X) and c.4883C > G (p.S1628X) of senataxin (SETX) gene were identified in one family with two affected cases. Both of the patients presented with early onset of unsteady walk, dysarthria, and diplopia. EMG test revealed decreased conduction velocity and evoked potential of both motor and sensory nerve. Moreover, elevated serum alpha-fetoprotein (AFP) and apparent cerebellar atrophy were observed. These features were typical features of ataxia with oculomotor apraxia type 2 (AOA2) and in line with the genetic results. However, no specific mutation was identified in the other two pedigrees. CONCLUSIONS: We identified novel compound heterozygous mutations of SETX in Chinese AOA2 pedigree, which broaden the mutation spectrum of SETX. To our knowledge, this is the first report concerning Chinese AOA2 cases with SETX mutations.

FTL mutation in a Chinese pedigree with neuroferritinopathy.

Neuroferritinopathy is a rare autosomal dominant movement disorder caused by mutations of the FTL gene.(1) It is clinically characterized by adult-onset progressive extrapyramidal syndrome, including chorea, dystonia, and parkinsonism.(2) Brain MRI demonstrates the deposition of iron and ferritin in the basal ganglia.(3) To date, several Caucasian families and 2 Japanese families have been reported worldwide.(2) We present a Chinese neuroferritinopathy pedigree with 5 patients and the FTL mutation.