Non-coding RNA in Fragile X Syndrome and Converging Mechanisms Shared by Related Disorders

Fragile X syndrome (FXS) is one of the most common forms of hereditary intellectual disability. It is also a well-known monogenic cause of autism spectrum disorders (ASD). Repetitive trinucleotide expansion of CGG repeats in the 5′-UTR of FMR1 is the pathological mutation. Full mutation CGG repeats epigenetically silence FMR1 and thus lead to the absence of its product, fragile mental retardation protein (FMRP), which is an indispensable translational regulator at synapsis. Loss of FMRP causes abnormal neural morphology, dysregulated protein translation, and distorted synaptic plasticity, giving rise to FXS phenotypes. Non-coding RNAs, including siRNA, miRNA, and lncRNA, are transcribed from DNA but not meant for protein translation. They are not junk sequence but play indispensable roles in diverse cellular processes. FXS is the first neurological disorder being linked to miRNA pathway dysfunction. Since then, insightful knowledge has been gained in this field. In this review, we mainly focus on how non-coding RNAs, especially the siRNAs, miRNAs, and lncRNAs, are involved in FXS pathogenesis. We would also like to discuss several potential mechanisms mediated by non-coding RNAs that may be shared by FXS and other related disorders

Age of onset correlates with clinical characteristics and prognostic outcomes in neuromyelitis optica spectrum disorder

ObjectiveNeuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease preferentially affects the optic nerve and the spinal cord. The first attack usually occurs in the third or fourth decade, though patients with disease onset in the fifties or later are not uncommon. This study aimed to investigate the clinical characteristics and prognosis in patients with different age of onset and to explore the correlations between age of onset and clinical characteristics and prognostic outcomes.MethodWe retrospectively reviewed the medical records of 298 NMOSD patients diagnosed according to the 2015 updated version of diagnostic criteria. Patients were divided into early-onset NMOSD (EO-NMOSD) (<50 years at disease onset) and late-onset NMOSD (LO-NMOSD) (≥50 years at disease onset) based on the age of disease onset. LO-NMOSD patients were divided into two subgroups: relative-late-onset NMOSD (RLO-NMOSD) (50~70 years at disease onset) and very-late-onset NMOSD (≥70 years at disease onset). Clinical characteristics, laboratory findings, neuroimaging features, and prognostic outcomes were investigated.ResultsCompared to EO-NMOSD patients, patients with LO-NMOSD showed more frequent transverse myelitis (TM) (58.20% vs. 36.00%, p = 0.007) while less frequent optic neuritis (ON) (23.10% vs. 34.80%, p = 0.031) and brainstem/cerebral attacks (7.50% vs. 18.30%, p = 0.006) as the first attack. Patients with LO-NMOSD showed less frequent relapses, higher Expanded Disability Status Scale (EDSS) score at the last follow-up, fewer NMOSD-typical brain lesions, and longer segments of spinal cord lesions. Patients with older onset age showed a higher proportion of increased protein levels in cerebrospinal fluid during the acute phase of attacks. Age at disease onset positively correlated with length of spinal cord lesions at first attack and at last follow-up, negatively correlated with ARR-1 (ARR excluding the first attack, calculated from disease onset to final follow-up), irrespective of AQP4-IgG serostatus. Patients with older age at disease onset progressed to severe motor disability sooner, and age of onset positively correlated with EDSS score at the last follow-up, irrespective of AQP4-IgG serostatus.ConclusionAge of disease onset affects clinical characteristics and prognosis outcomes of patients with NMOSD

Identification of <em>CHIP</em> as a novel causative gene for autosomal recessive cerebellar ataxia

Autosomal recessive cerebellar ataxias are a group of neurodegenerative disorders that are characterized by complex clinical and genetic heterogeneity. Although more than 20 disease-causing genes have been identified, many patients are still currently without a molecular diagnosis. In a two-generation autosomal recessive cerebellar ataxia family, we mapped a linkage to a minimal candidate region on chromosome 16p13.3 flanked by single-nucleotide polymorphism markers rs11248850 and rs1218762. By combining the defined linkage region with the whole-exome sequencing results, we identified a homozygous mutation (c.493CT) in CHIP (NM_005861) in this family. Using Sanger sequencing, we also identified two compound heterozygous mutations (c.389AT/c.441GT; c.621C>G/c.707GC) in CHIP gene in two additional kindreds. These mutations co-segregated exactly with the disease in these families and were not observed in 500 control subjects with matched ancestry. CHIP colocalized with NR2A, a subunit of the N-methyl-D-aspartate receptor, in the cerebellum, pons, medulla oblongata, hippocampus and cerebral cortex. Wild-type, but not disease-associated mutant CHIPs promoted the degradation of NR2A, which may underlie the pathogenesis of ataxia. In conclusion, using a combination of whole-exome sequencing and linkage analysis, we identified CHIP, encoding a U-box containing ubiquitin E3 ligase, as a novel causative gene for autosomal recessive cerebellar ataxia

original data of NMOSD patients

original data of NMOSD patients</p

Table_1_Age of onset correlates with clinical characteristics and prognostic outcomes in neuromyelitis optica spectrum disorder.docx

ObjectiveNeuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease preferentially affects the optic nerve and the spinal cord. The first attack usually occurs in the third or fourth decade, though patients with disease onset in the fifties or later are not uncommon. This study aimed to investigate the clinical characteristics and prognosis in patients with different age of onset and to explore the correlations between age of onset and clinical characteristics and prognostic outcomes.MethodWe retrospectively reviewed the medical records of 298 NMOSD patients diagnosed according to the 2015 updated version of diagnostic criteria. Patients were divided into early-onset NMOSD (EO-NMOSD) (ResultsCompared to EO-NMOSD patients, patients with LO-NMOSD showed more frequent transverse myelitis (TM) (58.20% vs. 36.00%, p = 0.007) while less frequent optic neuritis (ON) (23.10% vs. 34.80%, p = 0.031) and brainstem/cerebral attacks (7.50% vs. 18.30%, p = 0.006) as the first attack. Patients with LO-NMOSD showed less frequent relapses, higher Expanded Disability Status Scale (EDSS) score at the last follow-up, fewer NMOSD-typical brain lesions, and longer segments of spinal cord lesions. Patients with older onset age showed a higher proportion of increased protein levels in cerebrospinal fluid during the acute phase of attacks. Age at disease onset positively correlated with length of spinal cord lesions at first attack and at last follow-up, negatively correlated with ARR-1 (ARR excluding the first attack, calculated from disease onset to final follow-up), irrespective of AQP4-IgG serostatus. Patients with older age at disease onset progressed to severe motor disability sooner, and age of onset positively correlated with EDSS score at the last follow-up, irrespective of AQP4-IgG serostatus.ConclusionAge of disease onset affects clinical characteristics and prognosis outcomes of patients with NMOSD.</p

Genomic organization of the human CHIP gene and the domain structure of the CHIP protein.

<p>The CHIP gene consists of seven exons. The CHIP protein has two key domains: the TPR domains and the one U-box domain. The five mutations identified in CHIP are indicated with arrows. Three mutations [c.493 CγT (p.L165F); c.389A>T (p.N130I); c.441G>T (p.W147C); c.707G>C (p.S236T)] are were located between the third TPR domain and the second low complexity segment. The c.621C>G (p.Y207X) mutation encodes a truncated protein without a U-box domain and the S236T mutation is located in the U-box domain.</p

The pedigrees, brain MRIs, and CHIP mutations identified.

<p>(<b>A</b>) The pedigree of family 1 with autosomal-recessive spinocerebellar ataxia. (<b>B</b>) The brain MRI of II-5 in family 1. Panel (left): axial T1-weighted image showing atrophy of the cerebellar vermis. Panel (right): midline sagittal T1-weighted image showing cerebellar atrophy, particularly evident in the superior vermis, with enlargement of the fourth ventricle. (<b>C</b>) Sanger sequencing results of codons 164–166 in exon 1 of the CHIP gene in a WT subject (left), an individual carrying the heterozygous variant (middle), and an individual carrying the homozygous c.493C>T (p.L165F) mutation (right). (<b>D</b>) The L165F missense mutation occurred at an evolutionarily conserved amino acid (in red) in the CHIP. (<b>E</b> and <b>F</b>) The pedigrees of families 2 and 3. Sanger sequencing results of the members of these two families. The red arrows indicate the mutation sites. </p

Expression of CHIP in the mouse brain and the effect of ARCA-associcated mutations on its ability to promote the degradation of NR2A.

<p>(<b>A</b>) The expression of CHIP in the cerebellum (Cb), hippocampus (Hip), cerebral cortex (Ctx), pons (PN) and medulla oblongata (MO) of mouse brain as analyzed with immunohistochemistry. (<b>B</b>) Co-localization of CHIP (red) and calcium-binding protein calbindin D-28K (green) in Purkinje cells. (<b>C</b>) Co-localization of CHIP (red) and NR2A (green) in Cb, PN and MO. (<b>D</b>) Coexpression of flag-tagged WT, but not ARCA-associated CHIP mutants (CHIP^N130I, CHIP^W147C, CHIP^L165F, CHIP^Y207X, CHIP^S236T), with HA-Fbx2 promoted the degradation of NR2A. Expression vectors for CHIP, Fbx2 and NR2A were transfected into Human Embryonic Kidney 293 cells. At 36 h after transfection, cells were treated with cycloheximide (CHX, 100 μg/ml) and chased for different time periods. NR2A was detected with western blot using the Myc antibody. Quantitative analysis was performed using NIH ImageJ analysis software. Values represent the mean ± S.D. of three independent experiments.</p