KCTD10 regulates brain development by destabilizing brain disorder-associated protein KCTD13.

KCTD10 belongs to the KCTD (potassiumchannel tetramerization domain) family, many members of which are associated with neuropsychiatric disorders. However, the biological function underlying the association with brain disorders remains to be explored. Here, we reveal that Kctd10 is highly expressed in neuronal progenitors and layer V neurons throughout brain development. Kctd10 deficiency triggers abnormal proliferation and differentiation of neuronal progenitors, reduced deep-layer (especially layer V) neurons, increased upper-layer neurons, and lowered brain size. Mechanistically, we screened and identified a unique KCTD10-interacting protein, KCTD13, associated with neurodevelopmental disorders. KCTD10 mediated the ubiquitination-dependent degradation of KCTD13 and KCTD10 ablation resulted in a considerable increase of KCTD13 expression in the developing cortex. KCTD13 overexpression in neuronal progenitors led to reduced proliferation and abnormal cell distribution, mirroring KCTD10 deficiency. Notably, mice with brain-specific Kctd10 knockout exhibited obvious motor deficits. This study uncovers the physiological function of KCTD10 and provides unique insights into the pathogenesis of neurodevelopmental disorders.

Active N6-Methyladenine Demethylation by DMAD Regulates Gene Expression by Coordinating with Polycomb Protein in Neurons.

A ten-eleven translocation (TET) ortholog exists as a DNA N6-methyladenine (6mA) demethylase (DMAD) in Drosophila. However, the molecular roles of 6mA and DMAD remain unexplored. Through genome-wide 6mA and transcriptome profiling in Drosophila brains and neuronal cells, we found that 6mA may epigenetically regulate a group of genes involved in neurodevelopment and neuronal functions. Mechanistically, DMAD interacts with the Trithorax-related complex protein Wds to maintain active transcription by dynamically demethylating intragenic 6mA. Accumulation of 6mA by depleting DMAD coordinates with Polycomb proteins and contributes to transcriptional repression of these genes. Our findings suggest that active 6mA demethylation by DMAD plays essential roles in fly CNS by orchestrating through added epigenetic mechanisms.

GGC expansions in NOTCH2NLC contribute to Parkinson disease and dopaminergic neuron degeneration.

BACKGROUND AND PURPOSE: The role of GGC repeat expansions within NOTCH2NLC in Parkinson's disease (PD) and the substantia nigra (SN) dopaminergic neuron remains unclear. Here, we profile the NOTCH2NLC GGC repeat expansions in a large cohort of patients with PD. We also investigate the role of GGC repeat expansions within NOTCH2NLC in the dopaminergic neurodegeneration of SN. METHODS: A total of 2,522 patients diagnosed with PD and 1,085 health controls were analyzed for the repeat expansions of NOTCH2NLC by repeat-primed PCR and GC-rich PCR assay. Furthermore, the effects of GGC repeat expansions in NOTCH2NLC on dopaminergic neurons were investigated by using recombinant adeno-associated virus (AAV)-mediated overexpression of NOTCH2NLC with 98 GGC repeats in the SN of mice by stereotactic injection. RESULTS: Four PD pedigrees (4/333, 1.2%) and three sporadic PD patients (3/2189, 0.14%) were identified with pathogenic GGC repeat expansions (larger than 60 GGC repeats) in the NOTCH2NLC gene, while eight PD patients and one healthy control were identified with intermediate GGC repeat expansions ranging from 41 to 60 repeats. No significant difference was observed in the distribution of intermediate NOTCH2NLC GGC repeat expansions between PD cases and controls (Fisher's exact test p-value = 0.29). Skin biopsy showed P62-positive intranuclear NOTCH2NLC-polyGlycine (polyG) inclusions in the skin nerve fibers of patient. Expanded GGC repeats in NOTCH2NLC produced widespread intranuclear and perinuclear polyG inclusions, which led to a severe loss of dopaminergic neurons in the SN. Consistently, polyG inclusions were presented in the SN of EIIa-NOTCH2NLC-(GGC)98 transgenic mice and also led to dopaminergic neuron loss in the SN. CONCLUSIONS: Overall, our findings provide strong evidence that GGC repeat expansions within NOTCH2NLC contribute to the pathogenesis of PD and cause degeneration of nigral dopaminergic neurons.

Loss of Drosophila NUS1 results in cholesterol accumulation and Parkinson's disease-related neurodegeneration.

NgBR is the Nogo-B receptor, encoded by NUS1 gene. As NgBR contains a C-terminal domain that is similar to cis-isoprenyltransferase (cis-IPTase), NgBR was speculated to stabilize nascent Niemann-Pick type C 2 (NPC2) to facilitate cholesterol transport out of lysosomes. Mutations in the NUS1 were known as risk factors for Parkinson's disease (PD). In our previous study, it was shown that knockdown of Drosophila NUS1 orthologous gene tango14 causes decreased climbing ability, loss of dopaminergic neurons, and decreased dopamine contents. In this study, tango14 mutant flies were generated with a mutation in the C-terminal enzyme activity region using CRISPR/Cas9. Tango14 mutant showed a reduced lifespan with locomotive defects and cholesterol accumulation in Malpighian tubules and brains, especially in dopaminergic neurons. Multilamellar bodies were found in tango14 mutants using electron microscopy. Neurodegenerative-related brain vacuolization was also detected in tango14 knockdown flies in an age-dependent manner. In addition, tango14 knockdown increased α-synuclein (α-syn) neurotoxicity in α-syn-overexpressing flies, with decreased locomotive activities, dopamine contents, and the numbers of dopaminergic neurons in aging flies. Thus, these observations suggest a role of NUS1, the ortholog of tango14, in PD-related pathogenesis.

Diagnostic value of nerve conduction study in NOTCH2NLC-related neuronal intranuclear inclusion disease.

BACKGROUND AND AIMS: Neuronal intranuclear inclusion disease (NIID) is a rare progressive neurodegenerative disorder mainly caused by abnormally expanded GGC repeats within the NOTCH2NLC gene. Most patients with NIID show polyneuropathy. Here, we aim to investigate diagnostic electrophysiological markers of NIID. METHODS: In this retrospective dual-center study, we reviewed 96 patients with NOTCH2NLC-related NIID, 94 patients with genetically confirmed Charcot-Marie-Tooth (CMT) disease, and 62 control participants without history of peripheral neuropathy, who underwent nerve conduction studies between 2018 and 2022. RESULTS: Peripheral nerve symptoms were presented by 53.1% of patients with NIID, whereas 97.9% of them showed peripheral neuropathy according to electrophysiological examinations. Patients with NIID were characterized by slight demyelinating sensorimotor polyneuropathy; some patients also showed mild axonal lesions. Motor nerve conduction velocity (MCV) of the median nerve usually exceeded 35 m/s, and were found to be negatively correlated with the GGC repeat sizes. Regarding the electrophysiological differences between muscle weakness type (n = 27) and non-muscle weakness type (n = 69) of NIID, nerve conduction abnormalities were more severe in the muscle weakness type involving both demyelination and axonal impairment. Notably, specific DWI subcortical lace sign was presented in only 33.3% of muscle weakness type, thus it was difficult to differentiate them from CMT. Combining age of onset, distal motor latency, and compound muscle action potential of the median nerve showed the optimal diagnostic performance to distinguish NIID from major CMT (AUC = 0.989, sensitivity = 92.6%, specificity = 97.4%). INTERPRETATION: Peripheral polyneuropathy is common in NIID. Our study suggest that nerve conduction study is useful to discriminate NIID.

Expansion of Human-Specific GGC Repeat in Neuronal Intranuclear Inclusion Disease-Related Disorders.

Neuronal intranuclear inclusion disease (NIID) is a slowly progressing neurodegenerative disease characterized by eosinophilic intranuclear inclusions in the nervous system and multiple visceral organs. The clinical manifestation of NIID varies widely, and both familial and sporadic cases have been reported. Here we have performed genetic linkage analysis and mapped the disease locus to 1p13.3-q23.1; however, whole-exome sequencing revealed no potential disease-causing mutations. We then performed long-read genome sequencing and identified a large GGC repeat expansion within human-specific NOTCH2NLC. Expanded GGC repeats as the cause of NIID was further confirmed in an additional three NIID-affected families as well as five sporadic NIID-affected case subjects. Moreover, given the clinical heterogeneity of NIID, we examined the size of the GGC repeat among 456 families with a variety of neurological conditions with the known pathogenic genes excluded. Surprisingly, GGC repeat expansion was observed in two Alzheimer disease (AD)-affected families and three parkinsonism-affected families, implicating that the GGC repeat expansions in NOTCH2NLC could also contribute to the pathogenesis of both AD and PD. Therefore, we suggest defining a term NIID-related disorders (NIIDRD), which will include NIID and other related neurodegenerative diseases caused by the expanded GGC repeat within human-specific NOTCH2NLC.

Comprehensive Analysis of Fragile X Syndrome: Full Characterization of the FMR1 Locus by Long-Read Sequencing.

BACKGROUND: Fragile X syndrome (FXS) is the most frequent cause of inherited X-linked intellectual disability. Conventional FXS genetic testing methods mainly focus on FMR1 CGG expansions and fail to identify AGG interruptions, rare intragenic variants, and large gene deletions. METHODS: A long-range PCR and long-read sequencing-based assay termed comprehensive analysis of FXS (CAFXS) was developed and evaluated in Coriell and clinical samples by comparing to Southern blot analysis and triplet repeat-primed PCR (TP-PCR). RESULTS: CAFXS accurately detected the number of CGG repeats in the range of 93 to at least 940 with mass fraction of 0.5% to 1% in the background of normal alleles, which was 2-4-fold analytically more sensitive than TP-PCR. All categories of mutations detected by control methods, including full mutations in 30 samples, were identified by CAFXS for all 62 clinical samples. CAFXS accurately determined AGG interruptions in all 133 alleles identified, even in mosaic alleles. CAFXS successfully identified 2 rare intragenic variants including the c.879A > C variant in exon 9 and a 697-bp microdeletion flanking upstream of CGG repeats, which disrupted primer annealing in TP-PCR assay. In addition, CAFXS directly determined the breakpoints of a 237.1-kb deletion and a 774.0-kb deletion encompassing the entire FMR1 gene in 2 samples. CONCLUSIONS: Long-read sequencing-based CAFXS represents a comprehensive assay for identifying FMR1 CGG expansions, AGG interruptions, rare intragenic variants, and large gene deletions, which greatly improves the genetic screening and diagnosis for FXS.

Clinical features of NOTCH2NLC-related neuronal intranuclear inclusion disease.

BACKGROUND: Abnormal expanded GGC repeats within the NOTCH2HLC gene has been confirmed as the genetic mechanism for most Asian patients with neuronal intranuclear inclusion disease (NIID). This cross-sectional observational study aimed to characterise the clinical features of NOTCH2NLC-related NIID in China. METHODS: Patients with NOTCH2NLC-related NIID underwent an evaluation of clinical symptoms, a neuropsychological assessment, electrophysiological examination, MRI and skin biopsy. RESULTS: In the 247 patients with NOTCH2NLC-related NIID, 149 cases were sporadic, while 98 had a positive family history. The most common manifestations were paroxysmal symptoms (66.8%), autonomic dysfunction (64.0%), movement disorders (50.2%), cognitive impairment (49.4%) and muscle weakness (30.8%). Based on the initial presentation and main symptomology, NIID was divided into four subgroups: dementia dominant (n=94), movement disorder dominant (n=63), paroxysmal symptom dominant (n=61) and muscle weakness dominant (n=29). Clinical (42.7%) and subclinical (49.1%) peripheral neuropathies were common in all types. Typical diffusion-weighted imaging subcortical lace signs were more frequent in patients with dementia (93.9%) and paroxysmal symptoms types (94.9%) than in those with muscle weakness (50.0%) and movement disorders types (86.4%). GGC repeat sizes were negatively correlated with age of onset (r=-0.196, p<0.05), and in the muscle weakness-dominant type (median 155.00), the number of repeats was much higher than in the other three groups (p<0.05). In NIID pedigrees, significant genetic anticipation was observed (p<0.05) without repeat instability (p=0.454) during transmission. CONCLUSIONS: NIID is not rare; however, it is usually misdiagnosed as other diseases. Our results help to extend the known clinical spectrum of NOTCH2NLC-related NIID.

Clinical features and reclassification of essential tremor with NOTCH2NLC GGC repeat expansions based on a long-term follow-up.

BACKGROUND AND PURPOSE: NOTCH2NLC GGC repeat expansions have been identified to be associated with essential tremor (ET). Our aim was to characterize ET patients with NOTCH2NLC repeat expansions versus non-expansions and describe distinctive clinical features of repeat expanded patients with long-term follow-up according to the new tremor classification. METHODS: Participants included 597 ET pedigrees, 412 sporadic cases and 1085 healthy controls. Repeat expansions of GGC in NOTCH2NLC were screened, and comprehensive clinical features were investigated. A longitudinal clinical assessment and reclassification were performed in NOTCH2NLC expanded patients. RESULTS: In total, 27 ET pedigrees (27/597) and three sporadic patients (3/412) were identified with pathogenic NOTCH2NLC GGC repeat expansions (≥60 repeats). Intermediate-length GGC repeats (41-59 repeats) were found in four sporadic ET cases and one control subject, and the frequency was higher than that in control participants (4/412 vs. 1/1085, p = 0.022). About 46 ET patients (43 familial cases from 27 pedigrees and three sporadic cases) with NOTCH2NLC GGC repeat expansions had higher Essential Tremor Rating Assessment Scale I, Essential Tremor Rating Assessment Scale II and Non-Motor Symptoms Scale scores and lower Mini-Mental State Examination scores than the patients without expansions. Patients with pathogenic GGC repeats were reclassified as pure ET (25/46), ET-plus (11/46) and ET-neuronal intranuclear inclusion disease (10/46) subgroups at 2-8 years of follow-up. CONCLUSION: Our results further supported that NOTCH2NLC GGC repeat expansions were associated with ET. Patients with pathogenic GGC repeats presented with more severe motor and non-motor symptoms. Further long-term follow-up and subtype studies will help to define the role of NOTCH2NLC in ET.

[Clinical practice guidelines for Fragile X syndrome].

Fragile X syndrome (FXS) is the most common monogenic form of inherited intellectual disability and autism spectrum disorder (ASD). More than 99% of individuals with FXS are caused by the unstable expansion of CGG repeats located within the 5'-untranslated region of the FMR1 gene. The clinical features of FXS include various degrees of cognitive deficit, physical, behavioral and psychiatric problems. Early treatment and prevention from having further affected children can be guided by molecular genetic testing of the FMR1 gene. The following guideline has combined the relevant research, guidelines and consensus worldwide, and summarized the genetic knowledge and clinical treatment for FXS in order to achieve a standardized diagnosis, treatment and prevention for patients and families affected by this disease.

Biallelic Intronic AAGGG Expansion of RFC1 is Related to Multiple System Atrophy.

OBJECTIVE: A recessive biallelic repeat expansion, (AAGGG)exp , in the RFC1 gene has been reported to be a frequent cause of late-onset ataxia. For cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS), the recessive biallelic (AAGGG)exp genotype was present in ~92% of cases. This study aimed to examine whether the pentanucleotide repeat (PNR) was related to multiple system atrophy (MSA), which shares a spectrum of symptoms with CANVAS. METHODS: In this study, we screened the pathogenic (AAGGG)exp repeat and 5 other PNRs in 104 Chinese sporadic adult-onset ataxia of unknown aetiology (SAOA) patients, 282 MSA patients, and 203 unaffected individuals. Multiple molecular genetic tests were used, including long-range polymerase chain reaction (PCR), repeat-primed PCR (RP-PCR), Sanger sequencing, and Southern blot. Comprehensive clinical assessments were conducted, including neurological examination, neuroimaging, nerve electrophysiology, and examination of vestibular function. RESULTS: We identified biallelic (AAGGG)exp in 1 SAOA patient and 3 MSA patients. Additionally, 1 MSA patient had the (AAGGG)exp /(AAAGG)exp genotype with uncertain pathogenicity. We also described the carrier frequency for different PNRs in our cohorts. Furthermore, we summarized the distinct phenotypes of affected patients, suggesting that biallelic (AAGGG)exp in RFC1 could be associated with MSA and should be screened routinely in the MSA diagnostic workflow. INTERPRETATION: Our results expanded the clinical phenotypic spectrum of RFC1-related disorders and raised the possibility that MSA might share the same genetic background as CANVAS, which is crucial for re-evaluating the current CANVAS and MSA diagnostic criteria. ANN NEUROL 2020;88:1132-1143.

The UFM1 cascade times mitosis entry associated with microcephaly.

Posttranslational modifications enhance the functional diversity of the proteome by modifying the substrates. The UFM1 cascade is a novel ubiquitin-like modification system. The mutations in UFM1, its E1 (UBA5) and E2 (UFC1), have been identified in patients with microcephaly. However, its pathological mechanisms remain unclear. Herein, we observed the disruption of the UFM1 cascade in Drosophila neuroblasts (NBs) decreased the number of NBs, leading to a smaller brain size. The lack of ufmylation in NBs resulted in an increased mitotic index and an extended G2/M phase, indicating a defect in mitotic progression. In addition, live imaging of the embryos revealed an impaired E3 ligase (Ufl1) function resulted in premature entry into mitosis and failed cellularization. Even worse, the embryonic lethality occurred as early as within the first few mitotic cycles following the depletion of Ufm1. Knockdown of ufmylation in the fixed embryos exhibited severe phenotypes, including detached centrosomes, defective microtubules, and DNA bridge. Furthermore, we observed that the UFM1 cascade could alter the level of phosphorylation on tyrosine-15 of CDK1 (pY15-CDK1), which is a negative regulator of the G2 to M transition. These findings yield unambiguous evidence suggesting that the UFM1 cascade is a microcephaly-causing factor that regulates the progression of the cell cycle at mitosis phase entry.

Expansion of GGC repeat in the human-specific NOTCH2NLC gene is associated with essential tremor.

Essential tremor is one of the most common movement disorders. Despite its high prevalence and heritability, the genetic aetiology of essential tremor remains elusive. Up to now, only a few genes/loci have been identified, but these genes have not been replicated in other essential tremor families or cohorts. Here we report a genetic study in a cohort of 197 Chinese pedigrees clinically diagnosed with essential tremor. Using a comprehensive strategy combining linkage analysis, whole-exome sequencing, long-read whole-genome sequencing, repeat-primed polymerase chain reaction and GC-rich polymerase chain reaction, we identified an abnormal GGC repeat expansion in the 5' region of the NOTCH2NLC gene that co-segregated with disease in 11 essential tremor families (5.58%) from our cohort. Clinically, probands that had an abnormal GGC repeat expansion were found to have more severe tremor phenotypes, lower activities of daily living ability. Obvious genetic anticipation was also detected in these 11 essential tremor-positive families. These results indicate that abnormal GGC repeat expansion in the 5' region of NOTCH2NLC gene is associated with essential tremor, and provide strong evidence that essential tremor is a family of diseases with high clinical and genetic heterogeneities.

Coding mutations in NUS1 contribute to Parkinson's disease.

Whole-exome sequencing has been successful in identifying genetic factors contributing to familial or sporadic Parkinson's disease (PD). However, this approach has not been applied to explore the impact of de novo mutations on PD pathogenesis. Here, we sequenced the exomes of 39 early onset patients, their parents, and 20 unaffected siblings to investigate the effects of de novo mutations on PD. We identified 12 genes with de novo mutations (MAD1L1, NUP98, PPP2CB, PKMYT1, TRIM24, CEP131, CTTNBP2, NUS1, SMPD3, MGRN1, IFI35, and RUSC2), which could be functionally relevant to PD pathogenesis. Further analyses of two independent case-control cohorts (1,852 patients and 1,565 controls in one cohort and 3,237 patients and 2,858 controls in the other) revealed that NUS1 harbors significantly more rare nonsynonymous variants (P = 1.01E-5, odds ratio = 11.3) in PD patients than in controls. Functional studies in Drosophila demonstrated that the loss of NUS1 could reduce the climbing ability, dopamine level, and number of dopaminergic neurons in 30-day-old flies and could induce apoptosis in fly brain. Together, our data suggest that de novo mutations could contribute to early onset PD pathogenesis and identify NUS1 as a candidate gene for PD.

Neddylation activity modulates the neurodegeneration associated with fragile X associated tremor/ataxia syndrome (FXTAS) through regulating Sima.

Fragile X associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder caused by expansion of CGG repeats in the 5' UTR of the fragile X mental retardation 1 (FMR1) gene. Using the well-established FXTAS Drosophila model, we performed a high-throughput chemical screen using 3200 small molecules. NSC363998 was identified to suppress the neurodegeneration caused by riboCGG (rCGG) repeats. Three predicted targets of a NSC363998 derivative are isopeptidases in the neddylation pathway and could modulate the neurotoxicity caused by the rCGG repeats. Decreasing levels of neddylation resulted in enhancing neurodegeneration phenotypes, while up-regulation could rescue the phenotypes. Furthermore, known neddylation substrates, Cul3 and Vhl, and their downstream target, Sima, were found to modulate rCGG90-dependent neurotoxicity. Our results suggest that altered neddylation activity can modulate the rCGG repeat-mediated toxicity by regulating Sima protein levels, which could serve as a potential therapeutic target for FXTAS.

Amyotrophic Lateral Sclerosis-associated GGGGCC repeat expansion promotes Tau phosphorylation and toxicity.

Microtubule-associated protein Tau (MAPT) and GGGGCC (G4C2) repeat expansion in chromosome 9 open reading frame 72 (C9ORF72) are the major known genetic causes of frontotemporal dementia (FTD) and other neurodegenerative diseases, such as Amyotrophic Lateral Sclerosis (ALS). Although expanded G4C2 repeats and Tau traditionally are associated with different clinical presentations, pathological and genetic studies have suggested a strong association between them. Here we demonstrate a strong genetic interaction between expanded G4C2 repeats and Tau. We found that co-expression of expanded G4C2 repeats and Tau could produce a synergistic deterioration of rough eyes, motor function, life span and neuromuscular junction morphological abnormalities in Drosophila. Mechanistically, compared with the normal allele containing (G4C2)3 repeats, the (G4C2)30 allele increased Tau phosphorylation levels and promoted Tau R406W aggregation. These results together suggest a potential crosstalk between expanded G4C2 repeats and Tau in modulating neurodegeneration.

[Prenatal diagnosis for 30 women carrying a FMR1 mutation].

OBJECTIVE: To determine the CGG repeat number and methylation status of FMR1 gene for fetuses whose mothers have carried a FMR1 mutation. METHODS: For 30 pregnant women, the fetal CGG repeat number was determined with a GC-rich PCR system by using chorionic villus, amniotic fluid or umbilical blood samples. The methylation status of the FMR1 gene was confirmed with Southern blotting. RESULTS: In total 30 prenatal diagnoses were performed for 29 carriers of FMR1 gene mutations and 1 with FMR1 gene deletion mosaicism. Three fetuses were found to carry premutations, 9 were with full mutations and 1 with mosaicism of premutation and full mutations. Eighteen fetuses were normal. CONCLUSION: Considering the genetic complexity of Fragile X syndrome (FXS), single method may not suffice accurate determination of their genetic status. The pitfalls and technical limitations of protocols requires adoption of personalized strategy for its prenatal diagnosis.

5-Hydroxymethylation-associated epigenetic modifiers of Alzheimer's disease modulate Tau-induced neurotoxicity.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by progressive deterioration of cognitive function. Pathogenesis of AD is incompletely understood; evidence suggests a role for epigenetic regulation, in particular the cytosine modifications 5-methylcytosine and 5-hydroxymethylcytosine (5hmC). 5hmC is enriched in the nervous system and displays neurodevelopment and age-related changes. To determine the role of 5hmC in AD, we performed genome-wide analyses of 5hmC in DNA from prefrontal cortex of post-mortem AD patients, and RNA-Seq to correlate changes in 5hmC with transcriptional changes. We identified 325 genes containing differentially hydroxymethylated loci (DhMLs) in both discovery and replication datasets. These are enriched for pathways involved in neuron projection development and neurogenesis. Of these, 140 showed changes in gene expression. Proteins encoded by these genes form direct protein-protein interactions with AD-associated genes, expanding the network of genes implicated in AD. We identified AD-associated single nucleotide polymorphisms (SNPs) located within or near DhMLs, suggesting these SNPs may identify regions of epigenetic gene regulation that play a role in AD pathogenesis. Finally, using an existing AD fly model, we showed some of these genes modulate AD-associated toxicity. Our data implicate neuronal projection development and neurogenesis pathways as potential targets in AD. By incorporating epigenomic and transcriptomic data with genome-wide association studies data, with verification in the Drosophila model, we can expand the known network of genes involved in disease pathogenesis and identify epigenetic modifiers of Alzheimer's disease.

Drosophila CHIP protects against mitochondrial dysfunction by acting downstream of Pink1 in parallel with Parkin.

Mitochondrial kinase PTEN-induced putative kinase 1 (PINK1) and E3 ubiquitin ligase Parkin function in a common pathway to regulate mitochondrial homeostasis contributing to the pathogenesis of Parkinson disease. The carboxyl terminus of Hsc70-interacting protein (CHIP) acts as a heat shock protein 70/heat shock protein 90 cochaperone to mediate protein folding or as an E3 ubiquitin ligase to target proteins for degradation. In this study, overexpression of Drosophila CHIP suppressed a range of Pink1 mutant phenotypes in flies, including abnormal wing posture, thoracic indentation, locomotion defects, muscle degeneration, and loss of dopaminergic neurons. Mitochondrial defects of Pink1 mutant, such as excessive fusion, reduced ATP content, and crista disorganization, were rescued by CHIP but not its ligase-dead mutants. Similar phenotypes and mitochondrial impairment were ameliorated in Parkin mutant flies by wild-type CHIP. Inactivation of CHIP with null fly mutants resulted in mitochondrial defects, such as reduced thoracic ATP content at 3 d old, decreased thoracic mitochondrial DNA content, and defective mitochondrial morphology at 60 d old. CHIP mutants did not exacerbate the phenotypes of Pink1 mutant flies but markedly shortened the life span of Parkin mutant flies. These results indicate that CHIP is involved in mitochondrial integrity and may act downstream of Pink1 in parallel with Parkin.-Chen, J., Xue, J., Ruan, J., Zhao, J., Tang, B., Duan, R. Drosophila CHIP protects against mitochondrial dysfunction by acting downstream of Pink1 in parallel with Parkin.

[Genetic screening and prenatal diagnosis for high risk families of Fragile X syndrome].

OBJECTIVE: To assess the value of genetic testing for Fragile X syndrome (FXS). METHODS: A domestically made diagnostic kit based Tri-primer-PCR method was used to detect mutations of the FMR1 gene among 6 pedigrees with unexplained intellectual disability. The results were verified by methylation PCR and Southern blotting. RESULTS: Pedigrees 1 and 6 were positive for the screening. In pedigree 1, a full-mutation allele with methylation was identified in the proband and his mother, which was passed on to the fetus. In pedigree 6, the proband was mosaic for a full-mutation allele and a pre-mutation allele. His sister was asymptomatic with a full-mutation. His mother carried pre-mutation allele, while his father and sister's baby were normal. The number of CGG repeats of the pedigrees 2 to 5 were in the normal range. CONCLUSION: Genetic testing can provide an effective way to prevent FXS caused by FMR1 mutations and enable prenatal diagnosis for families with a high risk for the disease.