Jiong Qin

Submicroscopic subtelomeric aberrations in Chinese patients with unexplained developmental delay/mental retardation

BackgroundSubtelomeric imbalance is widely accepted as related to developmental delay/mental retardation (DD/MR). Fine mapping of aberrations in gene-enriched subtelomeric regions provides essential clues for localizing critical regions, and provides a strategy for identifying new candidate genes. To date, no large-scale study has been conducted on subtelomeric aberrations in DD/MR patients in mainland China.MethodsThis study included 451 Chinese children with moderate to severe clinically unexplained DD/MR. The subtelomere-MLPA (multiplex ligation dependent probe amplification) and Affymetrix human SNP array 6.0 were used to determine the subtelomeric copy number variations. The exact size and the breakpoint of each identified aberration were well defined.ResultsThe submicroscopic subtelomeric aberrations were identified in 23 patients, with a detection rate of 5.1%. 16 patients had simple deletions, 2 had simple duplications and 5 with both deletions and duplications. The deletions involved 14 different subtelomeric regions (1p, 2p, 4p, 6p, 7p, 7q, 8p, 9p, 10p, 11q, 14q, 15q, 16p and 22q), and duplications involved 7 subtelomeric regions (3q, 4p, 6q, 7p, 8p, 12p and 22q). Of all the subtelomeric aberrations found in Chinese subjects, the most common was 4p16.3 deletion. The sizes of the deletions varied from 0.6 Mb to 12 Mb, with 5-143 genes inside. Duplicated regions were 0.26 Mb to 11 Mb, with 6-202 genes inside. In this study, four deleted subtelomeric regions and one duplicated region were smaller than any other previously reported, specifically the deletions in 11q25, 8p23.3, 7q36.3, 14q32.33, and the duplication in 22q13. Candidate genes inside each region were proposed.ConclusionsSubmicroscopic subtelomeric aberrations were detected in 5.1% of Chinese children with clinically unexplained DD/MR. Four deleted subtelomeric regions and one duplicated region found in this study were smaller than any previously reported, which will be helpful for further defining the candidate dosage sensitive gene associated with DD/MR.

SCN1A, SCN1B, and GABRG2 gene mutation analysis in Chinese families with generalized epilepsy with febrile seizures plus.

AbstractGeneralized epilepsy with febrile seizures plus (GEFS+; MIM#604233) is a familial epilepsy syndrome characterized by phenotypic and genetic heterogeneity. It was associated with mutations in the neuronal voltage-gated sodium channel subunit gene (SCN1A, SCN2A, SCN1B) and ligand-gated gamma aminobutyric acid receptors genes (GABRG2, GABRD). We investigated the roles of SCN1A, SCN1B, and GABRG2 mutations in the etiology of Chinese GEFS+ families. Genomic deoxyribonucleic acid (DNA) was extracted from peripheral blood lymphocytes of 23 probands and their family members. The sequences of SCN1A, SCN1B, and GABRG2 genes were analyzed by polymerase chain reaction (PCR) and direct sequencing. The major phenotypes of affected members in the 23 GEFS+ families exhibited FS and FS+, whereas rare phenotypes afebrile generalized tonic-clonic seizures (AGTCS), myoclonic-astatic epilepsy (MAE), and partial seizures were also observed. A novel SCN1A mutation, p.N935H, was identified in one family and another novel mutation in GABRG2, p.W390X, in another family. However, no SCN1B mutation was identified. The combined frequency of SCN1A, SCN1B, and GABRG2 mutations was 8.7% (2/23), extending the distribution of SCN1A and GABRG2 mutations to Chinese GEFS+ families. There were still unidentified genes contributing to the pathogenesis of GEFS+.

Spinal Cord Demyelination Associated with Biotinidase Deficiency in 3 Chinese Patients

Biotinidase deficiency is a treatable cause of severe neurological disorders and skin problems. Spinal cord impairment is a rare complication of this disease and is commonly unrecognized. The authors encountered 3 Chinese patients with progressive spinal cord demyelination associated with biotinidase deficiency. Case 1 exhibited fatigue, proximal muscular weakness, and hypotonic paraplegia from the age of 7 years 4 months. Demyelination of cervical and thoracic cord was evident on magnetic resonance imaging (MRI). Case 2 developed visual impairment, blepharoconjunctivitis, and optic nerve atrophy from 5 years of age, which combined with progressive hypertonic paralysis, ataxia, and alopecia from the age of 7 years. His spinal MRI T2-weighted sequence revealed an extensive hyperintense lesion involving the cervical spinal cord C2 to C4. Bilateral optic nerves were significantly thick. In case 3, intercurrent wheezing, tachypnea, dyspnea, and lethargy occurred from the age of 1 year. Medulla and upper cervical spine edema and demyelination were found on MRI. Markedly elevated urine organic acids and decreased blood biotinidase activities were observed in the 3 patients. Biotin supplementation led to a dramatic improvement of clinical symptoms in 3 patients. The findings indicate that biotinidase deficiency should be considered in the differential diagnosis of unexplained spinal cord demyelination because prompt diagnosis and treatment with biotin may enable an excellent recovery.

Clinical and molecular survey in 124 Chinese patients with Leigh or Leigh-like syndrome

SummaryLeigh syndrome is the most common mitochondrial disorder in children characterized by necrotic lesions in the central nervous system. Both mitochondrial DNA (mtDNA) and nuclear DNA defects in the mitochondrial respiratory chain can lead to this disease. To characterize the clinical and genetic traits of Leigh or Leigh-like syndrome patients in China, 124 unrelated cases were collected between 1992 and 2005. Seventy-seven cases (62.1%) met the typical criteria of Leigh syndrome, including symmetrical bilateral abnormal signals in the basal ganglia, thalamus and brain stem, etc. Other cases (37.9%) belonged to Leigh-like syndrome with atypical clinical or radiological manifestations. Late-onset patients accounted for 20.2%, which is more than previously reported. Movement disorder was the most common symptoms in our patients. Thirty-two patients (25.8%) were confirmed to carry mutant genes. Among them, six cases (4.8%) have been demonstrated to have point mutations in mitochondrial DNA. Two separate patients were detected to have mutations on A8344G and A3243G. The T8993G point mutation was identified in one patient and T8993C in one other patient. SURF1 mutations associated with cytochrome-c oxidase deficiency were identified in 25 patients (20.2%). Four unreported variations have been identified in SURF1 gene from three patients. G604C was found in 22 patients. Only one patient had C214T mutation in the pyruvate dehydrogenase E1α subunit gene. In the remaining 92 patients (74.2%), a specific molecular dysfunction or underlying metabolic abnormality could not be identified.

Clinical and electrophysiological characteristics of startle epilepsy in childhood.

OBJECTIVE Startle epilepsy is one syndrome of reflex epilepsies. We studied its clinical and EEG characteristics. METHODS Analysis of the clinical and EEG characteristics of startle epilepsy. RESULTS Of 11 patients, five were female. Age of onset ranged from 5 months to 7.5 years. Abnormal etiologies were found in seven patients, as a result of perinatal and postnatal factors. Neuroimaging showed abnormalities, commonly focal atrophy, in nine patients. Spontaneous seizures preceded or followed the startle seizures and were present in all patients. Startle seizures experienced included tonic, myoclonic, tonic-myoclonic, tonic-atypical absence, asymmetric tonic motor seizure and tonic-clonic seizure. Diffuse electrodecremental pattern was the most common ictal EEG pattern seen. The triggering stimuli of the startle seizures were sound in seven patients, touch in three and both sound and touch in one. Interictal EEG revealed abnormalities in 10 patients including generalized, multifocal or focal discharges. Many different anti-epileptic drugs were often unsatisfactory. CONCLUSION Startle epilepsies were often symptomatic reflex epilepsies and there were several types of startle seizure. The ictal EEG often showed a diffuse electrodecremental pattern. This disease has a bad prognosis. SIGNIFICANCE We delineated the clinical and EEG characteristics of startle epilepsy in childhood.

Analysis of SCN1A mutation and parental origin in patients with Dravet syndrome

Dravet syndrome (DS) or severe myoclonic epilepsy of infancy is an intractable epileptic syndrome that is caused by mutations in the neuronal voltage-gated sodium channel α1 subunit gene SCN1A. We investigated SCN1A mutations in 63 Chinese patients with DS and analyzed its inheritance. Genomic DNA was extracted from peripheral blood lymphocytes of DS patients and their available parents. The SCN1A open reading frame sequence was analyzed by PCR–DNA sequencing and multiple ligation-dependent probe amplication (MLPA). If the mutation was de novo, we used allele-specific PCR (AS-PCR) to determine the parental origin. Of the 63 patients examined, 49 unrelated patients had SCN1A mutations. The mutation rate was 77.8% (49 of 63), in which 61.2% (30 of 49) were truncation mutations. The mutations included 19 missense mutations, 14 frame-shift mutations, 6 nonsense mutations, 8 splice-site mutations. Through MLPA analysis, deletions or duplications of large fragments accounted for 12.5% (2 of 16) in PCR-sequencing-negative patients. By testing parents for the mutation, 40 mutations were found to be de novo and one mutation was inherited from a mother who was mosaic for a mutation. By AS-PCR analysis in 12 patients with de novo mutations, 10 were confirmed paternal in origin and 2 were maternal in origin. Thirty of the SCN1A mutations reported here have not been previously reported. Approximately 80% of Chinese DS patients have SCN1A mutations. MLPA analysis was essential for PCR-sequencing-negative patients. The majority of SCN1A mutations were de novo, most of which were paternal origin.

Nitric oxide-mediated neuronal apoptosis in rats with recurrent febrile seizures through endoplasmic reticulum stress pathway.

Nitric oxide (NO), as a neurotransmitter, exerts various physiological and pathological effects on the brain. Excess NO is toxic to neurons and may cause neuronal apoptosis. However, the cascade of NO-mediated apoptosis is not fully understood. We utilized a recurrent febrile seizures (FS) rat model and found that plasma NO was increased, neuronal apoptosis was evident, the expression of glucose-regulated protein78 (GRP78, a well-established marker of ER stress) was elevated, and caspase-12 (an ER stress-specific proapoptosis molecule) was activated in the hippocampus in a time-dependent manner after recurrent FS. Administration of sodium nitroprusside (SNP, an NO donor) enhanced neuronal apoptosis, down-regulated the expression of GRP78, and increased that of caspase-12 in FS+SNP groups compared with FS groups. In contrast, treatment with N(G)-nitrol-l-arginine methyl ester (l-NAME, a competitive NO synthase inhibitor) inhibited neuronal apoptosis, up-regulated the expression of GRP78, and decreased that of caspase-12 in FS+l-NAME groups compared with FS groups. These results suggest that NO mediates neuronal apoptosis caused by recurrent FS, and that the ER stress pathway is involved in NO-mediated neuronal apoptosis.

Phaeohyphomycosis of the Central Nervous System Caused by Exophiala dermatitidis in a 3-Year-Old Immunocompetent Host:

An extremely rare case of cerebral phaeohyphomycosis caused by Exophiala dermatitidis is reported. We described an otherwise healthy young child whose presentation was a progressive intracranial hypertension and paraplegia, accompanied by urine retention and constipation. His blood test showed eosinophilia with the proportion of eosinophilic cell up to 28%. A computed tomography and magnetic resonance imaging of the brain and the spinal cord revealed multiple lesions. A cerebral biopsy was performed and the pathological report was cerebral phaeohyphomycosis. Cultures of the tissue and cerebrospinal fluid grew the same fungus. Extraction of genomic DNA from cultures was performed, and the DNA sequence displayed 99% sequence homologies with E dermatitidis. The patients response to therapy was poor, and the boy died 2 months later. Our experience suggests that phaeohyphomycosis should be included in the differential diagnosis in children with multiple intracranial lesions of unknown origin and eosinophilia.

Alpers syndrome with prominent white matter changes

Alpers syndrome is a fatal neurogenetic disorder caused by the mutations in POLG1 gene encoding the mitochondrial DNA polymerase gamma (polgamma). Two missense variants, c.248T > C (p.L83P), c.2662G > A (p.G888S) in POLG1 were detected in a 10-year-old Chinese girl with refractory seizures, acute liver failure after exposure to valproic acid, cortical blindness, and psychomotor regression. The pathology of left occipital lobe showed neuronal loss, spongiform degeneration, astrocytosis, and demyelination. In addition, there were prominent white matter changes in a series of brain magnetic resonance imaging (MRI) and increased immunological factors in CSF.

Identification of novel EIF2B mutations in Chinese patients with vanishing white matter disease

Vanishing white matter (VWM) disease, inherited in an autosomal recessive manner, is one of the most prevalent inherited leukoencephalopathies in childhood. It is a hereditary human disease resulting from the direct defects during protein synthesis, with the gene defects in EIF2B1–5 (identified in 2001–2002) encoding the five subunits of eukaryotic translation initiation factor (eIF2B α, β, γ, δ and ɛ), respectively. Most of the published studies were carried out in the white population. The analysis of clinical features and EIF2B mutation screening were performed in 11 Chinese patients for the first time. Mutations were identified exclusively in EIF2B5 and EIF2B3 in these patients, with six novel mutations, including five missense mutations (EIF2B5: c.185A>T, p.D62V; c.1004G>C, p.C335S; c.1126A>G, p.N376D; EIF2B3: c.140G>A, p.G47E; c.1037T>C, p.I346T) and one deletion leading to amino-acid deletion (EIF2B5: c.1827–1838del, p.S610–D613del). EIF2B3 mutation, accounting for 20% of the total number of mutations found in this study, is more prevalent than expected according to an earlier report (7%). A hot spot mutation in EIF2B3 was identified in this study. A unique EIF2B mutation spectrum in Chinese VWM patients was shown. A systemic study to assess mutation spectrum in different populations needs to be carried out.