Xinhua Bao

MECP2 and CDKL5 gene mutation analysis in Chinese patients with Rett syndrome

AbstractRett syndrome (RTT) is a progressive neurodevelopmental disorder that is caused by mutations in the X-linked methyl-CpG-binding protein2 (MECP2) gene. In this study, the MECP2 sequences in 121 unrelated Chinese patients with classical or atypical RTT were screened for deletions and mutations. In all, we identified 45 different MECP2 mutations in 102 of these RTT patients. The p. T158M mutation (15.7%) was the most common, followed in order of frequency by p. R168X (11.8%), p. R133C (6.9%), p. R270X (6.9%), p. G269fs (6.9%), p. R255X (4.9%), and p. R306C (3.9%). In addition, we identified five novel MECP2 mutations: three missense (p. K305E, p. V122M, p. A358T), one insertion (c.45-46insGGAGGA), and one 22 bp deletion (c.881-902del22). Large deletions represented 10.5% of all identified MECP2 mutations. Conversely, mutations in exon 1 appeared to be rare (0.9%). The remaining cases without MECP2 mutations were screened for the cyclin-dependent kinase-like 5 (CDKL5) gene using denaturing high-performance liquid chromatography (DHPLC). One synonymous mutation (p. I72I) was found in exon 5, suggesting that CDKL5 is a rare cause of RTT. The overall MECP2 mutation detection rate for this patient series was 84.3:87.9% in 107 classical RTT cases and 57.1% in 14 atypical RTT cases. Moreover, there were two patients with homozygous mutations and normal female karyotypes. However, we did not pinpoint a significant relationship between genotype and phenotype in these cases.

X chromosome inactivation in Rett Syndrome and its correlations with MECP2 mutations and phenotype.

Rett syndrome (RTT) is an X-linked dominant neurodevelopment disorder, which is mainly caused by gene mutation of methyl-CpG-binding protein 2 (MECP2). The correlations between genotype, X chromosome inactivation (XCI), and phenotype have been studied, but the results are conflicting. In the present study, XCI patterns in patients and their mothers, parental origin of skewed X chromosome in patients, and the correlations between XCI, genotype, and phenotype were analyzed in 52 cases of RTT with MECP2 mutations, 50 RTT mothers, and 48 normal female controls. The results showed XCI and genotype had limitations in explaining all the phenotypic manifestations of RTT. Other genomic factors have to be considered to explain the phenotypic differences.

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.

Mutational analysis of mitochondrial DNA of children with Rett syndrome.

The present study was undertaken to identify whether mitochondrial DNA (mtDNA) mutations were involved in the pathogenesis of Rett syndrome (RS). Mitochondrial DNA from 15 children with RS and 14 of their mothers was analyzed. No large deletions in mtDNA were found using Southern blot with a full-length mtDNA as a probe. Polymerase chain reaction amplification and single strand conformation polymorphism analysis showed mutations in region 2650-3000 encoding 16S rRNA of mtDNA in 13 cases of RS and 11 of their mothers. DNA sequence analysis and mismatch polymerase chain reaction results revealed a point mutation (C --> T) at position 2835 in 7 cases of RS and 6 of their mothers. The same mutation was not found in a total of 30 normal controls. These data indicate that mtDNA may play an important role in the pathogenesis of RS.

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.

Prevalence of peripheral neuropathy with insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is rare in Chinese children. There have been no reports on the prevalence of peripheral neuropathy in Chinese children with IDDM. This study aimed to determine prevalence of subclinical peripheral neuropathy in Chinese children with IDDM. Motor and sensory nerve conduction studies of both median, ulnar, peroneal, and tibial (motor nerves) and median, ulnar, and sural (sensory nerves) were performed in 38 children with IDDM (18 males, 20 females). The age was 4-21 years (mean = 12.7 years; median = 12 years, 6 months). The duration of diabetes was less than 5 years in 15, 5-10 years in 14, and more than 10 years in nine. Neurophysiologic evidence of subclinical peripheral neuropathy was present in 26 patients (68.4%) of which motor, sensory, or motor and sensory involvement was 26 (68.4%), eight (21.1%), and 26 (68.4%), respectively. Twelve (31.6%) and 14 (36.8%) children had mild and moderate degrees of peripheral neuropathy, respectively. Among the 26 children with abnormal nerve-conduction studies, two (7.7%) had symptoms of numbness and pain in the lower limbs. Thus, two children had symptomatic neuropathy and most (n = 24) had asymptomatic peripheral neuropathy. Two children had systemic hypertension, and one (3.8%) had laboratory evidence of early renal complications. Analysis of demographic and laboratory risk factors for the development of subclinical peripheral neuropathy revealed that the age of onset, duration of diabetes, level of hemoglobin A1c, triglyceride, cholesterol, serum creatinine, and urea, microalbumin/creatinine ratio, and urinary microalbumin excretion rate were significantly related to the development of subclinical peripheral neuropathy in specific nerves.

Clinical features and gene mutational spectrum of CDKL5 -related diseases in a cohort of Chinese patients

BackgroundMutations in the cyclin-dependent kinase-like 5 (CDKL5) (NM_003159.2) gene have been associated with early-onset epileptic encephalopathies or Hanefeld variants of RTT(Rett syndrome). In order to clarify the CDKL5 genotype-phenotype correlations in Chinese patients, CDKL5 mutational screening in cases with early-onset epileptic encephalopathies and RTT without MECP2 mutation were performed.MethodsThe detailed clinical information including clinical manifestation, electroencephalogram (EEG), magnetic resonance imaging (MRI), blood, urine amino acid and organic acid screening of 102 Chinese patients with early-onset epileptic encephalopathies and RTT were collected. CDKL5 gene mutations were analyzed by PCR, direct sequencing and multiplex ligation-dependent probe amplification (MLPA). The patterns of X-chromosome inactivation (XCI) were studied in the female patients with CDKL5 gene mutation.ResultsDe novo CDKL5 gene mutations were found in ten patients including one missense mutation (c.533G > A, p.R178Q) which had been reported, two splicing mutations (ISV6 + 1A > G, ISV13 + 1A > G), three micro-deletions (c.1111delC, c.2360delA, c.234delA), two insertions (c.1791 ins G, c.891_892 ins TT in a pair of twins) and one nonsense mutation (c.1375C > T, p.Q459X). Out of ten patients, 7 of 9 females with Hanefeld variants of RTT and the remaining 2 females with early onset epileptic encephalopathy, were detected while only one male with infantile spasms was detected. The common features of all female patients with CDKL5 gene mutations included refractory seizures starting before 4 months of age, severe psychomotor retardation, Rett-like features such as hand stereotypies, deceleration of head growth after birth and poor prognosis. In contrast, the only one male patient with CDKL5 mutation showed no obvious Rett-like features as females in our cohort. The X-chromosome inactivation patterns of all the female patients were random.ConclusionsMutations in CDKL5 gene are responsible for 7 with Hanefeld variants of RTT and 2 with early-onset epileptic encephalopathy in 71 girls as well as for 1 infantile spasms in 31 males. There are some differences in the phenotypes among genders with CDKL5 gene mutations and CDKL5 gene mutation analysis should be considered in both genders.

Early clinical features and diagnosis of Dravet syndrome in 138 Chinese patients with SCN1A mutations.

OBJECTIVE To summarize the early clinical features of Dravet syndrome (DS) patients with SCN1A gene mutations before the age of one. METHODS SCN1A gene mutation screening was performed by PCR-DNA sequencing and multiple ligation-dependent probe amplication (MLPA). The early clinical features of DS patients with SCN1A mutations were reviewed with attention to the seizures induced by fever and other precipitating factors before the first year of life. RESULTS The clinical data of 138 DS patients with SCN1A gene mutations were reviewed. The median seizure onset age was 5.3 months. Ninety-nine patients (71.7%) experienced seizures with duration more than 15 min in the first year of life. Two or more seizures induced by fever within 24h or the same febrile illness were observed in 93 patients (67.4%). 111 patients (80.4%) had hemi-clonic and (or) focal seizures. Seizures had been triggered by fever of low degree (T<38 °C) in 62.3% (86/138) before the first year of life. Vaccine-related seizures were observed in 34.8% (48/138). Seizures in 22.5% (31/138) of patients were triggered by hot bath. Carbamazepine, oxcarbazepine, lamotrigine, phenobarbital and phenytoin showed either no effect or exacerbating the seizures in our group. CONCLUSION The seizure onset age in DS patients was earlier than that was in common febrile seizures. When a baby exhibits two or more features of complex febrile seizures in the first year of life, a diagnosis of DS should be considered, and SCN1A gene mutation screening should be performed as early as possible. Early diagnosis of DS will help clinicians more effectively prescribe antiepileptic drugs for stronger prognosis.

Brainstem auditory-evoked potential evaluation in children with meningitis

Brainstem auditory-evoked potential (BAEP) was performed on 101 children with meningitis to assess the incidence of hearing impairment. Fifty-two (51.5%) children had bacterial meningitis, six (5.9%) had viral meningitis, and 43 (42.6%) had aseptic meningitis. Fifty-one (50.5%) patients were assessed before discharge and 50 (49.5%) 9 days to 17 months later (mean = 4 months). BAEP impairment was found in 28 (27.7%) of 101 patients; 24 had sensorineural and four had conductive type of hearing loss, and 17 (60.7%) had unilateral and 11 (39.3%) had bilateral impairment. Hearing threshold was elevated in 22 (21.8%) patients, and the other six had increased latency and interpeak latencies with normal threshold. Frequency of BAEP impairment or hearing loss associated with bacterial meningitis was 34.6% and 30.8%, respectively; frequency associated with aseptic meningitis was 20.9% and 13.9%, respectively. One child with viral meningitis (coxsackie virus) had mild BAEP impairment. Most of the BAEP impairment in the bacterial meningitis group was associated with H. influenzae. Prospective BAEP study was performed in 20 patients randomly at 0.3 to 18 months to assess hearing status after antibiotic treatment, 10 with normal and 10 with abnormal BAEP. All the initially normal BAEP patients remained normal. Of the 10 patients with abnormal BAEP results initially, four returned to normal, two improved, three remained unchanged, and one deteriorated. The incidence of hearing loss after bacterial and aseptic meningitis is high. BAEP is useful to screen for possible hearing loss in children with meningitis, and follow-up BAEP is necessary for those patients with initially abnormal BAEP.

Analysis of the Parental Origin of De Novo MECP2 Mutations and X Chromosome Inactivation in 24 Sporadic Patients With Rett Syndrome in China

Rett syndrome is an X-linked neurodevelopmental disorder that predominantly affects females. It is caused by mutations in methyl-CpG-binding protein 2 gene. Due to the sex-limited expression, it has been suggested that de novo X-linked mutations may exclusively occur in male germ cells and thus only females are affected. In this study, the authors have analyzed the parental origin of mutations and the X-chromosome inactivation status in 24 sporadic patients with identified methyl-CpG-binding protein2 gene mutations. The results showed that 22 of 24 patients have a paternal origin. Only 2 patients have a maternal origin. Except for 2 cases which were homozygotic at the androgen receptor gene locus, of the remaining 22 cases, 16 cases have a random X-chromosome inactivation pattern; the other 6 cases have a skewed X-chromosome inactivation and they favor expression of the wild allele. The relationship between X-chromosome inactivation and phenotype may need more cases to explore.