Search

Objective: To determine the frequency of mutations in CDKL5 in both male and female patients with infantile spasms or early onset epilepsy of unknown cause, and to consider whether the breadth of the reported phenotype would be extended by studying a different patient group., Methods: Two groups of patients were investigated for CDKL5 mutations. Group 1 comprised 73 patients (57 female, 16 male) referred to Cardiff for CDKL5 analysis, of whom 49 (42 female, 7 male) had epileptic seizure onset in the first six months of life. Group 2 comprised 26 patients (11 female, 15 male) with infantile spasms previously recruited to a clinical trial, the UK Infantile Spasms Study. Where a likely pathogenic mutation was identified, further clinical data were reviewed., Results: Seven likely pathogenic mutations were found among female patients from group 1 with epileptic seizure onset in the first six months of life, accounting for seven of the 42 in this group (17%). No mutations other than the already published mutation were found in female patients from group 2, or in any male patient from either study group. All patients with mutations had early signs of developmental delay and most had made little developmental progress. Further clinical information was available for six patients: autistic features and tactile hypersensitivity were common but only one had suggestive Rett-like features. All had a severe epileptic seizure disorder, all but one of whom had myoclonic jerks. The EEG showed focal or generalised changes and in those with infantile spasms, hypsarrhythmia. Slow frequencies were seen frequently with a frontal or fronto-temporal predominance and high amplitudes., Conclusions: The spectrum of the epileptic seizure disorder, and associated EEG changes, in those with CDKL5 mutations is broader than previously reported. CDKL5 mutations are a significant cause of infantile spasms and early epileptic seizures in female patients, and of a later intractable seizure disorder, irrespective of whether they have suspected Rett syndrome. Analysis should be considered in these patients in the clinical setting.

Background: People with useful speech after regression constitute a distinct group of those with mutation-positive Rett disorder, 6% (20/331) reported among mutation-positive people in the British Survey. We aimed to determine the physical, mental and genetic characteristics of this group and to gain insight into their experience of Rett syndrome., Methods: Clinical and molecular data for people with Rett, aged 10 or more years at follow-up (the study group, n = 13), with the ability to converse and a MECP2 mutation are presented. They were compared with an age-matched control group (n = 110), who could not converse and had a pathogenic MECP2 mutation., Results: The study group differed significantly from the control group with regard to their disease severity (P < 0.001); feeding difficulty scores (P < 0.001); health scores (P < 0.001); epilepsy (P < 0.001); head circumference (P < 0.004); age at onset of the regression period (P < 0.001) (six in the study group did not regress) and mutation frequency (C-terminal deletions P = 0.014, R133C P < 0.006). The results indicate that favourable skewing of X-inactivation is only present in a small proportion of mild cases. Speech was fragmented with a soft, breathless quality, and all but two had obviously irregular breathing. One person with an R168X mutation preferred signing to speech. All enjoyed interpersonal contact, showing affection and preferring people to objects, clearly distinguishing the condition from autism. Most were habitually anxious. Music was a source of pleasure and relaxation also providing a valuable educational asset. Even in these most able cases, understanding was severely restricted in most and little initiative was shown., Conclusions: While the Rett profile is present in these people they are commonly not classic, and the presence of speech, good head growth and lack of regression may lead to missed diagnoses. A strong association was demonstrated between this milder form of the disease and R133C and C-terminal deletions.

A translocation that disrupted the netrin G1 gene (NTNG1) was recently reported in a patient with the early seizure variant of Rett syndrome (RTT). The netrin G1 protein (NTNG1) has an important role in the developing central nervous system, particularly in axonal guidance, signalling and NMDA receptor function and was a good candidate gene for RTT. We recruited 115 patients with RTT (females: 25 classic and 84 atypical; 6 males) but no mutation in the MECP2 gene. For those 52 patients with epileptic seizure onset in the first 6 months of life, CDKL5 mutations were also excluded. We aimed to determine whether mutations in NTNG1 accounted for a significant subset of patients with RTT, particularly those with the early onset seizure variant and other atypical presentations. We sequenced the nine coding exons of NTNG1 and identified four sequence variants, none of which were likely to be pathogenic. Mutations in the NTNG1 gene appear to be a rare cause of RTT but NTNG1 function demands further investigation in relation to the central nervous system pathophysiology of the disorder., (Copyright 2006 Wiley-Liss, Inc.)

Among cases in the Australian Rett Syndrome Database, the nonsense mutation p.R270X is one of the most commonly occurring single pathogenic MECP2 mutations. In two recent published reports of the MECP2 mutational spectrum the p.R270X appeared to be under represented. We hypothesised that increased mortality arising from this mutation may underlie this apparent discrepancy. We investigated our hypothesis in two independent study groups from Australia and the UK with prospective data collections (total n=524). Only females with Rett syndrome and an identified MECP2 mutation were included. Significant differences in survival were detected among Rett syndrome cases grouped for the eight most frequent mutations (log-rank chi(2) (7)=15.71, P=0.03). Moreover, survival among cases with p.R270X, when compared with survival among cases with all the other mutations was reduced (log-rank chi(2) (2)=6.94, P=0.01). Our observation of a reduced survival associated with the p.R270X mutation offers an explanation for the under representation of p.R270X in older subjects with Rett syndrome.

Mutations in the CDKL5 gene (also known as STK9) have recently been shown to cause early onset epilepsy and severe mental retardation (ISSX or West syndrome). Patients with CDKL5 mutations sometimes also show features similar to those seen in Rett Syndrome (RTT). We have screened the CDKL5 gene in 94 patients with RTT or a RTT-like phenotype who had tested negative for MECP2 mutations (13 classical RTT female subjects, 25 atypical RTT female subjects, 40 RTT-like female and 16 RTT-like male subjects; 33 of the patients had early onset seizures). Novel pathogenic CDKL5 mutations were identified in three girls, two of whom had initially been diagnosed with the early onset seizure variant of RTT and the other with early onset seizures and some features of RTT. In addition, the 33 patients with early seizures were screened for the most common mutations in the ARX gene but none were found. Combining our three new cases with the previously published cases, 13/14 patients with CDKL5 mutations presented with seizures before the age of 3 months.

Telomeres are gene rich regions with a high recombination rate. Cryptic subtelomeric rearrangements are estimated to account for 5% of mental retardation/malformation syndromes. Here we present the first patient with a deletion of 19p13.3, identified by subtelomeric FISH analysis. His features included a distinctive facial appearance, cleft palate, hearing impairment, congenital heart malformation, keloid scarring, immune dysregulation, and mild learning difficulties. Subtelomeric FISH analysis identified a deletion of 19p13.3-pter. The deletion size was determined to be 1.2 Mb by FISH analysis. It extended from within the chromosomal region covered by BAC RP11-50C6 to 19pter. The deleted area encompassed approximately 60 genes. Fifteen possible candidate genes were considered with respect to the phenotype, including follistatin-related precursor 3 (FSTL3) and serine-threonine kinase 11 (STK-11)., (Copyright (c) 2005 Wiley-Liss, Inc.)

Mutations in MECP2 are a cause of Rett syndrome. Recently, a new isoform of MeCP2 was described, which has an alternative N-terminus, transcribed from exon 1. We screened exon 1 and the promoter region of MECP2 in 97 mutation-negative Rett syndrome cases. We found two sequence variants, but there was no evidence that they are pathogenic. Mutations in exon 1 and the promoter of MECP2 are not a common cause of Rett syndrome.