Objective-To determine if a relationship exists between the clinical features of Rett Syndrome, an X-linked dominant neurodevelopmental disorder, and specific mutations in MECP2.Method-Cross-sectional study of two hundred and forty-five girls and women with typical Rett Syndrome seen between 1990 and 2004 in tertiary academic out-patient specialty clinics and who had complete MECP2 mutation analysis. A structured clinical evaluation was completed for each participant. The results were grouped by MECP2 mutation and compared.Results-Participants with the R133C mutation are less severely affected than those with R168X or large DNA deletions (p<0.05). Likewise, individuals with the R168X mutation are more severely affected than those with R294X and late carboxy-terminal truncating mutations (p<0.05). Clinical differences are notable in ambulation, hand use, and language, (p<0.004) three cardinal features of Rett Syndrome. Individuals with R168X are less likely to walk (p=0.008), retain hand use (p=0.002), or use words (p=0.001). In contrast, those with carboxy-terminal truncations are more likely to walk (p=0.007) and use words (p<0.001). The R306C mutation, previously found to confer milder features, adversely affects only one clinical feature, language (p<0.05).Conclusions-Specific mutations in MECP2 confer different severity. These results allow the design of therapies targeted towards the amelioration of expected problems. Furthermore, the distinct effects of MECP2 mutations on clinical severity must be considered in clinical intervention trials.

A high-throughput, retrovirus-mediated mutagenesis method based on gene trapping in embryonic stem cells was used to identify a novel mouse gene. The human ortholog encodes a transmembrane protein containing five extracellular immunoglobulin-like domains that is structurally related to human NEPHRIN, a protein associated with congenital nephrotic syndrome. Northern analysis revealed wide expression in humans and mice, with highest expression in kidney. Based on similarity to NEPHRIN and abundant expression in kidney, this protein was designated NEPH1 and embryonic stem cells containing the retroviral insertion in the Neph1 locus were used to generate mutant mice. Analysis of kidney RNA from Neph1 ؊/؊ mice showed that the retroviral insertion disrupted expression of Neph1 transcripts. Neph1 ؊/؊ pups were represented at the expected normal Mendelian ratios at 1 to 3 days of age but at only 10% of the expected frequency at 10 to 12 days after birth, suggesting an early postnatal lethality. The Neph1 ؊/؊ animals that survived beyond the first week of life were sickly and small but without edema, and all died between 3 and 8 weeks of age. Proteinuria ranging from 300 to 2,000 mg/dl was present in all Neph1 ؊/؊ mice. Electron microscopy demonstrated NEPH1 expression in glomerular podocytes and revealed effacement of podocyte foot processes in Neph1 ؊/؊ mice. These findings suggest that NEPH1, like NEPHRIN, may play an important role in maintaining the structure of the filtration barrier that prevents proteins from freely entering the glomerular urinary space.NEPHRIN is a transmembrane protein of the immunoglobulin (Ig) superfamily that is expressed by epithelial podocytes of developing glomeruli (13, 17). Congenital nephrotic syndrome of the Finnish type results from mutations in NPHS1, the human gene encoding NEPHRIN, indicating a role for NEPHRIN in maintaining the filtration barrier that prevents proteins from freely entering the glomerular urinary space (6,17). Recent studies localized NEPHRIN to the slit diaphragms that form the junctions between podocyte foot processes interdigitating along the glomerular basement membrane. This and other studies suggest that NEPHRIN proteins extending toward each other from adjacent podocyte foot processes may interdigitate in a zipper-like structure to form the crucial filtration barrier in the slit diaphragm. The eight Ig-like domains of each NEPHRIN protein, which are of the C2 type of Ig domain known to be involved in cell-cell interactions, are thought to provide the homophilic interactions that bind these NEPHRIN proteins together (13, 17).We use a high-throughput mutagenesis method based on gene trapping in embryonic stem (ES) cells that allows automated production of sequence tags from the trapped and mutated genes (20). These ES cell clones are stored in a library called Omnibank, and the sequence tag from the gene trapped in each clone, referred to as the Omnibank sequence tag or OST, is entered into a searchable database. A protein with Ig domains was identified with...

Background: Rett syndrome (RTT) is a neurodevelopmental disorder primarily seen in females,

Objective We conducted a nationwide survey to determine the prevalence of common gastrointestinal and nutritional disorders in Rett syndrome (RTT) based on parental reporting and related the occurrence of these problems to age and methyl-CpG-binding protein 2 (MECP2) status. Methods We designed a questionnaire that probed symptoms, diagnoses, diagnostic tests, and treatment interventions related to gastrointestinal and nutritional problems in RTT. The International Rett Syndrome Foundation distributed the questionnaire to 1666 family-based members and forwarded their responses for our review. We interrogated the Rare Disease Clinical Research Network database to supplement findings related to medications used to treat gastrointestinal problems in RTT. Results Parents of 983 RTT females (59%) responded and identified symptoms and diagnoses associated with gastrointestinal dysmotility (92%); chewing and swallowing difficulties (81%); weight deficits or excess (47%); growth deficits (45%); low bone mineral content or fractures (37%); biliary tract disorders (3%). Height, weight, and BMI z-scores decreased significantly with age; height and weight, but not BMI, z-scores were significantly lower in females with MECP2 mutations than those without. Vomiting, nighttime awakening, gastroesophageal reflux, chewing difficulty, and choking with feeding were significantly less likely to occur with increasing age. Short stature, low bone mineral content, fractures, and gastrostomy placement were significantly more likely to occur with increasing age. Chewing difficulty, choking with feeding, and nighttime awakening were significantly less likely to occur, whereas short stature was significantly more likely to occur, in females with MECP2 mutations than those without. Diagnostic evaluations and therapeutic interventions were utilized less frequently than the occurrence of symptoms or diagnoses in the RTT cohort. Conclusion Gastrointestinal and nutritional problems perceived by parents are prevalent throughout life in girls and women with RTT and may pose a substantial medical burden for their caregivers. Physician awareness of these features of RTT may improve the health and quality of life of individuals affected with this disorder.