Distribution of hand function by age in individuals with Rett syndrome.

Objective: To determine the longitudinal distribution of hand function skills in individuals with classic Rett Syndrome (RTT), an X-linked dominant neurodevelopmental disorder, and correlate with MECP2 variants. Method: We conducted a longitudinal study of 946 girls and young women with typical RTT seen between 2006 and 2021 in the US Natural History Study (NHS) featuring a structured clinical evaluation to assess the level of hand function skills. The specific focus in this study was to assess longitudinal variation of hand skills from age 2 through age 18 years in relation to specific MECP2 variant groups. Results: Following the initial regression period, hand function continues to decline across the age spectrum in individuals with RTT. Specific differences are noted with steeper declines in hand function among those with milder variants (Group A: R133C, R294X, R306C, and C-terminal truncations) compared to groups composed of individuals with more severe variants. Conclusions: These temporal variations in hand use represent specific considerations which could influence the design of clinical trials that test therapies aiming to ameliorate specific functional limitations in individuals with RTT. Furthermore, the distinct impact of specific MECP2 variants on clinical severity, especially related to hand use, should be considered in such interventional trials.

Developing the Pediatric Refractory Epilepsy Questionnaire: a pilot study.

PURPOSE: Up to 14% of children with epilepsy continue to experience seizures despite having appropriate medical therapy and develop medically refractory epilepsy (MRE). Assessing clinical outcomes and therapeutic efficacy in children with MRE undergoing palliative epilepsy surgery has been challenging because of the lack of a quantitative instrument capable of estimating the clinical status of these patients. The ideal instrument would at once consider seizure control, neurodevelopment, caregiver burden, and quality of life. The purpose of this study was to develop and pilot the Pediatric Refractory Epilepsy Questionnaire (PREQ), a quantitative instrument to assess the severity and individual burden of epilepsy in children with MRE undergoing palliative epilepsy treatments. METHODS: The caregivers of 25 patients with MRE completed the PREQ and the Quality of Life in Childhood Epilepsy (QOLCE) measure and participated in a semistructured interview. Medical records of the patients were reviewed, an Early Childhood Epilepsy Severity Scale (E-CHESS) score was calculated, and a Global Assessment of Severity of Epilepsy (GASE) score was obtained for each patient. KEY FINDINGS: The initial PREQ was modified based on the analysis of responses, association with previously validated scales, comments from caregivers, and expertise of the PREQ panelists. Pediatric Refractory Epilepsy Questionnaire subscale scores were calculated based on clinical paradigm and compared with independent measures of seizure severity and quality of life. Significant correlations were observed between the seizure severity subscale and the GASE score (r=0.55) and between the mood subscale and the well-being score (r=0.61) on the QOLCE. Significant correlations were also observed between the caregiver rating of seizure severity and the GASE score (r=0.53), the social activity score (r=0.57), and the behavior score (r=0.43) on the QOLCE. Correlations between the caregiver rating of quality of life and the quality of life score (r=0.58) and the number of AEDs used (r=0.45) were also significant. SIGNIFICANCE: This pilot study is an initial, critical step in the development of the PREQ. The significant correlations between the PREQ subscales and the external epilepsy severity and quality of life measures lend preliminary support to our hypothesis that the PREQ is assessing the severity of epilepsy along with other important domains, such as mood, neurodevelopment, and quality of life. A larger prospective study of this modified PREQ is currently underway to further develop the PREQ.

Impact of pediatric epilepsy on sleep patterns and behaviors in children and parents.

PURPOSE: Disrupted sleep patterns in children with epilepsy and their parents are commonly described clinically. A number of studies have shown increased frequency of sleep disorders among pediatric epilepsy patients; however, few have characterized the association between epilepsy and parental sleep quality and household sleeping arrangements. The purpose of this study was to explore the effect of pediatric epilepsy on child sleep, parental sleep and fatigue, and parent-child sleeping arrangements, including room sharing and cosleeping. METHODS: Parents of children 2 to 10 years of age with and without epilepsy completed written questionnaires assessing seizure history, child and parent sleep, and household sleeping arrangements. Children's Sleep Habits Questionnaire (CSHQ) scores were used to evaluate sleep disturbances for the child. The Pittsburgh Sleep Quality Index (PSQI) and the Iowa Fatigue Scale (IFS) were used to evaluate parental sleep and fatigue, respectively. The Early Childhood Epilepsy Severity Scale (E-Chess) was used to assess epilepsy severity. KEY FINDINGS: One hundred five households with a child with epilepsy and 79 controls participated in this study. Households with a child with epilepsy reported increased rates of both parent-child room sharing (p < 0.001) and cosleeping (p = 0.005) compared to controls. Children with epilepsy were found to have greater sleep disturbance by total CSHQ score (p < 0.001) and the following subscores: parasomnias (p < 0.001), night wakings (p < 0.001), sleep duration (p < 0.001), daytime sleepiness (<0.001), sleep onset delay (p = 0.009), and bedtime resistance (p = 0.023). Parents of children with epilepsy had increased sleep dysfunction (p = 0.005) and were more fatigued (p < 0.001). Severity of epilepsy correlated positively with degree of child sleep dysfunction (0.192, p = 0.049), parental sleep dysfunction (0.273, p = 0.005), and parental fatigue (0.324, p = 0.001). Antiepileptic drug polytherapy was predictive of greater childhood sleep disturbances. Nocturnal seizures were associated with parental sleep problems, whereas room sharing and cosleeping behavior were associated with child sleep problems. Within the epilepsy cohort, 69% of parents felt concerned about night seizures and 44% reported feeling rested rarely or never. Finally, 62% of parents described decreased sleep quality and/or quantity with cosleeping. SIGNIFICANCE: Pediatric epilepsy can significantly affect sleep patterns for both the affected child and his or her parents. Parents frequently room share or cosleep with their child, adaptations which may have detrimental effects for many households. Clinicians must not only be attentive to the sleep issues occurring in pediatric patients with epilepsy, but also for the household as a whole. These data provide evidence of a profound clinical need for improved epilepsy therapeutics and the development of nocturnal seizure monitoring technologies.

Mammalian target of rapamycin (mTOR) inhibition: potential for antiseizure, antiepileptogenic, and epileptostatic therapy.

New epilepsy treatments are needed that not only inhibit seizures symptomatically (antiseizure) but also prevent the development of epilepsy (antiepileptogenic). The mammalian target of rapamycin (mTOR) pathway may mediate mechanisms of epileptogenesis and serve as a rational therapeutic target. mTOR inhibitors have antiepileptogenic and antiseizure effects in animal models of the genetic disease, tuberous sclerosis complex. The mTOR pathway is also implicated in epileptogenesis in animal models of acquired epilepsy and infantile spasms, although the effects of mTOR inhibitors are variable depending on the specific conditions and model. Furthermore, beneficial effects on seizures are lost when treatment is withdrawn, suggesting that mTOR inhibitors are "epileptostatic" in only stalling epilepsy progression during treatment. Clinical studies of rapamycin in human epilepsy are limited, but suggest that mTOR inhibitors at least have antiseizure effects in tuberous sclerosis patients. Further studies are needed to assess the full potential of mTOR inhibitors for epilepsy treatment.

Rescue of pituitary function in a mouse model of isolated growth hormone deficiency type II by RNA interference.

Splicing mutations in the human GH (hGH) gene (GH-1) that cause skipping of exon 3 result in a form of GH deficiency termed isolated GH deficiency type II (IGHD II). The GH-1 gene contains five exons; constitutive splicing produces the wild-type 22-kDa hormone, whereas skipping of exon 3 results in transcripts encoding a 17.5-kDa isoform that acts as a dominant-negative to block secretion of the wild-type hormone. Common characteristics of IGHD II include short stature due to impaired bone elongation, growth, and, in severe cases, anterior pituitary hypoplasia. Typically, IGHD II is treated by sc delivery of hGH, which can rescue stature but, unfortunately, does not inhibit pituitary hypoplasia. Direct destruction of transcripts encoding the dominant-negative 17.5-kDa isoform should both rescue stature and prevent hypoplasia. Here, we have used delivery of short hairpin RNAs to rescue a murine model of IGHD II by specifically targeting transcripts encoding the 17.5-kDa isoform using RNA interference. To our knowledge, this is the first example where a short hairpin RNA has been expressed to specifically degrade an incorrectly spliced transcript and rescue a dominant-negative disease phenotype in vivo.

GH1 splicing is regulated by multiple enhancers whose mutation produces a dominant-negative GH isoform that can be degraded by allele-specific small interfering RNA (siRNA).

The majority of mutations that cause isolated GH deficiency type II affect splicing of GH1 transcripts, leading to the production of a dominant-negative GH isoform. Because numerous mutations and polymorphisms throughout the GH1 gene have not yet been tested for aberrant splicing, we used a deletion mutagenesis screen across intron 2-exon 3-intron 3 to identify splicing regulatory sequences. These analyses identified a new enhancer element, ESE2, upstream of the cryptic splice site in exon 3 and further defined a previously described enhancer (ESE1) to include the first seven nucleotides of exon 3. Besides enhancers, the overall size of intron 3 is also crucial for exon inclusion. Given the deleterious effects of the dominant-negative 17.5-kDa isoform, these and previous studies underscore the extent to which splicing regulatory elements serve to prevent exon skipping. Importantly, we show here that small interfering RNAs can be used to specifically degrade exon 3-skipped transcripts, potentially a new avenue of therapeutic intervention in isolated GH deficiency II and other dominant disorders.

Disruption of exon definition produces a dominant-negative growth hormone isoform that causes somatotroph death and IGHD II.

Isolated growth hormone deficiency type II (IGHD II) is characterized by short stature due to dominant-negative mutations of the human growth hormone gene (GH1). Most of the known mutations responsible for IGHD II cause aberrant splicing of GH1 transcripts. We have recently shown that mutations that cause exon 3 skipping and produce a dominant-negative 17.5-kDa isoform in humans also cause a dose-dependent disruption of GH secretory vesicles when expressed in GC cells and transgenic mice. We show here that overexpression of the dominant-negative 17.5-kDa isoform also destroys the majority of somatotrophs, leading to anterior pituitary hypoplasia in transgenic mice. It is, therefore, important to understand the regulation of GH1 splicing and why its perturbation causes IGHD II. We demonstrate that dual splicing enhancers are required to ensure exon 3 definition to produce full-length 22-kDa hormone. We also show that splicing enhancer mutations that weaken exon 3 recognition produce variable amounts of the 17.5-kDa isoform, a result which could potentially explain the clinical variability observed in IGHD II. Non-canonical splicing mutations that disrupt splicing enhancers, such as those illustrated here, demonstrate the importance of enhancer elements in regulating alternative splicing to prevent human disease.