ABSTRACT
Autism spectrum disorder (ASD) is often grouped with other brain-related phenotypes into a broader category of neurodevelopmental disorders (NDDs). In clinical practice, providers need to decide which genes to test in individuals with ASD phenotypes, which requires an understanding of the level of evidence for individual NDD genes that supports an association with ASD. Consensus is currently lacking about which NDD genes have sufficient evidence to support a relationship to ASD. Estimates of the number of genes relevant to ASD differ greatly among research groups and clinical sequencing panels, varying from a few to several hundred. This Roadmap discusses important considerations necessary to provide an evidence-based framework for the curation of NDD genes based on the level of information supporting a clinically relevant relationship between a given gene and ASD.
Subject(s)
Autism Spectrum Disorder/genetics , Evidence-Based Medicine/methods , Genetic Association Studies/methods , Brain/growth & development , Cognition/physiology , Humans , Intellectual Disability/geneticsABSTRACT
PTEN hamartoma tumor syndrome (PHTS) is a complex neurodevelopmental disorder characterized by mechanistic target of rapamycin (mTOR) overactivity. Limited data suggest that mTOR inhibitors may be therapeutic. No placebo-controlled studies have examined mTOR inhibition on cognition and behavior in humans with PHTS with/without autism. We conducted a 6-month phase II, randomized, double-blinded, placebo-controlled trial to examine the safety profile and efficacy of everolimus (4.5 mg/m2) in individuals (5-45 years) with PHTS. We measured several cognitive and behavioral outcomes, and electroencephalography (EEG) biomarkers. The primary endpoint was a neurocognitive composite derived from Stanford Binet-5 (SB-5) nonverbal working memory score, SB-5 verbal working memory, Conners' Continuous Performance Test hit reaction time and Purdue Pegboard Test score. Forty-six participants underwent 1:1 randomization: n = 24 (everolimus) and n = 22 (placebo). Gastrointestinal adverse events were more common in the everolimus group (P < 0.001). Changes in the primary endpoint between groups from baseline to Month 6 were not apparent (Cohen's d = -0.10, P = 0.518). However, several measures were associated with modest effect sizes (≥0.2) in the direction of improvement, including measures of nonverbal IQ, verbal learning, autism symptoms, motor skills, adaptive behavior and global improvement. There was a significant difference in EEG central alpha power (P = 0.049) and central beta power (P = 0.039) 6 months after everolimus treatment. Everolimus is well tolerated in PHTS; adverse events were similar to previous reports. The primary efficacy endpoint did not reveal improvement. Several secondary efficacy endpoints moved in the direction of improvement. EEG measurements indicate target engagement following 6 months of daily oral everolimus. Trial Registration Information: ClinicalTrials.gov NCT02991807 Classification of Evidence: I.
Subject(s)
Autistic Disorder , Hamartoma Syndrome, Multiple , Autistic Disorder/drug therapy , Double-Blind Method , Everolimus/adverse effects , Humans , PTEN Phosphohydrolase , TOR Serine-Threonine Kinases , Treatment OutcomeABSTRACT
Phelan-McDermid syndrome (PMS) is a genetic condition caused by SHANK3 haploinsufficiency and characterized by a wide range of neurodevelopmental and systemic manifestations. The first practice parameters for assessment and monitoring in individuals with PMS were published in 2014; recently, knowledge about PMS has grown significantly based on data from longitudinal phenotyping studies and large-scale genotype-phenotype investigations. The objective of these updated clinical management guidelines was to: (1) reflect the latest in knowledge in PMS and (2) provide guidance for clinicians, researchers, and the general community. A taskforce was established with clinical experts in PMS and representatives from the parent community. Experts joined subgroups based on their areas of specialty, including genetics, neurology, neurodevelopment, gastroenterology, primary care, physiatry, nephrology, endocrinology, cardiology, gynecology, and dentistry. Taskforce members convened regularly between 2021 and 2022 and produced specialty-specific guidelines based on iterative feedback and discussion. Taskforce leaders then established consensus within their respective specialty group and harmonized the guidelines. The knowledge gained over the past decade allows for improved guidelines to assess and monitor individuals with PMS. Since there is limited evidence specific to PMS, intervention mostly follows general guidelines for treating individuals with developmental disorders. Significant evidence has been amassed to guide the management of comorbid neuropsychiatric conditions in PMS, albeit mainly from caregiver report and the experience of clinical experts. These updated consensus guidelines on the management of PMS represent an advance for the field and will improve care in the community. Several areas for future research are also highlighted and will contribute to subsequent updates with more refined and specific recommendations as new knowledge accumulates.
Subject(s)
Chromosome Disorders , Humans , Phenotype , Chromosome Disorders/diagnosis , Chromosome Disorders/epidemiology , Chromosome Disorders/genetics , Chromosome Deletion , Nerve Tissue Proteins/genetics , Chromosomes, Human, Pair 22/geneticsABSTRACT
Genome sequencing is often pivotal in the diagnosis of rare diseases, but many of these conditions lack specific treatments. We describe how molecular diagnosis of a rare, fatal neurodegenerative condition led to the rational design, testing, and manufacture of milasen, a splice-modulating antisense oligonucleotide drug tailored to a particular patient. Proof-of-concept experiments in cell lines from the patient served as the basis for launching an "N-of-1" study of milasen within 1 year after first contact with the patient. There were no serious adverse events, and treatment was associated with objective reduction in seizures (determined by electroencephalography and parental reporting). This study offers a possible template for the rapid development of patient-customized treatments. (Funded by Mila's Miracle Foundation and others.).
Subject(s)
Membrane Transport Proteins/genetics , Mutagenesis, Insertional , Neuronal Ceroid-Lipofuscinoses/drug therapy , Neuronal Ceroid-Lipofuscinoses/genetics , Oligonucleotides, Antisense/therapeutic use , Precision Medicine , Rare Diseases/drug therapy , Biopsy , Child , Child Development , Drug Discovery , Drugs, Investigational/therapeutic use , Electroencephalography , Female , Humans , Neuropsychological Tests , RNA, Messenger , Seizures/diagnosis , Seizures/drug therapy , Skin/pathology , Whole Genome SequencingABSTRACT
Bi-allelic loss-of-function variants in genes that encode subunits of the adaptor protein complex 4 (AP-4) lead to prototypical yet poorly understood forms of childhood-onset and complex hereditary spastic paraplegia: SPG47 (AP4B1), SPG50 (AP4M1), SPG51 (AP4E1) and SPG52 (AP4S1). Here, we report a detailed cross-sectional analysis of clinical, imaging and molecular data of 156 patients from 101 families. Enrolled patients were of diverse ethnic backgrounds and covered a wide age range (1.0-49.3 years). While the mean age at symptom onset was 0.8 ± 0.6 years [standard deviation (SD), range 0.2-5.0], the mean age at diagnosis was 10.2 ± 8.5 years (SD, range 0.1-46.3). We define a set of core features: early-onset developmental delay with delayed motor milestones and significant speech delay (50% non-verbal); intellectual disability in the moderate to severe range; mild hypotonia in infancy followed by spastic diplegia (mean age: 8.4 ± 5.1 years, SD) and later tetraplegia (mean age: 16.1 ± 9.8 years, SD); postnatal microcephaly (83%); foot deformities (69%); and epilepsy (66%) that is intractable in a subset. At last follow-up, 36% ambulated with assistance (mean age: 8.9 ± 6.4 years, SD) and 54% were wheelchair-dependent (mean age: 13.4 ± 9.8 years, SD). Episodes of stereotypic laughing, possibly consistent with a pseudobulbar affect, were found in 56% of patients. Key features on neuroimaging include a thin corpus callosum (90%), ventriculomegaly (65%) often with colpocephaly, and periventricular white-matter signal abnormalities (68%). Iron deposition and polymicrogyria were found in a subset of patients. AP4B1-associated SPG47 and AP4M1-associated SPG50 accounted for the majority of cases. About two-thirds of patients were born to consanguineous parents, and 82% carried homozygous variants. Over 70 unique variants were present, the majority of which are frameshift or nonsense mutations. To track disease progression across the age spectrum, we defined the relationship between disease severity as measured by several rating scales and disease duration. We found that the presence of epilepsy, which manifested before the age of 3 years in the majority of patients, was associated with worse motor outcomes. Exploring genotype-phenotype correlations, we found that disease severity and major phenotypes were equally distributed among the four subtypes, establishing that SPG47, SPG50, SPG51 and SPG52 share a common phenotype, an 'AP-4 deficiency syndrome'. By delineating the core clinical, imaging, and molecular features of AP-4-associated hereditary spastic paraplegia across the age spectrum our results will facilitate early diagnosis, enable counselling and anticipatory guidance of affected families and help define endpoints for future interventional trials.
Subject(s)
Adaptor Protein Complex 4/genetics , Corpus Callosum/diagnostic imaging , Magnetic Resonance Imaging/trends , Spastic Paraplegia, Hereditary/diagnostic imaging , Spastic Paraplegia, Hereditary/genetics , Adolescent , Adult , Child , Child, Preschool , Cohort Studies , Cross-Sectional Studies , Female , Humans , Infant , Magnetic Resonance Imaging/methods , Male , Middle Aged , Registries , Young AdultABSTRACT
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
ABSTRACT
PURPOSE: To examine the prevalence and spectrum of mosaic variant allele frequency (MVAF) in tuberous sclerosis complex (TSC) patients with low-level mosaicism and correlate genetic findings with clinical features and transmission risk. METHODS: Massively parallel sequencing was performed on 39 mosaic TSC patients with 170 different tissue samples. RESULTS: TSC mosaic patients (MVAF: 0-10%, median 1.7% in blood DNA) had a milder and distinct clinical phenotype in comparison with other TSC series, with similar facial angiofibromas (92%) and kidney angiomyolipomas (83%), and fewer seizures, cortical tubers, and multiple other manifestations (p < 0.0001 for six features). MVAF of TSC1/TSC2 pathogenic variants was highly variable in different tissue samples. Remarkably, skin lesions were the most reliable tissue for variant identification, and 6 of 39 (15%) patients showed no evidence of the variant in blood. Semen analysis showed absence of the variant in 3 of 5 mosaic men. The expected distribution of MVAF in comparison with that observed here suggests that there is a considerable number of individuals with low-level mosaicism for a TSC2 pathogenic variant who are not recognized clinically. CONCLUSION: Our findings provide information on variability in MVAF and risk of transmission that has broad implications for other mosaic genetic disorders.
Subject(s)
Tuberous Sclerosis/epidemiology , Tuberous Sclerosis/genetics , Adult , Disease Transmission, Infectious/statistics & numerical data , Female , Genotype , Humans , Male , Mosaicism , Mutation , Phenotype , Prevalence , Risk Factors , Tuberous Sclerosis Complex 1 Protein/genetics , Tuberous Sclerosis Complex 2 Protein/genetics , Tumor Suppressor Proteins/genetics , United StatesABSTRACT
PURPOSE: For neurodevelopmental disorders (NDDs), etiological evaluation can be a diagnostic odyssey involving numerous genetic tests, underscoring the need to develop a streamlined algorithm maximizing molecular diagnostic yield for this clinical indication. Our objective was to compare the yield of exome sequencing (ES) with that of chromosomal microarray (CMA), the current first-tier test for NDDs. METHODS: We performed a PubMed scoping review and meta-analysis investigating the diagnostic yield of ES for NDDs as the basis of a consensus development conference. We defined NDD as global developmental delay, intellectual disability, and/or autism spectrum disorder. The consensus development conference included input from genetics professionals, pediatric neurologists, and developmental behavioral pediatricians. RESULTS: After applying strict inclusion/exclusion criteria, we identified 30 articles with data on molecular diagnostic yield in individuals with isolated NDD, or NDD plus associated conditions (such as Rett-like features). Yield of ES was 36% overall, 31% for isolated NDD, and 53% for the NDD plus associated conditions. ES yield for NDDs is markedly greater than previous studies of CMA (15-20%). CONCLUSION: Our review demonstrates that ES consistently outperforms CMA for evaluation of unexplained NDDs. We propose a diagnostic algorithm placing ES at the beginning of the evaluation of unexplained NDDs.
Subject(s)
Neurodevelopmental Disorders/diagnosis , Neurodevelopmental Disorders/etiology , Neurodevelopmental Disorders/genetics , Autism Spectrum Disorder/genetics , Developmental Disabilities/genetics , Diagnostic Tests, Routine/methods , Exome/genetics , Genetic Testing/methods , Humans , Intellectual Disability/genetics , Exome Sequencing/methodsABSTRACT
The hereditary spastic paraplegias (HSPs) are a heterogeneous group of disorders characterized by degeneration of the corticospinal and spinocerebellar tracts leading to progressive spasticity. One subtype, spastic paraplegia type 47 (SPG47 or HSP-AP4B1), is due to bi-allelic loss-of-function mutations in the AP4B1 gene. AP4B1 is a subunit of the adapter protein complex 4 (AP-4), a heterotetrameric protein complex that regulates the transport of membrane proteins. Since 2011, 11 individuals from six families with AP4B1 mutations have been reported, nine of whom had homozygous mutations and were from consanguineous families. Here we report eight patients with AP4B1-associated SPG47, the majority born to non-consanguineous parents and carrying compound heterozygous mutations. Core clinical features in this cohort and previously published patients include neonatal hypotonia that progresses to spasticity, early onset developmental delay with prominent motor delay and severely impaired or absent speech development, episodes of stereotypic laughter, seizures including frequent febrile seizures, thinning of the corpus callosum, and delayed myelination/white matter loss. Given that some of the features of AP-4 deficiency overlap with those of cerebral palsy, and the discovery of the disorder in non-consanguineous populations, we believe that AP-4 deficiency may be more common than previously appreciated.
Subject(s)
Adaptor Protein Complex 4/genetics , Genetic Association Studies , Genetic Predisposition to Disease , Spastic Paraplegia, Hereditary/diagnosis , Spastic Paraplegia, Hereditary/genetics , Alleles , Brain/abnormalities , Brain/diagnostic imaging , Child , Child, Preschool , Diagnostic Imaging , Facies , Female , Genetic Association Studies/methods , Genotype , Humans , Magnetic Resonance Imaging , Male , Mutation , Phenotype , Symptom AssessmentABSTRACT
Tuberous sclerosis complex (TSC) is an autosomal dominant tumor suppressor gene syndrome due to germline mutations in either TSC1 or TSC2. 10-15% of TSC individuals have no mutation identified (NMI) after thorough conventional molecular diagnostic assessment. 53 TSC subjects who were NMI were studied using next generation sequencing to search for mutations in these genes. Blood/saliva DNA including parental samples were available from all subjects, and skin tumor biopsy DNA was available from six subjects. We identified mutations in 45 of 53 subjects (85%). Mosaicism was observed in the majority (26 of 45, 58%), and intronic mutations were also unusually common, seen in 18 of 45 subjects (40%). Seventeen (38%) mutations were seen at an allele frequency < 5%, five at an allele frequency < 1%, and two were identified in skin tumor biopsies only, and were not seen at appreciable frequency in blood or saliva DNA. These findings illuminate the extent of mosaicism in TSC, indicate the importance of full gene coverage and next generation sequencing for mutation detection, show that analysis of TSC-related tumors can increase the mutation detection rate, indicate that it is not likely that a third TSC gene exists, and enable provision of genetic counseling to the substantial population of TSC individuals who are currently NMI.
Subject(s)
Introns , Mosaicism , Mutation , Tumor Suppressor Proteins/genetics , Humans , Tuberous Sclerosis Complex 1 Protein , Tuberous Sclerosis Complex 2 ProteinABSTRACT
BACKGROUND/OBJECTIVES: Facial angiofibromas (AF) have the potential to cause disfigurement in children with tuberous sclerosis complex (TSC). Facial disfigurement can impact the quality of life (QoL) of individuals and their families, leading to negative psychosocial outcomes. QoL has not been studied in TSC patients with AF. METHODS: We conducted a cross-sectional survey study to investigate QoL of TSC patients with AF and their caregivers and to explore the current state of access to treatment for AF. TSC patients and caregivers in TSC clinic at Boston Children's Hospital and through the Tuberous Sclerosis Alliance were recruited to complete QoL surveys including the CADIS, CDLQI, and Skindex-teen questionnaires, and a survey on access to treatment of AF. RESULTS: Fifty-eight patients with TSC and 161 caregivers participated in the study. Caregivers of patients with AF had significantly poorer QoL scores compared to caregivers of those without AF, as measured by a modified CADIS questionnaire (mean 31.7 vs. 11.7, p = 0.004). Among patients with AF, those who received treatment had significantly better QoL scores compared with those without treatment, as measured by the CDLQI (mean 3.8 vs. 9.5, p = 0.001). Forty-one and two-tenths percent of subjects reported never receiving treatment for AF. Forty-seven and three-tenths percent of subjects were prescribed topical rapamycin, 47.7% of whom experienced difficulty with insurance coverage. CONCLUSIONS: Presence and lack of treatment of AF significantly impacts QoL in TSC patients and their caregivers. Access to care for AF is limited by multiple factors and should be addressed by clinicians working with this patient population.
Subject(s)
Angiofibroma/diagnosis , Caregivers/psychology , Facial Neoplasms/diagnosis , Health Services Accessibility , Quality of Life , Tuberous Sclerosis/complications , Adolescent , Angiofibroma/etiology , Angiofibroma/nursing , Angiofibroma/psychology , Boston , Child , Cross-Sectional Studies , Disease Management , Facial Neoplasms/etiology , Facial Neoplasms/nursing , Facial Neoplasms/psychology , Female , Hospitals, Pediatric , Humans , Male , Multivariate Analysis , Sickness Impact Profile , Statistics, Nonparametric , Tuberous Sclerosis/diagnosisABSTRACT
Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by mutations in the TSC1 or TSC2 genes. The TSC1 and TSC2 gene products, TSC1 and TSC2, form a complex that inhibits the mammalian target of rapamycin (mTOR) complex 1 (TORC1). Here, we investigate the effects of 78 TSC2 variants identified in individuals suspected of TSC, on the function of the TSC1-TSC2 complex. According to our functional assessment, 40 variants disrupted the TSC1-TSC2-dependent inhibition of TORC1. We classified 34 of these as pathogenic, three as probably pathogenic and three as possibly pathogenic. In one case, a likely effect on splicing as well as an effect on function was noted. In 15 cases, our functional assessment did not agree with the predictions of the SIFT amino acid substitution analysis software. Our data support the notion that different, nonterminating TSC2 mutations can have distinct effects on TSC1-TSC2 function, and therefore, on TSC pathology.
Subject(s)
Mutation , Signal Transduction/genetics , Tuberous Sclerosis/genetics , Tumor Suppressor Proteins/genetics , Amino Acid Substitution , HEK293 Cells , Humans , Immunoblotting , Mechanistic Target of Rapamycin Complex 1 , Multiprotein Complexes/genetics , Multiprotein Complexes/metabolism , Ribosomal Protein S6 Kinases/genetics , Ribosomal Protein S6 Kinases/metabolism , TOR Serine-Threonine Kinases/genetics , TOR Serine-Threonine Kinases/metabolism , Transfection , Tuberous Sclerosis/metabolism , Tuberous Sclerosis Complex 1 Protein , Tuberous Sclerosis Complex 2 Protein , Tumor Suppressor Proteins/metabolismABSTRACT
Background: Patient advocacy groups (PAGs) serve a vital role for rare disease patients and families by providing educational resources, support, and a sense of community. Motivated by patient need, PAGs are increasingly at the forefront of policy, research, and drug development for their disease of interest. Objectives: The study explored the current landscape of PAGs in order to guide new and existing PAGs on available resources and challenges to research engagement. We aim to inform industry, advocates, and healthcare personnel about PAG achievements and ways they are increasingly involved in research. Design: We chose PAGs from the Rare Diseases Clinical Research Network (RDCRN) Coalition for Patient Advocacy Groups (CPAG) listserv and the National Organization for Rare Disorders (NORD) 'Find a patient organization'. Methods: We surveyed eligible PAG leaders about the demographics, goals, and research activities of their organization. For analysis, PAGs were bucketed by size, age, prevalence of disease, and budget. Data were de-identified for cross-tabulation and multinomial logistic regression analysis with R. Results: Research engagement was an extremely important goal for most PAGs (81%), though ultra-rare disease and high-budget PAGs were most likely to cite it as the top priority. In total, 79% reported research engagement in some capacity, including registries, translational research, and clinical trials. 'Ultra-rare' PAGs were less likely than 'rare' PAGs to have an ongoing clinical trial. Conclusion: While PAGs of varying sizes, budgets, and maturity levels reported an interest in research, limited funding and lack of disease awareness continue to create barriers to achieving their goals. While support tools exist to make research more accessible, often their utility depends on the funding, sustainability, maturity of the PAG itself, and the level of investment of collaborators. Despite the availability of current support systems, there are challenges related to both the start-up and sustainability of patient-centric research efforts.
ABSTRACT
Background: Due to racial, cultural, and linguistic marginalization, some populations experience disproportionate barriers to genetic testing in both clinical and research settings. It is difficult to track such disparities due to non-inclusive self-reported race and ethnicity categories within the electronic health record (EHR). Inclusion and access for all populations is critical to achieve health equity and to capture the full spectrum of rare genetic disease. Objective: We aimed to create revised race and ethnicity categories. Additionally, we identified racial and ethnic under-representation amongst three cohorts: (1) the general Boston Children's Hospital patient population (general BCH), (2) the BCH patient population that underwent clinical genomic testing (clinical sequencing), and (3) Children's Rare Disease Cohort (CRDC) research initiative participants. Design and Methods: Race and ethnicity data were collected from the EHRs of the general BCH, clinical sequencing, and CRDC cohorts. We constructed a single comprehensive set of race and ethnicity categories. EHR-based race and ethnicity variables were mapped within each cohort to the revised categories. Then, the numbers of patients within each revised race and ethnicity category were compared across cohorts. Results: There was a significantly lower percentage of Black or African American/African, non-Hispanic/non-Latine individuals in the CRDC cohort compared with the general BCH cohort, but there was no statistically significant difference between the CRDC and the clinical sequencing cohorts. There was a significantly lower percentage of multi-racial, Hispanic/Latine individuals in the CRDC cohort than the clinical sequencing cohort. White, non-Hispanic/non-Latine individuals were over-represented in the CRDC compared to the two other groups. Conclusion: We highlight underrepresentation of certain racial and ethnic populations in sequencing cohorts compared to the general hospital population. We propose a range of measures to address these disparities, to strive for equitable future precision medicine-based clinical care and for the benefit of the whole rare disease community.
Racial and ethnic representation amongst general clinics, clinics that provide genetic testing, and genomic-based research at Boston Children's Hospital Background: Individuals who identify as belonging to a race or ethnicity that has been historically excluded from mainstream cultural, political, and economic activities ('historically marginalized') experience barriers to clinical care. These barriers are further complicated for families touched by rare genetic conditions. Obstacles can present as accessibility issues (transportation, financial, linguistic), low-quality medical care, or inadequate inclusion in research. It is important to have representation within rare disease research so that the full scope of these conditions is understood, leading to better patient care for all, and for health equity. Objective: We aimed to (1) to create new and inclusive race and ethnicity categories for the electronic health record (EHR) and (2) identify differences in racial and ethnic representation amongst patients generally seen at Boston Children's Hospital (general BCH), those who received genetic testing in a clinic at Boston Children's Hospital (clinical sequencing), and participants who enrolled in the CRDC research project at Boston Children's Hospital (CRDC). Design and Methods: We combined race and ethnicity categories to make more inclusive options than existing EHR categories. Differences in race and ethnicity representation were observed when looking at the three different patient groups (general BCH, clinical sequencing, and CRDC). Results: We observed a lower percentage of individuals who self-identify as Black or African American/African, non-Hispanic/non-Latine in the genetic testing groups (both research and clinical) than in the general BCH group. Individuals who self-identify as multi-racial, Hispanic/Latine are also under-represented in the CRDC research compared to the two other groups. The highest population percentage seen in all groups was that of patients who identify as White, non-Hispanic/non-Latine. This group was over-represented in the research CRDC group compared to the two others. Conclusion: Our study found that patients who are historically marginalized are underrepresented in clinical genetic testing and genomic research studies compared to their White counterparts. In order to benefit all patients with rare genetic conditions, these differences must be addressed by improving access to specialty physicians/researchers and incorporating inclusive language in the EHR, clinics, and research protocols.
ABSTRACT
Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by mutations in the TSC1 or TSC2 genes. The TSC1 and TSC2 gene products, TSC1 and TSC2, form a complex that inhibits the mammalian target of rapamycin (mTOR) complex 1 (TORC1). Previously, we demonstrated that pathogenic amino acid substitutions in the N-terminal domain of TSC1 (amino acids 50-224) are destabilizing. Here we investigate an additional 21 unclassified TSC1 variants. Our functional assessment identified four substitutions (p.L61R, p.G132D, p.F158S, and p.R204P) between amino acids 50 and 224 that reduced TSC1 stability and prevented the TSC1-TSC2-dependent inhibition of TORC1. In four cases (20%), our functional assessment did not agree with the predictions of the SIFT amino acid substitution analysis software. Our new data confirm our previous finding that the N-terminal region of TSC1 is essential for TSC1 function.
Subject(s)
Mutation, Missense/genetics , Tuberous Sclerosis/genetics , Tumor Suppressor Proteins/genetics , Animals , Humans , Immunoblotting , Tuberous Sclerosis Complex 1 Protein , Tuberous Sclerosis Complex 2 Protein , Tumor Suppressor Proteins/metabolismABSTRACT
Interest in gene-based therapies for neurodevelopmental disorders is increasing exponentially, driven by the rise in recognition of underlying genetic etiology, progress in genomic technology, and recent proof of concept in several disorders. The current prioritization of one genetic disorder over another for development of therapies is driven by competing interests of pharmaceutical companies, advocacy groups, and academic scientists. Although these are all valid perspectives, a consolidated framework will facilitate more efficient and rational gene therapy development. Here we outline features of Mendelian neurodevelopmental disorders that warrant consideration when determining suitability for gene therapy. These features fit into four broad domains: genetics, preclinical validation, clinical considerations, and ethics. We propose a simple mnemonic, GENE TARGET, to remember these features and illustrate how they could be scored using a preliminary scoring rubric. In this suggested rubric, for a given disorder, scores for each feature may be added up to a composite GENE TARGET suitability (GTS) score. In addition to proposing a systematic method to evaluate and compare disorders, our framework helps identify gaps in the translational pipeline for a given disorder, which can inform prioritization of future research efforts.
ABSTRACT
BACKGROUND: Computational phenotypes are most often combinations of patient billing codes that are highly predictive of disease using electronic health records (EHR). In the case of rare diseases that can only be diagnosed by genetic testing, computational phenotypes identify patient cohorts for genetic testing and possible diagnosis. This article details the validation of a computational phenotype for PTEN hamartoma tumor syndrome (PHTS) against the EHR of patients at three collaborating clinical research centers: Boston Children's Hospital, Children's National Hospital, and the University of Washington. METHODS: A combination of billing codes from the International Classification of Diseases versions 9 and 10 (ICD-9 and ICD-10) for diagnostic criteria postulated by a research team at Cleveland Clinic was used to identify patient cohorts for genetic testing from the clinical data warehouses at the three research centers. Subsequently, the EHR-including billing codes, clinical notes, and genetic reports-of these patients were reviewed by clinical experts to identify patients with PHTS. RESULTS: The PTEN genetic testing yield of the computational phenotype, the number of patients who needed to be genetically tested for incidence of pathogenic PTEN gene variants, ranged from 82 to 94% at the three centers. CONCLUSIONS: Computational phenotypes have the potential to enable the timely and accurate diagnosis of rare genetic diseases such as PHTS by identifying patient cohorts for genetic sequencing and testing.
Subject(s)
Genetic Testing , Hamartoma Syndrome, Multiple , Electronic Health Records , Hamartoma Syndrome, Multiple/diagnosis , Hamartoma Syndrome, Multiple/genetics , Hamartoma Syndrome, Multiple/pathology , Humans , PTEN Phosphohydrolase/genetics , PhenotypeABSTRACT
The effects of missense changes and small in-frame deletions and insertions on protein function are not easy to predict, and the identification of such variants in individuals at risk of a genetic disease can complicate genetic counselling. One option is to perform functional tests to assess whether the variants affect protein function. We have used this strategy to characterize variants identified in the TSC1 and TSC2 genes in individuals with, or suspected of having, Tuberous Sclerosis Complex (TSC). Here we present an overview of our functional studies on 45 TSC1 and 107 TSC2 variants. Using a standardized protocol we classified 16 TSC1 variants and 70 TSC2 variants as pathogenic. In addition we identified eight putative splice site mutations (five TSC1 and three TSC2). The remaining 24 TSC1 and 34 TSC2 variants were classified as probably neutral.
Subject(s)
Genetic Variation , Tuberous Sclerosis/genetics , Tumor Suppressor Proteins/genetics , Cells, Cultured , Humans , Models, Genetic , Tuberous Sclerosis/metabolism , Tuberous Sclerosis Complex 1 Protein , Tuberous Sclerosis Complex 2 ProteinABSTRACT
This randomized, double-blind controlled trial of everolimus in individuals with germline phosphatase and tensin homolog mutations (PTEN) was designed to evaluate the safety of everolimus compared with placebo and to evaluate the efficacy of everolimus on neurocognition and behavior compared to placebo as measured by standardized neurocognitive and motor measures as well as behavioral questionnaires. The safety profile of everolimus is characterized by manageable adverse events that are generally reversible and non-cumulative. The primary safety endpoint of this study was drop-out rate due to side effects, comparing everolimus versus placebo. We also sought to determine the frequency of adverse events by type and severity. The main efficacy endpoint was a neurocognitive composite computed in two ways: 1) an average for working memory, processing speed, and fine motor subtests; and 2) the same average as above except weighted 2/3, and an additional average based on all other available neurocognitive testing measures assessing the additional domains of nonverbal ability, visuomotor skills, verbal learning, and receptive and expressive language, weighted 1/3. Secondary efficacy endpoints examined the effect of everolimus on overall global clinical improvement, autism symptoms, behavioral problems, and adaptive abilities as measured by validated, standardized instruments. We predicted that the rate of adverse events would be no more than 10% higher in the everolimus group compared to placebo, and overall severity of side effects would be minimal. We also expected that individuals receiving everolimus would show more improvement, relative to those taking placebo, on the composite neurocognitive index.