APC7 mediates ubiquitin signaling in constitutive heterochromatin in the developing mammalian brain

Neurodevelopmental cognitive disorders provide insights into mechanisms of human brain development. Here, we report an intellectual disability syndrome caused by the loss of APC7, a core component of the E3 ubiquitin ligase anaphase promoting complex (APC). In mechanistic studies, we uncover a critical role for APC7 during the recruitment and ubiquitination of APC substrates. In proteomics analyses of the brain from mice harboring the patient-specific APC7 mutation, we identify the chromatin-associated protein Ki-67 as an APC7-dependent substrate of the APC in neurons. Conditional knockout of the APC coactivator protein Cdh1, but not Cdc20, leads to the accumulation of Ki-67 protein in neurons in vivo, suggesting that APC7 is required for the function of Cdh1-APC in the brain. Deregulated neuronal Ki-67 upon APC7 loss localizes predominantly to constitutive heterochromatin. Our findings define an essential function for APC7 and Cdh1-APC in neuronal heterochromatin regulation, with implications for understanding human brain development and disease.

Glutaric acidemia type 1: Treatment and outcome of 168 patients over three decades

Glutaric acidemia type 1 (GA1) is a disorder of cerebral organic acid metabolism resulting from biallelic mutations of GCDH. Without treatment, GA1 causes striatal degeneration in >80% of affected children before two years of age. We analyzed clinical, biochemical, and developmental outcomes for 168 genotypically diverse GA1 patients managed at a single center over 31 years, here separated into three treatment cohorts: children in Cohort I (n = 60; DOB 2006-2019) were identified by newborn screening (NBS) and treated prospectively using a standardized protocol that included a lysine-free, arginine-enriched metabolic formula, enteral l-carnitine (100 mg/kg•day), and emergency intravenous (IV) infusions of dextrose, saline, and l-carnitine during illnesses; children in Cohort II (n = 57; DOB 1989-2018) were identified by NBS and treated with natural protein restriction (1.0-1.3 g/kg•day) and emergency IV infusions; children in Cohort III (n = 51; DOB 1973-2016) did not receive NBS or special diet. The incidence of striatal degeneration in Cohorts I, II, and III was 7%, 47%, and 90%, respectively (p < .0001). No neurologic injuries occurred after 19 months of age. Among uninjured children followed prospectively from birth (Cohort I), measures of growth, nutritional sufficiency, motor development, and cognitive function were normal. Adherence to metabolic formula and l-carnitine supplementation in Cohort I declined to 12% and 32%, respectively, by age 7 years. Cessation of strict dietary therapy altered plasma amino acid and carnitine concentrations but resulted in no serious adverse outcomes. In conclusion, neonatal diagnosis of GA1 coupled to management with lysine-free, arginine-enriched metabolic formula and emergency IV infusions during the first two years of life is safe and effective, preventing more than 90% of striatal injuries while supporting normal growth and psychomotor development. The need for dietary interventions and emergency IV therapies beyond early childhood is uncertain.

Soy-Based Infant Formula is Associated with an Increased Prevalence of Comorbidities in Fragile X Syndrome

A large number of adults and children consume soy in various forms, but little information is available regarding potential neurological side effects. Prior work indicates an association between the consumption of soy-based diets and seizure prevalence in mouse models of neurological disease and in children with autism. Herein, we sought to evaluate potential associations between the consumption of soy-based formula during infancy and disease comorbidities in persons with fragile X syndrome (FXS), while controlling for potentially confounding issues, through a retrospective case-control survey study of participants with FXS enrolled in the Fragile X Online Registry with Accessible Research Database (FORWARD). There was a 25% usage rate of soy-based infant formula in the study population. We found significant associations between the consumption of soy-based infant formula and the comorbidity of autism, gastrointestinal problems (GI) and allergies. Specifically, there was a 1.5-fold higher prevalence of autism, 1.9-fold GI problems and 1.7-fold allergies in participants reporting the use of soy-based infant formula. The major reason for starting soy-based infant formula was GI problems. The average age of seizure and allergy onset occurred long after the use of soy-based infant formula. We conclude that early-life feeding with soy-based infant formula is associated with the development of several disease comorbidities in FXS.

Branched-chain α-ketoacid dehydrogenase deficiency (maple syrup urine disease): Treatment, biomarkers, and outcomes

Over the past three decades, we studied 184 individuals with 174 different molecular variants of branched-chain α-ketoacid dehydrogenase activity, and here delineate essential clinical and biochemical aspects of the maple syrup urine disease (MSUD) phenotype. We collected data about treatment, survival, hospitalization, metabolic control, and liver transplantation from patients with classic (i.e., severe; n = 176), intermediate (n = 6) and intermittent (n = 2) forms of MSUD. A total of 13,589 amino acid profiles were used to analyze leucine tolerance, amino acid homeostasis, estimated cerebral amino acid uptake, quantitative responses to anabolic therapy, and metabolic control after liver transplantation. Standard instruments were used to measure neuropsychiatric outcomes. Despite advances in clinical care, classic MSUD remains a morbid and potentially fatal disorder. Stringent dietary therapy maintains metabolic variables within acceptable limits but is challenging to implement, fails to restore appropriate concentration relationships among circulating amino acids, and does not fully prevent cognitive and psychiatric disabilities. Liver transplantation eliminates the need for a prescription diet and safeguards patients from life-threatening metabolic crises, but is associated with predictable morbidities and does not reverse pre-existing neurological sequelae. There is a critical unmet need for safe and effective disease-modifying therapies for MSUD which can be implemented early in life. The biochemistry and physiology of MSUD and its response to liver transplantation afford key insights into the design of new therapies based on gene replacement or editing.

Autism Spectrum Disorder in Fragile X Syndrome: Cooccurring Conditions and Current Treatment

BACKGROUND AND OBJECTIVE

Individuals with fragile X syndrome (FXS) are frequently codiagnosed with autism spectrum disorder (ASD). Most of our current knowledge about ASD in FXS comes from family surveys and small studies. The objective of this study was to examine the impact of the ASD diagnosis in a large clinic-based FXS population to better inform the care of people with FXS.

METHODS

The study employed a data set populated by data from individuals with FXS seen at specialty clinics across the country. The data were collected by clinicians at the patient visit and by parent report for nonclinical and behavioral outcomes from September 7, 2012 through August 31, 2014. Data analyses were performed by using χ² tests for association, t tests, and multiple logistic regression to examine the association between clinical and other factors with ASD status.

RESULTS

Half of the males and nearly 20% of females met Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria for current ASD. Relative to the FXS-only group, the FXS with ASD (FXS+ASD) group had a higher prevalence of seizures (20.7% vs 7.6%, P < .001), persistence of sleep problems later in childhood, increased behavior problems, especially aggressive/disruptive behavior, and higher use of α-agonists and antipsychotics. Behavioral services, including applied behavior analysis, appeared to be underused in children with FXS+ASD (only 26% and 16% in prekindergarten and school-age periods, respectively) relative to other populations with idiopathic ASD.

CONCLUSIONS

These findings confirm among individuals with FXS an association of an ASD diagnosis with important cooccurring conditions and identify gaps between expected and observed treatments among individuals with FXS+ASD.

Knowledge and perceptions about fragile X syndrome: implications for diagnosis, intervention, and research

We surveyed 439 professionals in the field of autism to assess their knowledge and perceptions about fragile X syndrome (FXS) and related issues. Almost half had worked with at least one child diagnosed with FXS, yet most lacked basic knowledge about the condition, underestimated its significance in the etiology of autism spectrum disorders, and rarely accessed fragile X-specific resources. A majority perceived etiology to be an important variable in therapeutic response while three quarters felt that professionals in the field of autism should play an active role in referring children for etiological evaluation. Despite these opinions, most respondents either rarely or never inquired about etiology when working with a new client. The survey results underscore the need for training and education so that autism professionals can become effective partners in diagnostic genetic referral and in research and implementation of syndrome-specific interventions.

A longitudinal follow-up study of autistic symptoms in children and adults with duplications of 15q11-13

We completed a longitudinal follow-up of autistic symptoms in a cohort of children and young adults with duplications of chromosome 15q11-13. In our initial investigation of 29 individuals, tentative conclusions were drawn based on cross-sectional data suggesting that autistic symptoms increased with age, most specifically in the area of social interaction. We were able to re-assess 22 individuals from the original study an average of 7 years later using the same standardized autism screening measure. As predicted, autistic symptoms were found to increase for the younger children in the cohort but remained constant for the older participants. This global change in autistic symptoms among the younger children could not be ascribed to any particular autism subscale and reflects small but cumulatively significant increases across several domains.

Genetics, mental retardation, and the forging of new alliances

The lives of people with intellectual disabilities are tightly intermeshed with the philosophies and practices of special educators, therapists, psychologists, social workers, and others who make up the mental retardation field. These nonmedical workers represent a kind of extended family, which can strongly influence the decisions made and services received by the people they serve. By contrast, most individuals with mental retardation do not have extraordinary medical needs, and healthcare professionals play only a minor role in their human services family. There are deeply rooted historical differences between the medical model of mental retardation with which genetics professionals are familiar and the philosophies embraced by nonmedical workers who dominate the mental retardation field. These contrasts have an important impact on the genetic diagnostic process, as well as a more global effect on mental retardation research. Without the full participation of teachers, therapists, psychologists, and others outside the medical setting, many practical applications of genetic research can neither be implemented nor expanded upon, and an important opportunity for cross-fertilization is lost. It is in the interest of the genetics community to take advantage of recent overtures by the mental retardation field to forge new alliances and broaden its perspectives on intellectual disability.

The spasmodic upper-body squeeze: a characteristic behavior in Smith-Magenis syndrome

The authors have observed a hand- and arm-squeezing behavior that seems to be highly characteristic of Smith-Magenis syndrome (SMS). This behavior serves as a useful diagnostic marker for SMS, a disorder in which the physical phenotype is often subtle. The squeezing behavior appears to be part of a complex upper-body tic which is exacerbated by happiness, excitement or overstimulation. The tic most often manifests as a 'self-hug', and is frequently associated with facial grimacing. Fleeting arm- and hand-squeezing movements may be repeated hundreds of times over the course of a day, but they do not significantly interfere with other hand functions. The excitable self-hugging in people with SMS may be one of the more benign and appealing aspects of their behavioral phenotype.