Amarilis Sanchez-Valle

Identification of Uncommon Recurrent Potocki-Lupski Syndrome-Associated Duplications and the Distribution of Rearrangement Types and Mechanisms in PTLS

Nonallelic homologous recombination (NAHR) can mediate recurrent rearrangements in the human genome and cause genomic disorders. Smith-Magenis syndrome (SMS) and Potocki-Lupski syndrome (PTLS) are genomic disorders associated with a 3.7 Mb deletion and its reciprocal duplication in 17p11.2, respectively. In addition to these common recurrent rearrangements, an uncommon recurrent 5 Mb SMS-associated deletion has been identified. However, its reciprocal duplication predicted by the NAHR mechanism had not been identified. Here we report the molecular assays on 74 subjects with PTLS-associated duplications, 35 of whom are newly investigated. By both oligonucleotide-based comparative genomic hybridization and recombination hot spot analyses, we identified two cases of the predicted 5 Mb uncommon recurrent PTLS-associated duplication. Interestingly, the crossovers occur in proximity to a recently delineated allelic homologous recombination (AHR) hot spot-associated sequence motif, further documenting the common hot spot features shared between NAHR and AHR. An additional eight subjects with nonrecurrent PTLS duplications were identified. The smallest region of overlap (SRO) for all of the 74 PTLS duplications examined is narrowed to a 125 kb interval containing only RAI1, a gene recently further implicated in autism. Sequence complexities consistent with DNA replication-based mechanisms were identified in four of eight (50%) newly identified nonrecurrent PTLS duplications. Our findings of the uncommon recurrent PTLS-associated duplication at a relative prevalence reflecting the de novo mutation rate and the distribution of 17p11.2 duplication types in PTLS reveal insights into both the contributions of new mutations and the different underlying mechanisms that generate genomic rearrangements causing genomic disorders.

The severe end of the spectrum: Hypoplastic left heart in Potocki‐Lupski syndrome

Potocki‐Lupski syndrome (PTLS) is a recently described microduplication syndrome associated with duplication 17p11.2, including the RAI1 gene. Features of PTLS include hypotonia, feeding difficulties, failure to thrive, developmental delay and behavioral abnormalities including autistic spectrum disorder, anxiety, and inattention. Cardiovascular anomalies were not recognized as a feature of duplication 17p11.2 until 2007 when noted in over 50% of a clinically characterized cohort. We report a patient with hypoplastic left heart syndrome whose diagnosis of PTLS was delayed until a genetic evaluation at age 4 years because of severe expressive language impairment. We suggest that array comparative genomic hybridization be performed in infants with severe congenital heart defects.

HERV-Mediated Genomic Rearrangement of EYA1 in an Individual With Branchio-oto-renal Syndrome

Branchio‐oto‐renal syndrome is characterized by branchial defects, hearing loss, preauricular pits, and renal anomalies. Mutations in EYA1 are the most common cause of branchio‐oto‐renal and branchio‐otic syndromes. Large chromosomal aberrations of 8q13, including complex rearrangements occur in about 20% of these individuals. However, submicroscopic deletions and the molecular characterization of genomic rearrangements involving the EYA1 gene have rarely been reported. Using the array‐comparative genomic hybridization, we identified non‐recurrent genomic deletions including the EYA1 gene in three patients with branchio‐oto‐renal syndrome, short stature, and developmental delay. One of these deletions was mediated by two human endogenous retroviral sequence blocks, analogous to the AZFa microdeletion on Yq11, responsible for male infertility. This report describes the expanded phenotype of individuals, resulting from contiguous gene deletion involving the EYA1 gene and provides a molecular description of the genomic rearrangements involving this gene in branchio‐oto‐renal syndrome.

UX007 for the treatment of long chain-fatty acid oxidation disorders: Safety and efficacy in children and adults following 24 weeks of treatment

BACKGROUND Long-chain fatty acid oxidation disorders (LC-FAOD) lead to accumulation of high concentrations of potentially toxic fatty acid intermediates. Newborn screening and early intervention have reduced mortality, but most patients continue to experience frequent hospitalizations and significant morbidity despite treatment. The deficient energy state can cause serious liver, muscle, and heart disease, and may be associated with an increased risk of sudden death. Triheptanoin is a medium odd-chain fatty acid. Anaplerotic metabolites of triheptanoin have the potential to replace deficient tricarboxylic acid (TCA) cycle intermediates, resulting in net glucose production as a novel energy source for the treatment of LC-FAOD. STUDY DESIGN A single-arm, open-label, multicenter Phase 2 safety and efficacy study evaluated patients with severe LC-FAOD evidenced by ongoing related musculoskeletal, cardiac, and/or hepatic events despite treatment. After a four-week run-in on current regimen, investigational triheptanoin (UX007) was titrated to a target dose of 25-35% of total daily caloric intake. Patients were evaluated on several age/condition-eligible endpoints, including submaximal exercise tests to assess muscle function/endurance (12-minute walk test; 12MWT) and exercise tolerance (cycle ergometry), and health related quality of life (HR-QoL). Results through 24weeks of treatment are presented; total study duration is 78weeks. RESULTS Twenty-nine patients (0.8 to 58years) were enrolled; most qualified based on severe musculoskeletal disease. Twenty-five patients (86%) completed the 24-week treatment period. At Week 18, eligible patients (n=8) demonstrated a 28% increase (LS mean=+181.9 meters; p=0.087) from baseline (673.4meters) in 12MWT distance. At Week 24, eligible patients (n=7) showed a 60% increase in watts generated (LS mean=+409.3W; p=0.149) over baseline (744.6W) for the exercise tolerance test. Improvements in exercise tests were supported by significant improvements from baseline in the adult (n=5) self-reported SF-12v2 physical component summary score (LS mean=+8.9; p<0.001). No difference from baseline was seen in pediatric parent-reported (n=5) scores (SF-10) at Week 24. Eighteen patients (62%) had treatment-related adverse events, predominantly gastrointestinal (55%), mild-to-moderate in severity, similar to that seen with prior treatment with medium chain triglyceride (MCT) oil. One patient experienced a treatment-related serious adverse event of gastroenteritis. One patient discontinued from study due to diarrhea of moderate severity; the majority of patients (25/29; 86%) elected to continue treatment in the extension period. CONCLUSIONS In patients with severe LC-FAOD, UX007 interim study results demonstrated improved exercise endurance and tolerance, and were associated with positive changes in self-reported HR-QoL.

A randomized, placebo-controlled, double-blind study of sapropterin to treat ADHD symptoms and executive function impairment in children and adults with sapropterin-responsive phenylketonuria

Symptoms of attention deficit-hyperactivity disorder (ADHD), particularly inattention, and impairments in executive functioning have been reported in early and continuously treated children, adolescents, and adults with phenylketonuria (PKU). In addition, higher blood phenylalanine (Phe) levels have been correlated with the presence of ADHD symptoms and executive functioning impairment. The placebo-controlled PKU ASCEND study evaluated the effects of sapropterin therapy on PKU-associated symptoms of ADHD and executive and global functioning in individuals who had a therapeutic blood Phe response to sapropterin therapy. The presence of ADHD inattentive symptoms and executive functioning deficits was confirmed in this large cohort of 206 children and adults with PKU, of whom 118 responded to sapropterin therapy. In the 38 individuals with sapropterin-responsive PKU and ADHD symptoms at baseline, sapropterin therapy resulted in a significant improvement in ADHD inattentive symptoms in the first 4 weeks of treatment, and improvements were maintained throughout the 26 weeks of treatment. Sapropterin was well-tolerated with a favorable safety profile. The improvements in ADHD inattentive symptoms and aspects of executive functioning in response to sapropterin therapy noted in a large cohort of individuals with PKU indicate that these symptoms are potentially reversible when blood Phe levels are reduced.

ALG1-CDG: Clinical and Molecular Characterization of 39 Unreported Patients.

Congenital disorders of glycosylation (CDG) arise from pathogenic mutations in over 100 genes leading to impaired protein or lipid glycosylation. ALG1 encodes a β1,4 mannosyltransferase that catalyzes the addition of the first of nine mannose moieties to form a dolichol‐lipid linked oligosaccharide intermediate required for proper N‐linked glycosylation. ALG1 mutations cause a rare autosomal recessive disorder termed ALG1‐CDG. To date 13 mutations in 18 patients from 14 families have been described with varying degrees of clinical severity. We identified and characterized 39 previously unreported cases of ALG1‐CDG from 32 families and add 26 new mutations. Pathogenicity of each mutation was confirmed based on its inability to rescue impaired growth or hypoglycosylation of a standard biomarker in an alg1‐deficient yeast strain. Using this approach we could not establish a rank order comparison of biomarker glycosylation and patient phenotype, but we identified mutations with a lethal outcome in the first two years of life. The recently identified protein‐linked xeno‐tetrasaccharide biomarker, NeuAc‐Gal‐GlcNAc2, was seen in all 27 patients tested. Our study triples the number of known patients and expands the molecular and clinical correlates of this disorder.

Chronic Maternal Protein Deprivation in Mice Is Associated with Overexpression of the Cohesin-Mediator Complex in Liver of Their Offspring

Epigenetic mechanisms may play an important role in the developmental programming of adult-onset chronic metabolic diseases resulting from suboptimal fetal nutrition, but the exact molecular mechanisms are incompletely understood. Given the central role of the liver in metabolic regulation, we investigated whether chronic maternal dietary protein restriction has long-term effects on liver gene expression in the offspring. We fed adult C57BL/6J dams ad libitum an 8% maternal low-protein (MLP) or 20% protein control diet (C) from 4 wk prior to mating until the end of lactation. Male pups were weaned to standard nonpurified diet and singly housed at 21 d of age (d 21). Body weights were followed to 1 y of age (1 y). At d 21 and 1 y, organs were quantitatively dissected and analyzed. MLP offspring had significantly lower body weights at all ages and significantly lower serum activity of alanine aminotransferase and lactate dehydrogenase at 1 y. Gene expression profiling of liver at 1 y showed 521 overexpressed and 236 underexpressed genes in MLP compared to C offspring. The most important novel finding was the overexpression of genes found in liver that participate in organization and maintenance of higher order chromatin architecture and regulation of transcriptional activation. These included members of the cohesin-mediator complex, which regulate gene expression by forming DNA loops between promoters and enhancers in a cell type-specific fashion. Thus, our findings of increased expression of these factors in liver of MLP offspring implicate a possible novel epigenetic mechanism in developmental programming.

Dyschromatosis symmetrica hereditaria by ADAR1 mutations and viral encephalitis: a hidden link?

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A novel mutation in GLUD1 causing hyperinsulinism-hyperammonemia in a patient with high density of homozygosity on microarray: a case report

BackgroundHyperinsulinism-hyperammonemia syndrome is the second most common cause of congenital hyperinsulinism and is easily treated with diazoxide; however, the symptoms in our patient were very difficult to control with typical medical therapy. To the best of our knowledge, neither our patient’s mutation, nor a case of hyperinsulinism-hyperammonemia presenting with dysmorphic features and intrauterine growth restriction has previously been reported.Case presentationWe describe a 2-year-old Hispanic girl with an unusual presentation of dysmorphic features and intrauterine growth restriction who was later found to have hyperinsulinism-hyperammonemia syndrome. Chromosomal microarray analysis revealed no copy number variants but demonstrated a high density of noncontiguous regions of homozygosity consistent with limited outbreeding. Sequencing of her GLUD1 gene revealed a previously undescribed mutation of cytosine to thymine at position 1519 resulting in an amino acid change of histidine to tyrosine at position 507. Although no functional studies were performed, function prediction tools in combination with our patient’s phenotype support the hypothesis that the mutation is deleterious. Despite treatment with a maximum dose of diazoxide (15 mg/kg/day), phenobarbital (8.5 mg/kg/day divided twice daily) and a protein-restricted diet, she has global developmental delay, and continues to have seizures and recurrent episodes of hypoglycemia.ConclusionsIt remains unclear if her clinical presentation can be solely explained by hyperinsulinism-hyperammonemia syndrome or is the result of an undiagnosed recessive disorder related to her homozygosity. It is our hope that clinicians may learn from our patient when formulating treatment plans for refractory cases of hyperinsulinism-hyperammonemia and avoid the morbidities associated with delayed diagnosis and treatment.