Truncating SRCAP variants outside the Floating-Harbor syndrome locus cause a distinct neurodevelopmental disorder with a specific DNA methylation signature

Truncating variants in exons 33 and 34 of the SNF2-related CREBBP activator protein (SRCAP) gene cause the neurodevelopmental disorder (NDD) Floating-Harbor syndrome (FLHS), characterized by short stature, speech delay, and facial dysmorphism. Here, we present a cohort of 33 individuals with clinical features distinct from FLHS and truncating (mostly de novo) SRCAP variants either proximal (n = 28) or distal (n = 5) to the FLHS locus. Detailed clinical characterization of the proximal SRCAP individuals identified shared characteristics: developmental delay with or without intellectual disability, behavioral and psychiatric problems, non-specific facial features, musculoskeletal issues, and hypotonia. Because FLHS is known to be associated with a unique set of DNA methylation (DNAm) changes in blood, a DNAm signature, we investigated whether there was a distinct signature associated with our affected individuals. A machine-learning model, based on the FLHS DNAm signature, negatively classified all our tested subjects. Comparing proximal variants with typically developing controls, we identified a DNAm signature distinct from the FLHS signature. Based on the DNAm and clinical data, we refer to the condition as "non-FLHS SRCAP-related NDD.'' All five distal variants classified negatively using the FLHS DNAm model while two classified positively using the proximal model. This suggests divergent pathogenicity of these variants, though clinically the distal group presented with NDD, similar to the proximal SRCAP group. In summary, for SRCAP, there is a clear relationship between variant location, DNAm profile, and clinical phenotype. These results highlight the power of combined epigenetic, molecular, and clinical studies to identify and characterize genotype-epigenotype-phenotype correlations

Novel defect in phosphatidylinositol 4-kinase type 2-alpha (PI4K2A) at the membrane-enzyme interface is associated with metabolic cutis laxa

Inherited cutis laxa, or inelastic, sagging skin is a genetic condition of premature and generalised connective tissue ageing, affecting various elastic components of the extracellular matrix. Several cutis laxa syndromes are inborn errors of metabolism and lead to severe neurological symptoms. In a patient with cutis laxa, a choreoathetoid movement disorder, dysmorphic features and intellectual disability we performed exome sequencing to elucidate the underlying genetic defect. We identified the amino acid substitution R275W in phosphatidylinositol 4-kinase type II alpha, caused by a homozygous missense mutation in thePI4K2Agene. We used lipidomics, complexome profiling and functional studies to measure phosphatidylinositol 4-phosphate synthesis in the patient and evaluated PI4K2A deficient mice to define a novel metabolic disorder. The R275W residue, located on the surface of the protein, is involved in forming electrostatic interactions with the membrane. The catalytic activity of PI4K2A in patient fibroblasts was severely reduced and lipid mass spectrometry showed that particular acyl-chain pools of PI4P and PI(4,5)P(2)were decreased. Phosphoinositide lipids play a major role in intracellular signalling and trafficking and regulate the balance between proliferation and apoptosis. Phosphatidylinositol 4-kinases such as PI4K2A mediate the first step in the main metabolic pathway that generates PI4P, PI(4,5)P(2)and PI(3,4,5)P-3. Although neurologic involvement is common, cutis laxa has not been reported previously in metabolic defects affecting signalling. Here we describe a patient with a complex neurological phenotype, premature ageing and a mutation inPI4K2A, illustrating the importance of this enzyme in the generation of inositol lipids with particular acylation characteristics.Medical Biochemistr

Metabolic cutis laxa syndromes

Cutis laxa is a rare skin disorder characterized by wrinkled, redundant, inelastic and sagging skin due to defective synthesis of elastic fibers and other proteins of the extracellular matrix. Wrinkled, inelastic skin occurs in many cases as an acquired condition. Syndromic forms of cutis laxa, however, are caused by diverse genetic defects, mostly coding for structural extracellular matrix proteins. Surprisingly a number of metabolic disorders have been also found to be associated with inherited cutis laxa. Menkes disease was the first metabolic disease reported with old-looking, wrinkled skin. Cutis laxa has recently been found in patients with abnormal glycosylation. The discovery of the COG7 defect in patients with wrinkled, inelastic skin was the first genetic link with the Congenital Disorders of Glycosylation (CDG). Since then several inborn errors of metabolism with cutis laxa have been described with variable severity. These include P5CS, ATP6V0A2-CDG and PYCR1 defects. In spite of the evolving number of cutis laxa-related diseases a large part of the cases remain genetically unsolved. In metabolic cutis laxa syndromes the clinical and laboratory features might partially overlap, however there are some distinct, discriminative features. In this review on metabolic diseases causing cutis laxa we offer a practical approach for the differential diagnosis of metabolic cutis laxa syndromes

Truncating SRCAP variants outside the Floating-Harbor syndrome locus cause a distinct neurodevelopmental disorder with a specific DNA methylation signature

Truncating variants in exons 33 and 34 of the SNF2-related CREBBP activator protein (SRCAP) gene cause the neurodevelopmental disorder (NDD) Floating-Harbor syndrome (FLHS), characterized by short stature, speech delay, and facial dysmorphism. Here, we present a cohort of 33 individuals with clinical features distinct from FLHS and truncating (mostly de novo) SRCAP variants either proximal (n = 28) or distal (n = 5) to the FLHS locus. Detailed clinical characterization of the proximal SRCAP individuals identified shared characteristics: developmental delay with or without intellectual disability, behavioral and psychiatric problems, non-specific facial features, musculoskeletal issues, and hypotonia. Because FLHS is known to be associated with a unique set of DNA methylation (DNAm) changes in blood, a DNAm signature, we investigated whether there was a distinct signature associated with our affected individuals. A machine-learning model, based on the FLHS DNAm signature, negatively classified all our tested subjects. Comparing proximal variants with typically developing controls, we identified a DNAm signature distinct from the FLHS signature. Based on the DNAm and clinical data, we refer to the condition as "non-FLHS SRCAP-related NDD.'' All five distal variants classified negatively using the FLHS DNAm model while two classified positively using the proximal model. This suggests divergent pathogenicity of these variants, though clinically the distal group presented with NDD, similar to the proximal SRCAP group. In summary, for SRCAP, there is a clear relationship between variant location, DNAm profile, and clinical phenotype. These results highlight the power of combined epigenetic, molecular, and clinical studies to identify and characterize genotype-epigenotype-phenotype correlations.Genetics of disease, diagnosis and treatmen

Complex Phenotypes in Inborn Errors of Metabolism: Overlapping Presentations in Congenital Disorders of Glycosylation and Mitochondrial Disorders

Congenital disorders of glycosylation (CDG) and mitochondrial disorders have overlapping clinical features, including central nervous system, cardiac, gastrointestinal, hepatic, muscular, endocrine, and psychiatric disease. Specific abnormalities orienting the clinician toward the right diagnostic approach include abnormal fat distribution, coagulation abnormalities, together with anticoagulation abnormalities, hyperinsulinism, and congenital malformations in CDG. Diabetes, sensorineural deafness, and depression are very rare in CDG but common in mitochondrial disease. Chronic lactic acidosis is highly suggestive of mitochondrial dysfunction. Serum transferrin isoform analysis is specific for glycosylation abnormalities but not abnormal in all types of CDG

Wrinkled skin and fat pads in patients with ALG8-CDG: revisiting skin manifestations in congenital disorders of glycosylation

Glycosylation is the posttranslational coupling of sugar chains to proteins or lipids. Proper glycosylation is essential for normal protein structure, function, and trafficking. Mutations in the glycosylation pathway lead to a phenotypically heterogeneous group of metabolic disorders, the congenital disorders of glycosylation (CDG). Some of these conditions, including PMM2-CDG, frequently present with recognizable skin abnormalities such as abnormal fat distribution, skin wrinkling, or peau d'orange, whereas others, such as COG7-CDG and ATP6V0A2-CDG, have been described in association with cutis laxa: wrinkled, inelastic, and sagging skin. Ichthyosis is also common in several types of CDG. ALG8-CDG is a severe disorder characterized by dysmorphic features, failure to thrive, protein-losing enteropathy, neurologic and ophthalmologic problems, and developmental delay. We reviewed the clinical features in all nine previously reported patients diagnosed with ALG8-CDG with a special focus on their skin signs. Three of the nine patients had abnormal fat distribution and skin wrinkling. As the spectrum of CDG presenting with skin signs expands further, we suggest screening for CDG in all patients presenting with any type of central nervous involvement and wrinkled skin, cutis laxa, severe ichthyosis, or abnormal fat distribution.status: publishe

Wrinkled skin and fat pads in patients with ALG8-CDG: revisiting skin manifestations in congenital disorders of glycosylation

Contains fulltext : 137227.pdf (publisher's version ) (Closed access)Glycosylation is the posttranslational coupling of sugar chains to proteins or lipids. Proper glycosylation is essential for normal protein structure, function, and trafficking. Mutations in the glycosylation pathway lead to a phenotypically heterogeneous group of metabolic disorders, the congenital disorders of glycosylation (CDG). Some of these conditions, including PMM2-CDG, frequently present with recognizable skin abnormalities such as abnormal fat distribution, skin wrinkling, or peau d'orange, whereas others, such as COG7-CDG and ATP6V0A2-CDG, have been described in association with cutis laxa: wrinkled, inelastic, and sagging skin. Ichthyosis is also common in several types of CDG. ALG8-CDG is a severe disorder characterized by dysmorphic features, failure to thrive, protein-losing enteropathy, neurologic and ophthalmologic problems, and developmental delay. We reviewed the clinical features in all nine previously reported patients diagnosed with ALG8-CDG with a special focus on their skin signs. Three of the nine patients had abnormal fat distribution and skin wrinkling. As the spectrum of CDG presenting with skin signs expands further, we suggest screening for CDG in all patients presenting with any type of central nervous involvement and wrinkled skin, cutis laxa, severe ichthyosis, or abnormal fat distribution

Recognizable phenotype with common occurrence of microcephaly, psychomotor retardation, but no spontaneous bone fractures in autosomal recessive cutis laxa type IIB due to PYCR1 mutations

Contains fulltext : 97299.pdf (publisher's version ) (Closed access

Long-term clinical outcome, therapy and mild mitochondrial dysfunction in hyperprolinemia

Although hyperprolinemia type-II has a discriminative metabolic phenotype and is frequently associated with neurological system involvement, the casual relation between the metabolic abnormalities and the clinical features, except for those of the secondary B6 deficiency, has been frequently debated. In order to evaluate disease frequency and the neuro-metabolic outcome we searched our laboratory database between 1992 and 2010, including 20,991 urinary organic acid profiles. From these individuals 16,720 parallel blood samples were available, and were investigated by serum amino acid analysis. We also evaluated the clinical, neurological, psychological features, laboratory data and vitamin levels and therapeutic effect in metabolically confirmed hyperprolinemia. Due to the mitochondrial localization of both ALDH4A1 and PRODH mitochondrial enzyme complex activity was evaluated and oxygen consumption was measured to assess ATP production in patient-fibroblasts. The Mitochondrial Disease Score was used to evaluate clinical mitochondrial dysfunction. The child behavior checklist was used to screen for psychopathology. We found four patients with increased urinary P5C diagnosed with hyperprolinemia type II, and only one patient had hyperprolinemia type I. All children with hyperprolinemia type II had low normal B6 concentration, and three of the patients had biochemical markers suggesting mitochondrial dysfunction. Mitochondrial dysfunction was confirmed in a muscle biopsy in one case. Intellectual disability was found in two adolescent patients. All patients showed seizures and significant behavioral problems, including anxiety and hallucinations. The clinical course was non-progressive and independent from the B6 concentration and B6 therapy. Hyperprolinemia is a rare inborn error. Individuals with hyperprolinemia should be monitored closely due to their frequent behavioral problems.status: publishe