ABSTRACT
BACKGROUND: De novo mutations in PURA have recently been described to cause PURA syndrome, a neurodevelopmental disorder characterised by severe intellectual disability (ID), epilepsy, feeding difficulties and neonatal hypotonia. OBJECTIVES: To delineate the clinical spectrum of PURA syndrome and study genotype-phenotype correlations. METHODS: Diagnostic or research-based exome or Sanger sequencing was performed in individuals with ID. We systematically collected clinical and mutation data on newly ascertained PURA syndrome individuals, evaluated data of previously reported individuals and performed a computational analysis of photographs. We classified mutations based on predicted effect using 3D in silico models of crystal structures of Drosophila-derived Pur-alpha homologues. Finally, we explored genotype-phenotype correlations by analysis of both recurrent mutations as well as mutation classes. RESULTS: We report mutations in PURA (purine-rich element binding protein A) in 32 individuals, the largest cohort described so far. Evaluation of clinical data, including 22 previously published cases, revealed that all have moderate to severe ID and neonatal-onset symptoms, including hypotonia (96%), respiratory problems (57%), feeding difficulties (77%), exaggerated startle response (44%), hypersomnolence (66%) and hypothermia (35%). Epilepsy (54%) and gastrointestinal (69%), ophthalmological (51%) and endocrine problems (42%) were observed frequently. Computational analysis of facial photographs showed subtle facial dysmorphism. No strong genotype-phenotype correlation was identified by subgrouping mutations into functional classes. CONCLUSION: We delineate the clinical spectrum of PURA syndrome with the identification of 32 additional individuals. The identification of one individual through targeted Sanger sequencing points towards the clinical recognisability of the syndrome. Genotype-phenotype analysis showed no significant correlation between mutation classes and disease severity.
Subject(s)
DNA-Binding Proteins/genetics , Face/abnormalities , Intellectual Disability/genetics , Mutation , Transcription Factors/genetics , DNA-Binding Proteins/chemistry , Drosophila Proteins/chemistry , Drosophila Proteins/genetics , Eye Abnormalities/genetics , Female , Genetic Association Studies , Humans , Infant, Newborn , Muscle Hypotonia/etiology , Muscle Hypotonia/genetics , Pregnancy , Structural Homology, Protein , Syndrome , Transcription Factors/chemistryABSTRACT
The HSPs (hereditary spastic paraplegias) are genetic conditions in which there is distal degeneration of the longest axons of the corticospinal tract, resulting in spastic paralysis of the legs. The gene encoding spartin is mutated in Troyer syndrome, an HSP in which paralysis is accompanied by additional clinical features. There has been controversy over the subcellular distribution of spartin. We show here that, at steady state, endogenous spartin exists in a cytosolic pool that can be recruited to endosomes and to lipid droplets. Cytosolic endogenous spartin is mono-ubiquitinated and we demonstrate that it interacts via a PPXY motif with the ubiquitin E3 ligases AIP4 [atrophin-interacting protein 4; ITCH (itchy E3 ubiquitin protein ligase homologue] [corrected] and AIP5 (WWP1). Surprisingly, the PPXY motif, AIP4 and AIP5 are not required for spartin's ubiquitination, and so we propose that spartin acts as an adaptor for these proteins. Our results suggest that spartin is involved in diverse cellular functions, which may be of relevance to the complex phenotype seen in Troyer syndrome.
Subject(s)
Endosomes/metabolism , Lipid Metabolism , Proteins/metabolism , Repressor Proteins/metabolism , Ubiquitin-Protein Ligases/metabolism , Animals , Cell Cycle Proteins , HeLa Cells , Humans , Lipid Metabolism/physiology , Liposomes/metabolism , Mice , PC12 Cells , Protein Binding , Rats , Tumor Cells, Cultured , UbiquitinationABSTRACT
A 52-year-old man was found to have a severely dilated aortic root and a Stanford type A dissection on familial screening echocardiography, following diagnosis of a dilated aorta in his son. The dissection required urgent surgical repair. Clinical examination suggested features of Loeys-Dietz syndrome type II, and subsequent demonstration of a mutation in the TGFBR1 gene in the patient and his son confirmed the diagnosis. This article highlights the high prevalence of inherited conditions in dilated aortic root presentations and the importance of family screening and surveillance to allow early surgical intervention.
Subject(s)
Loeys-Dietz Syndrome/diagnosis , Diagnosis, Differential , Echocardiography , Humans , Loeys-Dietz Syndrome/genetics , Loeys-Dietz Syndrome/surgery , Male , Middle Aged , Mutation , Pedigree , Protein Serine-Threonine Kinases/genetics , Receptor, Transforming Growth Factor-beta Type I , Receptors, Transforming Growth Factor beta/genetics , Tomography, X-Ray ComputedABSTRACT
In this review we focus on Charcot-Marie-Tooth (CMT) neuropathies and hereditary spastic paraplegias (HSPs). Although these diseases differ in whether they primarily affect the peripheral or central nervous system, both are genetically determined, progressive, long axonopathies that affect motor and sensory pathways. This commonality suggests that there might be similarities in the molecular pathology underlying these conditions, and here we compare the molecular genetics and cellular pathology of the two groups.