ABSTRACT
BACKGROUND: Oliver-McFarlane syndrome is characterised by trichomegaly, congenital hypopituitarism and retinal degeneration with choroidal atrophy. Laurence-Moon syndrome presents similarly, though with progressive spinocerebellar ataxia and spastic paraplegia and without trichomegaly. Both recessively inherited disorders have no known genetic cause. METHODS: Whole-exome sequencing was performed to identify the genetic causes of these disorders. Mutations were functionally validated in zebrafish pnpla6 morphants. Embryonic expression was evaluated via in situ hybridisation in human embryonic sections. Human neurohistopathology was performed to characterise cerebellar degeneration. Enzymatic activities were measured in patient-derived fibroblast cell lines. RESULTS: Eight mutations in six families with Oliver-McFarlane or Laurence-Moon syndrome were identified in the PNPLA6 gene, which encodes neuropathy target esterase (NTE). PNPLA6 expression was found in the developing human eye, pituitary and brain. In zebrafish, the pnpla6 curly-tailed morphant phenotype was fully rescued by wild-type human PNPLA6 mRNA and not by mutation-harbouring mRNAs. NTE enzymatic activity was significantly reduced in fibroblast cells derived from individuals with Oliver-McFarlane syndrome. Intriguingly, adult brain histology from a patient with highly overlapping features of Oliver-McFarlane and Laurence-Moon syndromes revealed extensive cerebellar degeneration and atrophy. CONCLUSIONS: Previously, PNPLA6 mutations have been associated with spastic paraplegia type 39, Gordon-Holmes syndrome and Boucher-Neuhäuser syndromes. Discovery of these additional PNPLA6-opathies further elucidates a spectrum of neurodevelopmental and neurodegenerative disorders associated with NTE impairment and suggests a unifying mechanism with diagnostic and prognostic importance.
Subject(s)
Blepharoptosis/enzymology , Blepharoptosis/genetics , Carboxylic Ester Hydrolases/genetics , Dwarfism/enzymology , Dwarfism/genetics , Genetic Predisposition to Disease , Hypertrichosis/enzymology , Hypertrichosis/genetics , Intellectual Disability/enzymology , Intellectual Disability/genetics , Laurence-Moon Syndrome/enzymology , Laurence-Moon Syndrome/genetics , Retinitis Pigmentosa/enzymology , Retinitis Pigmentosa/genetics , Alleles , Amino Acid Sequence , Animals , Carboxylic Ester Hydrolases/chemistry , Central Nervous System/pathology , Developmental Disabilities/enzymology , Developmental Disabilities/genetics , Embryonic Development/genetics , Gene Expression Regulation, Developmental , Humans , Molecular Sequence Data , Mutation/genetics , Phenotype , Phospholipases/chemistry , Phospholipases/genetics , Protein Structure, Tertiary , Retina/pathology , Zebrafish/embryologyABSTRACT
Leigh syndrome is a rare pediatric neurodegenerative disorder attributed to impaired mitochondrial energy metabolism. Mutations in SURF1 have been described in several patients with Leigh syndrome associated with cytochrome c oxidase deficiency. We report a new 18-bp deletion (821del18), spanning the splice donor junction of exon 8 of SURF1, in an infant presenting with cytochrome c oxidase-deficient Leigh syndrome and hypertrichosis. cDNA sequencing demonstrated that this deletion results in a messenger lacking exon 8. RT-PCR experiments suggested a rapid degradation of the aberrant mRNA species from the 5'-end.
