Private practice and general practice

Abstract

<h3>Background</h3> 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. <h3>Methods</h3> Whole-exome sequencing was performed to identify the genetic causes of these disorders. Mutations were functionally validated in zebrafish <i>pnpla6</i> 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. <h3>Results</h3> Eight mutations in six families with Oliver–McFarlane or Laurence–Moon syndrome were identified in the <i>PNPLA6</i> gene, which encodes neuropathy target esterase (NTE). <i>PNPLA6</i> expression was found in the developing human eye, pituitary and brain. In zebrafish, the <i>pnpla6</i> curly-tailed morphant phenotype was fully rescued by wild-type human <i>PNPLA6</i> 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. <h3>Conclusions</h3> Previously, <i>PNPLA6</i> mutations have been associated with spastic paraplegia type 39, Gordon–Holmes syndrome and Boucher–Neuhäuser syndromes. Discovery of these additional <i>PNPLA6</i>-opathies further elucidates a spectrum of neurodevelopmental and neurodegenerative disorders associated with NTE impairment and suggests a unifying mechanism with diagnostic and prognostic importance.