Poppe, B. | Search bioRxiv

bioRxiv2021

Loss of adipocyte phospholipase gene PLAAT3 causes lipodystrophy and insulin resistance due to inactivated arachidonic acid-mediated PPAR signaling

PLAAT3 is a phospholipid modifying enzyme predominantly expressed in white adipose tissue (WAT). It is a candidate drug target as Plaat3 deficiency in mice protects against picornavirus infection and diet-induced obesity. We identified four patients with homozygous loss-of-function mutations in PLAAT3, presenting with partial lipodystrophy, severe insulin resistance and dyslipidemia. PLAAT3-deficient WAT showed a failure to liberate arachidonic acid (AA) from membrane phospholipids resulting in an inactive gene network downstream of adipogenesis master regulator and anti-diabetic drug target PPARG. These findings establish PLAAT3 deficiency in humans as a novel type of partial lipodystrophy due to an AA- and PPARG-dependent defect in WAT differentiation and function.

genetics↗

bioRxiv2018

Loss-of-function in IRF2BPL is associated with neurological phenotypes

The Interferon Regulatory Factor 2 Binding Protein Like (IRF2BPL) gene encodes a member of the IRF2BP family of transcriptional regulators. Currently the biological function of this gene is obscure, and the gene has not been associated with a Mendelian disease. Here we describe seven individuals affected with neurological symptoms who carry damaging heterozygous variants in IRF2BPL. Five cases carrying nonsense variants in IRF2BPL resulting in a premature stop codon display severe neurodevelopmental regression, hypotonia, progressive ataxia, seizures, and a lack of coordination. Two additional individuals, both with missense variants, display global developmental delay and seizures and a relatively milder phenotype than those with nonsense alleles. The bioinformatics signature for IRF2BPL based on population genomics is consistent with a gene that is intolerant to variation. We show that the IRF2BPL ortholog in the fruit fly, called pits (protein interacting with Ttk69 and Sin3A), is broadly expressed including the nervous system. Complete loss of pits is lethal early in development, whereas partial knock-down with RNA interference in neurons leads to neurodegeneration, revealing requirement for this gene in proper neuronal function and maintenance. The nonsense variants in IRF2BPL identified in patients behave as severe loss-of-function alleles in this model organism, while ectopic expression of the missense variants leads to a range of phenotypes. Taken together, IRF2BPL and pits are required in the nervous system in humans and flies, and their loss leads to a range of neurological phenotypes in both species.

genetics↗