Whole-exome sequencing identifies ADRA2A mutation in atypical familial partial lipodystrophy

Despite identification of causal genes for various lipodystrophy syndromes, the molecular basis of some peculiar lipodystrophies remains obscure. In an African-American pedigree with a novel autosomal dominant, atypical familial partial lipodystrophy (FPLD), we performed linkage analysis for candidate regions and whole-exome sequencing to identify the disease-causing mutation. Affected adults reported marked loss of fat from the extremities, with excess fat in the face and neck at age 13-15 years, and developed metabolic complications later. A heterozygous g.112837956C>T mutation on chromosome 10 (c.202C>T, p.Leu68Phe) affecting a highly conserved residue in adrenoceptor alpha 2A (ADRA2A) was found in all affected subjects but not in unaffected relatives. ADRA2A is the main presynaptic inhibitory feedback G protein-coupled receptor regulating norepinephrine release. Activation of ADRA2A inhibits cAMP production and reduces lipolysis in adipocytes. As compared with overexpression of a wild-type ADRA2A construct in human embryonic kidney-293 cells and differentiated 3T3-L1 adipocytes, the mutant ADRA2A produced more cAMP and glycerol, which were resistant to the effects of the alpha 2-adrenergic receptor agonist clonidine and the a2-adrenergic receptor antagonist yohimbine, suggesting loss of function. We conclude that heterozygous p.Leu68Phe ADRA2A mutation causes a rare atypical FPLD, most likely by inducing excessive lipolysis in some adipose tissue depots.