Inside Lab Invest

Abstract

Pseudoxanthoma elasticum (PXE) is a connective tissue disease caused by a deficiency in the ABCC6 gene, which encodes the multidrug resistanceassociated protein 6 (MRP6). ABCC6 is a member of the large ATP binding-cassette (ABC) transporter superfamily. To date, very little is known about the function of MRP6, except that it is highly expressed in the liver and the kidney, in which it is assumed to serve as an efflux pump transporting intracellular organic anions into the blood. Very low MRP6 levels are found in the tissues directly affected by PXE, such as dermal fibroblasts. Consequently, the causative link between MRP6 deficiency and PXE has not been deciphered. In this issue, Hendig et al hypothesize that compensatory expression of some of the other members of the large ABC transporter family could impair the function of elastic fibers in connective tissues. The authors compared the expression of 47 ABC transporter genes between dermal fibroblasts from PXE patients and healthy controls and found that, in addition to ABCC6 deficiency, PXE patients exhibit a more than twofold altered expression in