Functional consequences of naturally occurring mutations in human uroporphyrinogen decarboxylase

Abstract

Functional consequences of 12 mutations-10 missense, 1 splicing defect, and 1 frameshift mutation-were characterized in the uroporphyrinogen decarboxylase (URO-D) gene found in Utah pedigrees with familial porphyria cutanea tarda (F-PCT). All but one mutation altered a restriction site in the URO-D gene, permitting identification of affected relatives using a combination of polymerase chain reaction and restriction enzyme digestion. In a bacterial expression system, 3 of the missense mutants were found in inclusion bodies, but 7 were expressed as soluble proteins. Enzymatic activity of soluble, recombinant mutant URO-D genes ranged from 29% to 94% of normal. URO-D mRNA levels in Epstein-Barrvirus transformed cells derived from patients were normal (with the exception of the frameshift mutation) even though protein levels were lower than normal, suggesting that missense mutations generally cause unstable URO-Ds in vivo. The crystal structures of 3 mutant URO-Ds were solved, and the structural consequences of the mutations were defined. All missense mutations reported here and by others were mapped to the crystal structure of URO-D, and structural effects were predicted. These studies define structural and functional consequences of URO-D mutations occurring in patients with F-PCT. (Blood. 2001;98:3179-3185)

Assignment of the ovine uroporphyrinogen decarboxylase (UROD) gene to chromosome 1p34→p36 by fluorescence in situ hybridization

“…Porphyrias are mainly hereditary; however, they can also be induced by exogenous factors. Depending on which enzyme of the heme biosynthesis is defective, different types of porphyrias can be discriminated (Phillips et al, 2001). Porphyria cutanea tarda (PCT), caused by a defect of the uroporphyrinogen decarboxylase, is a chronic hepatic porphyria and most often the form of porphyrias in man (Egger et al, 2002).…”

Structure of the Thermolabile Mutant Aldolase B, A149P: Molecular Basis of Hereditary Fructose Intolerance

“…[15][16][17][18] This is due to the inherent difficulty of structural analysis of unstable proteins. Here, the structure of one such protein, AP-aldolase, is determined by X-ray crystallography at 4 8C and 18 8C, revealing the molecular basis of the structural perturbations and loss of activity with increased temperature.…”

Familial and Sporadic Porphyria Cutanea Tarda: Characterization and Diagnostic Strategies

“…Gene-marker studies of c.578GϾC indicate that this variant is a founder mutation that originated in the northwestern part of southern Norway (data not shown). c.578GϾC was first reported in a patient in Utah (15 ), and gene-marker analysis demonstrated that this patient was a descendent of the same ancestor. The sequence variant c.636ϩ1GϾC, which has been found in several unrelated patients, represents either an ancient mutational event or a hot spot for recurrent mutations (3,15,16 ).…”

“…c.578GϾC was first reported in a patient in Utah (15 ), and gene-marker analysis demonstrated that this patient was a descendent of the same ancestor. The sequence variant c.636ϩ1GϾC, which has been found in several unrelated patients, represents either an ancient mutational event or a hot spot for recurrent mutations (3,15,16 ). All of our patients with the c.636ϩ1GϾC variant also carried the T allele in the single-nucleotide polymorphism c.636ϩ30GϾT (rs11211066), an observation compatible with a common origin of this mutation on a UROD haplotype with the rarer allele (T) in position c.636ϩ30.…”

“…We thank Solveig Blaaflat and Hanne Margrethe Jacobsen on behalf of the Norwegian Porphyria Centre and the Centre for Medical Genetics and Molecular Medicine, Haukeland University Hospital; Vo Tri Toan, University of Bergen, for his work on S65C in healthy Norwegians; and Dr. John D. Philips, University of Utah School of Medicine, for supplying a DNA sample from the previously described c.578GϾC patient (15 ).…”