Congenital erythropoietic porphyria: prenatal diagnosis and autopsy findings in two sibling fetuses

Congenital erythropoietic porphyria is an autosomal recessive disease characterized by a deficiency of uroporphyrinogen III cosynthetase activity, with diffuse tissue accumulation of specific type I porphyrins. The diagnosis of this disease was made in two fetuses, who were siblings, and from a Caucasian nonconsanguinous family. The first fetus died in utero with hydrops fetalis and anemia, but without an etiopathogenic diagnosis. In the second case, the diagnosis was based on pink fluorescence of the amniotic fluid examined fortuitously in sunlight. DNA analysis showed that the fetus was heteroallelic for the mutation C73R. The autopsy showed brown skin, and at histological examination, porphyrin pigment was deposited in many tissues. Retrospectively, similar deposits were found in the tissues of the first fetus.

Chromosomal localization of the human histone H2A.X gene to 11q23.2-q23.3 by fluorescence in situ hybridization

The human histone H2A.X gene is unusual in that its transcripts are alternatively processed to yield two species, one a 0.6-kb replication-linked histone mRNA and the other a 1.6-kb polyadenylated mRNA. The H2A.X gene has been localized by fluorescence in situ hybridization to chromosome 11q23.2-q23.3, away from the known clusters of human histone genes on chromosomes 1, 6, and 12. Assignment to chromosome 11 was substantiated by analysis of human-hamster somatic cell hybrid lines. As this work was being completed, an 89-bps sequence overlap was found between the downstream regions of the H2A.X gene and the recently sequenced hydroxymethylbilane (HMB)-synthase gene. The H2A.X and HMB-synthase genes have an unusual arrangement, being transcribed towards each other with their polyadenylation sites 330 bp apart. In addition the HMB-synthase gene contains constitutive and erythroid specific promoters. K562, an erythroid cell line, was found to contain a high concentration of the 1.6-kb polyadenylated H2A.X mRNA.

Evidence for an intermediate in the enzymatic formation of uroporphyrinogen III

Evidence for an azafulvene intermediate in the enzymatic formation of Uroporphyrinogen III has been obtained. Using conditions to slow down the enzyme activity (high pH, low temperature), the transient species was trapped with ammonium ions as aminomethylbilane and with sodium borohydride as methylbilane, and observed by 13C-NMR.