Pseudohypoaldosteronism: molecular characterization of the mineralocorticoid receptor.

Abstract

Mineralocorticoid resistance (pseudohypoaldosteronism) is a rare condition first described in 1958 and associated with failure to thrive, salt wasting, and dehydration in infancy. In the index case it has previously been shown that binding of aldosterone to mineralocorticoid receptors in peripheral blood lymphocytes is absent; here, we report results of the molecular characterization of the mineralocorticoid receptor in this patient. Genomic DNA extracted from peripheral blood lymphocytes was subjected to Southern blot analysis after digestion with various restriction enzymes. There was no evidence of a major gene rearrangement or deletion. Oligonucleotide primers were designed on the basis of the published human complementary DNA sequence to cover the entire open reading frame of the mineralocorticoid receptor (MR). Total messenger ribonucleic acid (RNA) from lymphocytes was subjected to reverse transcription and amplification using the reverse transcriptase-polymerase chain reaction; the resulting fragments were then purified, subcloned, and sequenced. The patient showed no abnormality in the complementary DNA sequence corresponding to the open reading frame of the MR molecule compared with the published sequence. In addition, semiquantitative assessment of the patient's MR messenger RNA based on the reverse transcriptase-polymerase chain reaction technique suggested that he was producing MR RNA in roughly normal quantities. The mechanism of mineralocorticoid resistance in this case, therefore, remains uncertain, and the possibility must be considered that the underlying abnormality is not in the MR gene, but in an independent gene acting through yet to be characterized processes.

Functional polymorphisms in the mineralocorticoid receptor and amirolide-sensitive sodium channel genes in a patient with sporadic pseudohypoaldosteronism

“…One MR allele is knocked out in affected members in the kindred described by Geller et al (1998) suggesting that full expression of both MR alleles is required for normal salt conservation. However, patients with PHA, especially with sporadic PHA, do not always exhibit abnormalities in the genes for ENaC or MR (Arai et al 1994(Arai et al , 1995(Arai et al , 1999Corvol and Funder 1994;Komesaroff et al 1994;Zennaro et al 1994). Polymorphisms in the genes for MR or ENaC are found not only in patients with PHA, but are also normal features of the population at large.…”

Human Mineralocorticoid Receptor Genomic Structure and Identification of Expressed Isoforms

“…DNA of positive clones was prepared following standard techniques (14). Cosmid and phage DNA was digested with different restriction enzymes and characterized by Southern blot analysis using specific [␥- 32 P]dATP-labeled oligonucleotides as probes (15,16). Positive restriction fragments were subcloned and sequenced by the dideoxy chain termination method (17) using Sequenase (U. S. Biochemical Corp.).…”

Syndromes of glucocorticoid and mineralocorticoid resistance

“…The discovery of decreased aldosterone binding in peripheral blood mononuclear leukocytes of several unrelated patients (108,109) has prompted a series of molecular studies to characterize the defect. However, analysis of MR in seven different patients, including both renal and generalized forms, familial autosomal dominant or recessive transmission and sporadic cases, has shown that no major rearrangement was present in the hMR gene (110)(111)(112)(113). Furthermore, hMR was shown to be expressed in apparently normal amounts in peripheral mononuclear cells, and no abnormality was found in the sequence of the hMR coding region and portions of the 5 0 -untranslated and regulatory regions.…”