Determinants of DNA sequence specificity of the androgen, progesterone, and glucocorticoid receptors: evidence for differential steroid receptor response elements.

While androgen, progesterone, and glucocorticoid receptors perform distinct physiological functions by regulating unique sets of genes, in vitro they can transactivate a common high-affinity DNA-binding target. Naturally occurring steroid response elements display nucleotide divergence that lowers binding affinity in comparison to the optimal binding element, but enhances receptor-type specificity. We investigated the role of nucleotide deviations within the DNA-binding site for contribution to steroid receptor specificity. We hypothesized that receptor specificity drives the evolution of binding site sequence, rather than strictly receptor-binding affinity. Receptor-selective targets can evolve by some nucleotides selected on the basis of additional bond energy, and others may be selected by differential tolerance to discourage binding from inappropriate receptors. To identify receptor-specific binding sites, we mimicked these dual selection pressures in a receptor-competitive environment in which DNA binding sites for the androgen or progesterone receptors were selected in the presence of the glucocorticoid receptor. These analyses also demonstrated that steroid receptors strongly select nucleotides in the spacer and flanking regions of the half-site and do so in an asymmetric fashion, indicating that steroid receptors interact with DNA in an allosteric manner that affects the transcriptional activation potential.

A grandpaternally derived de novo deletion within Xp21 initially presenting in carrier females diagnosed as Kugelberg-Welander syndrome.

We report on two sisters with a history of muscle weakness and an electromyogram (EMG) diagnosis of Kugelberg-Welander syndrome (KWS) or juvenile spinal muscular atrophy. A half-brother to these women was diagnosed to have Duchenne muscular dystrophy (DMD). Using molecular probes, we identified a deletion within Xp21 in this isolated case of DMD. Sequences detected by pXJ1.1 are deleted, while fragments detected by pERT87 are intact. Both of these probes are derived from the DMD locus. We have shown that the affected sisters share with their half-brother DNA markers that are linked to the DMD gene and inherited from their maternal grandfather. Dosage analysis of Southern blots show monosomy for pXJ1.1, which has allowed us to determine carrier status within this family and to show that the half-sisters are manifesting DMD carriers.

Prenatal diagnosis in Becker muscular dystrophy.

Prenatal diagnosis in a pregnancy at risk for Becker muscular dystrophy is reported. The diagnosis was made prior to 12 weeks of gestation by typing a CVS sample for DNA markers.

Isolation and characterization of DNA probes from a flow-sorted human chromosome 8 library that detect restriction fragment length polymorphism (RFLP).

We have used a recombinant DNA library constructed from flow-sorted human chromosome 8 as a source of single-copy human probes. These probes have been screened for restriction fragment length polymorphism (RFLP) by hybridization to Southern transfers of genomic DNA from five unrelated individuals. We have detected six RFLPs distributed among four probes after screening 741 base pairs for restriction site variation. These RFLPs all behave as codominant Mendelian alleles. Two of the probes detect rare variants, while the other two detect RFLPs with PIC values of .36 and .16. Informative probes will be useful for the construction of a linkage map for chromosome 8 and for the localization of mutant alleles to this chromosome.