Reorganization of inter-chromosomal interactions in the 2q37-deletion syndrome.

Chromosomes occupy distinct interphase territories in the three-dimensional nucleus. However, how these chromosome territories are arranged relative to one another is poorly understood. Here, we investigated the inter-chromosomal interactions between chromosomes 2q, 12, and 17 in human mesenchymal stem cells (MSCs) and MSC-derived cell types by DNA-FISH We compared our findings in normal karyotypes with a three-generation family harboring a 2q37-deletion syndrome, featuring a heterozygous partial deletion of histone deacetylase 4 (HDAC4) on chr2q37. In normal karyotypes, we detected stable, recurring arrangements and interactions between the three chromosomal territories with a tissue-specific interaction bias at certain loci. These inter-chromosomal interactions were confirmed by Hi-C. Interestingly, the disease-related HDAC4 deletion resulted in displaced inter-chromosomal arrangements and altered interactions between the deletion-affected chromosome 2 and chromosome 12 and/or 17 in 2q37-deletion syndrome patients. Our findings provide evidence for a direct link between a structural chromosomal aberration and altered interphase architecture that results in a nuclear configuration, supporting a possible molecular pathogenesis.

Clinical effects of phosphodiesterase 3A mutations in inherited hypertension with brachydactyly.

Autosomal-dominant hypertension with brachydactyly is a salt-independent Mendelian syndrome caused by activating mutations in the gene encoding phosphodiesterase 3A. These mutations increase the protein kinase A-mediated phosphorylation of phosphodiesterase 3A resulting in enhanced cAMP-hydrolytic affinity and accelerated cell proliferation. The phosphorylated vasodilator-stimulated phosphoprotein is diminished, and parathyroid hormone-related peptide is dysregulated, potentially accounting for all phenotypic features. Untreated patients die prematurely of stroke; however, hypertension-induced target-organ damage is otherwise hardly apparent. We conducted clinical studies of vascular function, cardiac functional imaging, platelet function in affected and nonaffected persons, and cell-based assays. Large-vessel and cardiac functions indeed seem to be preserved. The platelet studies showed normal platelet function. Cell-based studies demonstrated that available phosphodiesterase 3A inhibitors suppress the mutant isoforms. However, increasing cGMP to indirectly inhibit the enzyme seemed to have particular use. Our results shed more light on phosphodiesterase 3A activation and could be relevant to the treatment of severe hypertension in the general population.

PDE3A mutations cause autosomal dominant hypertension with brachydactyly.

Cardiovascular disease is the most common cause of death worldwide, and hypertension is the major risk factor. Mendelian hypertension elucidates mechanisms of blood pressure regulation. Here we report six missense mutations in PDE3A (encoding phosphodiesterase 3A) in six unrelated families with mendelian hypertension and brachydactyly type E (HTNB). The syndrome features brachydactyly type E (BDE), severe salt-independent but age-dependent hypertension, an increased fibroblast growth rate, neurovascular contact at the rostral-ventrolateral medulla, altered baroreflex blood pressure regulation and death from stroke before age 50 years when untreated. In vitro analyses of mesenchymal stem cell-derived vascular smooth muscle cells (VSMCs) and chondrocytes provided insights into molecular pathogenesis. The mutations increased protein kinase A-mediated PDE3A phosphorylation and resulted in gain of function, with increased cAMP-hydrolytic activity and enhanced cell proliferation. Levels of phosphorylated VASP were diminished, and PTHrP levels were dysregulated. We suggest that the identified PDE3A mutations cause the syndrome. VSMC-expressed PDE3A deserves scrutiny as a therapeutic target for the treatment of hypertension.