No abstract

Environmental factors shared by co-twins affect BMI in childhood, but little evidence for their contribution was found in late adolescence. Our results suggest that genetic factors play a major role in the variation of BMI in adolescence among populations of different ethnicities exposed to different environmental factors related to obesity.

All Mendelian hypertension syndromes described to date involve increased sodium reabsorption in the distal nephron. 5 The sole exception is autosomal-dominant hypertension with BDE (HTNB, OMIM #112410), first reported in a Turkish kindred. 2,6 HTNB was linked to chromosome 12p in six unrelated families. 2,7,8 The locus accounts for a ~50 mm Hg mean blood pressure difference at age 50 years. 2 The penetrance is 100% (Fig. 1a). Previously, we reported a rearrangement on chromosome 12p common to all families. 8,9 A linkage study in Chinese hypertensive families without BDE coincided with the HTNB locus, supporting relevance to essential hypertension. 10 Whole-genome sequencing of Turkish family members revealed a heterozygous missense mutation in PDE3A (Gene ID: 5139), a gene encoding a cGMP/cAMP phosphodiesterase with a prominent role in the heart, VSMC, oocytes and platelets. 11 Resequencing of all 48 affected persons in six unrelated families identified six independently clustered heterozygous missense mutations in exon 4 (Fig. 1a, b Supplementary Fig. 1).We detected none of the previously described chromosomal breakpoints on chromosome 12p12.2-12.1, perhaps due to high repetitive content in the breakpoint regions Fig. 2a-c). 4 A haplotype analysis identified a novel recombination that reduced the linkage interval and eliminated an inversion common to all affected individuals in the six families (Fig. 2c). 9 In contrast, the affected mother's haplotype showed co-segregation with the more severe brachydactyly phenotype.PDEs are involved during early stages of osteogenesis. 12 PDE4D mutations have been associated with severe brachydactyly in acrodysostosis. 13,14 In mice, Pde3a was expressed in the developing limbs, consistent with a role during chondrogenesis (Fig. 2d, Supplementary Fig. 3a, b). Chondrogenic downregulation of PTHLH encoding PTHrP was associated with BDE. 15 We also observed PTHLH downregulation in chondrogenically induced fibroblasts from affected persons (Fig. 2e, Supplementary Fig. 3c).We addressed the functional consequences of the identified PDE3A mutations in HeLa cells expressing the six mutations. Forskolin or L-arginine stimulated the adenylate or guanylate cyclases to enhance cellular cAMP or cGMP levels, respectively. 16,17 We detected significantly reduced cAMP levels, consistent with gain-of-function mutations with no change in cGMP levels for the PDE3A mutations ( Supplementary Fig. 4a, b). Three PDE3A isoforms, PDE3A1 (microsomal), PDE3A2 and PDE3A3 (microsomal and cytosolic), have been identified in human myocardium. 18,19 PDE3A3 does not contain the sequence harboring the detected mutations. The predominant isoform in VSMC is PDE3A2. 18,20 To directly elucidate the mutations' effects, we compared the Michaelis-Menten kinetics of cAMPhydrolytic activity for recombinant T445N FLAG-tagged PDE3A1 and PDE3A1-WT and the tagged A2 isoforms purified from transfected cells (Fig. 3a, b, Supplementary Fig. 4d-k). The T445N mutation increased the affinity of both enzyme's isoforms for cAM...

Objective: Serum-and glucocorticoid-inducible kinase 1 (SGK1) inhibits the ubiquitin ligase neuronal cell expressed developmentally downregulated 4-2 (Nedd4-2), which retards the retrieval of the epithelial Na ϩ channel ENaC. Accordingly, SGK1 enhances ENaC abundance in the cell membrane. The significance of this effect is shown by an association of an E8CC/CT;I6CC polymorphism in the SGK1 gene with increased blood pressure. However, strong expression of SGK1 in enterocytes not expressing ENaC points to further functions of SGK1. This study was performed to test for regulation of Na ϩ -coupled glucose transporter 1 (SGLT1) by Nedd4-2, SGK1, and/or the related kinases SGK3 and PKB. Additional studies searched for an association of the SGK1 gene with BMI. Research Methods and Procedures: mRNA encoding SGLT1, wild-type Nedd4-2, inactive C938S Nedd4-2, wild type SGK1, constitutively active S422D SGK1 or inactive K127N SGK1, wild-type SGK3, and constitutively active T308DS473D PKB or inactive T308AS473A PKB were injected into Xenopus oocytes, and glucose transport was quantified from glucose-induced current (I glc ). BMI was determined in individuals with or without the E8CC/CT;I6CC polymorphism. Results: I glc was significantly decreased by coexpression of Nedd4-2 but not of C938S Nedd4-2. Coexpression of SGK1, S422D SGK1, SGK3, or T308DS473D PKB, but not of K127N SGK1 or T308AS473A PKB, enhanced I glc and reversed the effect of Nedd4-2. SGK1 and SGK3 phosphorylated Nedd4-2. Deletion of the SGK/PKB phosphorylation sites in Nedd4-2 blunted the kinase effects. BMI was significantly (p Ͻ 0.008) greater in individuals with the E8CC/CT;I6CC polymorphism than in individuals without. Discussion: Overactivity of SGK1 may lead not only to excessive ENaC activity and hypertension but also to enhanced SGLT1 activity and obesity.