Sibpair studies implicate chromosome 18 in essential hypertension

Association of NEDD4L Ubiquitin Ligase With Essential Hypertension

NEDD4L is a ubiquitin ligase that controls cell surface expression of kidney epithelial Na+ channels by ubiquitin-mediated endocytosis and lysosome targeting. Thus, it is a significant determinant of Na+ reabsorption in the distal nephron. The NEDD4L gene is located on human chromosome 18q21 within several blood pressure quantitative trait loci, including those for familial orthostatic hypotension, essential hypertension, pulse pressure, and systolic blood pressure response to postural challenge. Because of the importance of NEDD4L to Na+ balance, many of these studies have proposed that mutations in NEDD4L may be responsible for these blood pressure phenotypes. To test this hypothesis, we fine-mapped the NEDD4L region in 2 families with orthostatic hypotension, which we previously reported to be linked to human chromosome 18q21 but failed to implicate NEDD4L in these families. We also typed multiple NEDD4L single-nucleotide polymorphisms (SNPs) in a collection of US whites, Greek whites, and African-Americans individuals with essential hypertension. A significant association between several SNPs and hypertension was observed in all 3 populations. One of the SNPs associated in African Americans is known to result in premature truncation of the NEDD4L protein. Thus, genetic variation in NEDD4L may play a role in the development or progression of some forms of abnormal blood pressure.

Autosomal genome scan for loci linked to blood pressure levels and trends since childhood: the Bogalusa Heart Study

Genetic loci influencing the long-term levels and trends of blood pressure over time were investigated using 775 white siblings, ages 13 to 43 years, enrolled in the Bogalusa Heart Study, and 357 microsatellite markers on the 22 autosomal chromosomes. Subjects had been examined serially 2 to 12 times with 4365 serial observations over an average of 22 years from childhood to adulthood. Total and incremental area under the curve was calculated based on a cubic growth curve and used as long-term levels and trends, respectively. After adjusting for age, sex, and body mass index, heritability estimates of total area were 0.66 for systolic and 0.68 for diastolic blood pressure. Heritability of incremental area was 0.38 for systolic and 0.46 for diastolic blood pressure. Significant linkage to the total area of diastolic blood pressure (peak logarithm of odds [LOD]=3.9 at 73 cM) was observed on chromosome 2, with a region spanning from 44 cM to 103 cM showing supporting linkage evidence of LOD >3.0. In addition, suggestive linkage for total area of systolic (LOD=1.6 at 182 cM) and diastolic blood pressure (LOD=2.0 at 36 cM) on chromosome 4 and diastolic blood pressure incremental area (LOD=2.2 at 28 cM) on chromosome 18 was noted. Several hypertension candidate genes such as alpha-adducin, beta-adducin, sodium bicarbonate co-transporter, and G protein-coupled receptor kinase 4 are located in these regions. Linkage evidence found in this community-based study indicates that regions on these chromosomes harbor genetic loci that affect the propensity for development of hypertension from childhood.