TRUSTEES OF BOSTON UNIVERSITY

Essential hypertension is a major public health concern due to its high prevalence and its role as a leading risk factor for leading causes of death and morbidity in the developed world - coronary artery disease, stroke, chronic renal disease and peripheral vascular disease. Elucidation of underlying genetic mechanism is critical but remains elusive due to its polygenic nature and added complexity brought on by environmental factors. We reported the association of ATP1A1 (alpha 1 Na,K-ATPase, P<0.000005) and DEspR (dual endothelin-1/vascular growth factor signal peptide receptor, P<0.03) with hypertension/normotension in a case-control hypertension cohort from northern Sardinia. We detected stronger association of both loci with hypertension/normotension in males than in females pointing to the 5'-regulatory region as harboring putative variants underlying their associations. Follow up studies identified a 4T deletion/insertion polymorphism (4Tdelins) and a C/T (rs6535847) polymorphism within the ATP1A1 and DEspR promoter regions respectively associated with decreased susceptibility to hypertension in the male population. The C/T (rs6535847) polymorphism modifies a CATAAAA sequence present in DEspR promoter region to generate a new TATAAAA- box, suggesting a putative effect on DEspR transcription. These results form the basis for our current application in which we plan to investigate the ATP1A1 4T ins and DEspR rs6535847 T alleles as potential functional variants accounting for the decreased risk of hypertension susceptibility conferred by these two protective alleles in the male Sardinian population. Thus, the following specific aims are prioritized: AIM 1: We will test the transcriptional activity of ATP1A1 promoter region carrying either the 4T ins (p4Tins) or the 4T del (p4Tdel) alleles and DEspR promoter region harboring either the rs6535847 C (pCATAAAA) or the rs6535847 T alleles (pTATAAAA) in tissue culture cells using SEAP (a secreted form of human placental alkaline phosphatase) as a reporter molecule to monitor activity. AIM 2: We will investigate the effect of DEspR and ATP1A1 haploinsufficiency on blood pressure by measuring blood pressure by radiotelemetry in young (4 months of age) and aging (16 months of age) DEspR, ATP1A1 and wild-type mice. This will assess in a biological context the putative effects of differential DEspR and ATP1A1 expression levels on blood pressure. Accomplishing the proposed specific aims will elucidate DEspR and ATP1A1 functional polymorphisms that confer sex- specific protection to essential hypertension in a genetically isolated population from northern Sardinia. Moreover, these results could shed key insight into setting the direction for the investigation of genetic susceptibility to hypertension in the general population. PUBLIC HEALTH RELEVANCE: Project Narrative Hypertension is a leading risk factor for heart disease, stroke and renal failure. Despite increasing efforts to decipher the genetic mechanisms of hypertension and its target organ associated complications, the genetic underpinnings of hypertension remain to be fully elucidated. Our research will help to establish two genetic factors associated with development of hypertension in a northern Sardinian population. This information will provide a framework to investigate further their respective roles in hypertension in the general population and help to improve intervention and prevention strategies for essential hypertension and its target organ complications.

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