Abstract 008: Genetic Studies Identify A Novel Role Of CCDC93 In Arterial Relaxation And Central Systolic Blood Pressure

Abstract

Previous genome-wide association studies (GWAS) have identified and validated variants at more than 1000 loci with modest effects on population blood pressure (BP), explaining in aggregate ~6% of the trait variance and highlighting genetic differences in BP regulation in ethnically diverse populations. We performed an exome-wide association study (EWAS) in Han Chinese population (N=5,954) from Beijing and identified 4 EWAS single nucleotide polymorphism (SNP)-trait associations with 3 SNPs, including two novel associations (rs2165468-peripheral systolic BP and rs33975708-central systolic BP (cSBP). rs33975708 is a coding variant in the coiled-coil domain containing 93 ( CCDC93 ) gene, c.535C>T, p.Arg179Cys (MAF=0.15%) and was associated with substantially increased cSBP (β=29.3 mmHg, P =1.23E-7) in Han Chinese population. CRISPR/Cas9 was used to introduce this variant in mice to investigate vascular molecular mechanisms. While this did not yield a viable mouse with the specific SNP, we did generate mice with an out of frame deletion making a gene knock-out. Ccdc93 deletion ( Ccdc93 -/- ) in its homozygous form was embryonic lethal (<E10.5). Ccdc93 +/- heterozygous mice were viable and morphologically normal and displayed 1.31-fold lower aortic Ccdc93 protein expression (P=0.0041, N=6). Systolic BP was higher in Ccdc93 +/- mice (110±8 mmHg vs 125±10 mmHg, P=0.016, N=5-7) and showed impaired acetylcholine (Ach)-induced relaxation (max Ach 86% vs 68%, P<0.03) and enhanced phenylephrine (PE)-induced contraction (max PE 123% vs 198% normalized to KCL response, P<0.03, N=5) in thoracic aorta ex vivo . Transcriptome analysis by RNA-seq of thoracic aorta identified significantly enriched biological processes in Ccdc93 +/- among the pathways altered in fatty acid metabolic process (adjusted P=2.9E-9) together with mitochondrial metabolism (P=1.3E-14). Plasma free fatty acid levels were higher in Ccdc93 +/- mice (96±7 μM vs 124±13 μM, P=0.0031, N=6) and aortic parkin protein expression, a marker of mitochondrial dysfunction, was 1.63-fold higher (P=0.028, N=6). In conclusion, our genetic and functional studies indicate a potential novel role of CCDC93 on blood pressure regulation through its effects on vascular mitochondrial function.