New Insights into the Impact of Genome-Wide Copy Number Variations on Complex Congenital Heart Disease in Saudi Arabia.

Congenital heart diseases (CHDs) are complex traits that manifest in diverse clinical phenotypes such as the Tetralogy of Fallot (TOF), valvular and ventricular/atrial septal defects. Genetic mechanisms of CHDs have remained largely unclear to date. Copy number variations (CNVs) have been implicated in many complex diseases but their impact has not been examined extensively in various forms of CHD lesions. We report in this study, to the best of our knowledge, the largest cohort of Saudi Arab CHD patients to date who were evaluated using genome-wide CNV analysis. In a sample of 134 Saudi Arab patients with CHD, 66 exhibited pathogenic or likely pathogenic CNVs. Notably, 21 copy number gains and 11 copy number losses were detected that encompassed 141 genes and 146 genes, respectively. The most frequent gains were on 17q21.31, 8p11.21, and 22q11.23, whereas the losses were primarily localized to 16p11.2. Interestingly, all lesions have had gains at 17q21.31. Septal defects had also gains at 8p11.21 and 22q11.23, valvular lesions at 8p11.21, 22q11.23, and 2q13, and TOF at 16p11.2. Functional and network analyses demonstrated that cardiovascular and nervous system development and function as well as cell death/survival were most significantly associated with CNVs, thus highlighting the potentially important genes likely to be involved in CHD, including NPHP1, PLCB1, KANSL1, and NR3C1. In conclusion, this genome-wide analysis identifies a high frequency of CNVs mostly in patients with septal defects, primarily influencing cardiovascular developmental and functional pathways, thereby offering a deeper insight into the complex networks involved in CHD pathogenesis.

Integrated Left Ventricular Global Transcriptome and Proteome Profiling in Human End-Stage Dilated Cardiomyopathy.

AIMS: The disease pathways leading to idiopathic dilated cardiomyopathy (DCM) are still elusive. The present study investigated integrated global transcriptional and translational changes in human DCM for disease biomarker discovery. METHODS: We used identical myocardial tissues from five DCM hearts compared to five non-failing (NF) donor hearts for both transcriptome profiling using the ABI high-density oligonucleotide microarrays and proteome expression with One-Dimensional Nano Acquity liquid chromatography coupled with tandem mass spectrometry on the Synapt G2 system. RESULTS: We identified 1262 differentially expressed genes (DEGs) and 269 proteins (DEPs) between DCM cases and healthy controls. Among the most significantly upregulated (>5-fold) proteins were GRK5, APOA2, IGHG3, ANXA6, HSP90AA1, and ATP5C1 (p< 0.01). On the other hand, the most significantly downregulated proteins were GSTM5, COX17, CAV1 and ANXA3. At least ten entities were concomitantly upregulated on the two analysis platforms: GOT1, ALDH4A1, PDHB, BDH1, SLC2A11, HSP90AA1, HSP90AB1, H2AFV, HSPA5 and NDUFV1. Gene ontology analyses of DEGs and DEPs revealed significant overlap with enrichment of genes/proteins related to metabolic process, biosynthetic process, cellular component organization, oxidative phosphorylation, alterations in glycolysis and ATP synthesis, Alzheimer's disease, chemokine-mediated inflammation and cytokine signalling pathways. CONCLUSION: The concomitant use of transcriptome and proteome expression to evaluate global changes in DCM has led to the identification of sixteen commonly altered entities as well as novel genes, proteins and pathways whose cardiac functions have yet to be deciphered. This data should contribute towards better management of the disease.

Data on common variants associated with coronary artery disease/myocardial infarction in ethnic Arabs.

The data shows results acquired in a large cohort of 5668 ethnic Arabs involved in a common variants association study for coronary artery disease (CAD) and myocardial infarction (MI) using the Affymetrix Axiom Genotyping platform ("A genome-wide association study reveals susceptibility loci for myocardial infarction/coronary artery disease in Saudi Arabs" Wakil et al. (2015) [1] ). Several loci were described that conferred risk for CAD or MI, some of which were validated in an independent set of samples. Principal Component (PCA) analysis suggested that the Saudi Cohort was close to the CEU and TSI populations, thus pointing to similarity with European populations.

A genome-wide association study reveals susceptibility loci for myocardial infarction/coronary artery disease in Saudi Arabs.

BACKGROUND: Multiple loci have been identified for coronary artery disease (CAD) by genome-wide association studies (GWAS), but no such studies on CAD incidence has been reported yet for any Middle Eastern population. METHODS: In this study, we performed a GWAS for CAD and myocardial infarction (MI) incidence in 5668 Saudis of Arab descent using the Affymetrix Axiom Genotyping platform. RESULTS: We describe SNPs at 16 loci that showed significant (P < 5 × 10(-8)) or suggestive GWAS association (P < 1 × 10(-5)) with CAD or MI, in the ethnic Saudi Arab population. Among the four variants reaching GWAS significance in the present study, the rs10738607_G [0.78(0.71-0.85); p = 2.17E-08] in CDNK2A/B gene was associated with CAD. Two other SNPs on the same gene, rs10757274_G [0.79(0.73-0.86); p = 2.98E-08] and rs1333045_C [0.79(0.73-0.86); p = 1.15E-08] as well as the rs9982601_T [1.38(1.23-1.55); p = 3.49E-08] on KCNE2 were associated with MI. These variants have been previously described in other populations. Several SNPs, including the rs7421388 (PLCL1) and rs12541758 (TRPA1) displaying a suggestive GWAS association (P < 1 × 10(-5)) with CAD as well as rs41411047 (RNF13), rs32793 (PDZD2) and rs4739066 (YTHDF3), similarly showing weak association with MI, were confirmed in an independent dataset. Furthermore, our estimation of heritability of CAD and MI based on observed genome-wide sharing in unrelated Saudi Arabs was approximately 33% and 44%, respectively. CONCLUSIONS: Our study has identified susceptibility variants for CAD/MI in ethnic Arabs. These findings provide further insights into pathways contributing to the susceptibility for CAD and will enable more comprehensive genetic studies of these diseases in Middle East populations.

The Affymetrix DMET Plus platform reveals unique distribution of ADME-related variants in ethnic Arabs.

BACKGROUND: The Affymetrix Drug Metabolizing Enzymes and Transporters (DMET) Plus Premier Pack has been designed to genotype 1936 gene variants thought to be essential for screening patients in personalized drug therapy. These variants include the cytochrome P450s (CYP450s), the key metabolizing enzymes, many other enzymes involved in phase I and phase II pharmacokinetic reactions, and signaling mediators associated with variability in clinical response to numerous drugs not only among individuals, but also between ethnic populations. MATERIALS AND METHODS: We genotyped 600 Saudi individuals for 1936 variants on the DMET platform to evaluate their clinical potential in personalized medicine in ethnic Arabs. RESULTS: Approximately 49% each of the 437 CYP450 variants, 56% of the 581 transporters, 56% of 419 transferases, 48% of the 104 dehydrogenases, and 58% of the remaining 390 variants were detected. Several variants, such as rs3740071, rs6193, rs258751, rs6199, rs11568421, and rs8187797, exhibited significantly either higher or lower minor allele frequencies (MAFs) than those in other ethnic groups. DISCUSSION: The present study revealed some unique distribution trends for several variants in Arabs, which displayed partly inverse allelic prevalence compared to other ethnic populations. The results point therefore to the need to verify and ascertain the prevalence of a variant as a prerequisite for engaging it in clinical routine screening in personalized medicine in any given population.

A new susceptibility locus for myocardial infarction, hypertension, type 2 diabetes mellitus, and dyslipidemia on chromosome 12q24.

We examined the role of hepatic nuclear factor-1 alpha (HNF1a) gene polymorphism on coronary artery disease (CAD) traits in 4631 Saudi angiographed individuals (2419 CAD versus 2212 controls) using TaqMan assay on ABI Prism 7900HT sequence detection system. Following adjustment for confounders, the rs2259820_CC (1.19 (1.01-1.42); P = 0.041), rs2464196_TT (1.19 (1.00-1.40); P = 0.045), and rs2259816_T (1.13 (1.01-1.26); P = 0.031) were associated with MI. The rs2259820_T (1.14 (1.03-1.26); P = 0.011) and rs2464196_C (1.12 (1.02-1.24); P = 0.024) were associated with type 2 diabetes mellitus (T2DM), while the rs2393791_T (1.14 (1.01-1.28); P = 0.032), rs7310409_G (1.16 (1.03-1.30); P = 0.013), and rs2464196_AG+GG (1.25 (1.05-1.49); P = 0.012) were implicated in hypertension. Hypertriglyceridemia was linked to the rs2393791_T (1.14 (1.02-1.27); P = 0.018), rs7310409_G (1.12 (1.01-1.25); P = 0.031), rs1169310_G (1.15 (1.04-1.28); P = 0.010), and rs1169313_CT+TT (1.24 (1.06-1.45); P = 0.008) and high low density lipoprotein-cholesterol levels were associated with rs2259820_T (1.23 (1.07-1.41); P = 0.004), rs2464196_T (1.22 (1.06-1.39); P = 0.004), and rs2259816_T (1.18 (1.02-1.36); P = 0.023). A 7-mer haplotype CATATAC (χ(2) = 7.50; P = 0.0062), constructed from the studied SNPs, was associated with MI, and CATATA implicated in T2DM (χ(2) = 3.94; P = 0.047). Hypertriglyceridemia was linked to TGCGGG (χ(2) = 4.26; P = 0.039), and obesity to ACGGGT (χ(2) = 5.04; P = 0.025). Our results suggest that the HNF1a is a common susceptibility gene for MI, T2DM, hypertension, and dyslipidemia.

A study of the role of GATA2 gene polymorphism in coronary artery disease risk traits.

The GATA2 is a multi-catalytic transcription factor believed to play an important role in regulating inflammatory processes, largely contributory to cardiovascular-related events. However, its role in coronary artery disease (CAD) risk traits remains poorly understood. In a preliminary study using Affymetrix 250K, we established a link on chromosome (chr) 3, which harbors the GATA2 gene, to early onset of CAD in two families with heterozygous familial hyperlipidemia (HFH), suggesting a role for the gene in metabolic-related CAD in the general population. We then sequenced the gene in the families and an additional 200 individuals in the general population, followed by an association study for 8 SNPs on CAD metabolic risk traits in a total of 4557 individuals (2386 CAD cases versus 2171 angiographed controls) by the Applied Biosystems real-time PCR system. The rs1573949_C [1.15(1.00-1.32); p=0.049] was associated with MI, rs7431368_AA [5.2(1.05-26.60); p=0.43] conferred risk for harboring low high density lipoprotein, and obesity was linked to rs10934857_AA [5.69(1.04-30.98); p=0.045] following Bonferroni corrections and multivariate adjustments for confounders. Furthermore, a haplotype CCCGGGTC (χ(2)=4.23; p=0.04) constructed from the eight studied SNPs and its 6-mer derivative CGGGTC (χ(2)=5.05; p=0.025) were associated with CAD. Obesity was associated with the 6-mer CATAAA (χ(2)=3.66; p=0.049), and hypercholesterolemia was linked to the 8-mer CCTGGACC (χ(2)=6.02; p=0.014), but most significantly so with its 5-mer derivative, CTGGA (χ(2)=6.75; p=0.009). On the other hand, high low density lipoprotein was linked to TGG (χ(2)=4.48; p=0.034). Our study points to an association of GATA2 at both SNP and haplotype levels with important metabolic risk traits for atherosclerosis.

A study of the role of GATA4 polymorphism in cardiovascular metabolic disorders.

BACKGROUND: The study was designed to evaluate the association of GATA4 gene polymorphism with coronary artery disease (CAD) and its metabolic risk factors, including dyslipidaemic disorders, obesity, type 2 diabetes and hypertension, following a preliminary study linking early onset of CAD in heterozygous familial hypercholesterolaemia to chromosome 8, which harbours the GATA4 gene. RESULTS: We first sequenced the whole GATA4 gene in 250 individuals to identify variants of interest and then investigated the association of 12 single-nucleotide polymorphisms (SNPs) with the disease traits using Taqman chemistry in 4,278 angiographed Saudi individuals. Of the studied SNPs, rs804280 (1.14 (1.03 to 1.27); p = 0.009) was associated with CAD (2,274 cases vs 2,004 controls), hypercholesterolaemia (1,590 vs 2,487) (1.61 (1.03-2.52); p = 0.037) and elevated low-density lipoprotein-cholesterol (hLDLC) (575 vs 3,404) (1.87 (1.10-3.15); p = 0.020). Additionally, rs3729855_T (1.52 (1.09-2.11; p = 0.013)) and rs17153743 (AG + GG) (2.30 (1.30-4.26); p = 0.005) were implicated in hypertension (3,312 vs 966), following adjustments for confounders. Furthermore, haplotypes CCCGTGCC (χ2 = 4.71; p = 0.041) and GACCCGTG (χ2 = 3.84; p = 0.050) constructed from the SNPs were associated with CAD and ACCCACGC (χ2 = 6.58; p = 0.010) with myocardial infarction, while hypercholesterolaemia (χ2 = 3.86; p = 0.050) and hLDLC (χ2 = 4.94; p = 0.026) shared the AACCCATGT, and AACCCATGTC was associated with hLDLC (χ2 = 4.83; p = 0.028). A 10-mer GACCCGCGCC (χ2 = 7.59; p = 0.006) was associated with obesity (1,631 vs 2,362), and the GACACACCC (χ2 = 4.05; p = 0.044) was implicated in type 2 diabetes mellitus 2,378 vs 1,900). CONCLUSION: Our study implicates GATA4 in CAD and its metabolic risk traits. The finding also points to the possible involvement of yet undefined entities related to GATA4 transcription activity or gene regulatory pathways in events leading to these cardiovascular disorders.

The 3'-UTR of the adiponectin Q gene harbours susceptibility loci for atherosclerosis and its metabolic risk traits.

BACKGROUND: Adiponectin Q is a hormone that modulates several metabolic processes and contributes to the suppression of biochemical pathways leading to metabolic syndrome. Hence, polymorphic changes in the adiponectin Q (ADIPOQ) gene are likely to contribute to metabolic disorders, and consequently lead to atherosclerosis. In the present study, we performed a population-based association study for 8 SNPs in 4646 Saudi individuals (2339 CAD cases versus angiographed 2307 controls) by real-time PCR. METHODS: Linkage analysis was done by the Affymetrix Gene Chip array, sequencing by the MegaBACE DNA analysis system and genotyping accomplished by TaqMan chemistry with the Applied Biosystem real-time Prism 7900HT Sequence Detection System. RESULTS: The rs2241766 (TG + GG) [Odds ratio(95% Confidence Interval = 1.35(1.01-1.72); p = 0.015] and rs9842733A > T [1.48(1.01-2.07); p = 0.042] were associated with hypertension [HTN; 3541 cases vs 1101 controls), following adjustment for the presence of other cardiovascular risk traits. The rs2241766 (TG + GG) was further implicated in harbouring of low high density lipoprotein levels (LHDL; 1353 versus 2156 controls) [1.35(1.10-1.67); p = 0.005], but lost its association with obesity after the adjustment for confounders. Besides, low high density lipoprotein was also linked with rs6444174 (TC + CC) [1.28(1.05-1.59)]. On the other hand, while initial univariate logistic regression analysis pointed to rs1063537 C > T (p = 0.010), rs2082940 C > T (p = 0.035) and rs1063539 G > C (p = 0.035) as being associated with myocardial infarction, significance levels of these relationships were diminished following adjustment for the influence of confounding covariates. Interestingly, haplotyping showed that an 8-mer haplotype GTGCCTCA and several of its derivatives constructed from the studied SNPs were commonly implicated in MI (χ² = 4.12; p = 0.042), HTN (χ² = 6.40; p = 0.011) and OBS (χ² = 5.18; p = 0.023). CONCLUSION: These results demonstrate that the ADIPOQ 3'UTR harbours common susceptibility variants for metabolic risk traits and CAD, pointing to the importance of this region in atherosclerosis disease pathways.

New susceptibility locus for obesity and dyslipidaemia on chromosome 3q22.3.

BACKGROUND: The muscle Ras (MRAS) gene resides on chromosome 3q22.3 and encodes a member of the membrane-associated Ras small GTPase proteins, which function as signal transducers in multiple processes including cell growth and differentiation. Its role in cardiovascular disease is not fully understood yet. In a preliminary study in heterozygous familial hypercholesterolaemia, we identified a locus linking the early onset of coronary artery disease (CAD) to chromosome 3q.22 and elected to sequence the MRAS gene using the MegaBACE DNA analysis system. In the present study, we investigated the association of seven single-nucleotide polymorphisms (SNPs) at this locus with CAD and its dyslipidaemia-related risk traits in 4,650 Saudi angiographed individuals using TaqMan assays by the Applied Biosystems real-time Prism 7900HT Sequence Detection System. RESULTS: Among the studied SNPs, rs6782181 (p = 0.017) and rs9818870T (p = 0.009) were associated with CAD following adjustment for sex, age and other confounding risk factors. The rs6782181_GG also conferred risk for obesity (1,764 cases vs. 2,586 controls) [1.16(1.03-1.30); p = 0.017], hypercholesterolaemia (1,686 vs. 2,744) [1.23(1.02-1.47); p = 0.019], hypertriglyceridaemia (1,155 vs. 3,496) [1.29(1.01-1.45); p = 0.043] and low high-density lipoprotein-cholesterol (lHDL-chol) levels (1,935 vs. 2,401) [1.15(1.02-1.30); p = 0.023] after adjustment. Additionally, rs253662_(CT+TT) [1.16(1.01-1.32); p = 0.030] was associated with lHDL-chol levels. Interestingly, rs253662 (p = 0.014) and rs6782181 (p = 0.019) were protective against acquiring high low-density lipoprotein-cholesterol (hLDL-chol) levels (p = 0.014), while rs1720819 showed similar effects against CAD (p < 0.0001). More importantly, a 7-mer haplotype, ACCTGAC (χ2 = 7.66; p = 0.0056), constructed from the studied SNPs, its 6-mer derivative CCTGAC (χ2 = 6.90; p = 0.0086) and several other shorter derivatives conferred risk for obesity. hLDL-chol was weakly linked to CTAA (χ2 = 3.79; p = 0.052) and CCT (χ2 = 4.32; p = 0.038), while several other haplotypes were protective against both obesity and hLDL-chol level. CONCLUSION: Our results demonstrate that the genomic locus for the MRAS gene confers risk for CAD, obesity and dyslipidaemia and point to the possible involvement of other genes or regulatory elements at this locus, rather than changes in the M-Ras protein function, in these events.

Association of the angiotensinogen gene polymorphism with atherosclerosis and its risk traits in the Saudi population.

BACKGROUND: Angiotensinogen (AGT) constitutes a central component of the renin-angiotensin system that controls the systemic blood pressure and several other cardiovascular functions and may play an important role in atherosclerosis pathways. In this study, we employed TaqMan genotyping assays to evaluate the role of 8 AGT variants in primary hypertension (HTN), type 2 diabetes mellitus (T2DM), and obesity as a possible trigger of coronary artery disease (CAD) in a population of 4615 angiographed native Saudi individuals. METHODS: Linkage analysis was done by using the Affymetrix Gene Chip array, sequencing by using the MegaBACE DNA analysis system and genotyping accomplished by TaqMan chemistry using the Applied Biosystem real-time Prism 7900HT Sequence Detection System. RESULTS: Six variants, rs2067853 GG [Odds ratio(95% Confidence Interval) = 1.44(1.17-1.78); p = 0.001], rs7079 [1.49(1.20-1.85); p < 0.0001], rs699 G [1.19(1.08-1.13); p < 0.0001], rs3789679 A [1.51(1.14-1.99); p = 0.004], rs2148582 GG [1.31(1.11-1.55); p = 0.002] and rs5051 TC + CC [1.32(1.13-1.60); p = 0.001] conferred risk for HTN (3521 cases versus 1094 controls). The rs2067853 (p = 0.042), rs699G (p = 0.007) and rs5051 (p = 0.051) also conferred risk for myocardial infarction (MI; 2982 vs 1633), while rs3789679 A (p < 0.0001) and GA + AA (p < 0.0001) as well as rs4762G (p = 0.019) were associated with obesity (1576 vs 2458). However, while these variants appeared to be also associated with CAD (2323 vs 2292), only the rs7079G (p = 0.035) retained its significant relationship. Interestingly, among the haplotypes constructed from these SNPs, the baseline 8-mer haplotype, GGTGGGGT (χ² = 7.02; p = 0.0081) and another GGCGGAGT (χ² = 5.10; p = 0.024), together with several of their derivatives were associated with HTN. T2DM was associated with two 8-mer haplotypes, GGTAGGAC (χ2 = 5.66; p = 0.017) and ATTGAGAC (χ² = 5.93; p = 0.015), obesity with GGCGGAGT (χ² = 9.49; p = 0.0021) and MI was linked to ATTGGGAC (χ² = 6.68; p = 0.010) and GGTGGGAT (χ² = 4.25; p = 0.039). Furthermore, several causative haplotypes were also shared among the risk traits as well as with CAD. CONCLUSION: These results point to AGT as independently conferring risk for various cardiovascular traits, and possibly interacting with these traits in events leading to atherosclerosis.

A study of the role of the Myocyte-specific Enhancer Factor-2A gene in coronary artery disease.

We evaluated the role of the MEF2A as a risk factor for coronary artery disease (CAD) in 1186 subjects with angiographically documented disease compared with 885 CAD-free individuals in the Saudi population. Screening the gene revealed exon 11 as the most polymorphic of all coding regions, harbouring several substitution polymorphisms and insertion/deletions (indels) at a locus containing an 11 CAG trinucleotide chain and a CCGCCGCCA sequence, which introduced frameshifts and premature stop codons at nt146637 and nt146647, nt146780 or nt146783. While these indels were not significantly associated with CAD, a causative relationship was established for rs1059759 G>C [1.21(1.02-1.43); p=0.029], and a borderline one for rs34851361 A>G [1.22(0.9-1.54); p=0.088]. Importantly, a haplotype 1A-2G-3G-4A-5C-6G-7G-8A constructed from the studied SNPs was also associated with CAD [6.39(0.93-43.75); p=0.0052]. These results identify MEF2A gene as a susceptibility gene for CAD.

Left ventricular global transcriptional profiling in human end-stage dilated cardiomyopathy.

We employed ABI high-density oligonucleotide microarrays containing 31,700 sixty-mer probes (representing 27,868 annotated human genes) to determine differential gene expression in idiopathic dilated cardiomyopathy (DCM). We identified 626 up-regulated and 636 down-regulated genes in DCM compared to controls. Most significant changes occurred in the tricarboxylic acid cycle, angiogenesis, and apoptotic signaling pathways, among which 32 apoptosis- and 13 MAPK activity-related genes were altered. Inorganic cation transporter, catalytic activities, energy metabolism and electron transport-related processes were among the most critically influenced pathways. Among the up-regulated genes were HTRA1 (6.9-fold), PDCD8(AIFM1) (5.2) and PRDX2 (4.4) and the down-regulated genes were NR4A2 (4.8), MX1 (4.3), LGALS9 (4), IFNA13 (4), UNC5D (3.6) and HDAC2 (3) (p<0.05), all of which have no clearly defined cardiac-related function yet. Gene ontology and enrichment analysis also revealed significant alterations in mitochondrial oxidative phosphorylation, metabolism and Alzheimer's disease pathways. Concordance was also confirmed for a significant number of genes and pathways in an independent validation microarray dataset. Furthermore, verification by real-time RT-PCR showed a high degree of consistency with the microarray results. Our data demonstrate an association of DCM with alterations in various cellular events and multiple yet undeciphered genes that may contribute to heart muscle disease pathways.

Differential functional expression of human myocardial G protein receptor kinases in left ventricular cardiac diseases.

The relationship between myocardial G protein receptor kinase (GRK) expression and beta-adrenoceptor signalling in human left heart diseases has not been fully elucidated yet. In this study, we characterized and compared the GRK2-7 expression in patients with left ventricular volume overload disorders and dilated cardiomyopathic hearts, and evaluated the relationship of this expression with alterations in myocardial beta-adrenoceptor signalling in volume overload, in order to test the notion that GRK functional expression is influenced in a disease-specific and selective fashion. We established that GRK2, GRK3, and GRK5 are well expressed, while GRK4, GRK6, and GRK7 are only scarcely detectable in the healthy human heart. Compared to control hearts (n=8), GRK2 mRNA expression was elevated by 71% (P<0.005) in the left ventricle, 110% (P<0.05) in the right ventricle, 130% (P<0.05) in the left atrium, and 1300% (P<0.005) in the right atrium (RA) of the dilated cardiomyopathy hearts (n=6). In the volume overload group (n=10), it was increased by approximately 40% (P<0.05) in the left ventricle, 38% in the right ventricle, 81% (P<0.05) in the left atrium, and 850% (P<0.005) in the right atrium. On the other hand, GRK5 was significantly elevated only in the left ventricle by 68% (P<0.05) in the dilated cardiomyopathy hearts and by 48% (P<0.01) in volume overload patients, while in contrast, GRK3 remained unchanged in dilated cardiomyopathy, but was slightly elevated by 36% (P=0.05) in the right ventricle of the volume overload patients. The alterations in GRK expression were accompanied with a decrease in myocardial beta(1)-adrenoceptor mRNA in all four chambers, and these trends in gene expression were paralleled with those of their immunodetectable protein levels. Furthermore, these changes were in association with a decrease in downstream receptor-stimulated, adenylyl cyclase-mediated functional expression and an increase in ventricular protein kinase A activity. The results point to differences in which myocardial GRKs are regulated in cardiac disease, whereby changes in GRK2 expression may be related to the global effects of the disease on myocardial adrenoceptor function and those in GRK5 may be localized to the ventricles, depending on the nature of the myocardial load.