Senior Corresponding Authors: Matthew E. Hurles, The Wellcome Trust Sanger Institute,

Dissecting the genetic basis of disease risk requires measuring all forms of genetic variation, including SNPs and copy number variants (CNVs), and is enabled by accurate maps of their locations, frequencies and population-genetic properties. We designed a hybrid genotyping array (Affymetrix SNP 6.0) to simultaneously measure 906,600 SNPs and copy number at 1.8 million genomic locations. By characterizing 270 HapMap samples, we developed a map of human CNV (at 2-kb breakpoint resolution) informed by integer genotypes for 1,320 copy number polymorphisms (CNPs) that segregate at an allele frequency>1%. More than 80% of the sequence in previously reported CNV regions fell outside our estimated CNV boundaries, indicating that large (>100 kb) CNVs affect much less of the genome than initially reported. Approximately 80% of observed copy number differences between pairs of individuals were due to common CNPs with an allele frequency >5%, and more than 99% derived from inheritance rather than new mutation. Most common, diallelic CNPs were in strong linkage disequilibrium with SNPs, and most low-frequency CNVs segregated on specific SNP haplotypes.

DNA copy number variation has long been associated with specific chromosomal rearrangements and genomic disorders, but its ubiquity in mammalian genomes was not fully realized until recently. Although our understanding of the extent of this variation is still developing, it seems likely that, at least in humans, copy number variants (CNVs) account for a substantial amount of genetic variation. Since many CNVs include genes that result in differential levels of gene expression, CNVs may account for a significant proportion of normal phenotypic variation. Current efforts are directed toward a more comprehensive cataloging and characterization of CNVs that will provide the basis for determining how genomic diversity impacts biological function, evolution, and common human diseases.

Background-Recent studies have identified critical roles for microRNAs (miRNAs) in a variety of cellular processes, including regulation of cardiomyocyte death. However, the signature of miRNA expression and possible roles of miRNA in the ischemic heart have been less well studied. Methods and Results-We performed miRNA arrays to detect the expression pattern of miRNAs in murine hearts subjected to ischemia/reperfusion (I/R) in vivo and ex vivo. Surprisingly, we found that only miR-320 expression was significantly decreased in the hearts on I/R in vivo and ex vivo. This was further confirmed by TaqMan real-time polymerase chain reaction. Gain-of-function and loss-of-function approaches were employed in cultured adult rat cardiomyocytes to investigate the functional roles of miR-320. Overexpression of miR-320 enhanced cardiomyocyte death and apoptosis, whereas knockdown was cytoprotective, on simulated I/R. Furthermore, transgenic mice with cardiac-specific overexpression of miR-320 revealed an increased extent of apoptosis and infarction size in the hearts on I/R in vivo and ex vivo relative to the wild-type controls. Conversely, in vivo treatment with antagomir-320 reduced infarction size relative to the administration of mutant antagomir-320 and saline controls. Using TargetScan software and proteomic analysis, we identified heat-shock protein 20 (Hsp20), a known cardioprotective protein, as an important candidate target for miR-320. This was validated experimentally by utilizing a luciferase/GFP reporter activity assay and examining the expression of Hsp20 on miR-320 overexpression and knockdown in cardiomyocytes. Conclusions-Our data demonstrate that miR-320 is involved in the regulation of I/R-induced cardiac injury and dysfunction via antithetical regulation of Hsp20. Thus, miR-320 may constitute a new therapeutic target for ischemic heart diseases. Key Words: apoptosis Ⅲ ischemia Ⅲ microRNA Ⅲ myocardial infarction Ⅲ reperfusion M ore than 1 million Americans suffer from myocardial infarction every year. 1 Both human autopsy data and evidence from rodent models of myocardial infarction indicate that most cell death happens by apoptosis during the initial 2 to 4 hours after coronary occlusion. 2,3 Clinical treatment of myocardial infarction by thrombolytic therapy and revascularization by percutaneous coronary intervention or coronary artery bypass graft surgery are effective. 1,3 However, given the health, economic, and personal burden caused by ischemic heart disease, research into additional treatment modalities is imperative. Furthermore, the molecular mechanisms that regulate gene expression during myocardial ischemia/reperfusion (I/R) are still not completely understood. Clinical Perspective on p 2366MicroRNAs (miRNAs) are a class of endogenous nonprotein-coding RNAs comprising Ϸ22 nucleotides. 4 -6 They regulate gene expression via RNA-induced silencing complexes, targeting them to mRNAs where they inhibit translation or direct destructive cleavage. 4 -6 Increasing evidence indicates the importa...