RESUMEN
Sequence polymorphisms in a 58-kilobase (kb) interval on chromosome 9p21 confer a markedly increased risk of coronary artery disease (CAD), the leading cause of death worldwide. The variants have a substantial effect on the epidemiology of CAD and other life-threatening vascular conditions because nearly one-quarter of Caucasians are homozygous for risk alleles. However, the risk interval is devoid of protein-coding genes and the mechanism linking the region to CAD risk has remained enigmatic. Here we show that deletion of the orthologous 70-kb non-coding interval on mouse chromosome 4 affects cardiac expression of neighbouring genes, as well as proliferation properties of vascular cells. Chr4(Delta70kb/Delta70kb) mice are viable, but show increased mortality both during development and as adults. Cardiac expression of two genes near the non-coding interval, Cdkn2a and Cdkn2b, is severely reduced in chr4(Delta70kb/Delta70kb) mice, indicating that distant-acting gene regulatory functions are located in the non-coding CAD risk interval. Allele-specific expression of Cdkn2b transcripts in heterozygous mice showed that the deletion affects expression through a cis-acting mechanism. Primary cultures of chr4(Delta70kb/Delta70kb) aortic smooth muscle cells exhibited excessive proliferation and diminished senescence, a cellular phenotype consistent with accelerated CAD pathogenesis. Taken together, our results provide direct evidence that the CAD risk interval has a pivotal role in regulation of cardiac Cdkn2a/b expression, and suggest that this region affects CAD progression by altering the dynamics of vascular cell proliferation.
Asunto(s)
Deleción Cromosómica , Cromosomas de los Mamíferos/genética , Enfermedad de la Arteria Coronaria/genética , Animales , Aorta/patología , Proliferación Celular , Células Cultivadas , Senescencia Celular/genética , Cromosomas Humanos Par 9/genética , Enfermedad de la Arteria Coronaria/patología , Inhibidor p15 de las Quinasas Dependientes de la Ciclina/deficiencia , Inhibidor p15 de las Quinasas Dependientes de la Ciclina/genética , Inhibidor p16 de la Quinasa Dependiente de Ciclina/deficiencia , Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Embrión de Mamíferos/embriología , Regulación de la Expresión Génica/genética , Predisposición Genética a la Enfermedad/genética , Humanos , Ratones , Miocitos del Músculo Liso/patología , Análisis de SupervivenciaRESUMEN
BACKGROUND: MicroRNAs (miRNAs) are short RNAs of around 22 nucleotides that regulate gene expression. The primary transcripts of miRNAs contain double-stranded RNA and are therefore potential substrates for adenosine to inosine (A-to-I) RNA editing. RESULTS: We have conducted a survey of RNA editing of miRNAs from ten human tissues by sequence comparison of PCR products derived from matched genomic DNA and total cDNA from the same individual. Six out of 99 (6%) miRNA transcripts from which data were obtained were subject to A-to-I editing in at least one tissue. Four out of seven edited adenosines were in the mature miRNA and were predicted to change the target sites in 3' untranslated regions. For a further six miRNAs, we identified A-to-I editing of transcripts derived from the opposite strand of the genome to the annotated miRNA. These miRNAs may have been annotated to the wrong genomic strand. CONCLUSION: Our results indicate that RNA editing increases the diversity of miRNAs and their targets, and hence may modulate miRNA function.