title: Variability in the incidence of miRNAs and genes in fragile sites and the role of repeats and CpG islands in the distribution of genetic material.
abstract: BACKGROUND
  Chromosomal fragile sites are heritable specific loci especially prone to breakage. Some of them are associated with human genetic disorders and several studies have demonstrated their importance in genome instability in cancer. MicroRNAs (miRNAs) are small non-coding RNAs responsible of post-transcriptional gene regulation and their involvement in several diseases such as cancer has been widely demonstrated. The altered expression of miRNAs is sometimes due to chromosomal rearrangements and epigenetic events, thus it is essential to study miRNAs in the context of their genomic locations, in order to find significant correlations between their aberrant expression and the phenotype.
  
  
  RESULTS
  Here we use statistical models to study the incidence of human miRNA genes on fragile sites and their association with cancer-specific translocation breakpoints, repetitive elements, and CpG islands. Our results show that, on average, fragile sites are denser in miRNAs and also in protein coding genes. However, the distribution of miRNAs and protein coding genes in fragile versus non-fragile sites depends on chromosome. We find also a positive correlation between fragility and repeats, and between miRNAs and CpG islands.
  
  
  CONCLUSIONS
  Our results show that the relationship between site fragility and miRNA density is far more complex than previously thought. For example, we find that protein coding genes seem to be following similar patterns as miRNAs, if considered their overall distribution. However, once we allow for differences at the chromosome level in our statistical analysis, we find that distribution of miRNA and protein coding genes in fragile sites is very different from that of miRNA. This is a novel result that we believe may help discover new potential correlations between the localization of miRNAs and their crucial role in biological processes and in the development of diseases.
authors.affiliation: Department of Mathematics and Computer Science, University of Catania, Catania, Italy. lagana@dmi.unict.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Laganà
authors.forename: Francesco
authors.initials: F
authors.lastname: Russo
authors.forename: Catarina
authors.initials: C
authors.lastname: Sismeiro
authors.forename: Rosalba
authors.initials: R
authors.lastname: Giugno
authors.forename: Alfredo
authors.initials: A
authors.lastname: Pulvirenti
authors.forename: Alfredo
authors.initials: A
authors.lastname: Ferro
mesh_terms: D043283:Chromosome Fragile Sites; D018899:CpG Islands; D042822:Genomic Instability; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D014178:Translocation, Genetic
chemical_list: D035683:MicroRNAs