Repetitive DNA is a major organizational component of eukaryotic genomes, being intrinsically related with their architecture and evolution. Tandemly repeated satellite DNAs (satDNAs) can be found clustered in specific heterochromatin-rich chromosomal regions, building vital structures like functional centromeres and also dispersed within euchromatin. Interestingly, despite their association to critical chromosomal structures, satDNAs are widely variable among species due to their high turnover rates. This dynamic behavior has been associated with genome plasticity and chromosome rearrangements, leading to the reshaping of genomes. Here we present the current knowledge regarding satDNAs in the light of new genomic technologies, and the challenges in the study of these sequences. Furthermore, we discuss how these sequences, together with other repeats, influence genome architecture, impacting its evolution and association with disease.

The Importance of Cancer Cell Lines as in vitro Models in Cancer Methylome Analysis and Anticancer Drugs Testing | InTechOpen, Published on: 2013-03-13. Authors: Daniela Ferreira, Filomena Adega and Raquel Chaves

Eukaryotic genomes contain far more DNA than needed for coding proteins. Some of these additional DNA sequences comprise non-coding repetitive DNA sequences, mostly satellite DNAs and also transposable elements usually located at the heterochromatic regions of chromosomes. Satellite DNAs consist of tandemly repeated DNA sequences inhabiting the mammalian genome, typically organized in long arrays of hundreds or thousands of copies. Different important functions have been ascribed to satellite DNA, from the imperative centromeric function in mitosis and meiosis to the recent discovery of its involvement in regulatory functions via satellite transcripts. Moreover, satellite DNAs, among other repetitive sequences, are believed to be the ‘engine’ triggering mammalian genome evolution. Repetitive DNAs are, most likely, the genetic factors responsible for promoting genomic plasticity and therefore higher rates of chromosome mutation. Furthermore, constitutive heterochromatin regions are thought to be ‘hotspots’ for structural chromosome rearrangements. A considerable collection of evidences places these sequences in the landscape of mammalian evolution. However, the mechanisms that could explain how this alliance between chromosome evolution and satellite DNA is made are still enigmatic and subject of debate. Throughout the mammalian taxa, different patterns of chromosome evolution have been widely registered from heterochromatin additions/eliminations, Robertsonian translocations, whole-arm reciprocal translocations to tandem translocations; the fact is genome’s repetitive fraction is playing a central role in mammalian genome structuring. Throughout this review we will focus on the evidences that associate satellite DNAs and constitutive heterochromatin to the process of chromosome evolution and consequently to domestic species genome’s remodeling.

The records are not clear, but Man has been sheltering the cat inside his home for over 12,000 years. The close proximity of this companion animal, however, goes beyond sharing the same roof; it extends to the great similarity found at the cellular and molecular levels. Researchers have found a striking resemblance between subtypes of feline mammary tumors and their human counterparts that goes from the genes to the pathways involved in cancer initiation and progression. Spontaneous cat mammary pre-invasive intraepithelial lesions (hyperplasias and neoplasias) and malignant lesions seem to share a wide repertoire of molecular features with their human counterparts. In the present review, we tried to compile all the genetics aspects published (i.e., chromosomal alterations, critical cancer genes and their expression) regarding cat mammary tumors, which support the cat as a valuable alternative in vitro cell and animal model (i.e., cat mammary cell lines and the spontaneous tumors, respectively), but also to present a critical point of view of some of the issues that really need to be investigated in future research.