Cytogenetics as a tool to study gene regulation.

Cell identity is determined by the nuclear program and established by a complex molecular interplay between DNA sequence and proteins. The past few years have witnessed major breakthroughs in the elucidation of this intricate mechanism of epigenetic gene regulation. Covalent modifications in cytosine residues of DNA and in histone tails are revealed as hallmarks that establish the functional status of chromatin domains. In particular, our knowledge of the functional implication of histone tail modifications, known as the histone code, has rapidly increased. Cytogenetics has taken a prominent share in this expanding research field by linking nuclear structures with biochemical features such as gene activity, DNA replication, histone modification and DNA methylation. This review summarizes the role of cytogenetics in exploring the mechanism underlying higher order gene regulation.