Chromosome extremities under the microscopy lens: molecular cytogenetics in telomere research

At the crossroads of DNA damage repair and genomic instability, telomere research significantly expands our knowledge on fundamental mechanisms involved in cancer initiation and progression, pledging novel tools for targeted and universal onco-therapies. Molecular cytogenetics through the application of a battery of fluorescent hybridization technologies plays an important role toward understanding telomere homeostasis. Herein, we review distinct molecular cytogenetic phenotypes associated with telomere repair, functionality, and elongation. We discuss the underlying mechanisms responsible for their formation or repair, focusing on Break-induced-Replication (BIR)-mediated conservative telomeric neo-synthesis, recently shown to drive the enigmatic Alternative Lengthening of Telomeres in neoplasia.