Clastogenic

Clastogenic is a term used in genetics, toxicology, and radiobiology to describe agents or conditions that induce structural chromosome damage in cells. Clastogens cause breaks and rearrangements in DNA, leading to aberrant chromosomes such as deletions, duplications, translocations, and inversions. This type of damage is commonly observed in dividing cells as chromosomal aberrations during mitosis and can result in genomic instability.

Mechanisms underlying clastogenicity typically involve the induction of DNA double-strand breaks, replication stress, or interference with DNA repair pathways. The breaks and misrepair that follow can produce chromosomal fragments, dicentric chromosomes, or complex rearrangements. Clastogenic effects are often detected by cytogenetic methods that reveal structural abnormalities, or by assays that measure DNA strand breaks and chromosomal fragments.

Clastogenicity is assessed using a variety of tests. In vitro chromosome aberration tests in cultured mammalian cells and in vivo micronucleus assays in rodents are standard methods. Supporting approaches include the comet assay, which detects DNA strand breaks, and γ-H2AX foci formation as a marker of double-strand breaks. The results inform toxicology and safety evaluations for chemicals, pharmaceuticals, and environmental exposures.

Relationship to related concepts is nuanced. Aneugens cause numerical changes in chromosome number rather than structural changes, whereas mutagens increase mutation rates at the sequence level. Some agents can be both clastogenic and mutagenic, and some can be clastogenic without being strongly mutagenic, depending on context and exposure.

Examples of clastogens include ionizing radiation and certain chemical agents such as some chemotherapeutic drugs that induce double-strand breaks. Understanding clastogenicity helps assess cancer risk and the potential impact of environmental and pharmaceutical exposures on genomic stability.