GENO-SİTOTOKSİSİTE ÇALIŞMALARINA SİTOM YAKLAŞIMI

ÖZET DNA hasarının kromozom seviyesinde çalışılması, genetik toksikoloji araştırmalarının temel dayanaklarındandır. Mikronükleus yöntemi, kromozom hasarını değerlendirmek amacıyla geliştirilen yöntemlerden biridir. Mikronükleuslar; sentromeri olmayan kromozom veya kromatid fragmentlerinden ya da anafazda geç kalıp kutuplara göç edemeyen kromozom veya kromatidlerden oluşan ve telofazda hücre zarı ile kuşatılarak kardeş hücre çekirdeklerine dahil olmadan sitoplazmada kalan, çekirdek dışı küçük cisimciklerdir. Bu yöntemde mikronükleusların yanısıra nükleoplazmik köprüler (NPK) ve nükleer tomurcuklar (NT) değerlendirilebilmekte ve hücre ölümü ile nükleer bölünme indeksi de ölçülebilmektedir. Disentrik kromozomların sentromerlerinin farklı kutuplara göç etmesinden orjinlenen NPK, DNA’nın yanlış onarımının; kromozom rearanjmanının, telomer uç birleşmesinin; NT ise gen amplifikasyonu ve/veya değişmiş gen dozajının göstergesi olarak sayılmaktadır. Ayrıca her hücrenin sahip olduğu çekirdek sayısının değerlendirilerek nükleer bölünme indeksinin hesaplanmasının yanısıra nekrotik ve apoptotik hücrelerin de belirlenebilmesi mitotik aktivite ve sitotoksisitenin tayinine olanak sağlamaktadır. Analiz edilebilen tüm bu parametreler mikronükleus yöntemini genetik kusurların, beslenme yetersizliklerinin veya ekzojen kaynaklı genotoksinlerin sebep olduğu kromozomal instabilite fenotipinin ve değişmiş hücresel canlılığın kapsamlı olarak ölçülebildiği “sitom” yöntemi haline getirmiştir. Bu derlemede mikronükleus yönteminin genotoksisite çalışmalarındaki yeri ve önemi ile sitom yaklaşımının bu yönteme kattığı yeniliklere değinilmiştir.

Anahtar Kelimeler:

Mikronükleus, Sitom, Genotoksisite, Sitotoksisite

CYTOM APPROACH TO GENO-CYTOTOXICITY STUDIES

ABSTRACT Working at the chromosomal level of DNA damage is the mainstay of the genetic toxicology researches. The micronucleus assay is one of the developed methods to evaluate chromosomal damage. Micronuclei are non-centromeric chromosomes/chromatids fragments, or chromosomes/chromatids which lagging in the anaphase and cannot migrate to the poles, located in the cytoplasm without being included in the sister cell nuclei and surrounded by cell membranes in telophase. In this method, besides micronuclei, nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) can be evaluated, cell death and nuclear division index (NDI) can be measured. NPBs originated from the centromeres of dicentric chromosomes migrating to different poles, are indicative of DNA mis-repair, chromosome rearrangement, telomere end-fusions. NBUDs are considered as markers of gene amplification and/or altered gene dosage. In addition to NDI, establishing to necrotic and apoptotic cells may allow the determination of mitotic activity and cytotoxicity. All these analysed parameters have transformed micronucleus method into "cytome" assay by which chromosomal instability phenotypes and altered cellular viability caused by genetic defects, nutritional deficiencies, genotoxins from exogenous sources can be measured comprehensively. In this review, the place and importance of micronucleus method in genotoxicity studies and the innovations caused by the cytome approach are mentioned.

Keywords:

Micronucleus, Cytome, Genotoxicity, Cytotoxicity,

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