Spectrum of stable and unstable rearrangements in lymphocytic chromosomes investigated in Bhopal population thirty year post MIC-disaster

Abstract

Immediate assessment of genetic damage in methyl isocyanate (MIC) gas exposed population in small and heterogeneous samples using diversified study designs and solid-stained metaphases could not depict the actual genetic impact of MIC on accidentally exposed individuals. The outcome of the then large multi-center genetic screening program was not available to the public and scientific community. Also the routine of the regular epidemiological health-survey does not capture the genetic and long-term effect of MIC. Therefore, genetic screening was carried out 30-years post disaster during 2015–2017 with a view to screen the present status of chromosomal consequences in lymphocytic cells. Participants were recruited from moderate (34) and severely (78) exposed, and unexposed (35) cohorts with their informed consent. Analysis of ~ 100 mitotic cells and karyotyping of at least 10–15 and all abnormal metaphases detected structural and numerical alterations, including stable and replicable ones. Clonal abnormalities were detected with monosomal and complex karyotype, trisomy 8, del5q/20q, loss of Y, etc. Among all, X-chromosome was frequently involved in numerical alterations. Structural aberrations appeared higher in the then exposed populations, though abnormalities cannot be linked directly to MIC-exposure 30-year post disaster. Collectively, all rearrangements were markedly higher in the severely exposed population. Altogether, the detected abnormalities appeared random and indicated genomic instability, suggesting follow-up at shorter intervals for the individuals detected with clonal aberrations. G-banding has facilitated recognition of chromosomal involvement and their breakpoints, and classification of structural rearrangements. The present data has been derived from the 30-years post-disaster genetic screening.