Non syndromic congenital malformations - a DNA study using comet assay

Abstract

Abstract Background and Objectives: The role of genomic instability resulting from chromosomal aberrations, gene mutations due to deletions, translocations and single gene defects is a known phenomenon leading to DNA damage. A deficient repair process is also attributed to the perpetuation of this damage. Placental insufficiency in pregnancy during late embryonic or early fetal period resulting in DNA damage gives rise to malformed phenotypes. An attempt was made to study the extent of DNA damage in non syndromic congenital malformations. Materials and Methods: A total of 20 children were studied. 10 of them, between 10 days to 5 years of age, presenting with non syndromic congenital anomalies formed the cases. An equal number of children matched for age criteria formed the controls. Lymphocytes collected from peripheral blood of these children were subjected to the standard comet assay, an highly sensitive, reliable, relatively inexpensive and reproducible single cell layer electrophoretic technique, where damaged DNA migrates out of the cell towards the anode forming a comet. The length of the tail is a measure of the DNA damage. Results: The malformations observed were those of urogenital, craniofacial and nervous systems. The mean comet tail lengths were 24.744 μm, 20.649 μm and 27.402 μm respectively. Comparing this to the mean tail length in controls with 1.992 μm, there was high statistical significance (P value <0.0001). Conclusion: Gene mutations, particularly involving Sex Region Determining (SRD) genes and Superoxide Dismutase (SOD) enzyme imbalances, have been implicated in these congenital malformations. Thus the comets seen in this study reflect the DNA damage due to the gene defects.