Background: Peri-conceptional use of folic acid contributes to protection against congenital malformations, such as neural tube defects and cleft lip with or without cleft palate (CL/P). Previous studies showed that low folate levels cause DNA damage, leading to chromosomal instability and aneusomy. This study seeks to confirm this finding and investigates whether the in vitro sensitivity towards aneusomy of chromosome 17 and 21 in the folate-deficient state differs between CL/P patients and controls. Methods: Epstein-Barr virus-immortalized B-lymphoblasts derived from 15 CL/P children and 15 controls, were cultured in medium with high and low concentrations - approximately 40. nM and 5. nM - of 5-methyltetrahydrofolate, respectively. Fluorescence in situ hybridization was used to detect specific fluorescence signals for chromosomes 17 and 21. Results: A significant increase in aneusomy of chromosomes 17 (2.3% vs 7.6%; p≤ 0.001) and 21 (2.5% vs 7.0%; p≤ 0.001) was observed after 10 days of culturing in low folate. These results were comparable in cell lines from patients and controls. Interestingly, for chromosome 17 the folate deficiency mainly resulted in an increase of monosomy (6%, p≤ 0.001), while for chromosome 21 the increase of trisomy was larger (4.9%, p≤ 0.001). Conclusions: These data suggest that folate deficiency is a significant risk factor in the development of aneusomy and may affect the distribution of chromosomes during cell division. The comparable aneusomy frequencies in CL/P and in controls suggest that other folate-related processes are involved in the pathogenesis of CL/P, and additional investigations are needed to identify the causal mechanisms.

Chromosome 17, Chromosome 21, Cleft lip with or without cleft palate, FISH, Folic acid, Genomic stability,
Mutation Research - Genetic Toxicology and Environmental Mutagenesis
Erasmus MC: University Medical Center Rotterdam

Bliek, B.J.B, Steegers-Theunissen, R.P.M, Douben, H, Lindemans, J, Steegers-Theunissen, R.P.M, & de Klein, J.E.M.M. (2012). Comparable levels of folate-induced aneusomy in B-lymphoblasts from oral-cleft patients and controls. Mutation Research - Genetic Toxicology and Environmental Mutagenesis, 741(1-2), 76–80. doi:10.1016/j.mrgentox.2011.10.015