Published online Mar 15, 2003. doi: 10.3748/wjg.v9.i3.578
Revised: October 25, 2002
Accepted: November 9, 2002
Published online: March 15, 2003
AIM: To explore the molecular spectra and mechanism of human hypoxanthine guanine phosphoribosyl transferase (hprt) gene mutation induced by ethyluitrosourea (ENU) and 60Co γ-rays.
METHODS: Independent human promyelocytic leukemia cells (HL-60) mutants at the hprt locus were isolated from untreated, ethyluitrosourea (ENU) and 60Co γ-ray-exposed cells, respectively, and verified by two-way screening. The genetic changes underlying the mutation were determined by multiplex polymerase chain reaction (PCR) amplification and electrophoresis technique.
RESULTS: With dosage increased, survival rate of plated cell reduced (in the group with dosage of ENU with 100-200 μg/mL, P < 0.01; in the group with dosage of 60Co γ-ray with 2-4 Gy, P < 0.05) and mutational frequency increased (in the group of ENU 12.5-200.0 μg/mL, P < 0.05; in the group of 60Co γ-ray with 1-4 Gy, P < 0.05) significantly. In the 13 spontaneous mutants analyzed, 92.3% of mutant clones did not show any change in number or size of exon, a single exon was lost in 7.7%, and no evidence indicated total gene deletion occurred in nine hprt exons. However, deletions were found in 79.7% of ENU-induced mutations (62.5%-89.4%, P < 0.01) and in 61.7% of gamma-ray-induced mutations (28.6%-76.5%, P < 0.01). There were deletion mutations in all 9 exons of hprt gene and the most of induced mutations were chain deletion with multiplex exons (97.9% in gamma-ray-induced mutants, 88.1% in ENU-induced mutants).
CONCLUSION: The spectra of spontaneous mutations differs completely from that induced by EUN or 60Co γ-ray. Although both ENU and γ-ray can cause destruction of genetic structure, mechanism of mutagenesis between them may be different.