Dynamic behavior of fragile X full mutations in cultured female fetal fibroblasts.

AIM

To assess mitotic stability of the fragile X full mutations and its relationship with DNA methylation.

METHODS

The length change of the expanded CGG repeats was examined and correlated it with the methylation status in the DNA samples isolated from the fibroblasts derived from a fragile X female fetus and a fragile X male adult, respectively.

RESULTS

A dramatic instability of the expanded CGG repeats in the female fetal fibroblasts was observed. Southern blot analysis revealed that the 6.9-kb major expanded band detected in passage 2 was completely replaced by a 7.7-kb band after passage 30. Fibroblast clones derived from the passage 3 displayed an unstable expansion of the CGG repeat during clonal proliferation, while methylation status of the CGG repeat region was maintained. In contrast, in fragile X male fibroblasts the expanded CGG repeats were stable during clonal proliferation.

CONCLUSION

The mitotic instability of expanded CGG repeat is not always restricted in early development window as proposed previously and other elements rather than DNA methylation could affect the stability of the expanded CGG repeats in fragile X female fetal fibroblast cells.