A t(X;15)(q23;q25) with Xq reactivation in a lymphoblastoid cell line from Fanconi anemia.
A t(X:15)(q23;q25) was detected during cytogenetic investigation of a lymphoblastoid cell line established from a female patient with Fanconi anemia. The translocation was apparently balanced at passage 300 and unbalanced at passage 13. A chromatid exchange between both the normal and the der(15), between the centromere and band 15q25, may explain these results. Replication studies, following BrdU incorporation, indicate that the segment Xq23----qter from the der(15) is early replicating whereas segment Xpter----q23 from the der(X) is late replicating. Since the normal X was early replicating, it is concluded that the segment of the long arm of chromosome X, separated from its inactivation center by the translocation, was reactivated. This interpretation is confirmed by the methylation patterns of the hypoxanthine phosphoribosyltransferase gene (HPRT), mapped on Xq26, which corresponds to that of an active gene, whereas that of phosphoglycerate kinase (PGK1), which remained on the der(X), corresponds to that of an inactive gene. This is the first example of reactivation of a segment of the X chromosome following a structural rearrangement in somatic cells.
Kokalj-Vokac
N
N
URA 620 CNRS, Institut Curie, Section de Biologie, Paris, France.
Saint-Ruf
C
C
Lefrançois
D
D
Viegas-Péquignot
E
E
Lemieux
N
N
Malfoy
B
B
Dutrillaux
B
B
D002460:Cell Line; D002871:Chromosome Banding; D002884:Chromosomes, Human, Pair 15; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005199:Fanconi Anemia / Q000235:genetics*; D005260:Female; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D007621:Karyotyping; D008214:Lymphocytes / Q000648:ultrastructure*; D008297:Male; D008745:Methylation; D009693:Nucleic Acid Hybridization; D010735:Phosphoglycerate Kinase / Q000235:genetics; D012854:Sister Chromatid Exchange; D014178:Translocation, Genetic; D014960:X Chromosome
D004247:DNA; D007041:Hypoxanthine Phosphoribosyltransferase; D010735:Phosphoglycerate Kinase