Asynchronous replication of biallelically expressed loci: a new phenomenon in Turner syndrome.
OBJECTIVE
Transcriptional activity of genes is related to their replication timing; alleles showing the common biallelic mode of expression replicate synchronously, whereas those with a monoallelic mode of expression replicate asynchronously. Here the level of synchronization in replication timing of alleles was determined in subjects with Turner syndrome.


METHODS
Fluorescence in situ hybridization was used for three loci not linked to X chromosome, in lymphocytes derived from 12 controls, 3 individuals with Turner, and 4 with mosaic Turner syndrome.


RESULTS
In cells derived from controls, each pair of alleles replicated synchronously; yet these same alleles replicated asynchronously in cells monosomic for X chromosome derived from Turner and mosaic Turner patients. When the level of 45,X was low in the mosaic samples, the replication pattern of the 46,XX cells was normal. However, in samples with a high level of mosaicism, a significantly increased asynchronous replication was detected in the 46,XX cells.


CONCLUSIONS
An altered temporal replication control in Turner syndrome affecting the aneuploid and euploid cells is shown. This alteration may potentially be involved in the determination of the syndrome.
Reish
Orit
O
Genetic Institute, Assaf Harofeh Medical Center, Zerifin, Israel.
Gal
Ron
R
Gaber
Elena
E
Sher
Carron
C
Bistritzer
Tzvy
T
Amiel
Aliza
A
D000483:Alleles; D004261:DNA Replication; D005260:Female; D005787:Gene Frequency; D016259:Genes, myc; D006801:Humans; D016160:Retinoblastoma Protein / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D014424:Turner Syndrome / Q000235:genetics*
D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53