demecolcine and Syndrome

Skin fibroblast cells from two unrelated male infants with a chromosome-instability disorder were analyzed for their response to colcemid-induced mitotic-spindle checkpoint. The infants both had severe growth and developmental retardation, microcephaly, and Dandy-Walker anomaly; developed Wilms tumor; and one died at age 5 mo, the other at age 3 years. Their metaphases had total premature chromatid separation (total PCS) and mosaic variegated aneuploidy. Mitotic-index analysis of their cells showed the absence of mitotic block after the treatment with colcemid, a mitotic-spindle inhibitor. Bromodeoxyuridine-incorporation measurement and microscopic analysis indicated that cells treated with colcemid entered G1 and S phases without sister-chromatid segregation and cytokinesis. Preparations of short-term colcemid-treated cells contained those cells with chromosomes in total PCS and all or clusters of them encapsulated by nuclear membranes. Cell-cycle studies demonstrated the accumulation of cells with a DNA content of 8C. These findings indicate that the infants' cells were insensitive to the colcemid-induced mitotic-spindle checkpoint.

Topics: Abnormalities, Multiple; Aneuploidy; Cells, Cultured; Child, Preschool; Chromatids; Chromosome Fragility; Chromosome Segregation; Demecolcine; DNA; Fibroblasts; Flow Cytometry; Growth Disorders; Humans; Infant; Male; Metaphase; Mitotic Index; Mosaicism; Nuclear Envelope; Skin; Spindle Apparatus; Syndrome; Wilms Tumor

Roberts syndrome (RS) is a rare autosomal recessive disorder characterized by pre- and postnatal growth retardation, limb reduction abnormalities, and craniofacial anomalies. Mitotic chromosomes from RS individuals display repulsion of heterochromatin regions or centromere splitting, leading to a railroad-track appearance of mitotic chromosomes. Abnormalities in metaphase duration, anaphase progression, nuclear morphology, and increased frequency of micronucleation have been reported in RS cells. Cells from RS heterozygotes are normal in these respects, and in vitro complementation of the defects in somatic cell hybrids has been reported. Therefore, in preparation for the isolation of cDNAs that complement the RS defect, we investigated various drug treatments to identify an agent that specifically involves the growth of RS cells. Based on the cytogenetic and cell biologic findings, we chose agents that increase micronucleation or inhibit protein synthesis. We found that RS cells are hypersensitive to gamma radiation, mitomycin C, G418 and hygromycin B, but not to colcemid or streptonigrin when compared to normal cells. DNA content and cell viability analysis confirmed that the sensitivity to gamma irradiation was primarily due to increased cell death.

Topics: Abnormalities, Multiple; Cell Cycle; Cell Division; Cell Line; Demecolcine; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Gamma Rays; Humans; Kinetics; Lymphocytes; Mitomycin; Protein Synthesis Inhibitors; Streptonigrin; Syndrome