Hypersensitivity to mitomycin C cell-killing in Roberts syndrome fibroblasts with, but not without, the heterochromatin abnormality.
Roberts syndrome (RS) is a rare genetic disorder, characterized clinically by severe pre- and post-natal growth retardation and symmetric limb reduction deformities. Some patients with RS have a distinctive abnormality of the constitutive heterochromatin (the RS effect) which has been described as a premature separation of the paracentromeric and nucleolar organizing regions of the chromosomes and the distal portion of the long arm of the Y chromosome (German, 1979). These patients [denoted RS(+)] are clinically indistinguishable from the RS(-) patients who lack the cytogenetic marker for Roberts syndrome. Recently, a mutant in Drosophila has been described which has both heterochromatin undercondensation and hypersensitivity to mutagen treatment (Gatti et al., 1983). The authors suggested that the uncondensed heterochromatin may be more accessible to damage by mutagens. Thus, the present study was an investigation of the mutagen sensitivity in Roberts syndrome, to determine whether there is a similar relationship between abnormal heterochromatin structure and mutagen sensitivity. Plating efficiency experiments were performed with RS(+) fibroblasts, RS(-) fibroblasts, RS heterozygous fibroblasts and a large assortment of appropriate control cells. The RS fibroblasts with the heterochromatin abnormality were consistently more sensitive (based on D10 values) to mitomycin C treatment than were any of the other cell strains tested, including RS(-) cells. These results support the hypothesis that mitomycin C sensitivity and abnormal heterochromatin structure in Roberts syndrome are related.
Burns
M A
MA
Department of Pediatrics, McMaster University, Hamilton, Ont., Canada.
Tomkins
D J
DJ
D000015:Abnormalities, Multiple / Q000235:genetics*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000187:drug effects; D006570:Heterochromatin / Q000187:drug effects* / Q000648:ultrastructure; D006801:Humans; D016685:Mitomycin; D008937:Mitomycins / Q000633:toxicity*; D009153:Mutagens; D013577:Syndrome
D006570:Heterochromatin; D008937:Mitomycins; D009153:Mutagens; D016685:Mitomycin