|Description||The problem. A patient, KB, diagnosed with the
autosomal recessive genetic disorder Bloom Syndrome on the basis of clinical features, had failed to display the characteristic cytogenetic features of the syndrome. This research compared the growth response to bovine pituitary
fibroblast growth factor, the mitotic index, and the sister chromatid exchange level of the KB fibroblasts with normal and known Bloom Syndrome control fibroblasts.
Procedure. The growth responses of the KB, normal, and Bloom Syndrome cell lines to fibroblast qrowth factor were determined by culturing the fibroblasts over a seven-day period in the presence of three concentrations of fibroblast
growth factor in medium supplemented with two levels of fetal bovine serum. Cell concentrations were measured at regular intervals over the culture period using a Coulter counter. Sister chromatid exchange levels were determined by culturing the fibroblasts for 72 hours in medium
supplemented with the thymidine analog 5-bromo-2'-
deoxyuridine. Following culture, cells were harvested and stained for differentiation of the sister chromatids using a fluorescence plus Giemsa technique, A mitotic index for each cell line was determined by counting the number of cells in division per 1000 cells on the slides prepared for
sister chromatid exchange analysis.
Findings. Like the normal cells, the KB fibroblasts utilized fibroblast growth factor for growth based on measurements of the population doubling time in the first 48 hours of culture. Unlike either of the control cell lines, however, the KB fibroblasts exhibited no response to
fibroblast growth factor as measured by maximum cell concentration attained. The mitocic index for the KB cell line was considerably lower than that determined for either control line. The sister chromatid exchange level seen in the KB fibroblasts corresponded with that seen in the normal control fibrobLasts and was unlike the elevated level seen in the Bloom Syndrome cells.
Conclusion. The diagnosis of Bloom Syndrome in the
patient, KB, is not supported an the basis of the growth responses of the patient's fibroblasts to fibroblast growth factor, the mitotic index, and the sister chromatid exchange rate.||en