Susanna F. Barrett

Bio: Susanna F. Barrett is an academic researcher from National Institutes of Health. The author has contributed to research in topics: Xeroderma pigmentosum & DNA repair. The author has an hindex of 10, co-authored 13 publications receiving 1210 citations.

Induction by ionizing radiation of the gadd45 gene in cultured human cells: lack of mediation by protein kinase C.

Abstract: The effect of ionizing radiation on the expression of two DNA-damage-inducible genes, designated gadd45 and gadd153, was examined in cultured human cells. These genes have previously been shown to be strongly and coordinately induced by UV radiation and alkylating agents in human and hamster cells. We found that the gadd45 but not the gadd153 gene is strongly induced by X rays in human cells. The level of gadd45 mRNA increased rapidly after X rays at doses as low as 2 Gy. After 20 Gy of X rays, gadd45 induction, as measured by increased amounts of mRNA, was similar to that produced by the most effective dose of the alkylating agent methyl methanesulfonate. No induction was seen after treatment of either human or hamster cells with 12-O-tetradecanoylphorbol-13-acetate, a known activator of protein kinase C (PKC). Therefore, gadd45 represents the only known mammalian X-ray-responsive gene whose induction is not mediated by PKC. However, induction was blocked by the protein kinase inhibitor H7, indicating that induction is mediated by some other kinase(s). Sequence analysis of human and hamster cDNA clones demonstrated that this gene has been highly conserved and encodes a novel 165-amino-acid polypeptide which is 96% identical in the two species. This gene was localized to the short arm of human chromosome 1 between p12 and p34. When induction in lymphoblast lines from four normal individuals was compared with that in lines from four patients with ataxia telangiectasia, induction by X rays of gadd45 mRNA was less in the cell lines from this cancer-prone radiosensitive disorder. Our results provide evidence for the existence of an X-ray stress response in human cells which is independent of PKC and which is abnormal in taxia telangiectasia.

Xeroderma pigmentosum neurological abnormalities correlate with colony-forming ability after ultraviolet radiation.

Abstract: Xeroderma pigmentosum is an autosomal recessive disease in which DNA repair processes are defective. All xeroderma pigmentosum patients develop premature aging of sun-exposed skin, and some develop neurological abnormalities due to premature death of nerve cells. Sensitivity to ultraviolet radiation of 24 xeroderma pigmentosum fibroblast strains was studied in vitro by measuring each strain's ability to divide and form colonies after irradiation. The most sensitive strains were derived from patients who had an early onset of neurological abnormalities; less sensitive strains were from patients with a later onset; and the most resistant strains were from patients without neurological abnormalities. The UV sensitivities of strains from each member of a sibling pair with xeroderma pigmentosum were identical, indicating that UV sensitivity of xeroderma pigmentosum strains is determined by the patient's inherited DNA repair defect. The results suggest that effective DNA repair is required to maintain the functional integrity of the human nervous system by preventing premature death of neurons.

Five complementation groups in xeroderma pigmentosum.

Abstract: A collaborative study was undertaken to determine the relationship between the three DNA repair complementation groups in xeroderma pigmentosum found at Erasmus University, Rotterdam, and the four groups found at the National Institutes of Health, Bethesda. The results of this study reveal that there are five currently known complementation groups in xeroderma pigmentosum.

Genetic heterogeneity in xeroderma pigmentosum: complementation groups and their relationship to DNA repair rates.

Abstract: Fibroblast strains from 12 patients with xeroderma pigmentosum had lower than normal rates of DNA repair, as determined by autoradiographic studies of ultraviolet-induced unscheduled nuclear DNA synthesis. The nuclei in binuclear cells, obtained by fusing fibroblasts from certain pairs of these strains, had a greater rate of DNA repair than the nuclei of either strain's unfused mononuclear cells. These results indicate that complementary corrections of the strains' repair defects had occurred in the fused cells. Four complementation groups were found, indicating that at least four mutations caused decreased DNA repair among these 12 strains. The unfused mononuclear cells of each group had a characteristic rate of repair that differed from the rates of the other groups.

Xeroderma Pigmentosum: Cutaneous, Ocular, and Neurologic Abnormalities in 830 Published Cases

Abstract: • Quantitative frequencies of clinical abnormalities in xeroderma pigmentosum were estimated by abstracting published descriptions of 830 patients in 297 articles obtained from a survey of the medical literature from 1874 to 1982. The median patient age was 12 years with nearly equal numbers of male and female patients. Cutaneous symptoms (sun sensitivity or freckling) had a median age of onset of between 1 and 2 years. Forty-five percent of the patients described had basal cell carcinoma or squamous cell carcinoma of the skin. The median age of first nonmelanoma skin cancer among patients with xeroderma pigmentosum was 8 years, more than 50 years less than that among patients with skin cancer in the United States. Melanomas were reported in 5% of patients. Ninety-seven percent of the reported basal and squamous cell carcinomas and 65% of the melanomas in patients with xeroderma pigmentosum occurred on the face, head, or neck. Seventy percent probability of survival was attained at age 40 years, a 28-year reduction in comparison with the US general population. Ocular abnormalities were reported in 40% of the patients described and were restricted to tissues exposed to ultraviolet radiation (lid, conjunctiva, and cornea) and included ectropion, corneal opacity leading to blindness, and neoplasms. Neurologic abnormalities were found in 18% of the cases reported, consisting of progressive mental deterioration, hyporeflexia or areflexia, and progressive deafness in some patients in association with dwarfism and immature sexual development. There was scant information concerning the efficacy of any therapeutic regimen. (Arch Dermatol1987;123:241-250)