Cutaneous manifestations of endocrine disorders.

Endocrine disorders such as diabetes or Cushing's syndrome often have cutaneous findings, including changes to the skin, hair, and nails. In this review, the major causes, clinical manifestations, laboratory workup, and treatment of the most important endocrine diseases are discussed.

Scurvy in an unrepentant carnivore.

For centuries, scurvy, or vitamin C deficiency, decimated crews of sailing ships on long sea voyages and populations deprived of fresh fruits and vegetables during times of war or famine. Today, scurvy is extremely rare in the United States, and its classic findings of perifollicular petechiae, edema and purpura of the lower extremities, corkscrew hairs, and hemorrhagic gingivitis may go unrecognized. We report the case of a man from rural Appalachia who developed typical signs and symptoms of scurvy on two separate occasions, approximately 2 years apart. Both times, the patient underwent an extensive work-up and was diagnosed with numerous other conditions before his vitamin C deficiency was recognized. We discuss the clinical presentation, pathophysiology, diagnosis, and treatment of scurvy, with attention to specific findings that should alert the clinician to this diagnosis.

The topoisomerase-related function gene TRF4 affects cellular sensitivity to the antitumor agent camptothecin.

Camptothecin is an antitumor agent that kills cells by converting DNA topoisomerase I into a DNA-damaging poison. Although camptothecin derivatives are now being used to treat tumors in a variety of clinical protocols, the cellular factors that influence sensitivity to the drug are only beginning to be understood. We report here that two genes required for sister chromatid cohesion, TRF4 and MCD1/SCC1, are also required to repair camptothecin-mediated damage to DNA. The hypersensitivity to camptothecin in the trf4 mutant does not result from elevated expression of DNA topoisomerase I. We show that Trf4 is a nuclear protein whose expression is cell cycle-regulated at a post-transcriptional level. Suppression of camptothecin hypersensitivity in the trf4 mutant by gene overexpression resulted in the isolation of three genes: another member of the TRF4 gene family, TRF5, and two genes that may influence higher order chromosome structure, ZDS1 and ZDS2. We have isolated and sequenced two human TRF4 family members, hTRF4-1 and hTRF4-2. The hTRF4-1 gene maps to chromosome 5p15, a region of frequent copy number alteration in several tumor types. The evolutionary conservation of TRF4 suggests that it may also influence mammalian cell sensitivity to camptothecin.

Cloning, mapping, and in vivo localization of a human member of the PKCI-1 protein family (PRKCNH1).

We report here the complete cDNA sequence, genomic mapping, and immunolocalization of the first human member of the protein kinase C inhibitor (PKCI-1) gene family. The predicted human protein (hPKCI-1) is 96% identical to bovine and 53% identical to maize members, indicating the great evolutionary conservation of this protein family. The hPKCI-1 gene (HGMV-approved symbol PRKCNH1) maps to human chromosome 5q31.2 by fluorescence in situ hybridization. Indirect immunofluorescence shows that hPKCI-1 localizes to cytoskeletal structures in the cytoplasm of a human fibroblast cell line and is largely excluded from the nucleus. The cytoplasmic localization of hPKCI-1 is consistent with a postulated role in mediating a membrane-derived signal in response to ionizing radiation.

The product of the ataxia-telangiectasia group D complementing gene, ATDC, interacts with a protein kinase C substrate and inhibitor.

Ataxia-telangiectasia (AT) is an autosomal recessive human genetic disease characterized by immunological, neurological, and developmental defects and an increased risk of cancer. Cells from individuals with AT show sensitivity to ionizing radiation, elevated recombination, cell cycle abnormalities, and aberrant cytoskeletal organization. The molecular basis of the defect is unknown. A candidate AT gene (ATDC) was isolated on the basis of its ability to complement the ionizing radiation sensitivity of AT group D fibroblasts. Whether ATDC is mutated in any AT patients is not known. We have found that the ATDC protein physically interacts with the intermediate-filament protein vimentin, which is a protein kinase C substrate and colocalizing protein, and with an inhibitor of protein kinase C, hPKCI-1. Indirect immunofluorescence analysis of cultured cells transfected with a plasmid encoding an epitope-tagged ATDC protein localizes the protein to vimentin filaments. We suggest that the ATDC and hPKCI-1 proteins may be components of a signal transduction pathway that is induced by ionizing radiation and mediated by protein kinase C.

Frequent novel DNA copy number increase in squamous cell head and neck tumors.

We have undertaken a study of DNA copy number changes in head and neck squamous cell carcinomas to identify novel DNA copy number changes and to determine the significance of previous findings of cytogenetic alterations in cultured cells. Comparative genomic hybridization was performed on genomic DNA extracted from ten tumors. A novel copy number gain on chromosome 3q26-27 and a loss of chromosome 3p were found at high frequency (> or = 50% of tumors). Many other novel chromosomal copy number changes were identified but occurred at a lower frequency. In addition, our data confirm that DNA copy number changes that frequently occur in cultured cells, such as loss of chromosome 3p, also occur in tumors. Frequently altered loci may encode oncogenes or tumor suppressor genes involved in head and neck squamous cell carcinoma tumorigenesis.

Identification of novel regions of altered DNA copy number in small cell lung tumors.

Identification of the genetic alterations that occur in tumors is an important approach to understanding tumorigenesis. We have used comparative genomic hybridization (CGH), a novel molecular cytogenetic method, to identify the gross DNA copy number changes that commonly occur in small cell lung cancer (SCLC). We analyzed ten SCLC tumors (seven primary tumors and three metastases) from eight patients. We found frequent increases in DNA copy number on chromosome arms 5p, 8q, 3q, and Xq and frequent decreases in copy number on chromosome arms 3p, 17p, 5q, 8p, 13q, and 4p. The increase in copy number at 8q24 (MYC) and decreases at 17p13 (TP53), 13q14 (RB), and 3p have previously been identified in SCLC with other methods. Many of the other regions in which we detected common copy number changes have not been reported to be regions of common alteration in SCLC tumors. Comparison of copy number changes between a primary tumor and a metastasis from the same patient showed that they were more closely related to each other than to any of the other tumors. The results of direct CGH analysis of SCLC tumors reported here confirm the existence of copy number changes that we identified previously by using cell lines.

Identification of frequent novel genetic alterations in small cell lung carcinoma.

We have performed a comprehensive analysis of the DNA copy number changes that occur in 18 small cell lung carcinoma cell lines using comparative genomic hybridization (Kallioniemi et al., Science (Washington DC). 258: 818-821, 1992). DNA copy number abnormalities detected in this study include previously identified increases at 1p22-32 (L-myc), 2p24-25 (N-myc), and 8q24 (c-myc) and decreases at 17p13 (p53), 13q14 (RB), and 3p. In addition, novel DNA copy number increases were detected at 5p, 1q24, and Xq26, and novel decreases were found at 22q12.1-13.1, 10q26, and 16p11.2. Many of the most common DNA copy number changes revealed are at loci not previously recognized to be important in small cell lung cancer. In addition, a number of the DNA copy number changes, including increases at 1p22-32, 2p24-25, and 3q22-25 and a decrease on 18p, were found to occur preferentially in small cell lung carcinoma lines of the "variant" phenotype. This correlation suggests that genes may reside at these loci whose overexpression or inactivation contributes to the radiation resistance or aggressive growth phenotypes characteristic of this subtype of small cell lung carcinoma.

The rRNA-encoding DNA array has an altered structure in topoisomerase I mutants of Saccharomyces cerevisiae.

All the chromosomes from isogenic TOP1 and top1 strains have similar mobility on pulsed-field gels except for chromosome XII, which fails to migrate into the gels in top1 mutants. Chromosome XII contains the tandem repeats of rRNA-encoding DNA (rDNA). When a segment of chromosome XII containing only rDNA is transferred to chromosome III by a recombination event, chromosome III fails to enter a pulsed-field gel in extracts from top1 strains, indicating that the aberrant migration of chromosome XII in top1 mutants is caused by the presence of rDNA. Failure of chromosome XII to migrate into a pulsed-field gel occurs only in preparations from exponentially growing top1 cultures and not in preparations from stationary-phase top1 cultures. rDNA from a top1 strain does enter the gel if it is cut with an enzyme (Pst I) that cuts the tandem rDNA array into single 9-kb repeat units, indicating that more than a single repeat unit is required to maintain the aberrant structure.

A novel mutation in DNA topoisomerase I of yeast causes DNA damage and RAD9-dependent cell cycle arrest.

DNA topoisomerases, enzymes that alter the superhelicity of DNA, have been implicated in such critical cellular functions as transcription, DNA replication, and recombination. In the yeast Saccharomyces cerevisiae, a null mutation in the gene encoding topoisomerase I (TOP1) causes elevated levels of mitotic recombination in the ribosomal DNA (rDNA), but has little effect on growth. We have isolated a missense mutation in TOP1 that causes mitotic hyper-recombination not only in the rDNA, but also at other loci, in addition to causing a number of other unexpected phenotypes. This topoisomerase I mutation (top1-103) causes slow growth, constitutive expression of DNA damage-inducible genes, and inviability in the absence of the double-strand break repair system. Overexpression of top1-103 causes RAD9-dependent cell cycle arrest in G2. We show that the Top1-103 enzyme nicks DNA in vitro, suggesting that it damages DNA directly. We propose that Top1-103 mimics the action of wild-type topoisomerase I in the presence of the anti-tumor drug, camptothecin.