John R. McGill

Human ferritin H and L sequences lie on ten different chromosomes

SummaryIn humans, the H (heavy) and L (light) chains of the iron-storage protein ferritin, are derived from multigene families. We have examined the chromosomal distribution of these H and L sequences by Southern analysis of hybrid cell DNA and by chrosomal in situ hybridization. Our results show that human ferritin H genes and related sequences are found on at least seven different chromosomes while L genes and related sequences are on at least three different chromosomes. Further, we have mapped the chromosomal location of expressed genes for human H and L ferritin chains and have found an H sequence which may be a useful marker for idiopathic hemochromatosis.

Evidence of gene amplification in the form of double minute chromosomes is frequently observed in lung cancer.

Amplification of cellular proto-oncogenes, important in tumor progression, has been correlated with a poor clinical outcome in a variety of human tumor types. Amplified genes are observed in two cytogenetically distinct entities, double minutes (DMs) and homogeneously staining regions (HSR). We examined 54 fresh lung tumor specimens obtained from patients with non-small cell lung cancer for cytogenetic evidence of gene amplification in the form of DMs. The majority of these patients had received no prior treatment. The cells were harvested within 24 hours after receiving the specimens, and the slides were stained with Giemsa to specifically look for DMs. We found DMs in 24 of 31 (77%) specimens that exhibited metaphase spreads. Similar incidences of DMs were found when histologic cell types, primary vs. non-primary tumors, and specimens from patients with prior treatment vs. no prior treatment were compared. Therefore, DMs occur frequently in non cultured lung tumor cells, providing evidence that gene amplification may be an important aspect of tumor behavior in patients with non-small cell lung carcinoma. Further investigation is warranted to identify the specific tumor-related genes located on these abnormal chromosomes. This also suggests that ongoing efforts to eliminate amplified drug-resistant genes or oncogenes contained on DMs in tumor cells may be relevant in patients with non-small cell lung cancer.

Localization of the haptoglobin α and β genes (HPA and HPB) to human chromosome 16q22 by in situ hybridization

Human haptoglobin (Hp) is a protein that binds free hemoglobin and circulates in plasma of vertebrates as a tetrachain (αβ)2 structure. This study maps HPA and H

Chromosomal localization of human lactotransferrin gene (LTF) by in situ hybridization

Lactotransferrin (LTF) is an important member of the transferrin family of proteins. These proteins play an essential role in the transport of iron in extracellular fluid (Aisen and Listowsky, 1980). Southern blot analysis of mouse-human somatic cell hybrids have localized the LTF gene to region q21----qter of human chromosome 3 (Teng et al., unpublished data). Using the same full-length mouse cDNA probe (2.2 kb), the LTF gene was mapped to human chromosomal bands 3q21----q23 by in situ hybridization. The sublocalization of the LTF gene to 3q21----q23 is in the region of human chromosome 3 where the gene loci of transferrin and transferrin receptor have been localized (Yang et al., 1984; van de Rijn et al., 1983).

cDNA Sequence, interspecies comparison, and gene mapping analysis of argininosuccinate lyase

A cDNA clone of the argininosuccinate lyase gene (ASL) was isolated from an adult human liver library by probing with synthetic oligonucleotide probes. This clone and a yeast genomic DNA fragment containing the ASL gene were sequenced using the M13-dideoxynucleotide method. Comparison of the yeast and human clones at the nucleotide and putative amino acid sequence levels indicated identities of 50 and 54%, respectively. The most conserved region of the yeast gene was used to detect human clones in the liver cDNA library to test phylogenetic screening capabilities of conserved genes. ASL was mapped to human chromosome 7pter----q22 using human-mouse somatic cell hybrid DNA and further mapped by in situ hybridization to chromosome 7cen----q11.2 on human metaphase chromosomes. The probe also detected a sequence on chromosome 22. Somatic cell hybrid DNA digested with PvuII revealed a mouse polymorphism between Balb/c and C3H mice in the ASL gene.

Chromosome localization of the human renin gene (REN) by in situ hybridization

Previous studies by Southern blot analysis of human X mouse somatic cell hybrids localized the renin gene to region p21----qter of human chromosome 1. Using a DNA insert encoding exons 2-5, the renin gene was mapped to human chromosome bands 1q25----q32 by in situ hybridization. The sublocalization of the renin gene will facilitate subsequent detailed linkage analysis of human chromosome 1.

Chromosomal localization of group-specific component by in situ hybridization

Group-specific component (GC), an alpha 2-globulin plasma protein synthesized primarily in the liver, is the major vitamin D-binding protein in plasma. It has two common phenotypes, GC1 and GC2, which appear in all human populations. Using the cDNA insert containing the entire coding sequence of GC2, the GC gene was mapped to human chromosomal bands 4q13----q21.1 by in situ hybridization.

Organization and Expression of Human Telomere Repeat Binding Factor Genes

The ends of mammalian chromosomes terminate in structures called telomeres. Recently a human telomere repeat binding factor (TRF1) that binds the vertebrate TTAGGG telomeric repeat in situ was isolated by Chong et al. (1). TRF1 regulates telomere length (2), which is often altered in cancer cells. To understand their genetic organization, TRF1 genes were localized to human chromosomes 13 cen, 21cen, and Xq13 by analysis of human monochromosomal hybrids, and by fluorescent in situ hybridization. We also confirmed the recent localization of a human TRF1 gene to chromosome 8, and provide evidence that this locus is alternatively spliced. In contrast to the TRF1 genes on chromosomes 8 and X, the chromosomes 13 and 21 TRF1 genes contained a 60 bp deletion in the coding region. The results suggest that two distinct forms of TRF1 are expressed and that the TRF1 gene family includes at least three pseudogenes whose dispersal in the human genome may have occurred via cDNA intermediates.

Pharmacokinetics of hydroxyurea in nude mice

Extrachromosomal DNA is the predominant form of gene amplification In human tumors. Hydroxyurea (HU) concentrations of 100-150 IAM have been promising In vitro for extrachromosomal DNA elimination. The study objective was to determine the HU dose-concentration relationship in nude mice with HU doses from 0 to 200 mg/kg. For HU t1/2 determination, mice were Injected with HU 100 mg/kg. A plasma concentration of 159 p.M was achieved and a t1/2 of 11.3 mln determined. Based on these findings, In vivo elimination studies will require frequent administration of HU to maintain plasma concentrations from 100 to 150 µM.

Human α2-HS-glycoprotein localized to 3q27→q29 by in situ hybridization

Human plasma protein α2-HS-glycoprotein (AHSG) is composed of two polypeptide chains, A and B, encoded by a single mRNA. Southern blot analysis of mouse × human somatic cell hybr