Localization of the gene encoding 3-hydroxy-3-methylglutaryl-coenzyme A synthase to human chromosome 5

Molecular cloning and cellular expression of the cholesterol synthesizing enzymes during the prenatal development of the optic nerve in the dromedary camel (Camelus Dromedarius)

The Cholesterol-synthesizing proteins (HMGCS1 and HMGCS2) are mitochondrial enzymes that believed to catalyze the first reaction of ketogenesis, the process by which energy is provided from fats in the absence of carbohydrates. Typically, astrocytes developed from its progenitor cells in the embryonic optic nerve and enriched with HMGCS1 and 2. However, the detailed histomorphology of camel HMGCS1 and 2 remains to be clearly defined. Here, we investigated the changes that associate with astrocytes differentiation within the developing camel optic nerve. Firstly, we isolated cDNAs encoding HMGCS1 and 2 from the optic nerve. Then, we found that HMGCS1 shared high similarity to human, while HMGCS2 showed a lower similarity and was more diverse. Immunohistochemical studies revealed that distinct correlation of astrocytes differentiation with HMGCS1 and 2 expressions in the developing camel optic nerve. Both encoded proteins were localized throughout the cytoplasm, as well as the nuclei of the astrocytes. In addition, semi-quantitative PCR analysis and western analysis confirmed that both HMGCS1 and 2 were highly expressed in camel optic nerve as well as other tissue, but they were lower in both skeletal and heart muscles. Moreover, various stains such as Sudan black and florescence filipin stains were used to visualize the free cholesterol in the astrocytes, indicating the enzymatic activity of HMGCS1 and 2. Together, our study reported the first comprehensive investigation of the molecular cloning and cellular expression of HMGCS1 and 2 in the optic nerve of dromedary camel.

Serum antioxidant and cholesterol levels in patients with different types of cancer

Serum antioxidant (urate, alpha-tocopherol) activity and cholesterol concentration in 142 patients of Indian and Arab (Kuwaitis and other Arabs) origin with different types of cancer (breast, colon, stomach, thyroid, oral, rectal, pancreatic, and renal) were compared to 100 age- and sex-matched control subjects. Values were expressed as medians (interquartile range). Urate concentration was significantly decreased in male patients compared to male controls (P < 0.0001) and in female patients and female breast cancer cases compared to female controls; P < 0.0001 and P = 0.001, respectively. Alpha-tocopherol concentration decreased significantly in total cancer, stomach, colon, rectal, and breast cancer cases than the controls; P < 0.0001, P < 0.0001, P < 0.0001, P = 0.012, and P = 0.022, respectively. Cholesterol concentration decreased significantly in stomach, oral, colon, and total cancer cases compared to the controls; P < 0.0001, P < 0.0001, P = 0.002, and P = 0.012, respectively. Among controls, females had significantly (P < 0.0001) lower concentrations of alpha-tocopherol than males. Among patients, cholesterol, urate, and alpha-tocopherol concentrations decreased significantly in smokers than in nonsmokers; P < 0.0001, P = 0.004, and P = 0.047, respectively. Generally, changes in alpha-tocopherol/cholesterol ratios mimicked changes in alpha-tocopherol concentration. Concentrations of all parameters decreased significantly in male patients compared to male controls. Age was positively associated with all three analytes with respect to the controls. Alpha-tocopherol correlated with cholesterol in cancer patients (r = 0.367; P < 0.0001) and with urate in the controls (r = 0.342; P < 0.0001). The data suggest cancer-related diminished synthesis of cholesterol and, generally, a greater antioxidant burden for alpha-tocopherol than urate in cancer-generated oxidative stress. The increased incidence of pancreatic cancer in Kuwaitis warrants further study.

High protein, saturated fat and cholesterol diet, and low levels of serum lipids in colorectal cancer

In a case-control study probing the role of diet on the occurrence of colorectal cancer and undertaken in Athens, Greece, sera were collected from 100 cases and 100 controls, and serum total cholesterol, high-density-lipoprotein (HDL) cholesterol and triglycerides were determined. The biochemical results were analyzed in conjunction with nutrient intakes and a dietary score that summarizes in a linear way the dietary contrast between high-risk (high protein, saturated fat and dietary cholesterol; low vegetable) and low-risk (low protein, saturated fat and cholesterol; high vegetable) patterns. Cases with colorectal cancer had significantly (p less than 0.001) and substantially lower values of serum total cholesterol and particularly HDL cholesterol, but these associations did not reflect dietary practices, since protein intake and, to a lesser (and nonsignificant) extent, saturated fat and dietary cholesterol intake were higher among cases than among controls. In absolute terms, the dietary effect (as summarized in the linear dietary score) is more evident among persons with low serum total cholesterol and HDL cholesterol than among those with high levels of these serum lipids. These results indicate that a diet beneficial with respect to the risk of coronary heart disease is also likely to reduce the risk of colorectal cancer, even though low levels of serum total cholesterol and particularly HDL cholesterol represent important independent correlates of clinically overt colorectal cancer.

Localization of the amphotropic murine leukemia virus receptor gene to the pericentromeric region of human chromosome 8

The host range of retroviruses is determined primarily by the presence of specific receptors on target cells which are recognized by the retroviral envelope glycoprotein. Somatic cell hybrids have been used to determine the chromosomal locations of several retroviral receptors in mice prior to their molecular cloning. Here we report that by using human-Chinese hamster somatic cell hybrids and a retroviral vector, we have mapped the receptor for the amphotropic murine leukemia virus to the pericentromeric region of human chromosome 8.

Characterization of somatic cell hybrids by bivariate flow karyotyping and fluorescence in situ hybridization

We report on the use of flow karyotyping and fluorescence in situ hybridization (FISH) to characterize the human chromosomes in somatic cell hybrids. The identity, DNA content, and relative frequency of human chromosomes are derived from flow karyotypes, i.e., measurements of Hoechst and chromomycin fluorescence intensities of chromosomes by dual beam flow cytometry. Chromosome integrity is assessed by comparing the peak position of a human chromosome in the flow karyotypes of a hybrid cell line and its human donor. When human donor cells are unavailable, the peak position of a human chromosome in a hybrid line is compared to the range of peak positions among normal individuals. The relative frequency of human chromosomes in subclones or hybrids grown in culture is monitored using the volumes of peaks in flow karyotypes. FISH with biotinylated human genomic DNA or chromosome-specific repeat sequence as probe is used in conjunction with flow karyotyping to confirm the number of human chromosomes in hybrids. Some small rearrangements are detected by flow karyotyping and not by FISH. On the other hand, translocations between human and rodent chromosomes are detected by FISH and not always by flow karyotyping. Flow karyotyping and FISH were used to characterize over 100 hybrid lines donated by other laboratories. A hybrid set useful for the construction of chromosome-enriched gene libraries is presented. In this set, each of the 24 human chromosome types is present and intact, as judged by these techniques, in a line containing little or no other human material.

The gene for the alpha 2 chain of the human fibrillar collagen type XI (COL11A2) assigned to the short arm of chromosome 6

A cosmid clone (CosHcol.11) containing the alpha 2(XI) collagen gene (COL11A2) has been isolated. The gene contains conserved DNA and amino-acid sequences characteristic of fibril forming collagen, which is in accordance with the classification of type XI collagen as a fibrillar collagen. The genomic clone containing the alpha 2(XI) gene has been used as probe in the Southern blot analysis of DNA from a panel of human/hamster somatic cell hybrids containing different numbers and combinations of human chromosomes. Synteny analysis revealed that only chromosome 6 showed complete concordant segregation with COL11A2. Furthermore, the gene was regionally mapped to the short arm of chromosome 6 by using a hybrid which contained only the long arm of the chromosome.

Mapping of the gene encoding the multifunctional protein carrying out the first three steps of pyrimidine biosynthesis to human chromosome 2

The CAD gene encodes a trifunctional protein that carries the activities of the first three enzymes (carbamyl phosphate synthetase II, aspartate transcarbamylase, and dihydroorotase) of de novo pyrimidine biosynthesis. Genomic fragments of the human CAD gene have been obtained by screening a human genomic library in bacteriophage lambda using a Syrian hamster cDNA clone as a probe. These human genomic clones have been used to assign the CAD gene to human chromosome 2 using in situ hybridization to human metaphase chromosomes and Southern blot hybridization analysis of DNA isolated from a panel of Chinese hamster/human hybrid cells. In situ hybridization analysis has allowed further localization of this gene to the chromosomal region 2p21-p22.

Further characterization of a somatic cell mutant defective in regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase

Two enzymes of mammalian cellular mevalonate biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase and HMG-CoA reductase, have been shown to be regulated by exogenous sterols. It has been demonstrated that these enzymes are regulated, at least in part, by transcriptional control of their synthesis. We have previously described a somatic cell mutant (CR1) of the CHO-K1 cell line that is defective in regulation of the activity of these enzymes in response to exogenous sterols. In this report, we demonstrate that this mutant is defective in regulation of the mRNA levels for HMG-CoA reductase and HMG-CoA synthase by 25-hydroxycholesterol and mevinolin. In the case of HMG-CoA reductase, this loss of apparent transcriptional control is not accompanied by a comparable loss in regulation of synthesis of this enzyme. This observation is consistent with prior studies suggesting that HMG-CoA reductase can be regulated translationally. We also show that CR1 cells exhibit a constitutively rapid rate of degradation of HMG-CoA reductase.

Characterization of HMG CoA synthase activity of rat liver and CHO-K1 cells

This report describes the characterization and partial purification of rat liver 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) synthase activity. A preliminary characterization of Chinese hamster ovary (CHO) cell HMG CoA synthase activity is also presented. Ion-exchange chromatography of ammonium sulfate precipitates of rat liver cytosol indicate the existence of two isoenzymes of HMG CoA synthase. These isoenzymes are physically, catalytically, and immunologically distinct. One of these isoenzymes, peak 1, resembles mitochondrial HMG-CoA synthase activity as evidenced by similarities in elution upon ion-exchange chromatography, inhibition by MgCl2, and cross reactivity with an antibody prepared against the mitochondrial enzyme. As peak 1 activity is unstable, further purification studies were performed on peak 2 activity. Peak 2 can be further resolved into two activities (peaks 2A and 2B) by gel filtration. In contrast, CHO-K1 cells (a permanent fibroblast line) possess only peak 2 type HMG CoA synthase activity.

Chromosomal assignment of the human erythropoietin gene and its DNA polymorphism

Erythropoietin (EPO), a glycoprotein hormone, is the major physiological regulator of erythrocyte production in mammals. A cDNA clone containing the entire human EPO-coding region was used for Southern blot analysis of a series of human-Chinese hamster somatic cell hybrids containing different combinations of human chromosomes. Synteny analysis revealed 100% concordance between the EPO gene and human chromosome 7. Further localization to the region q11-q22 was accomplished by in situ hybridization of 3H-labeled human EPO cDNA to metaphase chromosomes prepared from both human lymphocytes and the cell hybrid 879-2a that contained human chromosomes 5, 7, 9, 12, and 21. In addition, restriction fragment length polymorphisms were detected at a frequency of approximately 20% in a Chinese population using restriction enzymes either HindIII or HinfI. These polymorphisms were inherited in a Mendelian fashion. Thus, the EPO marker is reasonably polymorphic and should be useful in linkage analysis with other genetic markers on chromosome 7, including the locus for cystic fibrosis.