The structural gene for human coagulation factor X is located on chromosome 13q34

The gene coding for coagulation factor X was studied in a family segregating chromosomal abnormalities involving chromosomes 13 and 6. An individual monosomic for 13q34 was deficient in levels of clotting factors VII and X, while her brother, who is trisomic for 13q34, had elevated levels. DNA dosage studies with a cloned human factor X gene demonstrated that the low levels of factor X expression in the individual with the chromosome 13q34 deletion were due to the absence of one copy of the factor X structural gene. This confirms the assignment of the human gene coding for factor X to 13q34.     

The gene for human peptidase A is on band 18q23 and shows triplex and uniplex dosage effect

Summary Gene dosage effect for the enzyme peptidase A was studied in the red cells of subjects trisomic (seven cases) or monosomic (five cases) for the segment of chromosome 18 carrying the gene. The individual levels of enzyme activity in both groups were different from those of the controls, but with a wide overlap. The use of the ratio of the activity of each subject to the midparent activity eliminated the overlapping. The mean ratio was 0.94 for the controls, 2.36 for the trisomics, and 0.41 for the monosomics. The trisomic ratio is higher than expected on the assumption of a linear effect. Correlation with the cytogenetic data in four cases of ring 18 and one of 18q-firmly places the gene for peptidase A on band 18q23.     

Human chromosomal assignments for 14 argininosuccinate synthetase pseudogenes: cloned DNAs as reagents for cytogenetic analysis

There are multiple, processed, dispersed pseudogenes for human argininosuccinate synthetase. Chinese hamster X human somatic cell hybrids were used to map DNA fragment groups corresponding to the single expressed gene and 14 pseudogene loci. Each chromosomal assignment was confirmed using hybrids containing very few human chromosomes and/or by demonstrating monosomic or trisomic dosage in human cell lines with chromosomal abnormalities. Pseudogenes were mapped to chromosomes 2cen-p25, 3q12-qter, 4q21-qter, 5 (two loci), 6, 7, 9p13-q11, 9q11-q22, 11q, 12, Xp22-pter, Xq22-q26, and Ycen-q11. DNA fragments from the expressed gene were mapped to 9q34-qter in agreement with the previous assignment for enzyme activity. A high-frequency restriction fragment length polymorphism mapped to 9q11-q22. The analyses emphasized the feasibility of using chromosomally abnormal human cell lines for confirmation and regionalization of gene-mapping assignments made using somatic-cell hybrids. Conversely, cloned DNA probes, once mapped and characterized, can be very valuable for determining the chromosomal composition of interspecies hybrids and the dosage of loci in human cells. The argininosuccinate synthetase cDNA is a convenient reagent for dosage analysis of 15 human loci on 11 different chromosomes. Improved reagents could be designed that would simplify Southern blot patterns by eliminating overlapping DNA fragments and providing a single DNA fragment for each locus.     

The origin, identification, and plant morphology of five rice monosomics.

Five different monosomics of rice (Oryza sativa L.) were obtained by treatment of pollen with gamma irradiation, as a by-product of attempts to determine the cytological loci of certain marker genes, i.e., mature pollen carrying normal alleles at all loci was given gamma rays and used for pollinating strains that were homozygous for recessive marker genes. The monosomics showed distinguishable morphological features and had complete seed sterility. Cytological studies revealed that one monosomic was tertiary, the others primary. The tertiary monosomic was related to chromosome 10. Two primary monosomics for chromosomes 10 and 11 were identified. At metaphase I, the tertiary monosomic showed the chromosome configurations 1 III + 10 II, 11 II + 1 I, and 10 II + 3 I, and all primary ones showed the configuration 11 II + 1 I. All five monosomics showed very poor crossing ability and were not transmitted to the few progenies observed. A few trisomic plants were found in the progenies of a cross between monosomic and normal pollen in one monosomic. This is the first time that many monosomics in rice have been characterized. This information will be useful in studies of rice aneuploidy and cytogenetics. Key words : rice, monosomics, morphology, cytology, transmission, trisomics.     

Unequal distribution of genes and chromosomes refers to nuclear diversification in the binucleated Giardia intestinalis

The single-celled parasite Giardia intestinalis (Diplomonadida) has two equally sized nuclei in one cell. The nuclei have been considered identical. We have previously shown that they contain different chromosomal sets and proceed through the cell cycle with some asynchrony. Here, we demonstrate by fluorescence in situ hybridization that several genes from chromosome 5 are lost in one of the two nuclei of the WBc6 Giardia line. The missing segment stretches over at least 50 kb near the 5′ chromosome end. In both WB and WBc6 Giardia cell lines, chromosome 5 is trisomic in one nucleus and monosomic in the other nucleus. The described chromosomal deletion has always been observed at the monosomic chromosome in WBc6; however, the deletion was not detected in the parent line WB. The chromosomal segment was thus initially lost after biological cloning of WB, which gave rise to clone WBc6. We show that Giardia is capable of carrying out gene expression from only one nucleus. The two nuclei display a certain level of diversity, making each of them irreplaceable. The doubled karyomastigonts of diplomonads likely have separate functions both in the mastigont/flagellar organization and in chromosomal and gene content. To our knowledge, our results offer the first methodical approach to differentiating the two, so far indistinguishable nuclei.     

Chromosome constitution and its bearing on the chromosomal radiosensitivity in man

Blood samples obtained from patients with various types of inborn chromosome abnormalities were exposed to γ-rays and the relationship between the chromosome constitution and chromosomal radiosensitivity of lymphocytes was studied by analysing types and frequencies of radiation-induced chromosome aberrations. The results showed that the chromosomal radiosensitivity was consistently higher in the cells which were trisomic for the whole or a part of a chromosome than in the cells with normal karyotype, but it was not significantly influenced by the monosomic conditions, reciprocal translocation and inversion. Age of the subjects also affected the chromosomal radiosensitivity, which was elevated in the neonates.

The analysis of chromosome aberrations showed that the high frequency of radiation-induced chromosome aberrations was due to the increased production of exchange aberrations and that the level of deletions was not affected either by factors of the chromosome constitution or of the age of the subject. A hypothesis to explain the increased chromosomal radiosensitivity of the trisomic cells was given in line with the effects of altered enzyme activity on the production of exchange aberrations.

The parallelism between the increased chromosomal radiosensitivity in the trisomic cells and the susceptibility of the affected persons to neoplasia allowed us to recognize that the trisomic cells are particularly cancer-prone and that the illegitimate repair of chromosome damage, which is intrinsic to the trisomic cells, may play an important role in the development of cancer.     

A case of r(21) with stigmata of atypical Down syndrome

Summary A case of r(21) with stigmata of atypical Down syndrome is presented. Karyotype of the proposita was determined as 45,XX,-21/46,XX,-21, +r(21)/47,XX,-21,+r(21),+(21). Most ring chromosomes showed double-sized ring chromosomes, which were trisomic for 21p11-21q22.3 and monosomic for 21q22.3-qter. SOD-1 activity revealed only slight elevation. The mechanism of ring formation is discussed.     

Transfer of the herpes simplex thymidine kinase gene from human cells to mouse cells by means of metaphase chromosomes.

Thymidine kinase (TK)-deficient human cells were infected with ultraviolet light-inactivated Herpes simplex virus type 1, and "transformed" cells that expressed Herpes TK activity were isolated. Purified metaphase chromosomes were isolated from the transformed human line and incubated with TK-deficient mouse cells. TK+ cells were selected, and it was shown that these cells were gene transferents which expressed Herpes TK activity, identical to that found in the transformed human cells. The gene transferents contained no intact human chromosomes. When removed from selective pressure, the gene transferents rapidly lost the TK+ phenotype. However, upon continued growth in nonselective medium, a subpopulation in which the TK+ phenotype had become more stabilized appeared. These results suggest that the Herpes gene for thymidine kinase has integrated into the genome of the HSV-transformed human cells and that it can be transferred to other cells by means of purified metaphase chromosomes.     

Human mitochondrial thymidine kinase is coded for by a gene on chromosome 16 of the nucleus

The expression of human mitochondrial thymidine kinase (mt TK) was investigated by polyacrylamide electrophoresis in 19 independent human-mouse somatic cell hybrids which allowed all human chromosomes to be analyzed. In 8 hybrid clones the presence of this enzymatic activity could be demonstrated. Human mt TK segregated concordantly with human adenine phosphoribosyltransferase (APRT) and human chromosome 16. Discordant segregation with all other human chromosomes was demonstrated by karyotype and isozyme analyses. These results suggest that human mt TK is coded for by a gene on chromosome 16 of the nucleus. Thus human mt TK is genetically different from human cytosol thymidine kinase which is coded for by a gene on chromosome 17. The appearance of one heteropolymer band after electrophoretic separation of human and murine mt TK supports the notion that both enzymes have dimeric structures.     

Mitochondrial purine and pyrimidine metabolism and beyond

ABSTRACT

Carefully balanced deoxynucleoside triphosphate (dNTP) pools are essential for both nuclear and mitochondrial genome replication and repair. Two synthetic pathways operate in cells to produce dNTPs, e.g., the de novo and the salvage pathways. The key regulatory enzymes for de novo synthesis are ribonucleotide reductase (RNR) and thymidylate synthase (TS), and this process is considered to be cytosolic. The salvage pathway operates both in the cytosol (TK1 and dCK) and the mitochondria (TK2 and dGK). Mitochondrial dNTP pools are separated from the cytosolic ones owing to the double membrane structure of the mitochondria, and are formed by the salvage enzymes TK2 and dGK together with NMPKs and NDPK in postmitotic tissues, while in proliferating cells the mitochondrial dNTPs are mainly imported from the cytosol produced by the cytosolic pathways. Imbalanced mitochondrial dNTP pools lead to mtDNA depletion and/or deletions resulting in serious mitochondrial diseases. The mtDNA depletion syndrome is caused by deficiencies not only in enzymes in dNTP synthesis (TK2, dGK, p53R2, and TP) and mtDNA replication (mtDNA polymerase and twinkle helicase), but also in enzymes in other metabolic pathways such as SUCLA2 and SUCLG1, ABAT and MPV17. Basic questions are why defects in these enzymes affect dNTP synthesis and how important is mitochondrial nucleotide synthesis in the whole cell/organism perspective? This review will focus on recent studies on purine and pyrimidine metabolism, which have revealed several important links that connect mitochondrial nucleotide metabolism with amino acids, glucose, and fatty acid metabolism.     

Carrier DNA affects the integration of HSV-1 TK gene in the genome of L929TK- cells.

L929TK- cells were cotransfected with DNA mixtures containing tk gene of HSV-1, plasmids carrying LTR of MoMLV or RSV and carrier DNA of salmon sperm or chromosomal DNA of recipient cells. Selection of TK+ transformants was conducted in DMEM supplemented with HAT. Plasmids carrying LTR sequences of MoMLV or RSV retroviruses showed enhancing effect on the frequency of TK+ transformation. Southern blot analysis of chromosomal DNA of TK+ transformants demonstrated in clones deriving from cotransfections of tk gene and carrier DNA of L929TK- cells multiple copies of tk gene integrated into several genomic sites of host. Single copies of tk gene integrated into different sites of host genome occurred in chromosomal DNA of TK+ clones deriving from cotransfections of tk gene and carrier DNA of salmon sperm. Cells cotransfected with tk gene and plasmids carrying LTR sequences of MoMLV or RSV formed three dimensional colonies in semisolid agar medium. No effect of carrier DNA on the morphology of TK+ transformant clones was noticed.     

Chromosomal location of a gene suppressing powdery mildew resistance genes Pm8 and Pm17 in common wheat (Triticum aestivum L. em. Thell.)

The chromosomal location of a suppressor for the powdery mildew resistance genes Pm8 and Pm17 was determined by a monosomic set of the wheat cultivar Caribo. This cultivar carries a suppressor gene inhibiting the expression of Pm8 in cv Disponent and of Pm17 in line Helami-105. In disease resistance assessments, monosomic F₁ hybrids (2n=41) of Caribo x Disponent and Caribo x Helami-105 lacking chromosome 7D were resistant, whereas monosomic F₁ hybrids involving the other 20 chromosomes, as well as disomic F₁ hybrids (2n=42) of all cross combinations, were susceptible revealing that the suppressor gene for Pm8 and Pm17 is localized on chromosome 7D. It is suggested that genotypes without the suppressor gene be used for the exploitation of genes Pm8 and Pm17 in enhancing powdery mildew resistance in common wheat.     

Integration site(s) of herpes simplex virus type 1 thymidine kinase gene and regional assignment of the gene for aminoacylase-1 in human chromosomes

To investigate the chromosomal sites of integration of the herpes simplex virus type 1 (HSV-1) thymidine kinase (TK) gene in HSV-1-transformed human HeLa(BU25)/KOS 8-1 cells, the biochemically transformed cells were fused with TK-negative mouse LM(TK-) cells, and human-mouse somatic cell hybrid lines (LH81) were isolated using a HATG-ouabain selection system. The presence of HSV-1 TK activity in the hybrid lines was verified by disc polyacrylamide gel electrophoresis (PAGE) and by enzyme neutralization with type-specific rabbit anti-HSV-1 TK immunoglobulin. Karyotype analyses of several somatic cell hybrid clones using G-banding, Hoechst 33258 staining, and combined G-banding and Hoechst staining demonstrated that they retained only a few human chromosomes. A marker chromosome, M7, consisting of a chromosome 17 translocated to the short arm of 3, occurred in 25 of the 28 metaphases examined. Also chromosomes 8 and X were found in a minority of metaphases. Isozyme analyses showed that all 19 hybrid clones analyzed expressed human aminoacylase-1 (ACY1) and esterase D (ESD), markers for 3 and 13, respectively. Back-selection of somatic cell hybrid clones with 5-bromodeoxyuridine resulted in the isolation of several subclones lacking HSV-1 TK activity, human ACY1, human ESD, and the human chromosomes. These experiments suggest that the HSV-1 TK gene is associated with either M7 or a segment of 13, or both, in biochemically transformed HeLa(BU25)/KOS 8-1 cells. These experiments also permit localization of the ACY1 structural gene to the pter leads to p12 region of 3.     

Molecular and morphological characterization of monosomic additions in Beta vulgaris,carrying extra chromosomes of B. procumbens or B. patellaris

DNA fingerprinting with three repetitive DNA sequences (OPX2, PB6-4 and Sat-121) was carried out on a set of 10 monosomic additions of Beta procumbens and 75 anonymous B. patellaris-derived monosomic additions in B. vulgaris, for characterization of the alien chromosomes at the DNA level. The probes are Procumbentes-specific and distributed over all chromosomes. Morphological characteristics were also used for the classification of B. patellaris monosomic addition families and for comparison with the morphology of the addition families of B. procumbens.DNA fingerprinting revealed unique patterns for almost all individual addition chromosomes of B. procumbens. However, it was concluded that chromosomes 1 and 6 of B. procumbens may be identical with the only difference that the chromosome referred to as 6 carries a susceptible allele for beet cyst nematode (BCN) resistance. In contrast, it was concluded that the two addition types with chromosome 2 are carrying different chromosomes of B. procumbens, so that one of them was renumbered to become the new chromosome 6.DNA fingerprinting of 75 anonymous B. patellaris-derived monosomic additions facilitated the identification and characterization of the alien chromosomes and the grouping of these additions into nine different groups. Several of these groups could be divided in two sub-groups on the basis of small differences in banding patterns. The results of the DNA fingerprinting led to the conclusion that B. patellaris most likely is an allotetraploid. It was also deduced that the BCN gene(s) in this species are homozygous and located on chromosome 1, while the pair of homoeologous chromosomes does not carry such BCN gene(s). Because of the allotetraploid nature of B. patellaris, preferential association occurs between the two homologous chromosomes containing the allele(s) for BCN resistance. Each group of B. patellaris addition families united by DNA fingerprinting had comparable morphological characteristics. Some of these morphological traits appeared to be chromosome-specific and were very useful for primary classification of the addition families. However, the present study showed that these morphological traits are not adequate for the identification of all alien chromosomes without the aid of additional markers. Because of similarities observed between molecular characteristics or the effects on plant morphology of several chromosomes of B. procumbens and B. patellaris it was concluded that B. procumbens could have been involved in the evolutionary history of B. patellaris.     

PCR and sequence analysis of barley chromosome 2H subjected to the gametocidal action of chromosome 2C

Gametocidal (Gc) chromosomes induce various types of chromosomal mutations during gametogenesis in the chromosomes of common wheat and alien chromosomes added to common wheat. However, it is not yet known whether the Gc chromosome causes aberrations at the nucleotide level because mutations caused by Gc chromosomes have been studied only by cytological screening. In order to know whether the Gc chromosome induces point mutations, we conducted PCR analysis and sequencing with the progeny of a common wheat line that is disomic for barley chromosome 2H and monosomic for Gc chromosome 2C. We analyzed 18 2H-specific EST sequences using 81 progeny plants carrying a cytologically normal-appearing 2H chromosome and found no nucleotide changes in the analyzed 1,419 sequences (in total 647,075 bp). During this analysis, we found six plants for which some ESTs could not be PCR amplified, suggesting the presence of chromosomal mutations in these plants. The cytological and PCR analyses of the progeny of the six plants confirmed the occurrence of chromosomal mutations in the parental plants. These results suggested that the Gc chromosome mostly induced chromosomal aberrations, not nucleotide changes, and that the Gc-induced chromosomal mutations in the six plants occurred after fertilization.     

Unexpected Inheritance of a Balanced Homologous translocation t(22q;22q) from father to a phenotypically normal daughter

Rearrangements between homologous chromosomes are extremely rare and manifest mainly as monosomic or trisomic offsprings. There are remarkably few reports of balanced homologous chromosomal translocation t (22q; 22q) and only two cases of transmission of this balanced homohologous rearrangement from mother to normal daughter are reported. Robersonian translocation carriers in non-homologous chromosomes have the ability to have an unaffected child. However, it is not possible to have an unaffected child in cases with Robersonian translocations in homologous chromosomes. Carriers of homologous chromosome 22 translocations with maternal uniparental disomy do not have any impact on their phenotype. We are presenting a family with a history of multiple first trimester miscarriages and an unexpected inheritance of balanced homologous translocation of chromosome 22 with paternal uniparental disomy. There are no data available regarding the impact of paternal UPD 22 on the phenotype. We claim this to be the first report explaining that paternal UPD 22 does not impact the phenotype.     

Transmission of alien chromosomes from selfed progenies of a complete set of Allium monosomic additions: the development of a reliable method for the maintenance of a monosomic addition set.

Selfed progeny of a complete set of Allium fistulosum - Allium cepa monosomic addition lines (2n = 2x + 1 = 17, FF+1A-FF+8A) were produced to examine the transmission rates of respective alien chromosomes. All eight types of the selfed monosomic additions set germinable seeds. The numbers of chromosomes (2n) in the seedlings were 16, 17, or 18. The eight extra chromosomes varied in transmission rate (%) from 9 (FF+2A) to 49 (FF+8A). The complete set of monosomic additions was reproduced successfully by self-pollination. A reliable way to maintain a set of Allium monosomic additions was developed using a combination of two crossing methods, selfing and female transmission. FF+8A produced two seedlings with 18 chromosomes. Cytogenetical analyses, including GISH, showed that the seedlings were disomic addition plants carrying two entire homologous chromosomes from A. cepa in an integral diploid background of A. fistulosum. Flow cytometry analysis showed that a double dose of the alien 8A chromosome caused fluorescence intensity values spurring in DNA content, and isozyme analysis showed increased glutamate dehydrogenase activity at the gene locus Gdh-1.     

The Nucleolus Organizer Region of Maize (ZEA MAYS L.): Tests for Ribosomal Gene Compensation or Magnification

Ribosomal gene compensation and magnification that might be detected on a whole-plant basis was not found in maize. Plants monosomic for chromosome 6 (the NOR chromosome) were compared with monosomic-8 and monosomic-10 plants, disomic sibs, and parental lines. Assuming no rDNA compensation, monosomic-6 plants showed approximately the decrease expected in rRNA cistron number. Monosomic-8 had a normal ribosomal gene number, while monosomic-10 showed a decrease; but further documentation is needed. Besides demonstrating the absence of gene compensation, the results document our previous conclusion that maize chromosome 6 carries DNA complementary to ribosomal RNA. Further documentation was provided from studies with trisomic chromosome 6 plants showing proportional increases in ribosomal gene number. Progeny of the monosomic plants crossed as males to a standard singlecross hybrid possessed expected ribosomal gene numbers suggesting the lack of ribosomal gene magnification.—The ragged (rgd) mutant of maize, suspected of being deficient in rRNA cistrons, had a normal number.