Somatic cell genetics and gene families

A non-uniform bound on Poisson approximation in somatic cell hybrid model

The aim of this paper is a use of the Stein-Chen method to give a non-uniform bound for approximating the point probabilities of the number of pairs of chromosomes for which the Hamming distance is less than some fixed Hamming distance d by Poisson distribution.

Gene mapping of ocular diseases

Increasing awareness of the role of genetic factors in the causation of many human eye diseases has made ocular genetics one of the fastest growing areas of ophthalmology. The objective of this paper is to present the basic principles of gene mapping and their application to ophthalmology. The techniques used to map the genome are reviewed with emphasis placed on molecular genetics. The advances in this area have already provided the major impetus to the areas of diagnosis and prevention of some genetic eye disorders. Tables are presented that list the autosomal, X-linked and mitochondrial assignment of eye genes and disorders with ocular involvement.

Human acetylcholinesterase and butyrylcholinesterase are encoded by two distinct genes

1. Various hybridization approaches were employed to investigate structural and chromosomal interrelationships between the human cholinesterase genes CHE and ACHE encoding the polymorphic, closely related, and coordinately regulated enzymes having butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE) activities. 2. Homologous cosmid recombination with a 190-base pair 5' fragment from BuChEcDNA resulted in the isolation of four overlapping cosmid clones, apparently derived from a single gene with several introns. The Cosmid CHEDNA included a 700-base pair fragment known to be expressed at the 3' end of BuChEcDNA from nervous system tumors and which has been mapped by in situ hybridization to the unique 3q26-ter position. In contrast, cosmid CHEDNA did not hybridize with full-length AChEcDNA, proving that the complete CHE gene does not include AChE-encoding sequences either in exons or in its introns. 3. The chromosomal origin of BuChE-encoding sequences was further examined by two unrelated gene mapping approaches. Filter hybridization with DNA from human/hamster hybrid cell lines revealed BuChEcDNA-hybridizing sequences only in cell lines including human chromosome 3. However, three BuChEcDNA-homologous sequences were observed at chromosomal positions 3q21, 3q26-ter, and 16q21 by a highly stringent in situ hybridization protocol, including washes at high temperature and low salt. 4. These findings stress the selectivity of cosmid recombination and chromosome blots, raise the possibility of individual differences in BuChEcDNA-hybridizing sequences, and present an example for a family highly similar proteins encoded by distinct, nonhomologous genes.

Chromosomal mapping of human keratin genes: evidence of non-linkage

We have determined the chromosomal location of the genes for the human keratin intermediate filament proteins K1 (type II; 67 kDa) and K10 (type I; 57 kDa) by the use of specific cDNA clones in conjunction with somatic cell hybrid analysis and in situ hybridization. The K1 keratin gene maps to chromosome region 12q11----q13; the K10 keratin gene maps to chromosome region 17q12----q21. Each gene has been mapped relative to other genes known to be localized on chromosomes 12 and 17, respectively. In somatic cell hybrid analysis, the K1 gene segregates concordantly with the Hox-3 homeo box gene cluster at chromosome region 12p12----q13. The K10 gene localizes to a region proximal to a breakpoint at 17q21 which is involved in a t(17;21)(q21;q22) translocation associated with an acute leukemia. K10 appears to be distal (telomeric) to the gene loci for G-CSF, erb-A, and Her-2, which map to chromosome region 17q12----q21. The NGFR gene and Hox-2 homeo box locus are localized distal to the 17q21 break point and thus distal to the K10 gene. These data demonstrate that keratin genes K1 and K10, which are coexpressed in terminally differentiated epidermis, are not linked in the human genome, implying the existence of trans-acting factors involved in the regulation of expression of these genes.

Applications of coding theory to the design of somatic cell hybrid panels

The somatic cell hybridization technique for gene mapping depends on assembling panels of rodent-human hybrid clones containing random subsets of the human chromosomes. Such panels should be as informative as possible and permit error detection and error correction for assays of the human gene in the various clones. We derive estimates of the number of randomly generated clones required to be reasonably confident of accurately and unambiguously assigning a gene to a particular human chromosome. The collection of clones in such a random panel is contrasted with minimal panels suggested by algebraic coding theory. To approximate minimal panels we suggest the method of simulated annealing for selecting small, informative panels from larger existing collections of clones. These theoretical insights emphasize the need for more collaboration and coordination among gene mapping groups so that optimal clone panels can be assembled, stored, and distributed.

Molecular genetics and human disease. Implications for modern psychiatric research and practice

Techniques of molecular genetics, including recombinant-DNA technology, are likely to have a key role in modern psychiatric research and practice. This article reviews some methods of DNA analysis and their applications to clinical science: specifically, how these methods can be used to localise, identify, isolate, and clone clinically important genes, and how this should enable us to elucidate the molecular pathology of most inherited (psychiatric) disorders. The implications of these developments for prevention and treatment of genetic disease are discussed.

Chromosome maps of man and mouse, III

Data on loci whose positions are known in both man and mouse are presented in the form of chromosomal displays, a table, and autosomal and X-chromosomal grids. At least 40 conserved autosomal segments with two or more loci, as well as 17 homologous X-linked loci, are now known in the two species, in which mitochondrial DNA is also highly conserved. Apart from the Y, the only chromosome now lacking a conserved group is human 13. Human 17 has a single conserved group which includes both short and long arms, and so may have remained largely intact in mammalian evolution. Human and mouse chromosomal maps show the approximate locations of homologous genes while the mouse map also shows the positions of translocations used in gene location.

A membrane-specific tyrosinase chelate: the mitotic regulator?

Cancer's random, reversible, unstable transitions to "normal" structures imply their functional relation. Similar random, continuous, reversible oncogene "mutational transformation" also lacks a consistent hybrid. Positing cancer's "mutationally altered genotype" leads to medically foreign causes, qualities, inducers, suppressors, immune proteins, and viruses. Its random variation, however, opposes the functionally discrete, ordered, stable, irreversible hybrid variation and single-valued transforms of molecular genetics. There, "causal mutational operators" remain unspecified; only consistent single-valued DNA base and amino acid change, as "transform operand", are made explicit. A mitotically "blocked" (normal) and "unblocked" (malignant) stem cell "phenotype", operationally constructed from microscopic data, is therefore viewed within the homeostatic context of open-system enzyme-regulatory equilibrium. This functional, stochastic field distribution between "structurally bound" and "freely dividing" stem cell number discloses their putative regulatory mitotic-blocking factor. A tyrosinase complex, interacting by Cu2+-Fe2+ chelation with a proline hydroxylase divisional enzyme near stem cell ribosomes, maintains steady-state mitotic equilibrium. Based upon familiar medical, biochemical, and energy principles this confronts cancer's pigmentary-depigmentary signs, glycolytic metabolism, elevated serum tyrosinase, defective collagen production, exposed membrane binding sites, and tyrosine's recent growth control role.

Localization of a lymphocyte-specific protein tyrosine kinase gene (lck) at a site of frequent chromosomal abnormalities in human lymphomas

The murine lck gene is closely related to a family of cellular protooncogenes and encodes a lymphocyte-specific, membrane-associated protein tyrosine kinase. We and others have demonstrated that the lck gene is rearranged and overexpressed in the murine lymphoma LSTRA, most likely as a result of the insertion of Moloney murine leukemia virus DNA immediately adjacent to the gene. We now report that the lck gene is located at the distal end of murine chromosome 4 and on human chromosome 1 at position 1p32-35 near a site of frequent structural abnormalities in human lymphomas and neuroblastomas. These results raise the possibility that structural alteration of the lck gene through chromosomal rearrangement may contribute to transformation in human malignant disease.

Dispersed chromosomal localization of the proto-oncogenes transduced into the genome of Mill Hill 2 or E26 leukemia virus

Both Mill Hill 2 and E26 retroviruses have transduced two cellular genes--c-myc and c-mil/mht (Mill Hill 2) and c-myb and c-ets (E26). We localized the genes transduced by these viruses to different chromosomes: c-myc and c-myb to relatively large chromosomes and c-mil/mht and c-ets to microchromosomes. Thus, like avian erythroblastosis virus, each of these retroviruses has transduced two cellular genes unlinked in the chicken genome.

Dispersed human immunoglobulin kappa light-chain genes

The gene segments encoding the constant and variable regions of human immunoglobulin light chains of the kappa type (C kappa, V kappa) have been localized to chromosome 2. The distance between the C kappa and V kappa genes and the number of germline V kappa genes are unknown. As part of our work on the human V kappa locus, we have now mapped two solitary V kappa gene and a cluster of three V kappa genes to chromosomes 1, 15 and 22, respectively. The three genes that have been sequenced are nonprocessed pseudogenes, and the same may be true for the other two genes. This is the first time that V-gene segments have been found outside the C-gene-containing chromosomes. Our finding is relevant to current estimates of the size of the V kappa-gene repertoire. Furthermore, the dispersed gene regions have some unusual characteristics which may help to clarify the mechanism of dispersion.

Interferon-beta-related DNA on human chromosome 4

A DNA subclone (pPE-4000) derived from the lambda B4 interferon-beta-related human genomic DNA clone was used as a probe in blot-hybridization experiments of DNA from a panel of human-rodent somatic cell hybrids containing overlapping subsets of human chromosomes. The DNA hybridization experiments showed that the lambda B4 IFN-beta locus is localized to human chromosome 4. A provisional regional assignment to 4q12-qter was also obtained. Thus available hybridization data implicate human chromosomes 2, 4, and 9 in the human IFN-beta system while the available biological data also implicated human chromosome 5.

Isolation and characterization of rat and human glyceraldehyde-3-phosphate dehydrogenase cDNAs: genomic complexity and molecular evolution of the gene

Full length cDNAs encoding the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from rat and man have been isolated and sequenced. Many GAPDH gene-related sequences have been found in both genomes based on genomic blot hybridization analysis. Only one functional gene product is known. Results from genomic library screenings suggest that there are 300-400 copies of these sequences in the rat genome and approximately 100 in the human genome. Some of these related sequences have been shown to be processed pseudogenes. We have isolated several rat cDNA clones corresponding to these pseudogenes indicating that some pseudogenes are transcribed. Rat and human cDNAs are 89% homologous in the coding region, and 76% homologous in the first 100 base pairs of the 3'-noncoding region. Comparison of these two cDNA sequences with those of the chicken, Drosophila and yeast genes allows the analysis of the evolution of the GAPDH genes in detail.

Coordinate amplification of metallothionein I and II genes in cadmium-resistant Chinese hamster cells: implications for mechanisms regulating metallothionein gene expression

We describe here the derivation, characterization, and use of clonal cadmium-resistant (Cdr) strains of the Chinese hamster cell line CHO which differ in their metallothionein (MT) induction capacity. By nondenaturing polyacrylamide gel electrophoresis, we showed that the stable Cdr phenotype is correlated with the augmented expression of both isometallothioneins (MTI and MTII). In cells resistant to concentrations of CdCl2 exceeding 20 microM, coordinate amplification of genes encoding both isometallothioneins was demonstrated by using cDNA MT-coding sequence probes and probes specific for 3'-noncoding regions of Chinese hamster MTI and MTII genes. Molecular and in situ hybridization analyses supported close linkage of Chinese hamster MTI and MTII genes, which we have mapped previously to Chinese hamster chromosome 3. This suggests the existence of a functionally related MT gene cluster in this species. Amplified Cdr variants expressing abundant MT and their corresponding Cds parental CHO cells should be useful for future studies directed toward elucidating the mechanisms that regulate expression of the isometallothioneins.

Characterization of a mouse interferon gene locus I. Isolation of a cluster of four alpha interferon genes

A BALB/c mouse genomic library was screened with a murine interferon alpha 2 (MuIFN-alpha 2) cDNA coding region fragment. Eight clones were isolated which contain different mouse chromosomal segments related to the MuIFN-alpha 2 probe and a 28 kilobase (kb) region of mouse genomic DNA containing four different MuIFN-alpha genes (alpha 1, alpha 4, alpha 5 and alpha 6) was identified and characterized; an intergenic 1000 nucleotide long conserved sequence was found to be associated with three of these four alpha genes, indicating that this alpha-IFN gene cluster evolved through tandem duplications. Sequence analysis revealed the absence of a polyadenylation site in the 3' untranslated region of MuIFN-alpha 1, and showed that one of the genes (alpha 4) contains an internal deletion of 5 amino acids in the coding region.

Coordinate amplification of metallothionein I and II genes in cadmium-resistant Chinese hamster cells: implications for mechanisms regulating metallothionein gene expression

We describe here the derivation, characterization, and use of clonal cadmium-resistant (Cdr) strains of the Chinese hamster cell line CHO which differ in their metallothionein (MT) induction capacity. By nondenaturing polyacrylamide gel electrophoresis, we showed that the stable Cdr phenotype is correlated with the augmented expression of both isometallothioneins (MTI and MTII). In cells resistant to concentrations of CdCl2 exceeding 20 microM, coordinate amplification of genes encoding both isometallothioneins was demonstrated by using cDNA MT-coding sequence probes and probes specific for 3'-noncoding regions of Chinese hamster MTI and MTII genes. Molecular and in situ hybridization analyses supported close linkage of Chinese hamster MTI and MTII genes, which we have mapped previously to Chinese hamster chromosome 3. This suggests the existence of a functionally related MT gene cluster in this species. Amplified Cdr variants expressing abundant MT and their corresponding Cds parental CHO cells should be useful for future studies directed toward elucidating the mechanisms that regulate expression of the isometallothioneins.

Construction of linkage maps with DNA markers for human chromosomes

DNA markers and sampling of three-generation families can be used to construct complete linkage maps of human chromosomes. This is important in mapping disease loci and in determining the genetic or environmental component of a disease.

Chromosomal localization of the human apoprotein CI gene and of a polymorphic apoprotein AII gene

Human apoprotein(apo) CI and apo AII cDNA probes have been used to analyze the segregation of the human genes in panels of human-mouse hybrids. The apo CI (APOCI) gene segregates with chromosome 19 and the apo AII (APOA2) gene with chromosome 1. Somatic cell hybrids containing chromosome translocations were used to map the apo AII gene to the 1p21-1qter region. Human APOA2 is polymorphic for the restriction endonuclease Msp I. Comparison of human and mouse chromosome 1 reveals a conserved group including apo AII, renin and peptidase genes and suggests that APOA2 will be found distal to this group on human chromosome 1. The mouse apo AII gene is closely linked with genes that regulate HDL structure. Similar HDL regulatory genes will probably be found near human APOA2.

Cellular oncogenes (c-erb-A and c-erb-B) located on different chicken chromosomes can be transduced into the same retroviral genome

Avian erythroblastosis virus has transduced two cellular genes, c-erb-A and c-erb-B. Using fractionated chicken chromosomes, we found that the two genes are located on different chromosomes in the chicken genome: c-erb-A is on a microchromosome, and c-erb-B is on a large chromosome. The locations of two other cellular oncogenes (c-fps and c-myb) were also determined: c-fps is on a microchromosome, and c-myb is on chromosome of an intermediate size. Our results suggest that avian erythroblastosis virus had transduced the two cellular genes independently, conforming to previous indications that cellular oncogenes are dispersed among multiple chromosomes in every species that has been examined.

Assignment of the human tyrosine hydroxylase gene to chromosome 11

Using a panel of human-mouse somatic cell hydrids and a cDNA probe for human tyrosine hydroxylase, we have assigned the structural gene for tyrosine hydroxylase to chromosome 11 by Southern blotting techniques.

A genetic map of mouse chromosome 12 composed of polymorphic DNA fragments

Mouse chromosome 12 encodes the heavy chains of immunoglobulins (Igh), a family of T cell surface molecules, and a tumor antigen that may be homologous to immunoglobulins. To refine and extend the genetic map of this chromosome, a procedure has been developed to isolate chromosome 12-specific DNA fragments from a somatic cell hybrid carrying the chromosome on a Chinese hamster background. Five fragments have been isolated and characterized in detail. All are polymorphic, defining loci D12-1, 2, 3, 4, and 5. Using recombinant inbred mouse strains, a tentative linkage map of chromosome 12 has been worked out that incorporates these markers, the c-fos oncogene, Igh, and Pre-1/alpha 1 antitrypsin. This strategy should be applicable to any mouse chromosome or chromosomal region that can be isolated in a somatic cell hybrid.

Murine T cell receptor beta chain is encoded on chromosome 6

Southern blot analysis of somatic cell hybrid lines indicates that the beta chain of the T cell receptor for antigen maps to chromosome 6 of the mouse. An experiment testing hybridization of the constant region of this gene to DNA from a hybrid cell line containing a translocation of chromosome 6 supports the localization of this gene to the proximal (centromeric) one-third of chromosome 6, in the same general region as the immunoglobulin kappa chain locus. This may be another indication of the shared evolutionary origins of the genes encoding both T and B cell antigen recognition.

Chromosomal organization of the human dihydrofolate reductase genes: dispersion, selective amplification, and a novel form of polymorphism

The human dihydrofolate reductase (DHFR; tetrahydrofolate dehydrogenase; 5,6,7,8-tetrahydrofolate: NADP+ oxidoreductase, EC 1.5.1.3) gene family includes a functional gene (hDHFR) and at least four intronless genes. Three intronless genes (hDHFR-psi 2, hDHFR-psi 3, and hDHFR-psi 4) are identifiable as pseudogenes because of DNA sequence divergence from the functional gene with introns, while one intronless gene (hDHFR-psi 1) is completely homologous to the coding sequences of the functional gene. Analysis of genomic DNA from two panels of somatic human-rodent cell hybrids with specific molecular probes provide insight into the chromosomal organization and assignment of these genes. The five genes are dispersed in that each one is found on a different chromosome. The functional gene hDHFR has been assigned to chromosome 5, and one pseudogene (hDHFR-psi 4), to chromosome 3. In a human cell line (HeLa) that was selected for methotrexate resistance, the functional locus became amplified, while there was no amplification of the four intronless pseudogenes. hDHFR-psi 1 was found to be present in DNA of some individuals and absent from DNA of others, consistent with a recent evolutionary origin of this gene originally suggested by its sequence identity to the coding portions of the functional gene. The presence or absence of this intronless pseudogene represents a previously unreported form of DNA polymorphism.

Cellular oncogenes (c-erb-A and c-erb-B) located on different chicken chromosomes can be transduced into the same retroviral genome

Avian erythroblastosis virus has transduced two cellular genes, c-erb-A and c-erb-B. Using fractionated chicken chromosomes, we found that the two genes are located on different chromosomes in the chicken genome: c-erb-A is on a microchromosome, and c-erb-B is on a large chromosome. The locations of two other cellular oncogenes (c-fps and c-myb) were also determined: c-fps is on a microchromosome, and c-myb is on chromosome of an intermediate size. Our results suggest that avian erythroblastosis virus had transduced the two cellular genes independently, conforming to previous indications that cellular oncogenes are dispersed among multiple chromosomes in every species that has been examined.

The localization of the gene for apolipoprotein C-II to chromosome 19

Human apolipoprotein (apo) C-II, a 79 amino acid protein, functions as a cofactor for lipoprotein lipase, the enzyme which catalyzes the hydrolysis of plasma triglycerides. The chromosomal location of apoC-II has been determined by filter hybridization analysis of human-mouse hybrid cells. Southern blots of DNA from 21 human-mouse hybrid cells were hybridized with a 190 base pair nick translated probe prepared from a Hinf I digest of an apoC-II cDNA clone. Without exception, ApoC-II segregated with chromosome 19 thus establishing synteny with the apoE and LDL receptor genes known to be localized to this chromosome. The localization of the apoC-II gene to chromosome 19 will permit more detailed analysis of the genomic organization and linkages of the apolipoprotein genes.

The T cell receptor beta chain genes are located on chromosome 6 in mice and chromosome 7 in humans

Homologous clones that encode the beta chain of the T cell antigen receptor have been isolated recently from both murine and human cDNA libraries. These cDNA clones have been used in connection with interspecies hybrid cell lines to determine that the murine T cell receptor gene is located on chromosome 6 and the human gene on chromosome 7. In situ hybridization confirms these data and further localizes these genes to band B of chromosome 6 in the mouse and bands 7p13-21 in the human genome. The organization of the T cell antigen receptor J beta gene segments and C beta genes appears to be conserved, since very few intraspecies polymorphisms of restriction fragment length have been detected in either mouse or human DNA.

Strategies for multilocus linkage analysis in humans

The increasing number of DNA polymorphisms characterized in humans will soon allow the construction of fine genetic maps of human chromosomes. This advance calls for a reexamination of current methodologies for linkage analysis by the family method. We have investigated the relative efficiency of two-point and three-point linkage tests for the detection of linkage and the estimation of recombination in a variety of situations. This led us to develop the computer program LINKAGE to perform multilocus linkage analysis. The investigation also enables us to propose a method of location scores for the efficient detection of linkage between a disease locus, or a new genetic marker, and a linkage group previously established from a reference panel of families. The method is illustrated by an application to simulated pedigree data in a situation akin to Duchenne muscular dystrophy. These results show that considerable economy and efficiency can be brought to the mapping endeavor by resorting to appropriate strategies of detecting linkage and by constructing the human genetic map on a common reference panel of families.

Isolation and sequence of a human apolipoprotein CII cDNA clone and its use to isolate and map to human chromosome 19 the gene for apolipoprotein CII

cDNA clones encoding human apolipoprotein CII (apo CII) were identified by screening an adult human liver cDNA library with a mixed oligonucleotide probe corresponding to all possible codons for apo CII amino acid 6-10. One clone with an approximately equal to 500-base-pair (bp) insert, designated pCII -711, was selected for DNA sequence analysis. This clone contained a DNA sequence that corresponded with the previously reported amino acid sequence of apo CII with only minor differences. The DNA sequence specified a polypeptide of 79 amino acids, compared to the 78 amino acids previously reported. The pCII -711 clone contains a 36-bp DNA sequence upstream from that specifying the NH2-terminal threonine which, when read in frame, specifies the amino acid sequence Leu-Val-Leu-Leu-Val-Leu-Gly-Phe-Glu-Val-Gln-Gly and may be part of an apo CII signal peptide. The pCII -711 clone also contains a 144-bp region that corresponds to the 3' untranslated region of apo CII mRNA as well as a portion of the poly(A) tail. Clone pCII -711 was used to isolate and characterize by restriction endonuclease digestion the gene for apo CII from a human genomic library. In addition, through Southern blot analysis of DNA from human-rodent somatic cell hybrids, clone pCII -711 also was used to provisionally map the gene for apo CII to human chromosome 19.

Somatic cell hybrid mapping panels

The recent advances in human gene mapping have been largely due to the development of interspecies cell hybrids containing human chromosomes and their fragments. The importance of characterized panels of these hybrid lines has grown exponentially with the application of recombinant DNA technologies to human genetics. In this article, we discuss current strategies employed in the construction of somatic cell hybrid mapping panels.

Human apolipoprotein A-I--C-III gene complex is located on chromosome 11

The genes for two of the apolipoproteins, apo A-I and apo C-III, previously shown to be within 3kb in the genome, were localized to human chromosome 11 by Southern blot analysis of DNA from human-rodent somatic cell hybrids. These two genes were shown to exhibit polymorphisms associated with dyslipoproteinemia and premature atherosclerosis, and it will now be possible to examine the relationship of these genes to the many others that have been assigned to this chromosome.

The alpha-globin pseudogene on mouse chromosome 17 is closely linked to H-2

DNA sequences homologous to adult alpha-globin genes are dispersed in the mouse. Two functional genes are tightly linked on chromosome 11. Pseudogenes have been assigned to chromosomes 15 and 17 by analysis of interspecies somatic cell hybrids. We have now further characterized the second of these pseudogenes, Hba-a4. The gene is highly polymorphic, with three forms occurring in a panel of 15 inbred strains and a fourth occurring in an inbred strain derived from M. m. molossinus. Analysis of Hba-a4 alleles in CXB, BXH, and AKXL recombinant inbred strains placed Hba-a4 6.60 +/- 3.14 cM centromeric to H-2. Analysis of congenic mouse strains confirmed the linkage and the gene order. Hba-a4 is the first mammalian dispersed pseudogene to be localized in a linkage map, and should provide a useful marker for the region of chromosome 17 proximal to H-2.

U1 small nuclear RNA genes are located on human chromosome 1 and are expressed in mouse-human hybrid cells

The majority, and perhaps all, of the genes for human U1 small nuclear RNA (U1 RNA) were shown to be located on the short arm of human chromosome 1. These genes were mapped by Southern blot analysis of DNA from rodent-human somatic cell hybrids, using the 5' region of a human U1 RNA gene as a human-specific probe. This probe hybridized to DNA fragments present only in digests of total human DNA or to the DNAs of cell lines which contained human chromosome 1. The major families of human U1 RNA genes were identified, but some human genes may have gone undetected. Also, the presence of a few U1 RNA genes on human chromosome 19 could not be ruled out. In spite of the lack of extensive 5'-flanking-region homology between the human and mouse U1 RNA genes, the genes of both species were efficiently transcribed in the hybrid cells, and the U1 RNAs of both species were incorporated into specific ribonucleoprotein particles.

Lengths of chromosomal segments conserved since divergence of man and mouse

Linkage relationships of homologous loci in man and mouse were used to estimate the mean length of autosomal segments conserved during evolution. Comparison of the locations of greater than 83 homologous loci revealed 13 conserved segments. Map distances between the outermost markers of these 13 segments are known for the mouse and range from 1 to 24 centimorgans. Methods were developed for using this sample of conserved segments to estimate the mean length of all conserved autosomal segments in the genome. This mean length was estimated to be 8.1 +/- 1.6 centimorgans. Evidence is presented suggesting that chromosomal rearrangements that determine the lengths of these segments are randomly distributed within the genome. The estimated mean length of conserved segments was used to predict the probability that certain loci, such as peptidase-3 and renin, are linked in man given that homologous loci are chi centimorgans apart in the mouse. The mean length of conserved segments was also used to estimate the number of chromosomal rearrangements that have disrupted linkage since divergence of man and mouse. This estimate was shown to be 178 +/- 39 rearrangements.

Similarity of the Cin1 repetitive family of Zea mays to eukaryotic transposable elements

It has been suggested that the middle repetitive class of sequences that make up a large proportion of the eukaryotic genome have been amplified and dispersed by DNA transposition. Transposition is a phenomenon first postulated by Barbara McClintock on the basis of her genetic analysis of mutants in Zea mays. Since then, DNA transposition has been studied genetically in various plant systems and is well documented on the molecular level in both prokaryotes and eukaryotes. This has included the isolation of DNA inserts at various loci in several plants; however, the prevalence of transposition in plants is not established. We report here DNA nucleotide sequence data which show that some members of the Cin1 middle repetitive family of maize have features characteristic of known transposable elements. One cloned Cin1 repeat has a 6-base pair (bp) perfect inverted repeat sequence at its ends. The terminal five base pairs (5' TGTTG . . . CAACA 3') are identical to the termini of Drosophila copia transposable elements. Two other Cin1 alleles are flanked by 5-bp direct repeats. A comparison is made with the long terminal repeat (LTR) of the copia-Ty1-retrovirus families of moveable genetic elements.

The Giemsa-11 technique for species-specific chromosome differentiation. A simple stain modification leading to dependable direct and sequential staining procedures

Oxidizing Methylene Blue and adding the reaction products to Eosin Y and Azure B makes possible a highly reliable Giemsa-11 technique for discrimination of chromosomes in hybrid cells according to their parental origin. This staining can be combined in a sequential procedure with a fluorescent banding technique allowing the exact identification of the chromosomes.

Human interleukin 2 gene is located on chromosome 4

The interleukin-2 (IL2) gene is assigned to human chromosome 4. A synthetic oligonucleotide representing bases 285 to 324 of the IL2 cDNA clone described by Taniguchi et al. [Nature (London) 302:305-310, 1983] was used as hybridization probe in Southern blots. Eco RI digests of DNA derived from 11 somatic mouse-human cell hybrid clones were used. The IL2 gene was localized to human chromosome 4 based on the observed combinations of segregating chromosomes and bands. Under the conditions of stringency utilized, a single 3.6 kilobase Eco RI fragment hybridized to the oligonucleotide. Molecular weight standards were provided by rehybridizing the blots with an actin cDNA clone, pAct 1, which identified actin gene Eco RI fragments of defined size.

U1 small nuclear RNA genes are located on human chromosome 1 and are expressed in mouse-human hybrid cells

The majority, and perhaps all, of the genes for human U1 small nuclear RNA (U1 RNA) were shown to be located on the short arm of human chromosome 1. These genes were mapped by Southern blot analysis of DNA from rodent-human somatic cell hybrids, using the 5' region of a human U1 RNA gene as a human-specific probe. This probe hybridized to DNA fragments present only in digests of total human DNA or to the DNAs of cell lines which contained human chromosome 1. The major families of human U1 RNA genes were identified, but some human genes may have gone undetected. Also, the presence of a few U1 RNA genes on human chromosome 19 could not be ruled out. In spite of the lack of extensive 5'-flanking-region homology between the human and mouse U1 RNA genes, the genes of both species were efficiently transcribed in the hybrid cells, and the U1 RNAs of both species were incorporated into specific ribonucleoprotein particles.

Molecular cloning of the c-fms locus and its assignment to human chromosome 5

Molecular clones of the retroviral oncogene v-fms were used to isolate recombinant bacteriophages containing c-fms proto-oncogene sequences from a human placental DNA library. Viral and cellular fms sequences were used in Southern blotting experiments with a panel of 32 human X mouse somatic cell hybrids to assign the human c-fms proto-oncogene to human chromosome 5.

Identification and isolation of transcribed human X chromosome DNA sequences

A human X chromosome specific phage library has been used as a source of X-specific genomic DNA clones which hybridize with cellular RNA. Random cDNA clones were mapped for X chromosome sequence localization and 8 were identified as hybridizing to X chromosome Hind III fragments. All eight also hybridized with autosomal Hind III fragments. The X chromosome genomic sequences corresponding to two of these cDNA clones were isolated from a phage library constructed with the Hind III endonuclease digest products of X enriched DNA. One genomic DNA segment, localized to the short area of the X, shared sequence homology with at least one region of the human Y chromosome. The methodology developed represents a rapid means to obtain a specific genomic DNA clone from a single chromosome when multiple different genomic loci homologous to an expressed DNA sequence exist.

Karyotypic progression in human tumors

Karyotypic progression may be viewed in at least two ways. One approach seeks evidence for increasing and progressive deviation from the normal chromosome pattern in tumors. The clearest examples, found in some leukemias, are those in which successive karyotypic changes are superimposed on an already aberrant cell population. Evidence of chromosomal progression within solid tumors is far less frequent, possibly because the tumors themselves are at a relatively late stage in their evolution. An alternative approach, therefore, attempts to correlate the extent of karyotypic deviation with other aspects of tumor progression. Recent data, based on classical cytogenetic analyses and flow cytometry, are presented to determine relationships between karyotype and specific origin and morphology of tumors. The predominant theme which emerges, not surprisingly, is that the more deviant chromosome patterns are associated with other measures of increased biologic malignancy. What is surprising is the degree to which these properties are expressed in primary tumors and the relative lack of evidence for further karyotypic evolution with recurrence or metastasis. Examples of genetic instability, evolution through polyploidy, gene amplification, and selection for specific chromosomal rearrangement are found in populations of premalignant and malignant human cells. There is increasing recognition of the importance of tumor-specific chromosome aberrations in the stepwise progression from the normal to the fully neoplastic cell.