Showing papers by "Stephen J. O'Brien published in 1986"

Human endothelial cell growth factor: cloning, nucleotide sequence, and chromosome localization

Abstract: Several of the endothelial cell polypeptide mitogens that have been described probably play a role in blood vessel homeostasis. Two overlapping complementary DNA clones encoding human endothelial cell growth factor (ECGF) were isolated from a human brain stem complementary DNA library. Southern blot analysis suggested that there is a single copy of the ECGF gene and that it maps to human chromosome 5 at bands 5q31.3 to 33.2 A 4.8-kilobase messenger RNA was present in human brain stem messenger RNA. The complete amino acid sequence of human ECGF was deduced from the nucleic acid sequence of these clones; it encompasses all the well-characterized acidic endothelial cell polypeptide mitogens described by several laboratories. The ECGF-encoding open reading frame is flanked by translation stop codons and provides no signal peptide or internal hydrophobic domain for the secretion of ECGF. This property is shared by human interleukin-1, which is approximately 30 percent homologous to ECGF.

Morphological variability and asymmetry in the cheetah (acinonyx jubatus), a genetically uniform species.

Abstract: The African cheetah (Acinonyx jubatus) is an unusual species because of its extremely low amount of biochemical genetic variation. A comparative analysis of morphological variation of 16 cranial characters from four species of Felidae (ocelot, Leopardus pardalus; margay, L. wiedii; leopard, Panthera pardus; and cheetah) was undertaken to evaluate the consequence of biochemical monomorphism on morphological variation. The species were selected because the cheetah has been shown previously to possess extremely low amounts of biochemical genetic variation as opposed to the other three species which retain comparatively high levels of allozyme heterozygosity. The cheetah sample showed dramatically greater fluctuating asymmetry but was not outstanding in morphological variability. Elevated levels of fluctuating asymmetry have been interpreted as a reflection of developmental instability, which is a common consequence of inbreeding. The inverse correlation of genetic variation and developmental stability (homeostasis) observed here fulfills prior expectations and further emphasizes the genetic invariability of the cheetah species.

Cloning, characterization, expression, and chromosomal localization of a human ferritin heavy-chain gene

Abstract: A genomic phage clone containing a full-length copy of a functional human gene for ferritin heavy chain has been isolated. The gene consists of four exons spanning approximately 3 kilobases and has been localized to chromosome 11. The functionality of the gene was demonstrated by the fact that both transient transfectants and stable transformants of murine fibroblasts actively transcribe human ferritin heavy-chain mRNA.

Tetraploid partial hydatidiform moles: two cases with a triple paternal contribution and a 92,XXXY karyotype.

Abstract: In the course of a systematic study of cytogenetics, morphology, and clinical follow-up of hydatidiform moles we encountered two unusual cases of partial hydatidiform moles each with a 92,XXXY karyotype. Previously reported cases of tetraploidy, of 92,XXXX or 92,XXYY karyotype, resulted from a failure of the first mitotic division of a normal zygote. This is to our knowledge the first report of tetraploidy with XXXY sex chromosomes. Study of chromosomal heteromorphisms, isozymes, and restriction fragment length polymorphisms reveal that both present cases resulted from a combination of a haploid ovum with three haploid sets of paternal chromosomes either by the mechanism of trispermy (involving three separate haploid spermatozoa) or through dispermy (involving one haploid and one diploid sperm). Both cases resembled closely partial moles in their morphology; one gave a highly typical clinical picture while the other was recognized at an early voluntary abortion. Partial moles are ordinarily triploids of nearly always diandric constitution that evince focal villous swelling with cistern formation and focal trophoblastic hyperplasia. The findings here presented point to an association of molar phenotype with an excess of paternal over maternal haploid sets.

Genetic variation within and among lion tamarins

Abstract: The golden lion tamarin Leontopithecus rosalia rosalia, one of the rarest and most endangered of New World primates, has been the focus of an intensive research and conservation effort for two decades. During that period, managed breeding from 44 founders has brought the captive population to over 400 individuals, a number that equals or exceeds the estimated number of free-ranging golden lion tamarins. The extent of genetic variation among golden lion tamarins was estimated with an electrophoretic survey of 47 allozyme loci from 67 captive and 73 free-ranging individuals. The amount of variation was low, compared to 15 other primate species, with 4% of the loci being polymorphic (P), and with an average heterozygosity H estimate of 0.01 in these callitrichids. Electrophoretic analyses of captive and free-ranging animals (N = 31) of two allopatric morphotypes, Leontopithecus rosalia chrysopygus and L. r. chrysomelas, were similar to the L. r. rosalia findings insofar as they also revealed limited genetic polymorphism. Computation of the Neigenetic distance measurements showed that the three morphotypes were genetically very similar, although discernible differentiation had occurred at two loci. These data are consistent with the occurrence of recent reproductive isolations of these subspecies.

Amplification and chromosomal dispersion of human endogenous retroviral sequences

Abstract: Endogenous retroviral sequences in humans have undergone amplification events involving both viral and flanking cellular sequences. We cloned members of an amplified family of full-length endogenous retroviral sequences. Genomic blotting, employing a flanking cellular DNA probe derived from a member of this family, revealed a similar array of reactive bands in both humans and chimpanzees, indicating that an amplification event involving retroviral and associated cellular DNA sequences occurred before the evolutionary separation of these two primates. Southern analyses of restricted somatic cell hybrid DNA preparations suggested that endogenous retroviral segments are widely dispersed in the human genome and that amplification and dispersion events may be linked.

Genetic Monitors of Zoo Populations: Morphological and Electrophoretic Assays

Abstract: Zoo populations can be empirically studied and monitored genetically from three distinct and informative prospectives: (1) the careful collection of breeding and pedigree history; (2) biochemical genetic surveys of gene variation from electrophoretic data; and (3) the extent of variation in morphological characters. We present here a summary of the results and conclusions of biochemical genetic surveys performed to date in mammals and indicate those biochemical genetic loci most likely to be informative in management programs. The results of a number of studies of morphological variation (estimated by coefficients of variation or fluctuating asymmetry) as related to the genetic status of biological populations are reviewed. The applications of such measurements to the characterization of the South African cheetah are reviewed briefly with attention to captive vertebrate species. Specific recommendations for the evaluation of captive populations and for the monitoring of breeding programs by using biochemical and morphological characters are proposed.

Chromosomal mapping of beta-globin and albino loci in the domestic cat A conserved mammalian chromosome group

Abstract: Siamese cats are homozygous for the recessive cs allele of the color (albino) locus. The c locus is shown here by backcross analysis to be linked to the beta-hemoglobin (HBB) locus in the cat at a distance of approximately eight centiMorgans. The HBB locus and, by inference, the c locus were assigned to feline chromosome D1, by analysis of genomic DNAs from a panel of rodent X cat somatic cell hybrids with a molecular clone of the human beta-globin locus. Evolutionary conservation of the synthetic homology of feline chromosome D1 and human chromosome 11 is extensive. Comparison of high resolution G-trypsin-banded preparations of the two chromosomes permitted cytological alignment of the long arm of the conserved chromosomes providing that a minimum of one paracentric inversion is hypothesized. The placement of the albino locus on conserved syntenic groups of several markers (HBB, HRAS, LDHA) in both cat and mouse strongly indicates the conservative placement of the as yet unmapped human albino locus in the homologous syntenic group on human chromosome 11p.

Empirical demonstration that structural gene and morphometric variation of mandible traits are uncoupled between mouse strains

Abstract: The relationship between morphometric and structural gene variation was examined in a group of 15 inbred mouse strains. The genetic distance of Nei was calculated between each of the strains based upon 36–78 biochemical loci. Mahalanobis distances based on 11 mandibular measurements were computed between the strains as well. The correlation coefficient between genetic distance and metric distance was low ( r = 0.24 ± 0.1). Genetic distance was highly correlated with elapsed time of divergence of the strains ( r = 0.73 ± 0.15) while morphometric distance, though clearly heritable, was not significantly correlated with elapsed time. These results indicate that morphological change and biochemical change are poorly coupled in these strains and suggest that the cumulative differences in structural gene mutations may provide a more accurate measure of phylogenetic relationships between biological groups than do measures of morphological distance (such as mandibular characters) based upon multivariate analysis.

Comparative genetic mapping of cellular rel sequences in man, mouse, and the domestic cat.

Abstract: We used in situ hybridization techniques to assign the human c-rel locus to the centromere-proximal portion of the short arm of chromosome 2 (2cent-2p13). We also determined the chromosomal location of c-rel sequences in the domestic cat and the laboratory mouse by using a human c-rel fragment to screen panels of rodent X cat and hamster X mouse somatic cell hybrid DNAs. The c-rel locus apparently maintains similar syntenic relationships with other known genetic markers in the human and cat, but displays different linkage relationships in the mouse.

Chromosomal mapping of enzyme loci in the domestic cat: GSR to C2, ADA and ITPA to A3, and LDHA-ACP2 to D1.

Abstract: A panel of 42 rodent × cat somatic cell hybrids segregating individual cat chromosomes in different combinations was used to assign five isozyme structural loci to cat chromosomes. The feline homolog for glutathione reductase (GSR) was mapped to chromosome C2. Adenosine deaminase (ADA) and inosine triphosphatase (ITPA) were located on chromosome A3. Lactate dehydrogenase-A (LDHA) and acid phos-phatase-2 (ACP2) were reassigned to chromosome Dl. Localization of these genes increases the known feline genetic map and extends the known syntenic homologies between the cat and other mammalian species.

The avian and mammalian ets genes: molecular characterization, chromosome mapping, and implication in human leukemia.

Abstract: The mammalian homologs of the ets-region from the transforming gene of avian erythroblastosis virus, E26, consist of two distinct domains located on different chromosomes. Using somatic cell hybrid panels, the mammalian homologs of the 5' v-ets-domain, ets-1, were mapped to chromosome 11 in man, to chromosome 9 in mouse, and to chromosome D1 in cat. The mammalian homologs of the 3'v-ets domain, ets-2, were similarly mapped to human chromosome 21, to mouse chromosome 16, and to feline chromosome C2. We conclude that the ets sequence shared by the virus, chicken, and man is likely to contain at least two functionally dissociable domains, identifiable as ets-1 and ets-2. The human ets- locus is transcriptionally active and encodes a single mRNA of 6.8 kb, while the second locus, human ets-2 encodes three mRNAs of 4.7, 3.2 and 2.7 kb. By contrast, the chicken homolog, having a contiguous ets-1 and ets-2 sequence, is primarily expressed in normal chicken cells as a single 7.5 kb mRNA. Because chromosome translocations have been associated with different human hematopoietic malignancies, we have used our human probes to study specific translocations occurring in acute leukemias. The human ets- gene was found to translocate from chromosome 11 to 4 in t(4;11) (q21;23) and the human ets-2 gene was found to translocate from chromosome 21 to 8 in t(8;21) (q22;q22). Significantly, both translocations were associated with an expression of ets genes which differed from that found in normal diploid lymphoid cells.

Molecular Evolution of ets Genes from Avians to Mammals and Their Cytogenetic Localization to Regions Involved in Leukemia

Abstract: The mammalian homologues of the ets-region from the transforming gene of avian erythroblastosis virus, E26, consists of two distinct domains located on different chromosomes. Using somatic cell hybrid panels, the mammalian homolog of the 5' v-ets-domain (ets-1) was mapped to chromosome 11 in man, to chromosome 9 in mouse, and to chromosome D1 in cat. The mammalian homolog of the 3' v-ets domain (ets-2) was similarly mapped to human chromosome 21, to mouse chromosome 16, and to feline chromosome C2. To better define the human proto-ets domains, the genomic DNA was molecularly cloned and sequences analyzed. The ets-related sequences of human DNA on chromosomes 11 and 21 were found to be discontiguous, unlike that of the chicken and avian E26 virus genome, except for a small overlap region. We conclude that the ets sequence shared by the virus, the chicken and man is likely to contain at least two dissociable functional domains, identifiable as ets-1 and ets-2. The human ets-1 locus is transcriptionally active and encodes a single mRNA of 6.8 kb, while the second locus, human ets-2 encodes three mRNAs of 4.7, 3.2 and 2.7 kb. By contrast, the chicken homolog, having a contiguous ets-1 and ets-2 sequence, is primarily expressed in normal chicken cells as a single 7.5 kb mRNA. Because chromosome translocations have been associated with different human disorders, we have used our human probes with two panels of rodent-human cell hybrids to study specific translocations occurring in acute myeloid leukemias (AML). The human ets-1 gene was found to translocate from chromosome 11 to 4 in t(4;11)(q21;q23) and the human ets-2 gene was found to translocate from chromosome 21 to 8 in t(8;21)(q22;q22). Both translocations were found associated with the altered expression of ets.

Genetic analysis in mammals: past, present, and future.

Abstract: In the mid-1960s, when I first became interested in animal genetics as an undergraduate student, the revolution in biological and genetic technology which is realized today was a mere twinkle in the eye of practicing geneticists. The human gene map contained only a few loci, mostly on the X-chromosome, and Drosophila was the undisputed leader in genetic analysis of metazoans. The mouse genome was the prototype of mammalian gene studies because of the terrific advantages offered by the development of inbred mice. Mendel’s laws were (and still are) the cornerstone of eukaryote genetics and intuitive genetic analysis was a talent practiced by such pioneers as Bridges, Morgan, McClintock, Dobzhansky, and Green. Since that period, the field of animal genetics has grown appreciably due in no small way to the terrific explosion of molecular biology, parasexual genetic analysis, and DNA methodology. Today, we have in our scientific repertoire the ability to examine gene action virtually by direct observation and to put to the test the scores of intriguing hypotheses that have emerged during the deductive period of genetics.