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PubMed1995

Genetic characterization of isolates of Giardia duodenalis by enzyme electrophoresis: implications for reproductive biology, population structure, taxonomy, and epidemiology.

The nature and extent of genetic variation in Giardia was used to infer its mode of reproduction, population structure, taxonomy, and zoonotic potential. Ninety-seven isolates of Giardia duodenalis, from a defined area in Western Australia and throughout Australia and overseas, were obtained from humans, cats, cattle, sheep, dogs, goat, beaver, and rats. Enzyme electrophoresis revealed extensive genetic variation with 47 different zymodemes. The widespread occurrence of certain zymodemes and the similarity of relationships among isolates inferred from independent genetic markers suggests a clonal population structure for G. duodenalis, although occasional bouts of genetic exchange may occur. The 47 zymodemes clustered similarly in phenetic (UPGMA) and phylogenetic (Fitch-Margoliash) analyses. The level of genetic diversity in isolates from a defined geographical area in Western Australia was similar to the level of diversity in isolates from throughout Australia. These data suggest that clonal lineages within G. duodenalis are evolutionarily independent. Although there was a significant overall correlation between genetic distance separating zymodemes and occurrence in different host species, we found genetically identical isolates from humans and other animals and extensive genetic diversity between isolates from humans. We interpret this as evidence for zoonotic transmission of the parasite.

Animals↗
PubMed1995

Genetic characterization of ms (3) K81, a paternal effect gene of Drosophila melanogaster.

The vast majority of known male sterile mutants of Drosophila melanogaster fail to produce mature sperm or mate properly. The ms(3) K81(1) mutation is one of a rare class of male sterile mutations in which sterility is caused by developmental arrest after sperm entry into the egg. Previous studies showed that males homozygous for the K81(1) mutation produce progeny that arrest at either of two developmental stages. Most embryos arrest during early nuclear cycles, whereas the remainder are haploid embryos that arrest at a later stage. This description of the mutant phenotype was based on the analysis of a single allele isolated from a natural population. It was therefore unclear whether this unique paternal effect phenotype reflected the normal function of the gene. The genetic analysis and initial molecular characterization of five new K81 mutations are described here. Hemizygous conditions and heteroallelic combinations of the alleles were associated with male sterility caused by defects in embryogenesis. No other mutant phenotypes were observed. Thus, the K81 gene acted as a strict paternal effect gene. Moreover, the biphasic pattern of developmental arrest was common to all the alleles. These findings strongly suggested that the unusual embryonic phenotype caused by all five new alleles was due to loss of function of the K81+ gene. The K81 gene is therefore the first clear example of a strict paternal effect gene in Drosophila. Based on the embryonic lethal phenotypes, we suggest that the K81+ gene encodes a sperm-specific product that is essential for the male pronucleus to participate in the first few embryonic nuclear divisions.

Alleles↗
PubMed2005

Genetic characterization and fine mapping of a novel thermo-sensitive genic male-sterile gene tms6 in rice (Oryza sativa L.).

The application of genetic male sterility in hybrid rice production has great potential to revolutionize hybrid seed production methodology. The two-line breeding system by using thermo-sensitive genic male sterility (TGMS) has been discovered and successfully developed as a breeding strategy in rice. One TGMS gene was investigated by a spontaneous rice mutant line, Sokcho-MS, originated from a Korean japonica variety. It was shown that Sokcho-MS is completely sterile at a temperature higher than 27 degrees C and/or lower than 25 degrees C during the development of spikelets, but fertile at the temperature ranging from 25 to 27 degrees C regardless of the levels of day-length. Genetic analysis and molecular mapping based on SSR, STS and EST markers revealed that a single recessive gene locus involved the control of genic male sterility in Sokcho-MS. By using an F2 mapping population derived from a cross between Sokcho-MS and a fertile indica variety Neda, the new TGMS gene, designated as tms6, was mapped primarily to the long arm of chromosome 5 of Oryza sativa at the interval between markers E60663 (2.0 cM) and RM440 (5.8 cM). Subsequently, tms6 was fine mapped to the interval between markers RM3351 (0.1 cM) and E60663 (1.9 cM). As tms6 appeared to be independent of other mapped TGMS genes in rice, the genetic basis of Sokcho-MS was further discussed.

Breeding↗
PubMed2002

Enrichment, immunomorphological, and genetic characterization of fetal cells circulating in maternal blood.

Fetal cells circulating in the peripheral blood of pregnant women are a potential target for noninvasive genetic analyses. They include epithelial (trophoblastic) cells, which are larger than peripheral blood leukocytes. We enriched circulating trophoblastic cells using the isolation by size of epithelial tumor cells (ISET) method. Peripheral blood was obtained at 11 to 12 weeks of pregnancy. Cells isolated by ISET were stained by hematoxylin and eosin or by immunohistochemistry. Large epithelial cells were microdissected and fetal cell identification was obtained by polymerase chain reaction with short tandem repeats and/or Y-specific primers. By analyzing only 2 ml of blood, we found a variable number (n = 1 to 7) of Y-positive cells (overall 15 of 23) in all of the six mothers carrying a male fetus. In contrast, none of the 26 cells isolated from seven mothers carrying a female fetus scored positive. Eleven cells were analyzed by using short tandem repeat-specific markers: six of them showed a fetal profile and five showed a maternal profile consistently with Y-specific results. Only one-fifth of the single cell DNA was used for fetal cell assessment, leaving enough material for further genetic tests. We also show that the ISET approach allows the performance of fluorescence in situ hybridization analyses and the detection of DNA point mutations in single microdissected cells. We conclude that this is a powerful approach to enrich circulating fetal cells and prove their fetal origin, and that it may have implications for noninvasive prenatal diagnosis of genetic disorders.

Cell Separation↗
PubMed2006

Genetic characterization of Argentine and Bolivian Creole cattle breeds assessed through microsatellites.

In the present report, the polymorphisms from 9 microsatellites were used to assess genetic diversity and relationships in 4 Creole cattle breeds from Argentina and Bolivia, 4 European taurine breeds, and 2 American zebu populations. The Creole populations display a relatively high level of genetic variation as estimated by allelic diversity and heterozygosity, whereas the British breeds displayed reduced levels of genetic diversity. The analysis of molecular variance indicated that 7.8% of variance can be explained by differences among taurine and zebu breeds. Consistent with these results, the first principal component (PC), which comprised the 40% of the total variance, clearly distinguishes these 2 groups. In addition, all constructed phylogenetic trees cluster together Nelore and Brahman breeds with robust bootstrap values. Only 1% of variance was due to difference between American Creole and European taurine cattle. Although this secondary split was supported by the classical genetic distance and the second PC (15%), the topology of trees is not particularly robust. The presence of zebu-specific alleles in Creole cattle allowed estimating a moderate degree of zebu admixture. When these data were compared with mitochondrial and Y chromosomal studies, a clear pattern of male-mediated introgression was revealed. The results presented here contribute to the understanding of origin and history of the American Creole cattle.

Alleles↗
PubMed1995

Genetic characterization of two phototropism mutants of Phycomyces with defects in the genes madI and madJ.

Two Phycomyces genes, madI and madJ, which are involved in phototropism, were characterized by recombination and complementation analyses. The madI gene was located on linkage group IV of the genetic map of Phycomyces, 27 map units away from the gene carA. Complementation and recombination studies involving the genes madD, madE, madF, and madG, in combination with previous genetic studies, show that the recently isolated mad-407 mutation defines a novel behavioural gene, madJ, of Phycomyces. A regulatory role of the madJ gene product in the light-sensory transduction pathway is suggested.

Chromosome Mapping↗
PubMed2006

Genetic characterization of VP3 gene of group A rotaviruses.

We sequenced VP3 gene of four rotavirus strains and examined the diversity of VP3 and its other genetic characteristics in a total of 22 Group A rotaviruses. The 22 rotavirus strains were derived from six different host species (human, avian, bovine, equine, simian and porcine). Comparison of the partial VP3 peptide sequences (aa 141-294) showed identities ranging from 49 to 99% among different species. The phylogenetic analysis of VP3 sequences revealed segregation according to the species origin. This was further confirmed by identification of three host specific domains within the VP3 peptide. Thus, the host range restriction or attenuation previously shown to associate with VP3 may be attributed to the species-specific nature of the gene.

Amino Acid Sequence↗
PubMed2002

Cloning and genetic characterization of blood group carrier molecules and antigens.

Based on the astounding pace of growth in the field of molecular biology over the last 2 decades, we are now able to consider the allogenicity of transfused blood products in genetic terms. In this sense, the allogenic barriers to the transfusion-based transplantation are defined by differences between those portions of the donor and recipient genomes that define the antigenicity and immune response to transfused cells. The genetic basis of the major histocompatibility complex barrier described earlier is because of well-characterized transcription from a polymorphic locus on chromosome 6 in nonerythroid cells. In contrast, the allo-barrier of ABO-matched RBC transfusion is the result of differences in over 2 dozen independent genes expressed during erythropoiesis that encode a wide variety of molecules important in membrane biology. Variability in the structure of those genes among separate donors often provides the molecular basis of many blood group antigens and phenotypes. This article reviews our current knowledge of the human blood group systems in genetic terms, focusing on strategies used to identify the relevant genes and their polymorphisms.

Animals↗
PubMed1991

Genetic characterization of the APC locus involved in familial adenomatous polyposis.

Familial adenomatous polyposis is a rare disease inherited in a Mendelian dominant fashion. It is characterized by the occurrence of more than 100 adenomatous polyps in the large bowels of affected individuals. The genetic defect responsible for adenomatous polyposis resides at a locus called APC which has been localized to the long arm of human chromosome 5. In this study, the APC locus was mapped with respect to 11 markers known to map to this chromosomal segment. Linkage of APC to four of these markers had been previously reported. Three additional markers are shown here to be linked to APC. By multipoint analysis, the APC locus maps to an interval bounded by D5S49 and D5S58. The refined map of the APC locus and the new markers described here improve the informativeness and accuracy of the presymptomatic diagnosis of familial adenomatous polyposis.

Adenomatous Polyposis Coli↗
PubMed2006

Nonstarter lactobacilli isolated from soft and semihard Argentinean cheeses: genetic characterization and resistance to biological barriers.

Nonstarter lactic acid bacteria isolated from Argentinean cheeses were identified and characterized by focusing on their resistance to biological barriers, along with other physiological features of potential interest, in the search for future probiotic organisms. Lactobacilli were enumerated and isolated from semihard and soft cheeses made with multistrain Streptococcus thermophilus starters. Lactobacilli counts in 1-week-old cheeses were between 10(5) and 10(7) CFU/g and then reached 10(7) CFU/ g in all 1-month samples, while streptococci were always above 10(9) CFU/g. A total number of 22 lactobacilli isolates were retained, identified, and characterized by in vitro tests. Species identity was determined by carbohydrate metabolism and species-specific PCR assays. Genetic diversity was explored by random amplified polymorphic DNA (RAPD) PCR analysis. The Lactobacillus strains were assigned to the species L. casei, L. plantarum, L. rhamnosus, L. curvatus, L. fermentum, and L. perolens. All the strains studied tolerated 25 ppm of lysozyme, and most of them showed resistance to 0.3% bile. After incubation in gastric solution (pH 2.0), counts decreased by several log units, ranging from 3.2 to 7.0. The strains were able to grow in the presence of bile salts, but only three isolates were capable of deconjugation. The nonstarter lactobacilli that were assayed fermented the prebiotic substrates (especially lactulose and inulin). Some strains showed high cell hydrophobicity and beta-galactosidase activity, as well as inhibitory activity against pathogenic bacteria. It was concluded that most of the lactobacilli isolated in this study demonstrated resistance to biological barriers and physiological characteristics compatible with probiotic properties, which make them suitable for further research in in vivo studies aimed at identifying new probiotic organisms.

Argentina↗
PubMed1992

Genetic characterization of the secretory mutant MS-1 of Tetrahymena thermophila: vacuolarization and block in secretion of lysosomal hydrolases are caused by a single gene mutation.

The genetics and phenotypic features (light and electron microscopy) of a secretory mutant, MS-1 of Tetrahymena thermophila blocked in secretion of lysosomal acid hydrolases have been analyzed. Although blocked constitutively in secretion, MS-1 contains active lysosomal hydrolases in amounts equivalent to the wild type. The 3:1 segregation in F-2 in sib crosses and the 1:1 segregation in test crosses indicate that the block in secretion of lysosomal hydrolases is controlled by a recessive single gene locus termed sec. The sec allele of MS-1 proved also to be responsible for the highly vacuolarized phenotype the mutant developed when it was transferred from nutrient medium into buffers of low ionic strength. Deletion mapping by crossing MS-1 with nullisomic strains, all secreting lysosomal hydrolases at wild-type rates, was performed. The sec phenotype was expressed in monosomic-4 progeny only, indicating that the sec allele is located on chromosome 4 of T. thermophila.

Alleles↗
PubMed1996

Genetic characterization of two phenotypically distinct North American ovine lentiviruses and their possible origin from caprine arthritis-encephalitis virus.

Ovine and caprine lentiviruses are closely related genetically and antigenically although the diseases that these viruses cause in their respective host animals can vary greatly. In sheep, syndromes consist primarily of interstitial pneumonia with rare occurrences of arthritis and encephalitis, whereas in goats, the disease expresses mainly as arthritis in adult animals with rare cases of encephalitis in newborns. Experimentally, viruses from either sheep or goats can infect animals of the reciprocal species and many field strains of ovine lentivirus have biological properties similar to those of caprine viruses. However, a molecular correlation for the phenotypic differences between ovine and caprine lentivirus strains is unknown. To investigate this, we examined genetic characteristics of two phenotypically distinct North American ovine lentiviruses. Nucleotide sequence analysis of the envelope regions from virus strains 85/34 and 84/28 showed that despite significant biological differences, these viruses are closely related to each other and are genotypically more homologous to caprine arthritis-encephalitis virus (CAEV) than to visna virus of sheep. Furthermore, analysis of the nucleotide substitutions in their env regions indicated that when differences between the two ovine viruses and CAEV were found, the changes often resulted in nucleotides homologous with visna virus. These results suggest that the two field strains of ovine lentivirus may have originated from a cross-species infection of sheep by a CAEV-like virus and, evolution of their genomes toward that of ovine lentivirus may be reflective of adaptation of these viruses to the new ovine host.

Animals↗
PubMed2005

Immortalization of human extravillous cytotrophoblasts by human papilloma virus gene E6E7: sequential cytogenetic and molecular genetic characterization.

Extravillous cytotrophoblast (EVCT) cultures from the normal placentas of three pregnant women were transfected by HPVE6E7. Sequential cytogenetic and molecular analyses were performed to delineate genetic events that may be critical for cell immortalization. One line, PE1-E6E7, was immortalized successfully, whereas 2 other lines, PE3-E6E7 and PE4-E6E7, could not be maintained beyond crisis. Before crisis, the majority of cells in all lines were karyotypically normal. During the early stages of crisis, there was progressive telomere shortening. Most cells were karyotypically abnormal, with extreme cytogenetic divergence and a predominance of telomeric association and dicentric chromosomes affecting many chromosomes. At the later stages of crisis, the karyotype became more convergent with a drastic decrease in nonclonal aberrations. In PE1-E6E7, after crisis the karyotype was complex, with frequent centromeric rearrangements in the form of isochromosomes and whole-arm translocations. There were unbalanced structural aberrations and numerical changes, including loss of chromosome 13, that could be traced throughout the evolution of the line. These findings support the concept that immortalization is a relatively rare and nonrandom event that occurs only in cells that have acquired the necessary or critical genetic alterations. Telomeric dysfunction may be an important mechanism leading to the acquisition of complex karyotypical aberrations.

Cells, Cultured↗
PubMed1991

A genetic characterization of the nadC gene of Salmonella typhimurium.

The nadC gene of Salmonella encodes the pyridine biosynthetic enzyme PRPP-quinolinate phosphoribosyltransferase. Using a combination of genetic techniques, a deletion map for the Salmonella nadC gene has been generated which includes over 100 point mutants and 18 deletion intervals. The nadC alleles obtained by hydroxylamine mutagenesis include those suppressed by either amber, ochre, or UGA nonsense suppressors as well as alleles suppressed by the missense suppressor, sumA. Deletions were obtained by three separate protocols including spontaneous selection for loss of the nearby aroP gene, recombination between aroP::MudA and nadC::MudA insertion alleles, and selection for spontaneous loss of tetracycline resistance in a nearby guaC::Tn10dTc insertion mutant allele. The nadC mutants comprise one complementation group and the nadC+ allele is dominant to simple, nadC auxotrophic mutant alleles. Intragenic complementation of two nadC alleles, nadC493 and nadC494, mapping to deletion intervals 17 and 18, respectively, suggests that nadC encodes a multimeric enzyme. Both nadC and the nearby aroP locus are transcribed counterclockwise on the standard genetic map of Salmonella, in opposite orientation to the direction of chromosome replication.

Chromosome Mapping↗
PubMed2005

Preliminary genetic characterization of two lineages of black rats (Rattus rattus sensu lato) in Japan, with evidence for introgression at several localities.

We conducted a pilot survey of genetic diversity among 37 karyotyped individuals of the black rat Rattus rattus (sensu lato) from six localities on the Japanese Islands, using complete gene sequences of mitochondrial cytochrome b (cyt b) and nuclear interphotoreceptor retinoid binding protein (IRBP). Our sampling included two previously documented karyotypic groups: 'Oceanian' with 2n = 38 and 'Asian' with 2n = 42. Cyt b sequences for most individuals clustered according to their karyotypic groups, with an average between-group divergence of 3.8%. One exception was that individuals from Kagoshima (Kyushu Island) showed 'Asian' karyotypes combined with a cyt b haplotype that differed by a single nucleotide substitution from the haplotype of the 'Oceanian' karyotypic group. Six IRBP haplotypes were identified. They belonged to three distinct IRBP lineages (I-III), with an average inter-lineage divergence of 1%. Among homozygous individuals, these lineages showed good association with the karyotypic groups: IRBP lineage I occurred only with 'Oceanian' karyotypes, while IRBP lineages II and III both occurred with 'Asian' karyotypes. Individuals from Kagoshima all possessed IRBP of 'Asian' lineages, despite the presence of an 'Oceanian' mitochondrial type. The Chichijima population (Ogasawara Islands) featured exclusively 'Asian' karyotypes and cyt b sequences, but various combinations of all three IRBP lineages. The Kagoshima and Chichijima populations thus provide strong evidence of viable hybridization and genetic introgression between the two karyotypic groups, but with variable genetic outcomes. Our results demonstrate the potential of combined analysis of karyotypes and mitochondrial and nuclear gene sequences to elucidate the complex dispersal and population history of the black rat.

Animals↗