A genetic map of nine loci on bovine chromosome 2

Rescuing valuable genomes by animal cloning: a case for natural disease resistance in cattle

Tissue banking and animal cloning represent a powerful tool for conserving and regenerating valuable animal genomes. Here we report an example involving cattle and the rescue of a genome affording natural disease resistance. During the course of a 2-decade study involving the phenotypic and genotypic analysis for the functional and genetic basis of natural disease resistance against bovine brucellosis, a foundation sire was identified and confirmed to be genetically resistant to Brucella abortus. This unique animal was utilized extensively in numerous animal breeding studies to further characterize the genetic basis for natural disease resistance. The bull died in 1996 of natural causes, and no semen was available for AI, resulting in the loss of this valuable genome. Fibroblast cell lines had been established in 1985, cryopreserved, and stored in liquid nitrogen for future genetic analysis. Therefore, we decided to utilize these cells for somatic cell nuclear transfer to attempt the production of a cloned bull and salvage this valuable genotype. Embryos were produced by somatic cell nuclear transfer and transferred to 20 recipient cows, 10 of which became pregnant as determined by ultrasound at d 40 of gestation. One calf survived to term. At present, the cloned bull is 4.5 yr old and appears completely normal as determined by physical examination and blood chemistry. Furthermore, in vitro assays performed to date indicate this bull is naturally resistant to B. abortus, Mycobacterium bovis, and Salmonella typhimurium, as was the original genetic donor.

Molecular cloning, genetic mapping, and developmental expression of a bovine transforming growth factor beta (TGF-beta) type I receptor

A full-length cDNA encoding the bovine transforming growth factor beta (TGF-beta) receptor type I (bT beta R-I) was isolated from a placenta cDNA library. The deduced protein sequence of 499 residues contains a single transmembrane domain, a cysteinerich extracellular domain, and an intracellular kinase domain with predicted serine/threonine specificity. The amino acid sequence is 96% and 95% identical with its human and mouse homologues, respectively. Genetic mapping assigned the TGFBR1 gene to bovine chromosome 8 at a male genetic distance of 2 centimorgan from D8S28. Assuming conservation of gene order, the linkage data define a breakpoint in mammalian chromosome evolution. Both TGF-beta receptor type I and II mRNAs were found to be expressed in bovine oocytes and preimplantation two-cell, four-cell, eight-cell, morula-, and blastocyst-stage embryos, as determined by heminested reverse transcription polymerase chain reaction (RT-PCR). The mRNA expression patterns of TGF-beta receptor types I, II, and III in a variety of bovine organ tissues were examined by Northern blot hybridization, and highest levels were detected in lung and ovary.

Using PCR to Distinguish Diaporthe phaseolorum and Phomopsis longicolla from Other Soybean Fungal Pathogens and to Detect Them in Soybean Tissues

Restriction fragment length polymorphism analyses of polymerase chain reaction (PCR) amplified DNA were used to distinguish Diaporthe phaseolorum and Phomopsis longicolla isolates from other soybean fungal pathogens. Primers made to the conserved sequences of nuclear ribosomal DNA amplified the internal transcribed spacer (ITS) regions of D. phaseolorum var. meridionalis and P. longicolla. The PCR products were cloned and then sequenced. Specific-primers, Phom.I and Phom.II, were designed from the polymorphic regions of D. phaseolorum and P. longicolla isolates from soybean to distinguish them from other soybean fungal pathogens. These ITS-derived primers amplified a 337-bp-specific DNA fragment from P. longicolla, D. phaseolorum var. meridionalis, D. phaseolorum var. caulivora, D. phaseolorum var. sojae, and Phomopsis spp. from 20 different hosts. No amplified product was observed using DNA of seven other soybean fungal pathogens or soybean DNA. The detection limit of PCR using primers Phom.I and Phom.II was 2.5 × 10^-7 dilution of fungal DNA extracted from samples of 10 pooled seeds and as low as a 1:15 (Phomopsis:soybean) ratio when using 10 ng of DNA per μl from each P. longicolla and soybean. PCR did not produce products using primers Phom.I and Phom.II with DNA extracted from noninfected seeds, but specific bands were observed from samples of 10 pooled seeds and from individually infected seeds. A specific band was observed as well from DNA extracts of tissue samples from symptomless plants inoculated with P. longicolla and D. phaseolorum var. sojae.

Comparative FISH-mapping of villin (VIL) gene in river buffalo, sheep and goat chromosomes

Two genomic clones of the villin (VIL) gene were independently hybridized on river buffalo (Bubalus bubalis, BBU), sheep (Ovis aries, OAR) and goat (Capra hircus, CHI) chromosomes by using sequential fluorescence in situ hybridization (FISH) and R-banding (RBP- and RBA-banding). Clear hybridization signals revealed that VIL is located in BBU 2q33, OAR 2q33 and CHI 2q33. These chromosomes and chromosome bands are believed to be homologous and the VIL locus is the same as that previously found on cattle chromosome 2q43. VIL localization in these three species allows us tentatively to assign all cattle U17 to BBU and CHI 2q and to extend the physical map to OAR 2q.

Bovine natural resistance associated macrophage protein 1 (Nramp1) gene

The Bcg/Ity/Lsh locus is a major gene controlling early phases of infection with intracellular parasites in mice. Natural resistance associated macrophage protein 1 (Nramp1) has been shown to be the Bcg gene in mice. Analysis of a bovine cDNA homolog of murine Nramp1, designated as bovine NRAMP1, predicted a 548-amino-acid protein with hydrophobic domains, an amino-terminal SH3-binding domain, and a conserved consensus transport motif. Northern blotting indicated that bovine NRAMP1 was expressed primarily in macrophages and tissues of the recticuloendothelial system. Bovine NRAMP1 was mapped to BTA 2 within syntenic loci conserved on HSA 2q and MMU 1.

Comparative analysis of the cattle and human genomes: detection of ZOO-FISH and gene mapping-based chromosomal homologies

Comparative chromosome painting with individual human chromosome-specific libraries (CSLs) on cattle metaphase chromosomes delineated 46 homologous chromosomal segments between the two species. Continuous arrangement of these segments on individual cattle chromosomes demonstrates a nearly complete coverage of the bovine karyotype and shows physical boundaries of bovine chromosomal segments homologous to individual human chromosomes. Alignment of the available comparative gene mapping data with the homologous segments strongly supports the detected gross homologies between the karyotypes of the two species. In addition to cattle, four human CSLs were hybridized to sheep metaphase chromosomes also, to further verify the known karyotype homology within the Bovidae. Besides its application to karyotype evolution research, the comparative knowledge provides for rapid expansion of the much needed Type I locus-based bovine gene map.

Isolation and characterization of 45 polymorphic microsatellites from the bovine genome

A small-insert bovine genomic library was constructed in pBluescript II SK(+) and enriched for microsatellites by selective rescue of single-stranded pBluescript DNA carrying (CA)n/(TG)n tandem repeats. Approximately 50% of the clones in the enriched library contained (CA)n repeats or CA-rich sequences. Sequencing of clones selected for (CA)n repeats resulted in the identification and characterization of 45 (CA)n polymorphic microsatellites. Genotyping in 9 large paternal half-sib families indicated that 40 of these microsatellite markers exhibit autosomal Mendelian inheritance. The numbers of alleles range from 2 to 18, with an average of 6.3 per locus. The polymorphic microsatellite markers we have identified and characterized will contribute to the construction of a high-resolution linkage map of bovine genome.

Thirteen loci physically assigned to sheep chromosome 2 by cell hybrid analysis and in situ hybridization

Sheep x hamster cell hybrids containing sheep metacentric Chromosome (Chr) 2 were produced by fusing blood leukocytes from normal sheep with hamster auxotrophic Ade F-minus mutants. Cell clones that were isocitrate dehydrogenase 1 (IDH1) positive were cytogenetically characterized, confirming that they contained sheep Chr 2. The following loci were newly assigned by Southern hybridization to sheep Chr 2: lipoprotein lipase (LPL), glycoprotein-4-beta galactosyltransferase 2 (GGTB2), neurofilament light polypeptide (68 kDa; NEFL), surfactant-associated protein 2 (SFTP2), lymphocyte-specific protein tyrosine kinase (LCK), and nebulin (NEB). These new assignments and the in situ localization of gelsolin (GSN) to sheep Chr 2pter-p24 are consistent with the predicted homology of cattle Chr 8 (U18) with sheep Chr 2p, and of cattle Chr 2 (U17) with sheep 2q. In addition, the assignment by cell hybrid analysis of loci previously mapped to Chr 2 in sheep, viz., cholinergic receptor, nicotinic, delta polypeptide (CHRND), collagen type III alpha 1 (COL3A1), fibronectin 1 (FN1), isocitrate dehydrogenase (IDH1), and villin 1 (VIL1), confirmed the localization of sheep syntenic group U11 to this chromosome. By nutritional selection and complementation of the hamster auxotrophic Ade F mutation, the multifunctional enzyme locus phosphoribosylaminoimidazolecarboxamide formyltransferase (AICAR transformylase)/IMP cyclohydrolase (inosinicase) (provisionally given the symbol PRACFT) has also been newly assigned to sheep Chr 2. This report significantly extends the number of loci physically mapped to sheep Chr 2 and confirms its close homology with cattle Chrs 2 and 8.

Linkage information content and efficiency of full-sib and half-sib designs for gene mapping

The accuracy of a genetic map depends on the amount of linkage information contained in the data set used for construction of the map. The amount of linkage information is related to the designs employed for linkage analysis. The purpose of this study was to provide general formulations for various genotyping schemes and family structures in order to evaluate the amount of linkage information in a data set. Linkage information content (LIC) was defined as the frequency of fully informative gametes, which are gametes from doubly heterozygous parents with known linkage phases. Depending on the design, LIC is based on two generations if the parental phases are determined statistically, or three generations if the parental phases are determined genetically. Different schemes were considered in deriving LIC: (1) genotyping of one parent or two parents, and (2) genotyping of two or three generation families. The LIC for a full-sib design was found to be generally greater than for a half-sib design but requires typing a large number of individuals when at least one locus has only two alleles. The efficiency of the full-sib design is reduced significantly if a sex-specific linkage map is sought.