Description of bovine major histocompatibility complex class IIa haplotypes using parthenogenetic embryo-derived cells.

In this study, we report an approach to characterize individual BoLA haplotypes using cells from parthenogenetic bovine embryos derived from slaughterhouse ovaries. Eight of the 15 parthenogenetic embryos so obtained had not undergone meiotic recombination on the BoLA region and were suitable to describe BoLA haplotypes. Detailed analysis of the BoLA class IIa region identified seven different class IIa haplotypes, including six not previously described and two new alleles of BoLA-DQA and one BoLA-DQB. Our method provided reliable sources of homozygous DNA to describe BoLA haplotypes.

Genetic risk factors for insidious equine recurrent uveitis in Appaloosa horses.

Appaloosa horses are predisposed to equine recurrent uveitis (ERU), an immune-mediated disease characterized by recurring inflammation of the uveal tract in the eye, which is the leading cause of blindness in horses. Nine genetic markers from the ECA1 region responsible for the spotted coat color of Appaloosa horses, and 13 microsatellites spanning the equine major histocompatibility complex (ELA) on ECA20, were evaluated for association with ERU in a group of 53 Appaloosa ERU cases and 43 healthy Appaloosa controls. Three markers were significantly associated (corrected P-value <0.05): a SNP within intron 11 of the TRPM1 gene on ECA1, an ELA class I microsatellite located near the boundary of the ELA class III and class II regions and an ELA class II microsatellite located in intron 1 of the DRA gene. Association between these three genetic markers and the ERU phenotype was confirmed in a second population of 24 insidious ERU Appaloosa cases and 16 Appaloosa controls. The relative odds of being an ERU case for each allele of these three markers were estimated by fitting a logistic mixed model with each of the associated markers independently and with all three markers simultaneously. The risk model using these markers classified ~80% of ERU cases and 75% of controls in the second population as moderate or high risk, and low risk respectively. Future studies to refine the associations at ECA1 and ELA loci and identify functional variants could uncover alleles conferring susceptibility to ERU in Appaloosa horses.

Microsatellite variation in the equine MHC.

Genes within the major histocompatibility complex (MHC) encode proteins involved in innate and adaptive immune responses. Genetic variation in this region can influence the immune response of an individual animal to challenges from a variety of pathogens; however, a complete documentation of genetic variation in the MHC is lacking for most domestic animals, including horses. To provide additional genetic markers for study of the horse MHC, or ELA (equine lymphocyte antigen), we identified 37 polymorphic microsatellite repeats in ELA and used these variations separately and together with published SNPs to investigate linkage disequilibrium (LD) and haplotype structure in a sample of Thoroughbred horses. ELA SNPs alone detected little LD, but microsatellites, either separately or combined with SNPs, revealed substantially more LD. A subset of markers in very high LD across the breadth of ELA may be predictive of structural polymorphisms or linked epistases that are important drivers of haplotype structure in Thoroughbreds.

A high-resolution radiation hybrid map of the river buffalo major histocompatibility complex and comparison with BoLA.

The major histocompatibility complex (MHC) in mammals codes for antigen-presenting proteins. For this reason, the MHC is of great importance for immune function and animal health. Previous studies revealed this gene-dense and polymorphic region in river buffalo to be on the short arm of chromosome 2, which is homologous to cattle chromosome 23. Using cattle-derived STS markers and a river buffalo radiation hybrid (RH) panel (BBURH5000 ), we generated a high-resolution RH map of the river buffalo MHC region. The buffalo MHC RH map (cR5000 ) was aligned with the cattle MHC RH map (cR12000 ) to compare gene order. The buffalo MHC had similar organization to the cattle MHC, with class II genes distributed in two segments, class IIa and class IIb. Class IIa was closely associated with the class I and class III regions, and class IIb was a separate cluster. A total of 53 markers were distributed into two linkage groups based on a two-point LOD score threshold of ≥8. The first linkage group included 32 markers from class IIa, class I and class III. The second linkage group included 21 markers from class IIb. Bacterial artificial chromosome clones for seven loci were mapped by fluorescence in situ hybridization on metaphase chromosomes using single- and double-color hybridizations. The order of cytogenetically mapped markers in the region corroborated the physical order of markers obtained from the RH map and served as anchor points to align and orient the linkage groups.

Molecular basis of mouse microphthalmia (mi) mutations helps explain their developmental and phenotypic consequences.

Mutations in the mouse microphthalmia (mi) gene affect the development of a number of cell types including melanocytes, osteoclasts and mast cells. Recently, mutations in the human mi gene (MITF) were found in patients with Waardenburg Syndrome type 2 (WS2), a dominantly inherited syndrome associated with hearing loss and pigmentary disturbances. We have characterized the molecular defects associated with eight murine mi mutations, which vary in both their mode of inheritance and in the cell types they affect. These molecular data, combined with the extensive body of genetic data accumulated for murine mi, shed light on the phenotypic and developmental consequences of mi mutations and offer a mouse model for WS2.

Polymorphism and gene organization of water buffalo MHC-DQB genes show homology to the BoLA DQB region.

In cattle (Bos taurus), there is evidence of more than 50 alleles of BoLA-DQB (bovine lymphocyte antigen DQB) that are distributed across at least five DQB loci, making this region one of the most complex in the BoLA gene family. In this study, DQB alleles were analysed for the water buffalo (Bubalus bubalis), another economically important bovine species. Twelve alleles for Bubu-DQB (Bubalis bubalis DQB) were determined by nucleotide sequence analysis. A phylogenetic analysis revealed numerous trans-species polymorphisms, with alleles from water buffalo assigned to at least three different loci (BoLA-DQB1, BoLA-DQB3 and BoLA-DQB4) that are also found in cattle. These presumptive loci were analysed for patterns of synonymous (d(S)) and non-synonymous (d(N)) substitution. Like BoLA-DQB1, Bubu-DQB1 was observed to be under strong positive selection for polymorphism. We conclude that water buffalo and cattle share the current arrangement of their DQB region because of their common ancestry.

A conserved segmental duplication within ELA.

The assembled genomic sequence of the horse major histocompatibility complex (MHC) (equine lymphocyte antigen, ELA) is very similar to the homologous human HLA, with the notable exception of a large segmental duplication at the boundary of ELA class I and class III that is absent in HLA. The segmental duplication consists of a ∼ 710 kb region of at least 11 repeated blocks: 10 blocks each contain an MHC class I-like sequence and the helicase domain portion of a BAT1-like sequence, and the remaining unit contains the full-length BAT1 gene. Similar genomic features were found in other Perissodactyls, indicating an ancient origin, which is consistent with phylogenetic analyses. Reverse-transcriptase PCR (RT-PCR) of mRNA from peripheral white blood cells of healthy and chronically or acutely infected horses detected transcription from predicted open reading frames in several of the duplicated blocks. This duplication is not present in the sequenced MHCs of most other mammals, although a similar feature at the same relative position is present in the feline MHC (FLA). Striking sequence conservation throughout Perissodactyl evolution is consistent with a functional role for at least some of the genes included within this segmental duplication.

A 4,103 marker integrated physical and comparative map of the horse genome.

A comprehensive second-generation whole genome radiation hybrid (RH II), cytogenetic and comparative map of the horse genome (2n = 64) has been developed using the 5000rad horse x hamster radiation hybrid panel and fluorescence in situ hybridization (FISH). The map contains 4,103 markers (3,816 RH; 1,144 FISH) assigned to all 31 pairs of autosomes and the X chromosome. The RH maps of individual chromosomes are anchored and oriented using 857 cytogenetic markers. The overall resolution of the map is one marker per 775 kilobase pairs (kb), which represents a more than five-fold improvement over the first-generation map. The RH II incorporates 920 markers shared jointly with the two recently reported meiotic maps. Consequently the two maps were aligned with the RH II maps of individual autosomes and the X chromosome. Additionally, a comparative map of the horse genome was generated by connecting 1,904 loci on the horse map with genome sequences available for eight diverse vertebrates to highlight regions of evolutionarily conserved syntenies, linkages, and chromosomal breakpoints. The integrated map thus obtained presents the most comprehensive information on the physical and comparative organization of the equine genome and will assist future assemblies of whole genome BAC fingerprint maps and the genome sequence. It will also serve as a tool to identify genes governing health, disease and performance traits in horses and assist us in understanding the evolution of the equine genome in relation to other species.

A 1.3-Mb interval map of equine homologs of HSA2.

A comparative approach that utilizes information from more densely mapped or sequenced genomes is a proven and efficient means to increase our knowledge of the structure of the horse genome. Human chromosome 2 (HSA2), the second largest human chromosome, comprising 243 Mb, and containing 1246 known genes, corresponds to all or parts of three equine chromosomes. This report describes the assignment of 140 new markers (78 genes and 62 microsatellites) to the equine radiation hybrid (RH) map, and the anchoring of 24 of these markers to horse chromosomes by FISH. The updated equine RH maps for ECA6p, ECA15, and ECA18 resulting from this work have one, two, and three RH linkage groups, respectively, per chromosome/chromosome-arm. These maps have a three-fold increase in the number of mapped markers compared to previous maps of these chromosomes, and an increase in the average marker density to one marker per 1.3 Mb. Comparative maps of ECA6p, ECA15, and ECA18 with human, chimpanzee, dog, mouse, rat, and chicken genomes reveal blocks of conserved synteny across mammals and vertebrates.

Gene for ovarian granulosa cell tumor susceptibility, Gct, in SWXJ recombinant inbred strains of mice revealed by dehydroepiandrosterone.

Spontaneous, malignant ovarian granulosa cell (GC) tumors occur in pubertal SWR and specific SWXJ recombinant inbred strains of mice. Treatment of these mice with dehydroepiandrosterone (DHEA), an adrenal secretory steroid with anticancer actions against spontaneous and carcinogen-induced tumors of different tissues, gave unexpected results. Diet supplemented with 0.4% DHEA (a) induced significantly more GC tumors in spontaneous tumor-susceptible strains (SWR and SWXJ-1, -4, and -9), (b) induced the first GC tumors observed in five previously tumor-free strains (SWXJ-6, -7, -8, -10, and -12), and (c) failed to induce GC tumors in SJL and in the remaining six SWXJ strains (SWXJ-2, -3, -5, -11, -13, and -14). The strain distribution pattern of DHEA-induced GC tumor susceptibility versus resistance was compared with strain distribution patterns for 35 different loci known to distinguish SWR and SJL progenitor strains. A complete match of DHEA-induced GC tumors with pancreas-2 (Pan-2) on mouse chromosome 4 was found. We have named this new locus GC tumor susceptibility (Gct), with the Gcts (susceptible) allele found in SWR and the Gctr (resistant) allele found in SJL mice. The Gct locus is closely linked to pancreas-2, Pan-2, but the order of genes is not yet confirmed. In addition, data from F1 progeny of matings between SWR and selected inbred strains provide suggestive evidence for a second gene controlling GC tumor incidence that we hypothesize involves steroid metabolism. Differences in GC tumor incidence data from reciprocal F1 progeny of matings between SWR and SJL mice reveal a strong maternal effect that may represent yet a third gene. These data support a heritable basis for GC tumorigenesis in the SWR model involving a small number of genes.

Antibody titers to vaccination are not predictive of level of protection against a BVDV type 1b challenge in Bos indicus - Bos taurus steers.

Subclinical illness associated with infection is thought to reduce performance and increase production costs in feedlot cattle, but underlying components remain largely unidentified. Vaccination is frequently used in feedlot settings but producers lack metrics that evaluate the effectiveness of vaccination programs. The goal of this study was to determine if levels of serum neutralizing antibody titers were predictive of levels of vaccine protection in a commercial setting. During this four-year study, Angus-Nellore steers housed in a production feedlot setting were assigned to 1 of 3 vaccine treatments: killed vaccine (kV), modified live virus (MLV) vaccine, or no vaccine (control), and were challenged with a noncytopathic 1b field strain of bovine viral diarrhea virus. Rectal temperature and levels of circulating lymphocytes and platelets were monitored following challenge. While no animals were diagnosed as clinically ill with respiratory disease, indicators of disease (pyrexia, lymphopenia, and thrombocytopenia) were observed. The MLV treatment elicited higher antibody titers to the vaccination than the kV, and calves in the MLV treatment had higher mean titers at challenge. The year that elicited the highest antibody response to the vaccination and the year with the lowest frequency of phenotypic responses to the challenge were not concurrent. The MLV treatment had the highest proportion, 34.68%, of animals that were protected against the challenge regardless of the pre-challenge antibody titer and had the fewest number of lymphopenia cases in response to the challenge. Both vaccine treatments mitigated thrombocytopenia when compared to the control treatment, and the MLV treatment reduced lymphopenia; however, these symptoms were not completely eliminated in vaccinated animals. Pyrexia was present in 40.11% of the animals, but no difference in the frequency of cases between treatments was observed. Pre-challenge vaccination response was not indicative of the level of protection nor was anamnestic antibody response correlated with health status.

Genetic variation at a locus (TAM-1) for submaxillary gland protease in the mouse and its location on chromosome No. 7.

Electrophoretic and activity variants for a testosterone-induced esteroprotease have been discovered in submaxillary glands from inbred strains of mice. The enzyme is tentatively designated tamase [TAM-1] and the variant genetic locus is Tam-1. The alleles Tam-1a and Tam-1b determine electrophoretically distinct zones of tamase activity, while Tam-lc produces no detectable enzyme activity. Data from recombinant inbred strains and B6AF1 X B6 and B6D2F1 X B6 backcrosses established linkage of Tam-1 to glucose phosphate isomerase (Gpi-1), pink-eyed dilution [p] and beta-hemoglobin (Hbb) on chromosome 7. The gene order is Gpi-1--Tam-1--p--HBB. Analysis of congenic resistant strains indicates that Tam-1 is closely linked to the minor histocompatibility locus, H-4. TAM-1 was not cross-reactive with antisera to mouse nerve growth factor, submaxillary renin, or tamases A and D.

The locus encoding alpha A-crystallin is closely linked to H-2K on mouse chromosome 17.

We have used a complementary DNA (cDNA) for mouse alpha A-crystallin to probe genomic DNA for restriction fragment length polymorphisms which could be used to map the alpha A-crystallin gene locus (Acry-1) in the mouse genome. Ten of 12 restriction endonucleases produced fragment polymorphism among various inbred strains of mice. A comprehensive strain survey conducted with six endonucleases resulted in the discovery of six allelic forms of Acry-1. Linkage analysis was conducted on DNA from three sets of recombinant inbred strains of mice and demonstrated close linkage of Acry-1 with the major histocompatibility complex (H-2) on chromosome 17. Analysis of congenic and recombinant congenic strains of mice confirmed the linkage of Acry-1 and H-2 and located the alpha A gene to the region between glyoxylase (Glo-1) and H-2K.

Analysis of a mouse alpha-globin gene mutation induced by ethylnitrosourea.

A DBA/2 mouse treated with ethylnitrosourea sired an offspring whose hemoglobin showed an extra band following starch gel electrophoresis. The variant hemoglobin migrated to a more cathodal position in starch gel. Isoelectric focusing indicated that chain 5 of the mutant hemoglobin migrated to a more cathodal position than the normal chain 5 from DBA/2 mice and that the other alpha-globin, chain 1, was not affected. On focusing gels the phenotype of the mutant allele, Hbay9, was expressed without dominance to normal chain 5, and Hbay9/Hbay9 homozygotes were fully viable in the laboratory. The molecular basis for the germinal mutation was investigated by analyzing the amino acid sequence of chain 5y9, the mutant form of alpha-chain 5. A single amino acid substitution (His leads to Leu) at position 89 was found in chain 5y9. We propose that ethylnitrosourea induced an A leads to T transversion in the histidine codon at position 89 (CAC leads to CTC). This mutation has apparently not been observed previously in humans, mice or other mammals, and its novel occurrence may be indicative of other unusual mutational events that do not ordinarily occur in the absence of specific mutagen exposure.

Conserved linkage within a 4-cM region of mouse chromosome 9 and human chromosome 11.

A six-point cross was carried out to determine the gene order and distances among loci on mouse chromosome 9. Our results are consistent with the following arrangement: centromere - Lap-1 - (1.2 +/- 0.8) - Es-17 - (3.0 +/- 1.0) - Ups - (1.3 +/- 0.7) - Alp-1 - (23.1 +/- 3.4) - Mod-1 - (10.9 +/- 2.6) - Acy-1. This study provides the first estimate of the distances between Es-17, Ups and Alp-1. Exceptions to the preferred association of alleles of Es-17 and Ups have been found in three feral populations and one inbred strain. Evidence is presented for the homology of this chromosome region with the ESA4 - UPS - APO-AI region on the long arm of human chromosome 11.

Polymorphism and linkage of the alpha A-crystallin gene in t-haplotypes of the mouse.

Restriction fragment polymorphisms were used to order the alpha A-crystallin locus (Crya-1) relative to other genes in mouse t-chromatin and to investigate the relatedness of alpha-A-crystallin sequences among different t-haplotypes. Analysis of DNA from t-recombinant mice mapped Crya-1 to the K end of the H-2 complex and within the distal inverted region characteristic of t-haplotypes. Hybridization with Crya-1 cDNA revealed three distinct phenotypic groups among the 17 different t-haplotypes studied. A majority (9 of 17) of the t-haplotypes were classified into a novel group (Crya-1t) characterized by restriction fragments apparently unique to t-chromosomes and therefore thought to contain alpha A-crystallin sequences descended from the original t-chromosome. A second group of t-haplotypes had restriction fragment patterns indistinguishable from those observed among many common inbred strains of mice of the Crya-1a type, and a third restriction fragment pattern, observed only in the tw121 haplotype, was indistinguishable from the fragment pattern for C3H/DiSn (Crya-1b) and several other inbred strains of mice. Thus, with respect to sequences around the Crya-1 locus, different t-haplotypes show restriction fragment polymorphisms, some of which are comparable to those found in wild-type chromosomes and provide further evidence for genetic heterogeneity in DNA from the distal region of t-haplotypes.

Two steroid 15 alpha-hydroxylase genes and a homologous gene family in mice.

Steroid 15 alpha-hydroxylase (P45015 alpha) activity is concomitant with the expression of two types of mRNA in the mouse liver. Two discrete genes, designated 15 alpha oh-1 and 15 alpha oh-2, that encode the two mRNAs were recovered from total genomic libraries of the inbred mouse strains 129/J and C57Bl/6J and identified by cDNA hybridization, restriction-site analysis and partial nucleotide sequence. Both genes are approx. 9 kb long and share significant homology, including flanking regions, over a region of at least 30 kb. The two distinct 15 alpha oh genes are members of a larger family of homologous genes and/or pseudogenes of unknown function. The most extensive sequence homology among family members in the 3' portion of the gene with progressively less homology toward the 5' end. The far 5' portions of 15 alpha oh-1 and 15 alpha oh-2 are very similar to one another but there is no observed homology with other genes of the family. The two 15 alpha oh genes and the homologous family have been localized to mouse chromosome 7 by somatic cell hybrid mapping. Analysis of a restriction fragment length polymorphism in recombinant inbred mice shows a close linkage of 15 alpha oh-1 and 15 alpha oh-2 with the Coh locus.

An ordered BAC contig map of the equine major histocompatibility complex.

A physical map of ordered bacterial artificial chromosome (BAC) clones was constructed to determine the genetic organization of the horse major histocompatibility complex. Human, cattle, pig, mouse, and rat MHC gene sequences were compared to identify highly conserved regions which served as source templates for the design of overgo primers. Thirty-five overgo probes were designed from 24 genes and used for hybridization screening of the equine USDA CHORI 241 BAC library. Two hundred thirty-eight BAC clones were assembled into two contigs spanning the horse MHC region. The first contig contains the MHC class II region and was reduced to a minimum tiling path of nine BAC clones that span approximately 800 kb and contain at least 20 genes. A minimum tiling path of a second contig containing the class III/I region is comprised of 14 BAC clones that span approximately 1.6 Mb and contain at least 34 genes. Fluorescence in situ hybridization (FISH) using representative clones from each of the three regions of the MHC localized the contigs onto ECA20q21 and oriented the regions relative to one another and the centromere. Dual-colored FISH revealed that the class I region is proximal to the centromere, the class II region is distal, and the class III region is located between class I and II. These data indicate that the equine MHC is a single gene-dense region similar in structure and organization to the human MHC and is not disrupted as in ruminants and pigs.

Hematology of a murine beta-thalassemia: a longitudinal study.

Mice homozygous for a spontaneous mutation, in which the beta-major globin gene is deleted, have clinical symptoms of beta-thalassemia. These mice have a hypocellular, hypochromic, microcytic anemia that becomes more severe with increasing age. The defective red cell morphology, decreased osmotic fragility of erythrocytes and shortened red cell life span found in beta-thalassemic mice are similar to those observed in human beta-thalassemia. Synthesis of beta-globin is depressed but not as much as might be expected because the expression of the beta-minor globin gene is enhanced to encode two to three times more globin than in normal mice. Splenomegaly, an enlarged pool of stem cells for erythropoiesis, and iron overloading occur in older mice. The fact that these mice remain moderately healthy makes them a very suitable animal model in which to develop and test alternative techniques of gene therapy that could be successfully applied to the treatment of human thalassemia. Homozygous beta-thalassemic mice have large deposits of iron in their tissues, which might make these mice also useful for in vivo tests of the effectiveness and possible long-term side effects of newly developed iron chelators.