Central to an animal's defence system is the ability to differentiate self from non-self and, thu... more Central to an animal's defence system is the ability to differentiate self from non-self and, thus, protect itself from disease. This unique quality is determined, in large part, by the major histocompatibility complex (MHC) genes of each species. In farm animals, the knowledge of the MHC genes has been growing, especially since the rapid advances in molecular biology. The general structure of the MHC of the pig, cow, chicken and horse is presented in this chapter. Disease and immune response associations are also described. Although in many instances these data are limited, it is clear that the MHC is strongly associated with health traits in farm animals. Understanding these MHC-disease resistance and immune-responsiveness relationships will allow genetic improvement to be made by marker-assisted selection, rather than by direct challenge of populations with pathogens. Disciplines
A DBA/2 mouse treated with ethylnitrosourea sired an offspring whose hemoglobin showed an extra b... more 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 cy-globin, chain 1, was not affected. On focusing gels the phenotype of the mutant allele, HbaP, was expressed without dominance to normal chain 5 , and Hba@/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 5*, the mutant form of a-chain 5. A single amino acid substitution (His + Leu) at position 89 was found in chain 5y9. We propose that ethylnitrosourea induced an A + T transversion in the histidine codon at position 89 (CAC + 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.
The major histocompatibility complex (MHC) in mammals codes for antigen-presenting proteins. For ... more 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 (BBURH 5000), we generated a high-resolution RH map of the river buffalo MHC region. The buffalo MHC RH map (cR 5000) was aligned with the cattle MHC RH map (cR 12000) 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.
SummaryThe bovine major histocompatibility complex (MHC) or BoLA is organized differently from ty... more SummaryThe bovine major histocompatibility complex (MHC) or BoLA is organized differently from typical mammalian MHCs in that a large portion of the class II region, called class IIb, has been transposed to a position near the centromere on bovine chromosome 23. Gene mapping indicated that the rearrangement resulted from a single inversion, but the boundaries and gene content of the inverted segment have not been fully determined. Here, we report the genomic sequence of BoLA IIb. Comparative sequence analysis with the human MHC revealed that the proximal inversion breakpoint occurred approximately 2.5 kb from the 3′ end of the glutamate‐cysteine ligase, catalytic subunit (GCLC) locus and that the distal breakpoint occurred about 2 kb from the 5′ end from a divergent class IIDRβ‐like sequence designated DSB. Gene content, order and orientation of BoLA IIb are consistent with the single inversion hypothesis when compared with the corresponding region of the human class II MHC (HLA class II). Differences with HLA include the presence of a single histone H2B gene located between the proteasome subunit, beta type, 9 (PSMB9) and DMB loci and a duplicated TAP2 with a variant splice site. BoLA IIb spans approximately 450 kb DNA, with 20 apparently intact genes and no obvious pseudogenes. The region contains 227 simple sequence repeats (SSRs) and approximately 167 kb of retroviral‐related repetitive DNA. Nineteen of the 20 genes identified in silico are supported by bovine EST data indicating that the functional gene content of BoLA IIb has not been diminished because it has been transposed from the remainder of BoLA genes.
Three genes in the testosterone 16 alpha-hydroxylase (C-P-450(16 alpha)) family, ca, cb, and cc, ... more Three genes in the testosterone 16 alpha-hydroxylase (C-P-450(16 alpha)) family, ca, cb, and cc, are characterized. The sizes of the genes are approximately 4.5 to 5.2 kilobase pairs, and all three consist of nine exons with junctions at identical sites. Gene ca is identified as the male-specific, androgen-dependent C-P-450(16 alpha) gene in adult mice, since the exonic sequence matched 100% to the cDNA, pc16 alpha-2 (Wong, G., Kawajiri, K., and Negishi, M. (1987) Biochemistry 26, 8683-8690). Gene cb and cc are organized in tandem within 18-kilobase pair DNA. Their encoded P-450s contain an approximate 94% nucleotide sequence similarity to the C-P-450(16 alpha). The high similarity in gene nucleotide sequences, including the introns and flanking regions, suggests a combination of an ancestral gene duplication and gene conversion as a mechanism for evolution of the C-P-450(16 alpha) family. Gene ca shows male-specific expression in mouse kidney as well as in liver; gene cb, neither sex-specific nor androgen-dependent, is seen only in liver; gene cc is not expressed in either adult mouse liver or kidney. Expression of these three genes is not detected in adult mouse lung. It appears, therefore, that the C-P-450(16 alpha) gene family includes a large number of genes whose expressions are differentially regulated. Southern hybridization of C-P-450(16 alpha) cDNA to genomic DNAs from mouse-hamster somatic hybrid cells localizes tentatively this gene family on mouse chromosome 15. The recombination frequency in BXD recombinant inbred mice suggests that the C-P-450(16 alpha) gene family is approximately 16M from the 55-kDa locus.
In this study, we report an approach to characterize individual BoLA haplotypes using cells from ... more 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.
Type I and type II keratins are major constituents of intermediate filaments that play a fundamen... more Type I and type II keratins are major constituents of intermediate filaments that play a fundamental role in the cytoskeletal network. By using both somatic cell hybrids and conventional and interspecific linkage crosses, several genes encoding type I keratins, including the epidermal keratin KlO, were shown to be closely linked to the homeobox-2 complex and the rex locus on mouse chromosome 11. The absence of crossovers between type I keratin-encoding genes and rex (N = 239), a locus affecting hair development, raises the possibility that mutations at rex and neighboring loci affecting skin and hair development involve type I keratin genes.
Central to an animal's defence system is the ability to differentiate self from non-self and, thu... more Central to an animal's defence system is the ability to differentiate self from non-self and, thus, protect itself from disease. This unique quality is determined, in large part, by the major histocompatibility complex (MHC) genes of each species. In farm animals, the knowledge of the MHC genes has been growing, especially since the rapid advances in molecular biology. The general structure of the MHC of the pig, cow, chicken and horse is presented in this chapter. Disease and immune response associations are also described. Although in many instances these data are limited, it is clear that the MHC is strongly associated with health traits in farm animals. Understanding these MHC-disease resistance and immune-responsiveness relationships will allow genetic improvement to be made by marker-assisted selection, rather than by direct challenge of populations with pathogens. Disciplines
A DBA/2 mouse treated with ethylnitrosourea sired an offspring whose hemoglobin showed an extra b... more 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 cy-globin, chain 1, was not affected. On focusing gels the phenotype of the mutant allele, HbaP, was expressed without dominance to normal chain 5 , and Hba@/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 5*, the mutant form of a-chain 5. A single amino acid substitution (His + Leu) at position 89 was found in chain 5y9. We propose that ethylnitrosourea induced an A + T transversion in the histidine codon at position 89 (CAC + 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.
The major histocompatibility complex (MHC) in mammals codes for antigen-presenting proteins. For ... more 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 (BBURH 5000), we generated a high-resolution RH map of the river buffalo MHC region. The buffalo MHC RH map (cR 5000) was aligned with the cattle MHC RH map (cR 12000) 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.
SummaryThe bovine major histocompatibility complex (MHC) or BoLA is organized differently from ty... more SummaryThe bovine major histocompatibility complex (MHC) or BoLA is organized differently from typical mammalian MHCs in that a large portion of the class II region, called class IIb, has been transposed to a position near the centromere on bovine chromosome 23. Gene mapping indicated that the rearrangement resulted from a single inversion, but the boundaries and gene content of the inverted segment have not been fully determined. Here, we report the genomic sequence of BoLA IIb. Comparative sequence analysis with the human MHC revealed that the proximal inversion breakpoint occurred approximately 2.5 kb from the 3′ end of the glutamate‐cysteine ligase, catalytic subunit (GCLC) locus and that the distal breakpoint occurred about 2 kb from the 5′ end from a divergent class IIDRβ‐like sequence designated DSB. Gene content, order and orientation of BoLA IIb are consistent with the single inversion hypothesis when compared with the corresponding region of the human class II MHC (HLA class II). Differences with HLA include the presence of a single histone H2B gene located between the proteasome subunit, beta type, 9 (PSMB9) and DMB loci and a duplicated TAP2 with a variant splice site. BoLA IIb spans approximately 450 kb DNA, with 20 apparently intact genes and no obvious pseudogenes. The region contains 227 simple sequence repeats (SSRs) and approximately 167 kb of retroviral‐related repetitive DNA. Nineteen of the 20 genes identified in silico are supported by bovine EST data indicating that the functional gene content of BoLA IIb has not been diminished because it has been transposed from the remainder of BoLA genes.
Three genes in the testosterone 16 alpha-hydroxylase (C-P-450(16 alpha)) family, ca, cb, and cc, ... more Three genes in the testosterone 16 alpha-hydroxylase (C-P-450(16 alpha)) family, ca, cb, and cc, are characterized. The sizes of the genes are approximately 4.5 to 5.2 kilobase pairs, and all three consist of nine exons with junctions at identical sites. Gene ca is identified as the male-specific, androgen-dependent C-P-450(16 alpha) gene in adult mice, since the exonic sequence matched 100% to the cDNA, pc16 alpha-2 (Wong, G., Kawajiri, K., and Negishi, M. (1987) Biochemistry 26, 8683-8690). Gene cb and cc are organized in tandem within 18-kilobase pair DNA. Their encoded P-450s contain an approximate 94% nucleotide sequence similarity to the C-P-450(16 alpha). The high similarity in gene nucleotide sequences, including the introns and flanking regions, suggests a combination of an ancestral gene duplication and gene conversion as a mechanism for evolution of the C-P-450(16 alpha) family. Gene ca shows male-specific expression in mouse kidney as well as in liver; gene cb, neither sex-specific nor androgen-dependent, is seen only in liver; gene cc is not expressed in either adult mouse liver or kidney. Expression of these three genes is not detected in adult mouse lung. It appears, therefore, that the C-P-450(16 alpha) gene family includes a large number of genes whose expressions are differentially regulated. Southern hybridization of C-P-450(16 alpha) cDNA to genomic DNAs from mouse-hamster somatic hybrid cells localizes tentatively this gene family on mouse chromosome 15. The recombination frequency in BXD recombinant inbred mice suggests that the C-P-450(16 alpha) gene family is approximately 16M from the 55-kDa locus.
In this study, we report an approach to characterize individual BoLA haplotypes using cells from ... more 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.
Type I and type II keratins are major constituents of intermediate filaments that play a fundamen... more Type I and type II keratins are major constituents of intermediate filaments that play a fundamental role in the cytoskeletal network. By using both somatic cell hybrids and conventional and interspecific linkage crosses, several genes encoding type I keratins, including the epidermal keratin KlO, were shown to be closely linked to the homeobox-2 complex and the rex locus on mouse chromosome 11. The absence of crossovers between type I keratin-encoding genes and rex (N = 239), a locus affecting hair development, raises the possibility that mutations at rex and neighboring loci affecting skin and hair development involve type I keratin genes.
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Papers by Loren Skow