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Seung-chul Kim - One of the best experts on this subject based on the ideXlab platform.
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Phylogeography and Ecological Niche Modeling Reveal Reduced Genetic Diversity and Colonization Patterns of Skunk Cabbage (Symplocarpus foetidus; Araceae) From Glacial Refugia in Eastern North America.
Frontiers in plant science, 2018Co-Authors: Seon-hee Kim, Myong-suk Cho, Seung-chul KimAbstract:Alternating glacial and interglacial periods during the Quaternary have dramatically affected the distribution and population genetic structure of plant and animal species throughout the northern hemisphere. Surprisingly, little is known about the postglacial recolonization history of wetland herbaceous perennials that are widely distributed in the understory of deciduous or mixed deciduous-evergreen forests in eastern North America. In this study, we investigated infraspecific variation among 32 populations of skunk cabbage, Symplocarpus foetidus, to test the hypothesis that the extant species diversity of skunk cabbage is the result of a postglacial range expansion from southern refugia during the Quaternary Ice Age. A total of 4041 base pairs (bp) of the chloroplast intergenic spacer region (cpDNA) was sequenced from 485 individuals sampled from glaciated (18 populations, 275 individuals) and unglaciated (14 populations, 210 individuals) regions east and west of the Appalachian Mountains. Haplotype number, haplotype diversity, and nucleotide diversity were calculated, and genetic variation within and among populations was assessed by analysis of molecular variance (AMOVA). The geographic pattern of genetic differentiation was further investigated with a spatial analysis of molecular variance (SAMOVA). A total of eight Haplotypes and three genetic groups (SAMOVA) were recovered and a much higher haplotype number (eight Haplotypes) and haplotype diversity (0.7425) was observed in unglaciated compared to glaciated populations (five Haplotypes, haplotype diversity = 0.6099). All Haplotypes found in glaciated regions represented a subset of Haplotypes found in unglaciated regions. Haplotypes of S. foetidus likely diverged during the Tertiary (mid-Miocene and late Pliocene), predating the last glacial maximum (LGM). Predictions based on ecological niche modeling (ENM) suggested that there was considerably less suitable habitat for skunk cabbage during the LGM, and the habitat range was further south compared to the current distribution. Reduced variation and a subset of Haplotypes in glaciated regions suggest a founder effect associated with range expansion via long-distance seed dispersal. Our results do not support the “Driftless Area” scenario for the northern refugium, rather the data suggest a “Northeastern” refugium near the southernmost extent of the LGM.
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Image_1_Phylogeography and Ecological Niche Modeling Reveal Reduced Genetic Diversity and Colonization Patterns of Skunk Cabbage (Symplocarpus foetidus; Araceae) From Glacial Refugia in Eastern North America.pdf
2018Co-Authors: Seon-hee Kim, Myong-suk Cho, Seung-chul KimAbstract:Alternating glacial and interglacial periods during the Quaternary have dramatically affected the distribution and population genetic structure of plant and animal species throughout the northern hemisphere. Surprisingly, little is known about the post-glacial recolonization history of wetland herbaceous perennials that are widely distributed in the understory of deciduous or mixed deciduous-evergreen forests in eastern North America. In this study, we investigated infraspecific variation among 32 populations of skunk cabbage, Symplocarpus foetidus, to test the hypothesis that the extant species diversity of skunk cabbage is the result of a post-glacial range expansion from southern refugia during the Quaternary Ice Age. A total of 4041 base pairs (bp) of the chloroplast intergenic spacer region (cpDNA) was sequenced from 485 individuals sampled from glaciated (18 populations, 275 individuals) and unglaciated (14 populations, 210 individuals) regions east and west of the Appalachian Mountains. Haplotype number, haplotype diversity, and nucleotide diversity were calculated, and genetic variation within and among populations was assessed by analysis of molecular variance (AMOVA). The geographic pattern of genetic differentiation was further investigated with a spatial analysis of molecular variance (SAMOVA). A total of eight Haplotypes and three genetic groups (SAMOVA) were recovered and a much higher haplotype number (eight Haplotypes) and haplotype diversity (0.7425) was observed in unglaciated compared to glaciated populations (five Haplotypes, haplotype diversity = 0.6099). All Haplotypes found in glaciated regions represented a subset of Haplotypes found in unglaciated regions. Haplotypes of S. foetidus likely diverged during the Tertiary (mid-Miocene and late Pliocene), predating the last glacial maximum (LGM). Predictions based on ecological niche modeling (ENM) suggested that there was considerably less suitable habitat for skunk cabbage during the LGM, and the habitat range was further south compared to the current distribution. Reduced variation and a subset of Haplotypes in glaciated regions suggest a founder effect associated with range expansion via long-distance seed dispersal. Our results do not support the “Driftless Area” scenario for the northern refugium, rather the data suggest a “Northeastern” refugium near the southernmost extent of the LGM.
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Table_2_Phylogeography and Ecological Niche Modeling Reveal Reduced Genetic Diversity and Colonization Patterns of Skunk Cabbage (Symplocarpus foetidus; Araceae) From Glacial Refugia in Eastern North America.docx
2018Co-Authors: Seon-hee Kim, Myong-suk Cho, Seung-chul KimAbstract:Alternating glacial and interglacial periods during the Quaternary have dramatically affected the distribution and population genetic structure of plant and animal species throughout the northern hemisphere. Surprisingly, little is known about the post-glacial recolonization history of wetland herbaceous perennials that are widely distributed in the understory of deciduous or mixed deciduous-evergreen forests in eastern North America. In this study, we investigated infraspecific variation among 32 populations of skunk cabbage, Symplocarpus foetidus, to test the hypothesis that the extant species diversity of skunk cabbage is the result of a post-glacial range expansion from southern refugia during the Quaternary Ice Age. A total of 4041 base pairs (bp) of the chloroplast intergenic spacer region (cpDNA) was sequenced from 485 individuals sampled from glaciated (18 populations, 275 individuals) and unglaciated (14 populations, 210 individuals) regions east and west of the Appalachian Mountains. Haplotype number, haplotype diversity, and nucleotide diversity were calculated, and genetic variation within and among populations was assessed by analysis of molecular variance (AMOVA). The geographic pattern of genetic differentiation was further investigated with a spatial analysis of molecular variance (SAMOVA). A total of eight Haplotypes and three genetic groups (SAMOVA) were recovered and a much higher haplotype number (eight Haplotypes) and haplotype diversity (0.7425) was observed in unglaciated compared to glaciated populations (five Haplotypes, haplotype diversity = 0.6099). All Haplotypes found in glaciated regions represented a subset of Haplotypes found in unglaciated regions. Haplotypes of S. foetidus likely diverged during the Tertiary (mid-Miocene and late Pliocene), predating the last glacial maximum (LGM). Predictions based on ecological niche modeling (ENM) suggested that there was considerably less suitable habitat for skunk cabbage during the LGM, and the habitat range was further south compared to the current distribution. Reduced variation and a subset of Haplotypes in glaciated regions suggest a founder effect associated with range expansion via long-distance seed dispersal. Our results do not support the “Driftless Area” scenario for the northern refugium, rather the data suggest a “Northeastern” refugium near the southernmost extent of the LGM.
Donald W. Paty - One of the best experts on this subject based on the ideXlab platform.
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study of alleles of the second complement component c2 on canadian hla Haplotypes
Tissue Antigens, 2008Co-Authors: W. H. Marshall, John M Barnard, Nadir R Farid, R Grandy, Bodil Larsen, Ronald Payne, Verna M Skanes, David N. Churchill, George Cornell Ebers, Donald W. PatyAbstract:Typing for genetic variation in the second complement component C2 was performed on sera from HLA haplotyped Canadian families. Part of the data has been studied and analysed as a population; in addition there is a further random collection of Haplotypes bearing the C2*2 allele. In the population data there were 444 separate Haplotypes from unrelated parents or other founders: 4.7% of the Haplotypes carried the uncommon allele C2*2; one haplotype carried the rare C2*3. Study of C2 2–1 heterozygotes in the population data revealed 59 Haplotypes which carried the common C2*1 allele and one which carried a deficiency allele C2*0. The remaining Haplotypes carried either C2* 1 or else an undetectable C2*0 allele. In the entire data there were 281 meioses informative for C2. The only recombinant between HLA-B and C2 showed the C2 locus to be on the DR side of the B locus. Strong allelic association between C2 *2 and Bw22 and less strong association between C2 *2 and B15 suggested the possibility of two ancestral C2 mutants. Examination of other markers on these and subsequently collected Haplotypes do not conflict with this idea since the B15 Haplotypes mostly carry C4A *4, C4B*2 whilst the Bw22 Haplotypes mostly carry C4A*4, C4B*4. The alternative idea, that there was one original mutant which crossed over from a B15 to a Bw22 haplotype or vice versa is not excluded, however. Since approximate equilibrium has been reached between Bw22 and the HLA-A locus alleles on these C2*2 bearing Haplotypes, we conclude that this mutation is at least 5000 years old. Other Haplotypes carrying C2*2 are assumed to be ancestral recombinants; if this is true, the C2 locus map position between HLA-B and HLA-DR is confirmed. Study of C2 mutation may provide a model for understanding the genetics of some disease susceptibility genes in the HLA region.
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study of alleles of the second complement component c2 on canadian hla Haplotypes
Tissue Antigens, 2008Co-Authors: W. H. Marshall, John M Barnard, Nadir R Farid, R Grandy, Bodil Larsen, Ronald Payne, Verna M Skanes, David N. Churchill, George Cornell Ebers, Donald W. PatyAbstract:Typing for genetic variation in the second complement component C2 was performed on sera from HLA haplotyped Canadian families. Part of the data has been studied and analysed as a population; in addition there is a further random collection of Haplotypes bearing the C2*2 allele. In the population data there were 444 separate Haplotypes from unrelated parents or other founders: 4.7% of the Haplotypes carried the uncommon allele C2*2; one haplotype carried the rare C2*3. Study of C2 2–1 heterozygotes in the population data revealed 59 Haplotypes which carried the common C2*1 allele and one which carried a deficiency allele C2*0. The remaining Haplotypes carried either C2* 1 or else an undetectable C2*0 allele. In the entire data there were 281 meioses informative for C2. The only recombinant between HLA-B and C2 showed the C2 locus to be on the DR side of the B locus. Strong allelic association between C2 *2 and Bw22 and less strong association between C2 *2 and B15 suggested the possibility of two ancestral C2 mutants. Examination of other markers on these and subsequently collected Haplotypes do not conflict with this idea since the B15 Haplotypes mostly carry C4A *4, C4B*2 whilst the Bw22 Haplotypes mostly carry C4A*4, C4B*4. The alternative idea, that there was one original mutant which crossed over from a B15 to a Bw22 haplotype or vice versa is not excluded, however. Since approximate equilibrium has been reached between Bw22 and the HLA-A locus alleles on these C2*2 bearing Haplotypes, we conclude that this mutation is at least 5000 years old. Other Haplotypes carrying C2*2 are assumed to be ancestral recombinants; if this is true, the C2 locus map position between HLA-B and HLA-DR is confirmed. Study of C2 mutation may provide a model for understanding the genetics of some disease susceptibility genes in the HLA region.
Seon-hee Kim - One of the best experts on this subject based on the ideXlab platform.
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Phylogeography and Ecological Niche Modeling Reveal Reduced Genetic Diversity and Colonization Patterns of Skunk Cabbage (Symplocarpus foetidus; Araceae) From Glacial Refugia in Eastern North America.
Frontiers in plant science, 2018Co-Authors: Seon-hee Kim, Myong-suk Cho, Seung-chul KimAbstract:Alternating glacial and interglacial periods during the Quaternary have dramatically affected the distribution and population genetic structure of plant and animal species throughout the northern hemisphere. Surprisingly, little is known about the postglacial recolonization history of wetland herbaceous perennials that are widely distributed in the understory of deciduous or mixed deciduous-evergreen forests in eastern North America. In this study, we investigated infraspecific variation among 32 populations of skunk cabbage, Symplocarpus foetidus, to test the hypothesis that the extant species diversity of skunk cabbage is the result of a postglacial range expansion from southern refugia during the Quaternary Ice Age. A total of 4041 base pairs (bp) of the chloroplast intergenic spacer region (cpDNA) was sequenced from 485 individuals sampled from glaciated (18 populations, 275 individuals) and unglaciated (14 populations, 210 individuals) regions east and west of the Appalachian Mountains. Haplotype number, haplotype diversity, and nucleotide diversity were calculated, and genetic variation within and among populations was assessed by analysis of molecular variance (AMOVA). The geographic pattern of genetic differentiation was further investigated with a spatial analysis of molecular variance (SAMOVA). A total of eight Haplotypes and three genetic groups (SAMOVA) were recovered and a much higher haplotype number (eight Haplotypes) and haplotype diversity (0.7425) was observed in unglaciated compared to glaciated populations (five Haplotypes, haplotype diversity = 0.6099). All Haplotypes found in glaciated regions represented a subset of Haplotypes found in unglaciated regions. Haplotypes of S. foetidus likely diverged during the Tertiary (mid-Miocene and late Pliocene), predating the last glacial maximum (LGM). Predictions based on ecological niche modeling (ENM) suggested that there was considerably less suitable habitat for skunk cabbage during the LGM, and the habitat range was further south compared to the current distribution. Reduced variation and a subset of Haplotypes in glaciated regions suggest a founder effect associated with range expansion via long-distance seed dispersal. Our results do not support the “Driftless Area” scenario for the northern refugium, rather the data suggest a “Northeastern” refugium near the southernmost extent of the LGM.
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Image_1_Phylogeography and Ecological Niche Modeling Reveal Reduced Genetic Diversity and Colonization Patterns of Skunk Cabbage (Symplocarpus foetidus; Araceae) From Glacial Refugia in Eastern North America.pdf
2018Co-Authors: Seon-hee Kim, Myong-suk Cho, Seung-chul KimAbstract:Alternating glacial and interglacial periods during the Quaternary have dramatically affected the distribution and population genetic structure of plant and animal species throughout the northern hemisphere. Surprisingly, little is known about the post-glacial recolonization history of wetland herbaceous perennials that are widely distributed in the understory of deciduous or mixed deciduous-evergreen forests in eastern North America. In this study, we investigated infraspecific variation among 32 populations of skunk cabbage, Symplocarpus foetidus, to test the hypothesis that the extant species diversity of skunk cabbage is the result of a post-glacial range expansion from southern refugia during the Quaternary Ice Age. A total of 4041 base pairs (bp) of the chloroplast intergenic spacer region (cpDNA) was sequenced from 485 individuals sampled from glaciated (18 populations, 275 individuals) and unglaciated (14 populations, 210 individuals) regions east and west of the Appalachian Mountains. Haplotype number, haplotype diversity, and nucleotide diversity were calculated, and genetic variation within and among populations was assessed by analysis of molecular variance (AMOVA). The geographic pattern of genetic differentiation was further investigated with a spatial analysis of molecular variance (SAMOVA). A total of eight Haplotypes and three genetic groups (SAMOVA) were recovered and a much higher haplotype number (eight Haplotypes) and haplotype diversity (0.7425) was observed in unglaciated compared to glaciated populations (five Haplotypes, haplotype diversity = 0.6099). All Haplotypes found in glaciated regions represented a subset of Haplotypes found in unglaciated regions. Haplotypes of S. foetidus likely diverged during the Tertiary (mid-Miocene and late Pliocene), predating the last glacial maximum (LGM). Predictions based on ecological niche modeling (ENM) suggested that there was considerably less suitable habitat for skunk cabbage during the LGM, and the habitat range was further south compared to the current distribution. Reduced variation and a subset of Haplotypes in glaciated regions suggest a founder effect associated with range expansion via long-distance seed dispersal. Our results do not support the “Driftless Area” scenario for the northern refugium, rather the data suggest a “Northeastern” refugium near the southernmost extent of the LGM.
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Table_2_Phylogeography and Ecological Niche Modeling Reveal Reduced Genetic Diversity and Colonization Patterns of Skunk Cabbage (Symplocarpus foetidus; Araceae) From Glacial Refugia in Eastern North America.docx
2018Co-Authors: Seon-hee Kim, Myong-suk Cho, Seung-chul KimAbstract:Alternating glacial and interglacial periods during the Quaternary have dramatically affected the distribution and population genetic structure of plant and animal species throughout the northern hemisphere. Surprisingly, little is known about the post-glacial recolonization history of wetland herbaceous perennials that are widely distributed in the understory of deciduous or mixed deciduous-evergreen forests in eastern North America. In this study, we investigated infraspecific variation among 32 populations of skunk cabbage, Symplocarpus foetidus, to test the hypothesis that the extant species diversity of skunk cabbage is the result of a post-glacial range expansion from southern refugia during the Quaternary Ice Age. A total of 4041 base pairs (bp) of the chloroplast intergenic spacer region (cpDNA) was sequenced from 485 individuals sampled from glaciated (18 populations, 275 individuals) and unglaciated (14 populations, 210 individuals) regions east and west of the Appalachian Mountains. Haplotype number, haplotype diversity, and nucleotide diversity were calculated, and genetic variation within and among populations was assessed by analysis of molecular variance (AMOVA). The geographic pattern of genetic differentiation was further investigated with a spatial analysis of molecular variance (SAMOVA). A total of eight Haplotypes and three genetic groups (SAMOVA) were recovered and a much higher haplotype number (eight Haplotypes) and haplotype diversity (0.7425) was observed in unglaciated compared to glaciated populations (five Haplotypes, haplotype diversity = 0.6099). All Haplotypes found in glaciated regions represented a subset of Haplotypes found in unglaciated regions. Haplotypes of S. foetidus likely diverged during the Tertiary (mid-Miocene and late Pliocene), predating the last glacial maximum (LGM). Predictions based on ecological niche modeling (ENM) suggested that there was considerably less suitable habitat for skunk cabbage during the LGM, and the habitat range was further south compared to the current distribution. Reduced variation and a subset of Haplotypes in glaciated regions suggest a founder effect associated with range expansion via long-distance seed dispersal. Our results do not support the “Driftless Area” scenario for the northern refugium, rather the data suggest a “Northeastern” refugium near the southernmost extent of the LGM.
Charles N Rotimi - One of the best experts on this subject based on the ideXlab platform.
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whole genome sequence based Haplotypes reveal single origin of the sickle allele during the holocene wet phase
American Journal of Human Genetics, 2018Co-Authors: Daniel Shriner, Charles N RotimiAbstract:Five classical designations of sickle Haplotypes are made on the basis of the presence or absence of restriction sites and are named after the ethno-linguistic groups or geographic regions from which the individuals with sickle cell anemia originated. Each haplotype is thought to represent an independent occurrence of the sickle mutation rs334 (c.20A>T [p.Glu7Val] in HBB). We investigated the origins of the sickle mutation by using whole-genome-sequence data. We identified 156 carriers from the 1000 Genomes Project, the African Genome Variation Project, and Qatar. We classified Haplotypes by using 27 polymorphisms in linkage disequilibrium with rs334. Network analysis revealed a common haplotype that differed from the ancestral haplotype only by the derived sickle mutation at rs334 and correlated collectively with the Central African Republic (CAR), Cameroon, and Arabian/Indian Haplotypes. Other Haplotypes were derived from this haplotype and fell into two clusters, one composed of Senegal Haplotypes and the other composed of Benin and Senegal Haplotypes. The near-exclusive presence of the original sickle haplotype in the CAR, Kenya, Uganda, and South Africa is consistent with this haplotype predating the Bantu expansions. Modeling of balancing selection indicated that the heterozygote advantage was 15.2%, an equilibrium frequency of 12.0% was reached after 87 generations, and the selective environment predated the mutation. The posterior distribution of the ancestral recombination graph yielded a sickle mutation age of 259 generations, corresponding to 7,300 years ago during the Holocene Wet Phase. These results clarify the origin of the sickle allele and improve and simplify the classification of sickle Haplotypes.
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whole genome sequence based Haplotypes reveal single origin of the sickle allele during the holocene wet phase
bioRxiv, 2017Co-Authors: Daniel Shriner, Charles N RotimiAbstract:Five classical designations of sickle Haplotypes are based on the presence/absence of restriction sites and named after ethnic groups or geographic regions from which patients originated. Each haplotype is thought to represent an independent occurrence of the sickle mutation. We investigated the origins of the sickle mutation using whole genome sequence data. We identified 156 carriers from the 1000 Genomes Project, the African Genome Variation Project, and Qatar. We defined a new haplotypic classification using 27 polymorphisms in linkage disequilibrium with rs334. Network analysis revealed a common haplotype that differed from the ancestral haplotype only by the derived sickle mutation at rs334 and correlated collectively with the Central African Republic/Bantu, Cameroon, and Arabian/Indian designations. Other Haplotypes were derived from this haplotype and fell into two clusters, one comprised of Haplotypes correlated with the Senegal designation and the other comprised of Haplotypes correlated with both the Benin and Senegal designations. The near-exclusive presence of the original sickle haplotype in the Central African Republic, Kenya, Uganda, and South Africa is consistent with this haplotype predating the Bantu Expansion. Modeling of balancing selection indicated that the heterozygote advantage was 15.2%, an equilibrium frequency of 12.0% was reached after 87 generations, and the selective environment predated the mutation. The posterior distribution of the ancestral recombination graph yielded an age of the sickle mutation of 259 generations, corresponding to 7,300 years and the Holocene Wet Phase. These results clarify the origin of the sickle allele and improve and simplify the classification of sickle Haplotypes.
W. H. Marshall - One of the best experts on this subject based on the ideXlab platform.
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study of alleles of the second complement component c2 on canadian hla Haplotypes
Tissue Antigens, 2008Co-Authors: W. H. Marshall, John M Barnard, Nadir R Farid, R Grandy, Bodil Larsen, Ronald Payne, Verna M Skanes, David N. Churchill, George Cornell Ebers, Donald W. PatyAbstract:Typing for genetic variation in the second complement component C2 was performed on sera from HLA haplotyped Canadian families. Part of the data has been studied and analysed as a population; in addition there is a further random collection of Haplotypes bearing the C2*2 allele. In the population data there were 444 separate Haplotypes from unrelated parents or other founders: 4.7% of the Haplotypes carried the uncommon allele C2*2; one haplotype carried the rare C2*3. Study of C2 2–1 heterozygotes in the population data revealed 59 Haplotypes which carried the common C2*1 allele and one which carried a deficiency allele C2*0. The remaining Haplotypes carried either C2* 1 or else an undetectable C2*0 allele. In the entire data there were 281 meioses informative for C2. The only recombinant between HLA-B and C2 showed the C2 locus to be on the DR side of the B locus. Strong allelic association between C2 *2 and Bw22 and less strong association between C2 *2 and B15 suggested the possibility of two ancestral C2 mutants. Examination of other markers on these and subsequently collected Haplotypes do not conflict with this idea since the B15 Haplotypes mostly carry C4A *4, C4B*2 whilst the Bw22 Haplotypes mostly carry C4A*4, C4B*4. The alternative idea, that there was one original mutant which crossed over from a B15 to a Bw22 haplotype or vice versa is not excluded, however. Since approximate equilibrium has been reached between Bw22 and the HLA-A locus alleles on these C2*2 bearing Haplotypes, we conclude that this mutation is at least 5000 years old. Other Haplotypes carrying C2*2 are assumed to be ancestral recombinants; if this is true, the C2 locus map position between HLA-B and HLA-DR is confirmed. Study of C2 mutation may provide a model for understanding the genetics of some disease susceptibility genes in the HLA region.
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study of alleles of the second complement component c2 on canadian hla Haplotypes
Tissue Antigens, 2008Co-Authors: W. H. Marshall, John M Barnard, Nadir R Farid, R Grandy, Bodil Larsen, Ronald Payne, Verna M Skanes, David N. Churchill, George Cornell Ebers, Donald W. PatyAbstract:Typing for genetic variation in the second complement component C2 was performed on sera from HLA haplotyped Canadian families. Part of the data has been studied and analysed as a population; in addition there is a further random collection of Haplotypes bearing the C2*2 allele. In the population data there were 444 separate Haplotypes from unrelated parents or other founders: 4.7% of the Haplotypes carried the uncommon allele C2*2; one haplotype carried the rare C2*3. Study of C2 2–1 heterozygotes in the population data revealed 59 Haplotypes which carried the common C2*1 allele and one which carried a deficiency allele C2*0. The remaining Haplotypes carried either C2* 1 or else an undetectable C2*0 allele. In the entire data there were 281 meioses informative for C2. The only recombinant between HLA-B and C2 showed the C2 locus to be on the DR side of the B locus. Strong allelic association between C2 *2 and Bw22 and less strong association between C2 *2 and B15 suggested the possibility of two ancestral C2 mutants. Examination of other markers on these and subsequently collected Haplotypes do not conflict with this idea since the B15 Haplotypes mostly carry C4A *4, C4B*2 whilst the Bw22 Haplotypes mostly carry C4A*4, C4B*4. The alternative idea, that there was one original mutant which crossed over from a B15 to a Bw22 haplotype or vice versa is not excluded, however. Since approximate equilibrium has been reached between Bw22 and the HLA-A locus alleles on these C2*2 bearing Haplotypes, we conclude that this mutation is at least 5000 years old. Other Haplotypes carrying C2*2 are assumed to be ancestral recombinants; if this is true, the C2 locus map position between HLA-B and HLA-DR is confirmed. Study of C2 mutation may provide a model for understanding the genetics of some disease susceptibility genes in the HLA region.
