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Distinct Transcript Isoforms of the Atypical Chemokine Receptor 1 (ACKR1)/Duffy Antigen Receptor for Chemokines (DARC) Gene Are Expressed in Lymphoblasts and Altered Isoform Levels Are Associated with Genetic Ancestry and the Duffy-Null Allele.

Davis MB, Walens A, Hire R, Mumin K, Brown AM, Ford D, Howerth EW, Monteil M - PLoS ONE (2015)

Bottom Line: Additional alleles are associated with a myriad of clinical outcomes related to immune responses and inflammation.We conclude that the expression of both isoforms in combination with alternate alleles yields multiple Duffy antigens in ancestry groups, depending upon the haplotypes across the gene.Ultimately, this work will increase knowledge of biological mechanisms underlying disparate clinical outcomes of inflammatory-related diseases among ethnic and geographic ancestry groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Franklin College of Arts and Sciences, University of Georgia, Athens, GA, United States of America; Department of Molecular Biology and Biochemistry, Georgia Regents University-University of Georgia Medical Partnership, Athens, GA, United States of America.

ABSTRACT
The Atypical ChemoKine Receptor 1 (ACKR1) gene, better known as Duffy Antigen Receptor for Chemokines (DARC or Duffy), is responsible for the Duffy Blood Group and plays a major role in regulating the circulating homeostatic levels of pro-inflammatory chemokines. Previous studies have shown that one common variant, the Duffy Null (Fy-) allele that is specific to African Ancestry groups, completely removes expression of the gene on erythrocytes; however, these individuals retain endothelial expression. Additional alleles are associated with a myriad of clinical outcomes related to immune responses and inflammation. In addition to allele variants, there are two distinct transcript isoforms of DARC which are expressed from separate promoters, and very little is known about the distinct transcriptional regulation or the distinct functionality of these protein isoforms. Our objective was to determine if the African specific Fy- allele alters the expression pattern of DARC isoforms and therefore could potentially result in a unique signature of the gene products, commonly referred to as antigens. Our work is the first to establish that there is expression of DARC on lymphoblasts. Our data indicates that people of African ancestry have distinct relative levels of DARC isoforms expressed in these cells. We conclude that the expression of both isoforms in combination with alternate alleles yields multiple Duffy antigens in ancestry groups, depending upon the haplotypes across the gene. Importantly, we hypothesize that DARC isoform expression patterns will translate into ancestry-specific inflammatory responses that are correlated with the axis of pro-inflammatory chemokine levels and distinct isoform-specific interactions with these chemokines. Ultimately, this work will increase knowledge of biological mechanisms underlying disparate clinical outcomes of inflammatory-related diseases among ethnic and geographic ancestry groups.

No MeSH data available.


Related in: MedlinePlus

DARC/ACKR1 protein is differentially expressed among lymphoblasts derived from divergent ancestry groups in HAPMAP/ 1,000 (1K) Genomes populations.(A). Representative IHC images of DARC expression in the lymphoblasts of Africans (YRI) and European Americans (CEPH/CEU). DARC is stained with Vulcan Red chromogen nuclei are stained blue with hematoxylin. (B). Shows a distribution analysis of IHC scores across ancestry groups and Fy- genotypes. The full range of scores (0–4) were observed in our cohort, with clear trends within groups. European Americans were the only ancestry group to have a 0 score, indicating no DARC expression in these cells, correlating with lower transcription of the gene. Similarly, individuals with a homozygous Duffy-positive (TT) genotype were the only to have a score of 0, indicating that lowest levels of DARC expression in lymphoblast are associated with the European lineage and the TT genotype, in contrast to higher DARC expression in the lymphocytes of African lineages. Accordingly, the majority of high lymphoblast IHC scores (3 or 4) were in the African lineage. All African Americans only showed moderate expression levels in lymphoblasts.
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pone.0140098.g002: DARC/ACKR1 protein is differentially expressed among lymphoblasts derived from divergent ancestry groups in HAPMAP/ 1,000 (1K) Genomes populations.(A). Representative IHC images of DARC expression in the lymphoblasts of Africans (YRI) and European Americans (CEPH/CEU). DARC is stained with Vulcan Red chromogen nuclei are stained blue with hematoxylin. (B). Shows a distribution analysis of IHC scores across ancestry groups and Fy- genotypes. The full range of scores (0–4) were observed in our cohort, with clear trends within groups. European Americans were the only ancestry group to have a 0 score, indicating no DARC expression in these cells, correlating with lower transcription of the gene. Similarly, individuals with a homozygous Duffy-positive (TT) genotype were the only to have a score of 0, indicating that lowest levels of DARC expression in lymphoblast are associated with the European lineage and the TT genotype, in contrast to higher DARC expression in the lymphocytes of African lineages. Accordingly, the majority of high lymphoblast IHC scores (3 or 4) were in the African lineage. All African Americans only showed moderate expression levels in lymphoblasts.

Mentions: In order to investigate ancestry related DARC distinctions, we chose to utilize the lymphoblast lines from the HAPMAP resources. Several genome-wide investigations have indicated DARC/ACKR1 expression in many tissues [40–45], including low level transcripts from microarray data in the cell lineages that were used to derive the HAPMAP lines (S1 Fig). However, there were no explicit reports of these cells expressing the DARC/ACKR1 gene product. Therefore, we conducted IHC staining of our set of HAPMAP lines to measure DARC/ACKR1 protein expression. We observed a large amount of variation of expression across the cohort, documenting the full spectrum of IHC scoring; from 0 (no expression) to 4 (very high expression) (Fig 2A). An analysis of the IHC score distributions among ancestry groups and Fy- genotypes suggests a trend of expression that may be linked to ancestry (Fig 2B). We observed that only the CEPH/CEU ancestry group and the homozygous TT (Fy+) genotype groups have individuals who displayed a score of 0, indicating no expression. Over half of this group only had low to moderate expression (score of 1–2) which correlates with our observed lower transcript levels of the DARC isoforms as well. While this might indicate that some individuals of European descent may not typically express high levels of DARC/ACKR1 in lymphoblasts, almost half of this group also displayed high levels of DARC/ACKR1. This suggests that DARC/ACKR1 expression is highly variable in these cells. In contrast, we observe that the YRI and ASW groups primarily displayed the highest scores (3) indicating very high levels of DARC/ACKR1 product in lymphoblasts from these groups. This suggests that these groups would typically have higher levels of DARC/ACKR1 expression in these cells, with few individuals showing low levels.


Distinct Transcript Isoforms of the Atypical Chemokine Receptor 1 (ACKR1)/Duffy Antigen Receptor for Chemokines (DARC) Gene Are Expressed in Lymphoblasts and Altered Isoform Levels Are Associated with Genetic Ancestry and the Duffy-Null Allele.

Davis MB, Walens A, Hire R, Mumin K, Brown AM, Ford D, Howerth EW, Monteil M - PLoS ONE (2015)

DARC/ACKR1 protein is differentially expressed among lymphoblasts derived from divergent ancestry groups in HAPMAP/ 1,000 (1K) Genomes populations.(A). Representative IHC images of DARC expression in the lymphoblasts of Africans (YRI) and European Americans (CEPH/CEU). DARC is stained with Vulcan Red chromogen nuclei are stained blue with hematoxylin. (B). Shows a distribution analysis of IHC scores across ancestry groups and Fy- genotypes. The full range of scores (0–4) were observed in our cohort, with clear trends within groups. European Americans were the only ancestry group to have a 0 score, indicating no DARC expression in these cells, correlating with lower transcription of the gene. Similarly, individuals with a homozygous Duffy-positive (TT) genotype were the only to have a score of 0, indicating that lowest levels of DARC expression in lymphoblast are associated with the European lineage and the TT genotype, in contrast to higher DARC expression in the lymphocytes of African lineages. Accordingly, the majority of high lymphoblast IHC scores (3 or 4) were in the African lineage. All African Americans only showed moderate expression levels in lymphoblasts.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608815&req=5

pone.0140098.g002: DARC/ACKR1 protein is differentially expressed among lymphoblasts derived from divergent ancestry groups in HAPMAP/ 1,000 (1K) Genomes populations.(A). Representative IHC images of DARC expression in the lymphoblasts of Africans (YRI) and European Americans (CEPH/CEU). DARC is stained with Vulcan Red chromogen nuclei are stained blue with hematoxylin. (B). Shows a distribution analysis of IHC scores across ancestry groups and Fy- genotypes. The full range of scores (0–4) were observed in our cohort, with clear trends within groups. European Americans were the only ancestry group to have a 0 score, indicating no DARC expression in these cells, correlating with lower transcription of the gene. Similarly, individuals with a homozygous Duffy-positive (TT) genotype were the only to have a score of 0, indicating that lowest levels of DARC expression in lymphoblast are associated with the European lineage and the TT genotype, in contrast to higher DARC expression in the lymphocytes of African lineages. Accordingly, the majority of high lymphoblast IHC scores (3 or 4) were in the African lineage. All African Americans only showed moderate expression levels in lymphoblasts.
Mentions: In order to investigate ancestry related DARC distinctions, we chose to utilize the lymphoblast lines from the HAPMAP resources. Several genome-wide investigations have indicated DARC/ACKR1 expression in many tissues [40–45], including low level transcripts from microarray data in the cell lineages that were used to derive the HAPMAP lines (S1 Fig). However, there were no explicit reports of these cells expressing the DARC/ACKR1 gene product. Therefore, we conducted IHC staining of our set of HAPMAP lines to measure DARC/ACKR1 protein expression. We observed a large amount of variation of expression across the cohort, documenting the full spectrum of IHC scoring; from 0 (no expression) to 4 (very high expression) (Fig 2A). An analysis of the IHC score distributions among ancestry groups and Fy- genotypes suggests a trend of expression that may be linked to ancestry (Fig 2B). We observed that only the CEPH/CEU ancestry group and the homozygous TT (Fy+) genotype groups have individuals who displayed a score of 0, indicating no expression. Over half of this group only had low to moderate expression (score of 1–2) which correlates with our observed lower transcript levels of the DARC isoforms as well. While this might indicate that some individuals of European descent may not typically express high levels of DARC/ACKR1 in lymphoblasts, almost half of this group also displayed high levels of DARC/ACKR1. This suggests that DARC/ACKR1 expression is highly variable in these cells. In contrast, we observe that the YRI and ASW groups primarily displayed the highest scores (3) indicating very high levels of DARC/ACKR1 product in lymphoblasts from these groups. This suggests that these groups would typically have higher levels of DARC/ACKR1 expression in these cells, with few individuals showing low levels.

Bottom Line: Additional alleles are associated with a myriad of clinical outcomes related to immune responses and inflammation.We conclude that the expression of both isoforms in combination with alternate alleles yields multiple Duffy antigens in ancestry groups, depending upon the haplotypes across the gene.Ultimately, this work will increase knowledge of biological mechanisms underlying disparate clinical outcomes of inflammatory-related diseases among ethnic and geographic ancestry groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Franklin College of Arts and Sciences, University of Georgia, Athens, GA, United States of America; Department of Molecular Biology and Biochemistry, Georgia Regents University-University of Georgia Medical Partnership, Athens, GA, United States of America.

ABSTRACT
The Atypical ChemoKine Receptor 1 (ACKR1) gene, better known as Duffy Antigen Receptor for Chemokines (DARC or Duffy), is responsible for the Duffy Blood Group and plays a major role in regulating the circulating homeostatic levels of pro-inflammatory chemokines. Previous studies have shown that one common variant, the Duffy Null (Fy-) allele that is specific to African Ancestry groups, completely removes expression of the gene on erythrocytes; however, these individuals retain endothelial expression. Additional alleles are associated with a myriad of clinical outcomes related to immune responses and inflammation. In addition to allele variants, there are two distinct transcript isoforms of DARC which are expressed from separate promoters, and very little is known about the distinct transcriptional regulation or the distinct functionality of these protein isoforms. Our objective was to determine if the African specific Fy- allele alters the expression pattern of DARC isoforms and therefore could potentially result in a unique signature of the gene products, commonly referred to as antigens. Our work is the first to establish that there is expression of DARC on lymphoblasts. Our data indicates that people of African ancestry have distinct relative levels of DARC isoforms expressed in these cells. We conclude that the expression of both isoforms in combination with alternate alleles yields multiple Duffy antigens in ancestry groups, depending upon the haplotypes across the gene. Importantly, we hypothesize that DARC isoform expression patterns will translate into ancestry-specific inflammatory responses that are correlated with the axis of pro-inflammatory chemokine levels and distinct isoform-specific interactions with these chemokines. Ultimately, this work will increase knowledge of biological mechanisms underlying disparate clinical outcomes of inflammatory-related diseases among ethnic and geographic ancestry groups.

No MeSH data available.


Related in: MedlinePlus