Limits...
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

Differential expression of DARC isoforms in lymphoblasts derived from 1K Genomes populations.(A) Shows the relative expression levels of DARC 1 and DARC 2 transcripts among our HAPMAP cohort panel. The Fy- genotypes are indicated in the X axis of the top graph (A) and correlated HAPMAP cell line IDs are indicated in the X axis of the bottom graph (B). The “C” allele indicates the Duffy Null mutation. There is a clear trend of higher expression in the African and African Americans, with DARC 1 showing prominent expression. (B) Shows the relative ratios of DARC1/DARC2 isoforms in our cohort. The average ratio values for each ancestry category are shown as overlapping shaded box insets to display the values of each ancestry group. The highest ratio in the African category indicates the greatest difference between isoform expression values. C. ANOVA statistics indicate there are significant differences in DARC isoform transcripts across the cohort groups. The overall fitness across the entire group is mainly due to correlated expression of the isoforms for individuals with the C allele. There is clear trend of higher expression of the DARC 1 isoform in African and African American lineages, relative to European Americans. These data show a trend for lower expression in the European American (CEPH) categories and TT homozygotes for both DARC isoforms. These data indicate differences in isoform regulation, associated with the Fy- “Duffy Null” allele.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4608815&req=5

pone.0140098.g003: Differential expression of DARC isoforms in lymphoblasts derived from 1K Genomes populations.(A) Shows the relative expression levels of DARC 1 and DARC 2 transcripts among our HAPMAP cohort panel. The Fy- genotypes are indicated in the X axis of the top graph (A) and correlated HAPMAP cell line IDs are indicated in the X axis of the bottom graph (B). The “C” allele indicates the Duffy Null mutation. There is a clear trend of higher expression in the African and African Americans, with DARC 1 showing prominent expression. (B) Shows the relative ratios of DARC1/DARC2 isoforms in our cohort. The average ratio values for each ancestry category are shown as overlapping shaded box insets to display the values of each ancestry group. The highest ratio in the African category indicates the greatest difference between isoform expression values. C. ANOVA statistics indicate there are significant differences in DARC isoform transcripts across the cohort groups. The overall fitness across the entire group is mainly due to correlated expression of the isoforms for individuals with the C allele. There is clear trend of higher expression of the DARC 1 isoform in African and African American lineages, relative to European Americans. These data show a trend for lower expression in the European American (CEPH) categories and TT homozygotes for both DARC isoforms. These data indicate differences in isoform regulation, associated with the Fy- “Duffy Null” allele.

Mentions: Using the well-defined genetic ancestry HAPMAP cohort, we investigated whether the Fy- genotype was associated with differential expression of DARC isoforms. We anticipated that the Fy- allele may facilitate removal of DARC/ACKR1expression from lymphocytes if the hematopoietic transcription factor (GATA-3), reported to be the regulator in erythrocytes [49], was also the regulator in lymphoblasts. Therefore, we decided to determine if this would also be true of lymphocyte lineages. However, we found the opposite to be true. Using RT-PCR we were able to detect mRNA expression of both DARC/ACKR1 isoforms, (DARC1/A and DARC2/B) in all individuals, including those with Fy- genotypes. However, the levels of DARC isoform transcripts were very dynamic among the cohort. Therefore, we quantified the differential levels of isoform-specific transcripts using qPCR (Fig 3A). An ANOVA across the entire group indicated the overall isoform transcript levels were significantly variant (p = 0.0007), suggesting the transcripts have distinct expression among our lymphoblast lines, derived from divergent ancestries (Fig 3A). The African and African American groups have a higher level of expression in these lines relative to CEPH-European Americans. The lower level of DARC/ACKR1 isoform transcripts also correlates with the lower IHC scores in this population (Fig 2B). These findings illustrate the Fy- allele may be linked to altered expression of the gene in different cell types or tissues and not just removal of its expression in erythrocytes.


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)

Differential expression of DARC isoforms in lymphoblasts derived from 1K Genomes populations.(A) Shows the relative expression levels of DARC 1 and DARC 2 transcripts among our HAPMAP cohort panel. The Fy- genotypes are indicated in the X axis of the top graph (A) and correlated HAPMAP cell line IDs are indicated in the X axis of the bottom graph (B). The “C” allele indicates the Duffy Null mutation. There is a clear trend of higher expression in the African and African Americans, with DARC 1 showing prominent expression. (B) Shows the relative ratios of DARC1/DARC2 isoforms in our cohort. The average ratio values for each ancestry category are shown as overlapping shaded box insets to display the values of each ancestry group. The highest ratio in the African category indicates the greatest difference between isoform expression values. C. ANOVA statistics indicate there are significant differences in DARC isoform transcripts across the cohort groups. The overall fitness across the entire group is mainly due to correlated expression of the isoforms for individuals with the C allele. There is clear trend of higher expression of the DARC 1 isoform in African and African American lineages, relative to European Americans. These data show a trend for lower expression in the European American (CEPH) categories and TT homozygotes for both DARC isoforms. These data indicate differences in isoform regulation, associated with the Fy- “Duffy Null” allele.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0140098.g003: Differential expression of DARC isoforms in lymphoblasts derived from 1K Genomes populations.(A) Shows the relative expression levels of DARC 1 and DARC 2 transcripts among our HAPMAP cohort panel. The Fy- genotypes are indicated in the X axis of the top graph (A) and correlated HAPMAP cell line IDs are indicated in the X axis of the bottom graph (B). The “C” allele indicates the Duffy Null mutation. There is a clear trend of higher expression in the African and African Americans, with DARC 1 showing prominent expression. (B) Shows the relative ratios of DARC1/DARC2 isoforms in our cohort. The average ratio values for each ancestry category are shown as overlapping shaded box insets to display the values of each ancestry group. The highest ratio in the African category indicates the greatest difference between isoform expression values. C. ANOVA statistics indicate there are significant differences in DARC isoform transcripts across the cohort groups. The overall fitness across the entire group is mainly due to correlated expression of the isoforms for individuals with the C allele. There is clear trend of higher expression of the DARC 1 isoform in African and African American lineages, relative to European Americans. These data show a trend for lower expression in the European American (CEPH) categories and TT homozygotes for both DARC isoforms. These data indicate differences in isoform regulation, associated with the Fy- “Duffy Null” allele.
Mentions: Using the well-defined genetic ancestry HAPMAP cohort, we investigated whether the Fy- genotype was associated with differential expression of DARC isoforms. We anticipated that the Fy- allele may facilitate removal of DARC/ACKR1expression from lymphocytes if the hematopoietic transcription factor (GATA-3), reported to be the regulator in erythrocytes [49], was also the regulator in lymphoblasts. Therefore, we decided to determine if this would also be true of lymphocyte lineages. However, we found the opposite to be true. Using RT-PCR we were able to detect mRNA expression of both DARC/ACKR1 isoforms, (DARC1/A and DARC2/B) in all individuals, including those with Fy- genotypes. However, the levels of DARC isoform transcripts were very dynamic among the cohort. Therefore, we quantified the differential levels of isoform-specific transcripts using qPCR (Fig 3A). An ANOVA across the entire group indicated the overall isoform transcript levels were significantly variant (p = 0.0007), suggesting the transcripts have distinct expression among our lymphoblast lines, derived from divergent ancestries (Fig 3A). The African and African American groups have a higher level of expression in these lines relative to CEPH-European Americans. The lower level of DARC/ACKR1 isoform transcripts also correlates with the lower IHC scores in this population (Fig 2B). These findings illustrate the Fy- allele may be linked to altered expression of the gene in different cell types or tissues and not just removal of its expression in erythrocytes.

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