Allelic imbalance modulates surface expression of the tolerance-inducing HLA-G molecule on primary trophoblast cells

TY - JOUR

T1 - Allelic imbalance modulates surface expression of the tolerance-inducing HLA-G molecule on primary trophoblast cells

AU - Djurisic, S

AU - Teiblum, S

AU - Tolstrup, C K

AU - Christiansen, O B

AU - Hviid, T V F

N1 - © The Author 2014. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: [email protected].

PY - 2014/9/23

Y1 - 2014/9/23

N2 - The HLA-G molecule is expressed on trophoblast cells at the feto-maternal interface, where it interacts with local immune cells, and upholds tolerance against the semi-allogeneic fetus. Aberrant HLA-G expression in the placenta and reduced soluble HLA-G levels are observed in pregnancy complications, partly explained by HLA-G polymorphisms which are associated with differences in the alternative splicing pattern and of the stability of HLA-G mRNA. Of special importance is a 14 bp insertion/deletion polymorphism located in the 3'-untranslated region of the HLA-G gene. In the current study, we present novel evidence for allelic imbalance of the 14 bp insertion/deletion polymorphism, using a very accurate and sensitive Digital droplet PCR technique. Allelic imbalance in heterozygous samples was observed as differential expression levels of 14 bp insertion/deletion allele-specific mRNA transcripts, which was further associated with low levels of HLA-G surface expression on primary trophoblast cells. Full gene sequencing of HLA-G allowed us to study correlations between HLA-G extended haplotypes and single-nucleotide polymorphisms and HLA-G surface expression. We found that a 1:1 expression (allelic balance) of the 14 bp insertion/deletion mRNA alleles was associated with high surface expression of HLA-G and with a specific HLA-G extended haplotype. The 14 bp del/del genotype was associated with a significantly lower abundance of the G1 mRNA isoform, and a higher abundance of the G3 mRNA isoform. Overall, the present study provides original evidence for allelic imbalance of the 14 bp insertion/deletion polymorphism, which influences HLA-G surface expression on primary trophoblast cells, considered to be important in the pathogenesis of pre-eclampsia and other pregnancy complications.

AB - The HLA-G molecule is expressed on trophoblast cells at the feto-maternal interface, where it interacts with local immune cells, and upholds tolerance against the semi-allogeneic fetus. Aberrant HLA-G expression in the placenta and reduced soluble HLA-G levels are observed in pregnancy complications, partly explained by HLA-G polymorphisms which are associated with differences in the alternative splicing pattern and of the stability of HLA-G mRNA. Of special importance is a 14 bp insertion/deletion polymorphism located in the 3'-untranslated region of the HLA-G gene. In the current study, we present novel evidence for allelic imbalance of the 14 bp insertion/deletion polymorphism, using a very accurate and sensitive Digital droplet PCR technique. Allelic imbalance in heterozygous samples was observed as differential expression levels of 14 bp insertion/deletion allele-specific mRNA transcripts, which was further associated with low levels of HLA-G surface expression on primary trophoblast cells. Full gene sequencing of HLA-G allowed us to study correlations between HLA-G extended haplotypes and single-nucleotide polymorphisms and HLA-G surface expression. We found that a 1:1 expression (allelic balance) of the 14 bp insertion/deletion mRNA alleles was associated with high surface expression of HLA-G and with a specific HLA-G extended haplotype. The 14 bp del/del genotype was associated with a significantly lower abundance of the G1 mRNA isoform, and a higher abundance of the G3 mRNA isoform. Overall, the present study provides original evidence for allelic imbalance of the 14 bp insertion/deletion polymorphism, which influences HLA-G surface expression on primary trophoblast cells, considered to be important in the pathogenesis of pre-eclampsia and other pregnancy complications.

KW - 3' Untranslated Regions

KW - Abortion, Legal

KW - Alleles

KW - Allelic Imbalance

KW - Alternative Splicing

KW - Base Sequence

KW - Female

KW - HLA-G Antigens

KW - Haplotypes

KW - Heterozygote

KW - Humans

KW - INDEL Mutation

KW - Immune Tolerance

KW - Molecular Sequence Data

KW - Polymerase Chain Reaction

KW - Polymorphism, Genetic

KW - Pregnancy

KW - Pregnancy Trimester, First

KW - Primary Cell Culture

KW - Sequence Analysis, DNA

KW - Trophoblasts

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1093/molehr/gau108

DO - 10.1093/molehr/gau108

M3 - Journal article

C2 - 25425608

SN - 1360-9947

VL - 21

SP - 281

EP - 295

JO - Molecular Human Reproduction

JF - Molecular Human Reproduction

IS - 3

ER -