Missense mutations in the C-terminal portion of the B4GALNT2-encoded glycosyltransferase underlying the Sd(a−) phenotype

Abstract

Sd a is a high-frequency carbohydrate histo-blood group antigen, GalNAcβ1-4(NeuAcα2-3)Galβ, implicated in pathogen invasion, cancer, xenotransplantation and transfusion medicine. Complete lack of this glycan epitope results in the Sd(a−) phenotype observed in 4% of individuals who may produce anti-Sd a . A candidate gene ( B4GALNT2 ), encoding a Sd a -synthesizing β-1,4- N -acetylgalactosaminyltransferase (β4GalNAc-T2), was cloned in 2003 but the genetic basis of human Sd a deficiency was never elucidated. Experimental and bioinformatic approaches were used to identify and characterize B4GALNT2 variants in nine Sd(a−) individuals. Homozygosity for rs7224888:T > C dominated the cohort (n = 6) and causes p.Cys466Arg, which targets a highly conserved residue located in the enzymatically active domain and is judged deleterious to β4GalNAc-T2. Its allele frequency was 0.10–0.12 in different cohorts. A Sd(a−) compound heterozygote combined rs7224888:T > C with a splice-site mutation, rs72835417:G > A, predicted to alter splicing and occurred at a frequency of 0.11–0.12. Another compound heterozygote had two rare nonsynonymous variants, rs148441237:A > G (p.Gln436Arg) and rs61743617:C > T (p.Arg523Trp), in trans . One sample displayed no differences compared to Sd(a+). When investigating linkage disequilibrium between B4GALNT2 variants, we noted a 32-kb block spanning intron 9 to the intergenic region downstream of B4GALNT2 . This block includes RP11-708H21.4 , a long non-coding RNA recently reported to promote tumorigenesis and poor prognosis in colon cancer. The expression patterns of B4GALNT2 and RP11-708H21.4 correlated extremely well in >1000 cancer cell lines. In summary, we identified a connection between variants of the cancer-associated B4GALNT2 gene and Sd a , thereby establishing a new blood group system and opening up for the possibility to predict Sd(a+) and Sd(a‒) phenotypes by genotyping.

Comparative Gene Signature of (−)-Oleocanthal Formulation Treatments in Heterogeneous Triple Negative Breast Tumor Models: Oncological Therapeutic Target Insights

“…Furthermore, β1,4-N-acetylgalactosaminyltransferase 2 (B4GALNT2) is a biosynthetic enzyme of histo-blood group antigens Sda antigen, a natural component of the red blood cells in the healthy colon of a vast majority of people [ 71 ]. Prior studies have shown that the downregulation of B4GALNT2 can be a marker for colon and gastrointestinal cancers [ 71 , 72 ]. Direct upregulation of the B4GALNT2 gene level reduces the colon malignancy and the stem-associated malignant phenotype in a highly selective fashion [ 73 ].…”

The Sda Synthase B4GALNT2 Reduces Malignancy and Stemness in Colon Cancer Cell Lines Independently of Sialyl Lewis X Inhibition

“…B4GALNT2 and its cognate antigen Sd a play various important roles in different contexts [ 18 ]. The vast majority of Caucasians express the Sd a antigen on erythrocytes and in a few other tissues, although a minority lack Sd a because of an inactivating germline mutation of B4GALNT2 [ 19 ]. At least two different transcripts that only differ in the first exon are generated from the B4GALNT2 gene.…”

Targeted exome sequencing designed for blood group, platelet, and neutrophil antigen investigations: Proof‐of‐principle study for a customized single‐test system

“…We have identified a number of additional targets to be added to the next iteration of the panel which will increase its clinical utility. These include A4GALT Exon2a for P1/P2, 60 XG GATA box for Xg(a-), 12,13 SMYD1 associated with AnWj, 61 PIGT, 62 B4GALNT2 for the Sd a antigen, 40 and PRNP for the KANNO antigen. 39 Probes covering Exon 7 of CD177 will also be redesigned to match the HNA-2positive type, potentially improving genotyping for the HNA-2 system.…”

“…Gray rectangles indicate outputs related to SNV analyses and black rectangles indicate outputs related to copy number variant analysis reported after designing and testing the panel and therefore were not included. 39,40 The chosen targets and relevant chromosomal coordinates were presented to the Illumina concierge service who designed the initial panel probes to cover all coding regions. The probe panel was then reviewed and manually curated to include additional targets and ensure that all targets were covered before synthesis.…”