Use of the emm antigen as a biomarker of inherited gpi deficiencies

Glycosylphosphatidylinositol (GPI) is a glycolipid that anchors more than 150 proteins to the cell surface. Pathogenic variants in several genes that participate in GPI biosynthesis cause inherited GPI deficiency (IGD) disorders. Here, the inventors reported that homozygous null alleles of PIGG, a gene involved in GPI modification, are responsible for the rare Emm-negative blood phenotype. Using a panel of K562 cells defective in both the GPI-transamidase and GPI remodeling pathways, they demonstrate that the Emm antigen, whose molecular basis has remained unknown for decades, is carried only by free GPI and that its epitope is composed of the second and third ethanolamine of the GPI backbone. Importantly, the inventors show that the decrease in Emm expression in several IGD patients is indicative of GPI defects. Overall, our findings establish Emm as a novel blood group system and have important implications for understanding the biological function of human free GPI.

Keywords: Emm antigen, Inherited GPI deficiency, paroxysmal nocturnal hemoglobinuria
Patent Application number: EP20 306 520.6 on 09/12/2020
PCT/EP2021/084699 on 08/12/2021
Publications:
Blood 2021 Jul 1 Duval R et al. Inherited glycosylphosphatidylinositol defects cause the rare Emm-negative blood phenotype and developmental disorders doi: 10.1182/blood.2020009810.

Reference:

BIO20561-D1

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Pierre MAZOT
Pierre MAZOT
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Patent filling date: 2020-12-09
Rare disease: Yes

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