Novel variants in GALE cause syndromic macrothrombocytopenia by disrupting glycosylation and thrombopoiesis
Authors
Marín Quilez, Ana; Di Buduo, Christian Andrea; Diaz-Ajenjo, Lorena; Abbonante, Vittorio; Vuelta Ramos, Elena; [et al.]Identifiers
Permanent link (URI): http://hdl.handle.net/10017/60508DOI: 10.1182/blood.2022016995
ISSN: 0006-4971
Date
2022-11-17Bibliographic citation
Blood, 2022, v. 141, n. 4, p. 406-421
Document type
info:eu-repo/semantics/article
Version
info:eu-repo/semantics/publishedVersion
Rights
Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Access rights
info:eu-repo/semantics/openAccess
Abstract
Glycosylation is recognized as a key process for proper megakaryopoiesis and platelet formation. The enzyme uridine diphosphate (UDP)-galactose-4-epimerase, encoded by GALE, is involved in galactose metabolism and protein glycosylation. Here, we studied 3 patients from 2 unrelated families who showed lifelong severe thrombocytopenia, bleeding diathesis, mental retardation, mitral valve prolapse, and jaundice. Whole-exome sequencing revealed 4 variants that affect GALE, 3 of those previously unreported (Pedigree A, p.Lys78ValfsX32 and p.Thr150Met; Pedigree B, p.Val128Met; and p.Leu223Pro). Platelet phenotype analysis showed giant and/or grey platelets, impaired platelet aggregation, and severely reduced alpha and dense granule secretion. Enzymatic activity of the UDP-galactose-4-epimerase enzyme was severely decreased in all patients. Immunoblotting of platelet lysates revealed reduced GALE protein levels, a significant decrease in N-acetyl-lactosamine (LacNAc), showing a hypoglycosylation pattern, reduced surface expression of gylcoprotein Ib alpha-IX-V (GPIb alpha-IX-V) complex and mature beta 1 integrin, and increased apoptosis. In vitro studies performed with patients-derived megakaryocytes showed normal ploidy and maturation but decreased proplatelet formation because of the impaired glycosylation of the GPIb alpha and beta 1 integrin, and reduced externalization to megakaryocyte and platelet membranes. Altered distribution of filamin A and actin and delocalization of the von Willebrand factor were also shown. Overall, this study expands our knowledge of GALE-related thrombocytopenia and emphasizes the critical role of GALE in the physiological glycosylation of key proteins involved in platelet production and function.
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