OC 64.3 - Novel GNE gene variants associated with severe congenital thrombocytopenia and platelet sialylation defect - follow up data after hematopoietic stem cell transplantation

Tuesday, July 12, 2022

3:15 PM – 3:30 PM

Location: ExCel Center, ICC Capital Suite Room 14-16

Presentation Format: In-Person

Presenting Author(s)

BZ

Barbara Zieger

Head of the Section Haemostaseology
Department of Pediatrics and Adolescent Medicine, Division of Pediatric Hematology and Oncology, Medical Center, Faculty of Medicine, University of Freiburg
Freiburg, Baden-Wurttemberg, Germany

Co-Author(s)

Doris Boeckelmann, PhD

Research associate
Division of Pediatric Hematology and Oncology, Medical Center, Faculty of Medicine, University of Freiburg
Freiburg, Baden-Wurttemberg, Germany
WA

Waseem Anani

Associate Medical Director, BloodCenter of Wisconsin
Translational Glycomics Center, Versiti Blood Research Institute
Milwaukee, Wisconsin, United States
Hervé Falet, PhD

Principal Investigator
The Medical College of Wisconsin
Milwaukee, Wisconsin, United States
JZ

Jieqing Zhu

Associate Adjunct Professor
Translational Glycomics Center, Versiti Blood Research Institute
Milwaukee, Wisconsin, United States
HG

Hannah Glonnegger

Pediatric Resident Oncology and Hematology
Department of Pediatrics and Adolescent Medicine, Division of Pediatric Hematology and Oncology, Medical Center, Faculty of Medicine, University of Freiburg
Freiburg, Baden-Wurttemberg, Germany
HF

Hermann Full

Pediatrician
Clinic for Pediatric and Adolescent Medicine, SLK-Kliniken Heilbronn
Heilbronn, Baden-Wurttemberg, Germany
FA

Felicia Andresen

Pediatric Resident Oncology and Hematology
Department of Pediatrics and Adolescent Medicine, Division of Pediatric Hematology and Oncology, Medical Center, Faculty of Medicine, University of Freiburg
Freiburg, Baden-Wurttemberg, Germany
ME

Miriam Erlacher

Physician Scientist
Department of Pediatrics and Adolescent Medicine, Division of Pediatric Hematology and Oncology, Medical Center, Faculty of Medicine, University of Freiburg
Freiburg, Baden-Wurttemberg, Germany
EL

Ekkehart Lausch

Head, Section of Pediatric Genetics
Pediatric Genetics Section, Department of Pediatrics, University of Freiburg
Freiburg, Baden-Wurttemberg, Germany
SF

Salome Fels

Medical Graduate Student
Department of Pediatrics and Adolescent Medicine, Division of Pediatric Hematology and Oncology, Medical Center, Faculty of Medicine, University of Freiburg
Freiburg, Baden-Wurttemberg, Germany
BS

Brigitte Strahm

Senior Physician
Department of Pediatrics and Adolescent Medicine, Division of Pediatric Hematology and Oncology, Medical Center, Faculty of Medicine, University of Freiburg
Freiburg, Baden-Wurttemberg, Germany
PL

Peter Lang

Acting Medical Director
University Children’s Hospital Tuebingen, Department I – General Pediatrics, Hematology/Oncology, Tuebingen, Germany
Tuebingen, Baden-Wurttemberg, Germany
KH

Karin M. Hoffmeister, MD

Director, Professor
Versiti Translational Glycomics Center
Milwaukee, Wisconsin, United States

Background: The GNE gene encodes an enzyme that initiates and regulates the biosynthesis of N-acetylneuraminic acid, a precursor of sialic acids. GNE mutations are classically associated with Nonaka myopathy and sialuria, following an autosomal recessive and autosomal dominant inheritance pattern. Single patients have been described with GNE variants, which only cause isolated thrombocytopenia.

Aims: To characterize the platelet defect in a young girl (6 month old) with life-threatening intracranial bleeding and severe congenital thrombocytopenia (lowest platelet count 5 G/L), who needed weekly platelet transfusions.

Methods: Bone marrow analysis and comprehensive analyses for inherited thrombocytopenia: blood smear, platelet aggregometry (LTA), platelet flow cytometry (FC) and lectin array analysis of platelet glycoproteins. Molecular analysis was performed by HTS panel and direct sequencing. Protein modelling using PyMOL.

Results: Bone marrow analysis indicated slightly increased megakaryopoiesis with mature megakaryocytes of normal morphology and hypolobulated, immature cells. LTA showed severe impaired response to Col, ADP, and Epi. FC showed moderately impaired VWF-binding after stimulation with ristocetin and severely decreased agonist-induced alpha and dense granules secretion. HTS identified two novel compound heterozygous variants in GNE (NM_005476.6:c.1250C>T and c.1259G>A.). Both alterations (p.Thr417Met and p.Arg420Gln) are located in the nucleotide-binding site of the N-acetylmannosamin kinase domain of GNE. Crystal structure of GNE kinase domain in complex with ADP shows the hydrogen-bonding interactions of T417 and R420 with ADP and in silico mutations of T417M and R420Q suggest disruption of ADP binding. Lectin array showed decreased α-2,3 sialylation on platelets, consistent with loss of sialic acid synthesis and indicative of rapid platelet clearance.

Conclusion(s): The findings led to hematopoietic stem cell transplantation (HSCT) which normalized platelet counts (follow up 15 months after HSCT: 423 G/L, no signs of myopathy). The child developed normally. To our knowledge, this was the first time that HSCT was successfully performed in a patient with GNE defect.