Novel GATA1 mutation in residue D218 leads to macrothrombocytopenia and clinical bleeding problems

• GATA1
• megakaryopoiesis
• transcription factor
• thrombocytopenia

To the editor,

We studied two related patients (III.4 and III.10) with spontaneous clinical bleeding problems and a family history suggestive of X-linked inherited thrombocytopenia (Figure 1A). Both patients presented with hematomas, ecchymosis, epistaxis, and gingival bleeding symptoms since childhood and developed splenomegaly. Hematological investigations (after the patient was splenectomized) showed the presence of macrothrombocytopenia combined with mild features of dyserythropoiesis including poikilocytosis, anisocytosis, and schizocytes, Howell–Jolly bodies in erythrocytes and stomatocytes but no anemia (Table I). Both patients did not respond to immune thrombocytopenic purpura-specific therapy such as intravenous immunoglobulins, steroids, or splenectomy. Bone marrow analysis showed hypermegakaryopoiesis with an increased number of immature megakaryoblasts but no features of dysmyelopoiesis. Platelet functional studies for patient III:4 showed normal aggregations for collagen and ristocetin (amplitudes of 84% and 86%, respectively) and mildly reduced for ADP (amplitude of 40%). The PFA100 closure time with collagen/epinephrine for patient III:4 was prolonged (>300 s; nl: 82–142 s) while normal with collagen/ADP.

Figure 1. (A) Patients with thrombocytopenia are represented by filled symbols. (B) Schematic presentation of the N-terminal zinc finger of GATA1 with the mutations that are reported and the D218N mutation presented in the present study. (C) Sequencing analysis of GATA1 exon 4 using gDNA of patient III:4 and a control male. A basepair substitution G to A was found that converted aspartic acid (D) into asparagine (N). (D) Platelet count profiles for patients with the different D218 GATA1 mutations and an unrelated healthy control subject. The histogram plots present the platelet count (PLT) in function of the mean platelet volume (MPV) as indicated.

Table I. Hematological profiles of patients with GATA D218 mutations.

Patients	GATA1 mutation	Hgb g/dl (10.5–16)	RBCs ×10^9/l (3.9–5.2)	MCV fl (85–95)	LDH U/l (150–460)* (98-192)**	PLTs ×10^9/l (150–350)	MPV fl (7.5–9.2)
Propositus III.4	D218N	14.7	4.98	89.6	261**	68–71	12.8
III.10	D218N	14.2	4.25	91.7	NA	19–36	12.6
Propositus V:3 (2)	D218G	13.4	4.38	90.7	1607*	12–35	>max value
Propositus III.1 (3)	D218Y	9.7	3.42	92.8	818*	9–21	>max value

Hgb indicates Hemoglobin; Hct, Hematocrit; RBCs, red blood cells; MCV, Mean Corpuscular Volume; LDH, Lactate Dehydrogenase; PLTs, platelets; MPV, Mean Platelet Volume. LDH reference values according to different laboratories (* or **).

X-linked macrothrombocytopenia with platelet dysfunction has been described by others and us for patients with mutations in the gene for the transcription factor GATA1 [1–10]. The GATA family of nuclear regulatory proteins serves as a prototype for the action of lineage-restricted transcription factors. The GATA1 protein is typically present in the more differentiated cells of the erythroid, megakaryocytic, mast, and eosinophilic lineages, whereas GATA2 expression is limited to HSCs and early haematopoietic progenitors [11]. Remarkably since its first description in 2001, still only a limited number of families are presently reported with germline GATA1 missense mutations and these presented with closely related but still somewhat altered hematological disorders. They comprise severe dyserythropoietic anemia with macrothrombocytopenia (V205M, G208R, and D218Y), macrothrombocytopenia with mild dyserythropoietic features (G208S, D218G), macrothrombocytopenia with mild β-thalassemia (R216Q), and congenital erythropoietic porphyria (R216W) [1–10]. Figure 1(B) shows the position of these mutations that are all present in the N-terminal zinc finger of GATA1. Males with these mutations have enlarged platelets with a paucity of alpha granules and a reduced function. Some patients also present with splenomegaly [7, 9] or myelodysplasia with marked organomegaly [10], likely due to ineffective and consequential extramedullary hematopoiesis. Genotype–phenotype correlations are hampered by the low numbers of families with a GATA1 mutation to date, with only two mutations (R216Q [6–8] and G208R [5, 10]) being identified in more than one family.

Sanger sequencing of the different GATA1 exons using leukocyte gDNA of patient III:4 showed the presence of a missense mutation gac (D) to aac (N) at codon 218 (Figure 1C). Interestingly, we already have described two other missense mutations in this residue for two unrelated families for which patients presented with mild macrothrombocytopenia with dyserythropoiesis (D218G) [2] and severe macrothrombocytopenia with anemia (D218Y) [3]. A genomic DNA sample was not available from subject III:10 to confirm the presence to the GATA1 D218N variant. The D218N GATA1 variant was not present in the dbSNP or 1000 genomes databases (www.1000genomes.org). In addition, SIFT (sift.jcvi.org) predicted GATA1 variants D218G/Y and N to be damaging.

The platelet defect for propositus III:4 and his relative III:10 seems milder than found for subjects with the D218G or D218Y mutations as the degree of thrombocytopenia is less severe and especially their platelets are large but not giant (Table I and Figure 1D). Actually, without having evidence of an X-linked inheritance patterns in this family, a single patient with this type of platelet defect might escape the genetic diagnosis of GATA1. This could be a reason why still only few patients have been described with GATA1 mutations still giving us no idea about the frequency of this disorder. Therefore, it remains important to report also these milder cases.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

This work was supported by research grants G.0490.10 N, G.0743.09, and G.0B17.13 N from the Fund for Scientific Research – Flanders (FWO-Vlaanderen, Belgium) and GOA/2009/13 from the Research Council of the University of Leuven (Onderzoeksraad KULeuven‚ Belgium). CVG is holder of a clinical-fundamental research mandate of the FWO-Vlaanderen, Belgium and of the Bayer and Norbert Heimburger (CSL Behring) Chairs.