A Novel GATA1 (E200K) Germline Mutation Causing Hydrops Fetalis with Spontaneous Resolution of Erythropoiesis

GATA1 is an X-linked gene that encodes a transcription factor essential for human hematopoiesis. Germline mutations in GATA1 have been associated with a spectrum of congenital red cell and megakaryocyte disorders, including Diamond-Blackfan Anemia, dyserythropoietic anemia, and hemolytic anemia with or without thrombocytopenia. These mutations can lead to varying degrees of anemia, ranging from mild dyserythropoiesis to severe hydrops fetalis. Here, we describe a novel germline GATA1 mutation causing hydrops fetalis with spontaneous resolution of erythropoiesis.

A 33-year-old nulliparous woman was found to carry a male fetus with cystic hygroma during her first trimester prenatal ultrasound. Other than mild thrombocytopenia during pregnancy, she was otherwise healthy. Her non-invasive prenatal genetic screening was negative for trisomy 13, 18, 21, and sex chromosome aneuploidies. At 20 weeks and 4 days gestation, fetal anatomy ultrasound demonstrated worsening cystic hygroma, pericardial effusion, and generalized ascites consistent with hydrops fetalis. Abnormal middle cerebral artery peak systolic velocity (MCA-PSV) suggested fetal anemia. Fetal echocardiography revealed ventricular hypertrophy without structural cardiac defects. She elected for invasive prenatal genetic testing via amniocentesis, and the sample was sent for SNP microarray and trio-based whole exome sequencing. A third trimester prenatal ultrasound showed interval resolution of hydrops with normalization of MCA-PSV. The fetus did not require any red cell transfusions. The infant was delivered through elective cesarean section without bleeding complications. Initial CBC showed Hb 13.9 g/dL (normal 13-20 g/dL), MCV 115 fL (normal 91-106 fL), reticulocyte 0.8% (normal 1.6-2.7%), platelets 58 k/uL (normal 150-450 k/uL), and MPV 13 fL (normal 10-12 fL). The newborn exam was remarkable for short neck with excessive nuchal folds, hypospadias, and mild truncal hypotonia. Serial CBC in the outpatient setting showed mild macrocytic anemia, reticulocytopenia, and mild macrothrombocytopenia. The platelet aggregation study suggested a storage pool disorder, confirmed on electron microscopy.

Genomic studies identified a previously unreported mutation at a highly conserved residue in the first zinc finger (ZnF) domain of GATA1 (c.598G>A/p.E200K). No additional germline single nucleotide or copy number variants were identified. As the mutation is near the exon-intron 3 junction, RNA sequencing using peripheral mononuclear cells was performed to assess altered splicing/expression levels of GATA1. Although cumulative GATA1 expression levels were comparable to tissue-matched controls, approximately 80% of the sequenced transcripts showed aberrant intron 3 inclusion. Additionally, in 7% of the transcripts, a novel aberrant splice donor site within exon 3 was observed. In 13% of the sequenced reads, canonical junction across intron 3 was seen.

To better understand the cellular defect, we generated two HUDEP2 clones expressing E200K mutant using the CRISPR/Cas9 system. Compared to wild-type HUDEP2 cells, the GATA1 expression in E200K-expressing HUDEP2 cells was comparable. However, HUDEP2 cells expressing GATA1^E200K demonstrated impaired erythropoiesis with drastically reduced cell proliferation, delayed terminal erythroid differentiation, and hemoglobinization. Several missense mutations in the first ZnF domain, namely V205M, G208R, and D218G/Y/N, have been reported to cause dyserythropoiesis due to altered binding of GATA1 to its essential cofactor FOG1. Additionally, GATA1 mutations that impair DNA binding, such as R216Q and R216W, have been found in individuals with macrothrombocytopenia and β-thalassemia. Further in-vitro functional studies using the HUDEP2 cell line to assess protein interaction and gene expression profiles are currently ongoing.

In summary, we describe a novel germline GATA1 missense mutation in the ZnF domain presenting with severe fetal anemia and hydrops fetalis with spontaneous resolution of erythropoiesis.