Thrombocytopenia and CD34 expression is decoupled from α-granule deficiency with mutation of the first growth factor-independent 1B zinc finger.
J Thromb Haemost
; 15(11): 2245-2258, 2017 11.
Article
em En
| MEDLINE
| ID: mdl-28880435
ABSTRACT
Essentials The phenotypes of different growth factor-independent 1B (GFI1B) variants are not established. GFI1B variants produce heterogeneous clinical phenotypes dependent on the site of mutation. Mutation of the first non-DNA-binding zinc-finger causes a mild platelet and clinical phenotype. GFI1B regulates the CD34 promoter; platelet CD34 expression is an indicator of GFI1B mutation. SUMMARY:
Background Mutation of the growth factor-independent 1B (GFI1B) fifth DNA-binding zinc-finger domain causes macrothrombocytopenia and α-granule deficiency leading to clinical bleeding. The phenotypes associated with GFI1B variants disrupting non-DNA-binding zinc-fingers remain uncharacterized. Objectives To determine the functional and phenotypic consequences of GFI1B variants disrupting non-DNA-binding zinc-finger domains. Methods The GFI1B C168F variant and a novel GFI1B c.2520 + 1_2520 + 8delGTGGGCAC splice variant were identified in four unrelated families. Phenotypic features, DNA-binding properties and transcriptional effects were determined and compared with those in individuals with a GFI1B H294 fs mutation of the fifth DNA-binding zinc-finger. Patient-specific induced pluripotent stem cell (iPSC)-derived megakaryocytes were generated to facilitate disease modeling. Results The DNA-binding GFI1B variant C168F, which is predicted to disrupt the first non-DNA-binding zinc-finger domain, is associated with macrothrombocytopenia without α-granule deficiency or bleeding symptoms. A GFI1B splice variant, c.2520 + 1_2520 + 8delGTGGGCAC, which generates a short GFI1B isoform that lacks non-DNA-binding zinc-fingers 1 and 2, is associated with increased platelet CD34 expression only, without quantitative or morphologic platelet abnormalities. GFI1B represses the CD34 promoter, and this repression is attenuated by different GFI1B zinc-finger mutations, suggesting that deregulation of CD34 expression occurs at a direct transcriptional level. Patient-specific iPSC-derived megakaryocytes phenocopy these observations. Conclusions Disruption of GFI1B non-DNA-binding zinc-finger 1 is associated with mild to moderate thrombocytopenia without α-granule deficiency or bleeding symptomatology, indicating that the site of GFI1B mutation has important phenotypic implications. Platelet CD34 expression appears to be a common feature of perturbed GFI1B function, and may have diagnostic utility.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas Repressoras
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Trombocitopenia
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Megacariócitos
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Dedos de Zinco
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Proteínas Proto-Oncogênicas
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Antígenos CD34
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Grânulos Citoplasmáticos
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Células-Tronco Pluripotentes Induzidas
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Mutação
Tipo de estudo:
Diagnostic_studies
/
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
J Thromb Haemost
Assunto da revista:
HEMATOLOGIA
Ano de publicação:
2017
Tipo de documento:
Article
País de afiliação:
Austrália