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Sieff, Colin

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Sieff

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Colin

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Sieff, Colin

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2014 - 20152

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Author's Publications: search.filters.isAuthorOfPublication.da9e6734-7a37-4b0e-896f-bbe83975e768

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    Altered translation of GATA1 in Diamond-Blackfan anemia
    (2014) Ludwig, Leif S.; Gazda, Hanna; Eng, Jennifer C.; Eichhorn, Stephen W.; Thiru, Prathapan; Ghazvinian, Roxanne; George, Tracy I.; Gotlib, Jason R.; Beggs, Alan; Sieff, Colin; Lodish, Harvey F.; Lander, Eric; Sankaran, Vijay
    Ribosomal protein haploinsufficiency occurs in diverse human diseases including Diamond-Blackfan anemia (DBA),1,2 congenital asplenia,3 and T-cell leukemia.4 Yet how mutations in such ubiquitously expressed proteins result in cell-type and tissue specific defects remains a mystery.5 Here, we show that GATA1 mutations that reduce full-length protein levels of this critical hematopoietic transcription factor can cause DBA in rare instances. We show that ribosomal protein haploinsufficiency, the more common cause of DBA, can similarly reduce translation of GATA1 mRNA - a phenomenon that appears to result from this mRNA having a higher threshold for initiation of translation. In primary hematopoietic cells from patients with RPS19 mutations, a transcriptional signature of GATA1 target genes is globally and specifically reduced, confirming that the activity, but not the mRNA level, of GATA1 is reduced in DBA patients with ribosomal protein mutations. The defective hematopoiesis observed in DBA patients with ribosomal protein haploinsufficiency can be at least partially overcome by increasing GATA1 protein levels. Our results provide a paradigm by which selective defects in translation due to mutations in ubiquitous ribosomal proteins can result in human disease.
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    A missense mutation in TFRC, encoding transferrin receptor 1, causes combined immunodeficiency
    (2015) Jabara, Haifa H.; Boyden, Steven E.; Chou, Janet; Ramesh, Narayanaswamy; Massaad, Michel; Benson, Halli; Bainter, Wayne; Fraulino, David; Rahimov, Fedik; Sieff, Colin; Liu, Zhi-Jian; Alshemmari, Salem H.; Al-Ramadi, Basel K.; Al-Dhekri, Hasan; Arnaout, Rand; Abu-Shukair, Mohammad; Vatsayan, Anant; Silver, Eli; Ahuja, Sanjay; Davies, E. Graham; Sola-Visner, Martha; Ohsumi, Toshiro; Andrews, Nancy C.; Notarangelo, Luigi; Fleming, Mark; Al-Herz, Waleed; Kunkel, Louis; Geha, Raif
    Patients with a combined immunodeficiency characterized by normal numbers, but impaired function, of T and B cells had a homozygous p.Tyr20His mutation in transferrin receptor 1 (TfR1), encoded by TFRC. The mutation disrupts the TfR1 internalization motif, resulting in defective receptor endocytosis and markedly increased TfR1 surface expression. Iron citrate rescued the lymphocyte defects and transduction of wild type, but not mutant, TfR1 rescued impaired transferrin uptake in patient fibroblasts. TfrcY20H/Y20H mice recapitulated the patients’ immunologic defects. Despite the critical role of TfR1 in erythrocyte development and function, the patients had only mild anemia and only slightly increased TfR1 expression in erythroid precursors. We show that STEAP3, a metalloreductase expressed in erythroblasts, associates with TfR1 and partially rescues transferrin uptake in patient fibroblasts, suggesting that STEAP3 may provide an accessory TfR1 endocytosis signal that spares the patients from severe anemia. These findings demonstrate the importance of TfR1 in adaptive immunity.