FBP Knock-Out Leads to a Hematopoietic Maturation Defect.
Edgardo Parrilla-Castellar, Weixin Zhou, Juhong Liu, Lino Tessarollo, David Levens. National Institutes of Health, Bethesda, MD; National Institutes of Health, Frederick, MD
Background: As a critical regulator of proliferation, growth, differentiation and senescence, the expression of c-Myc is under tight control. A key regulator of c-Myc expression is the FarUpStream Element (FUSE) Binding Protein (FBP). Although the mechanism of FBP-mediated regulation of c-Myc expression has been studied in cell culture, the role of FBP in development has not been studied.
Design: To study FBP function in mice, a 2037 bp fragment encompassing the DNA binding domains KH2, KH3 and part of the KH4 of FBP was deleted. Expression of the knockout allele was not detectable. The phenotype of the FBP knockout was examined.
Results: FBP-deficient mice were embryonic and fetal lethal. Intrauterine death occurred over a broad range of development (E12.5-birth). Mouse embryonic fibroblasts derived from E12.5 embryos showed complete loss of FBP and decreased c-Myc protein expression. Morphologic evaluation of FBP-KO mice at E19.5 showed intrauterine growth delay and ecchymotic discoloration of the skin suggesting a bleeding diathesis. Additionally, histologic examination revealed dysmorphogenesis of the embryonic placenta with increased calcifications. Because c-Myc has been linked to hematopoiesis and placental development in mice, we examined FBP-KO hematopoietic precursors from E13.5 fetal livers. Flow cytometry showed an excess of CD48-/CD150+ stem cells (10.65%) compared to wild type (P<0.001) (2.70%) and a deficit of Tert119-positive erythroid precursors indicating a maturation defect.
Conclusions: FBP plays a critical role in vertebrate development due at least in part to its role in hematopoiesis. The broad range in embryonic demise is consistent with the notion that FBP may serve to regulate stochastic variation in c-Myc expression.
Tuesday, March 1, 2011 2:30 PM
Platform Session: Section H, Tuesday Afternoon