Mouse Lycat controls the development of hematopoietic and endothelial lineages during in vitro embryonic stem-cell differentiation

Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China.
Blood (Impact Factor: 10.45). 12/2007; 110(10):3601-9. DOI: 10.1182/blood-2007-04-086827
Source: PubMed


The blast colony-forming cell (BL-CFC) was identified as an equivalent to the hemangioblast during in vitro embryonic stem (ES) cell differentiation. However, the molecular mechanisms underlying the generation of the BL-CFC remain largely unknown. Here we report the isolation of mouse lysocardiolipin acyltransferase (Lycat) based on homology to zebrafish lycat, a candidate gene for the cloche locus. Mouse Lycat is expressed in hematopoietic organs and is enriched in the Lin(-)C-Kit(+)Sca-1(+) hematopoietic stem cells in bone marrow and in the Flk1(+)/hCD4(+)(Scl(+)) hemangioblast population in embryoid bodies. The forced Lycat transgene leads to increased messenger RNA expression of hematopoietic and endothelial genes as well as increased blast colonies and their progenies, endothelial and hematopoietic lineages. The Lycat small interfering RNA transgene leads to a decrease expression of hematopoietic and endothelial genes. An unbiased genomewide microarray analysis further substantiates that the forced Lycat transgene specifically up-regulates a set of genes related to hemangioblasts and hematopoietic and endothelial lineages. Therefore, mouse Lycat plays an important role in the early specification of hematopoietic and endothelial cells, probably acting at the level of the hemangioblast.

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Available from: Patrick W. Faloon, Jan 08, 2014
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    • "Interestingly, lysocardiolipin acyltransferase (Lycat), involved in the development of hematopoietic and endothelial lineages during embryogenesis [31], was enhanced in both spleens (Figure 6A) and pancreata of drug-treated mice (Figure 6B). The expression of the gene encoding the receptor of migration inhibition factor (MIF), CD74 was also enhanced in spleens (Figure 6A) but not in the pancreas of cured mice (Figure 6B). "
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    • "exhibiting structural identity to the human alpha subunit of trifunctional protein (αTFP) lacking the first N-terminal 227 amino acids [22] (Figure 1), 2. Tafazzin, a mitochondrial CL transacylase reaction first described in rat liver [23] that has been found to be the defective gene product in Barth Syndrome [24], and 3. acyllysocardiolipin acyltransferase-1 (ALCAT1) [25]. ALCAT-1 may play a role in the early specification of hematopoietic and endothelial cells [26], [27] through acyl-Coenzyme A-dependent reacylation of MLCL to CL in microsomes [25]. Here we characterize a possible fourth CL remodeling enzyme, mitochondrial αTFP, which also exhibits in vitro and in vivo MLCL AT activity. "
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    ABSTRACT: Cardiolipin (CL) is a mitochondrial membrane phospholipid which plays a key role in apoptosis and supports mitochondrial respiratory chain complexes involved in the generation of ATP. In order to facilitate its role CL must be remodeled with appropriate fatty acids. We previously identified a human monolysocardiolipin acyltransferase activity which remodels CL via acylation of monolysocardiolipin (MLCL) to CL and was identical to the alpha subunit of trifunctional protein (αTFP) lacking the first 227 amino acids. Full length αTFP is an enzyme that plays a prominent role in mitochondrial β-oxidation, and in this study we assessed the role, if any, which this metabolic enzyme plays in the remodeling of CL. Purified human recombinant αTFP exhibited acyl-CoA acyltransferase activity in the acylation of MLCL to CL with linoleoyl-CoA, oleoyl-CoA and palmitoyl-CoA as substrates. Expression of αTFP increased radioactive linoleate or oleate or palmitate incorporation into CL in HeLa cells. Expression of αTFP in Barth Syndrome lymphoblasts, which exhibit reduced tetralinoleoyl-CL, elevated linoleoyl-CoA acylation of MLCL to CL in vitro, increased mitochondrial respiratory Complex proteins and increased linoleate-containing species of CL. Knock down of αTFP in Barth Syndrome lymphoblasts resulted in greater accumulation of MLCL than those with normal αTFP levels. The results clearly indicate that the human αTFP exhibits MLCL acyltransferase activity for the resynthesis of CL from MLCL and directly links an enzyme of mitochondrial β-oxidation to CL remodeling.
    Full-text · Article · Nov 2012 · PLoS ONE
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    • "With time-lapse photography , many more cellular events and pathways have been detected during hemangioblast development. Involved regulatory factors include genes such as those causing stem cell leukemia (Scl), fetal liver kinase 1 (Flk-1), acute myeloid leukemia 1 (AML1), sonic hedgehog (Shh), hematopoietically expressed homeobox (Hhex); transcription factors such as vascular endothelial growth factor (VEGF), runt-related transcription factor 1 (Runx1), and others such as Smad proteins and Thrombopoietin (TOP) (Wang et al., 2007; Ng et al., 2010). Following the generation of hemangioblasts, this cell line has many other roles. "
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    ABSTRACT: The hemangioblast hypothesis has been hotly debated for over a century. Hemangioblasts are defined as multipotent cells that can give rise to both hematopoietic cells and endothelial cells. The existence of hemangioblasts has now been confirmed and many important molecules and several signaling pathways are involved in their generation and differentiation. Fibroblast growth factor, renin-angiotensin system and runt-related transcription factor 1 (Runx1) direct the formation of hemangioblasts through highly selective gene expression patterns. On the other hand, the hemogenic endothelium theory and a newly discovered pattern of hematopoietic/endothelial differentiation make the genesis of hemangioblasts more complicated. But how hemangioblasts are formed and how hematopoietic cells or endothelial cells are derived from remains largely unknown. Here we summarize the current knowledge of the signaling pathways and molecules involved in hemangioblast development and suggest some future clinical applications.
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