Identification of the earliest B lineage stage in mouse bone marrow.
We have identified a very early stage of B lineage cells in the CD45R (B220)+CD24 (HSA) pre-pro-B fraction of mouse bone marrow delineated by expression of AA4.1, a molecule found on stem cells and early B lineage cells. These cells are B lineage precursors based on their capacity to generate B lineage cells rapidly in stromal-dependent culture and their expression of high levels of germline IgH transcripts in the absence of Rag-1/2. Half of these AA4.1+ precursors express low levels of CD4, characteristic of lymphoid progenitors, but few if any have up-regulated CD19, a molecule expressed very early in the B lineage. Furthermore, expression of genes encoding pre-B and B cell receptor components (mb-1, B29, and lambda 5) and transcription factors necessary for B lineage differentiation (BSAP, E12, E47, and Id) provide further support for designating these cells as the earliest B cell precursors.
Li
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Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Wasserman
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Hayakawa
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Hardy
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RR
D000818:Animals; D000943:Antigens, Differentiation; D016175:B-Lymphocyte Subsets; D001402:B-Lymphocytes; D001853:Bone Marrow / Q000196:embryology*; D001854:Bone Marrow Cells; D002454:Cell Differentiation; D002458:Cell Fractionation; D019070:Cell Lineage; D004268:DNA-Binding Proteins; D005260:Female; D015870:Gene Expression; D006412:Hematopoietic Stem Cells; D018398:Homeodomain Proteins; D007132:Immunoglobulin Isotypes / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D010641:Phenotype; D014176:Protein Biosynthesis; D014157:Transcription Factors / Q000096:biosynthesis; D014158:Transcription, Genetic
D000943:Antigens, Differentiation; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D007132:Immunoglobulin Isotypes; C499308:Rag2 protein, mouse; D014157:Transcription Factors; C064655:V(D)J recombination activating protein 2; C064658:RAG-1 protein