Gene expression profiles in single cells from distinct B-lineage stages.

Surface CD34⁺CD19⁺IgM⁻ (A) and CD34⁻CD19⁺IgM⁺ (B) sorted cells are analyzed for mRNA expression of the indicated genes after multiplex RT-PCR. In the left panel, the bands in each of the twelve tracks (numbers 1-12), aligned in the 6 electrophoresis gels, show correlated amplification of gene products from individual CD34⁺CD19⁺IgM⁻ cells (ie, cell 1 is VpreB⁺, TdT⁺, RAG-1⁺, mb-1/CD79⁺, recombined V-D-J$H−$⁠). The right panel shows electrophoresis of the gene products amplified from tubes containing titrated numbers of CD34⁻CD19⁺IgM⁺ B cells: tracks 1 to 6, one cell; tracks 7 to 9, 10 cells; tracks 10 to 12, 100 cells. Similarly processed positive controls (+) correspond to individual Nalm-6 pre-B leukemia single cells, whereas no cells are added in the negative controls (−). The identity of the amplified gene products is ascertained by direct sequencing of the cDNA in the excised bands and by molecular weight estimation (ladders). Note that the lower bands in the V-D-J gel in panel A correspond to primer artifacts and do not contain V-D-J_H products, as determined by sequencing. L indicates ladder.