FIG. 3.

Differential expression of TdT, Polμ, Polλ, and Ku80 in lymphohematopoietic progenitors during mouse ontogeny. (A) CD19⁺ IgM⁻ B-cell precursors were purified from adult BM and newborn liver, and cKit⁺ CD45⁺ cells were purified from the indicated embryo organs (YS, yolk sac; AGM, aorta-gonad-mesonephros region). Semiquantitative RT-PCRs were done as described in Materials and Methods. GαS gene expression was used as a reference for the total mRNA per sample. The negative and positive control samples were non-cDNA and adult thymus, respectively. (B) Normalized TdT, Polμ, and Polλ transcript levels relative to newborn 2^−ΔΔCT. The expression of each specific gene was normalized to that of the control GαS gene, and the values obtained for both adult and embryo samples are relative to those obtained for newborn samples. The data shown are the means plus standard deviations of at least three different samples per experimental group. The symbols are as in Fig. 1.