Measurement of absolute numbers of Ahi/AHI-1 transcripts in subpopulations of normal murine and human BM cells. (Ai) Real-time RT-PCR SYBR Green1 fluorescence versus cycle number of 10- or 100-fold serial dilutions of cDNA prepared from an in vitro–transcribed sense RNA transcript of a vector containing the full-length AHI-1 cDNA. (Aii) Linear regression generated by plotting the Ct values, with 95% confidence intervals, against the logarithm of the initial transcript numbers from a series of measurements of independently diluted vector transcript. (Bi) Ahi-1 transcript numbers per microgram of RNA calculated as described “Patients, materials, and methods” from real-time RT-PCR analyses of RNA extracts obtained from each FACS-purified population shown (murine BM subpopulations, n = 3; normal human BM subpopulations, n = 4). (Bii) A similar analysis performed on RNA isolated from specific subsets of lin⁺ murine (n = 3) and human BM cells (n = 4). The number of Ahi-1/AHI-1 transcripts from each population was calculated by an absolute standard curve. Values shown are the mean ± SEM.