ESTIMATION OF THE NUMBER OF HEMATOPOIETIC PRECURSOR CELLS DURING FETAL MOUSE DEVELOPMENT BY COVARIANCE ANALYSIS

Differentiation of hematopoietic precursor cells results in the format ion of clonally related descendent cells. Using the mosaic expression of beta-galactosidase in female mouse fetuses heterozygous for an X-li nked lacZ transgene, we analyzed the clonal relationship of the hemato poietic progeny, The proportion of beta-galactosidase positive cells f or different T- and B-lymphoid and myeloid cell populations was determ ined at different stages of fetal development. We found excellent corr elations of the proportion of beta-galactosidase expressing cells for all hematopoietic lineages confirming that they share a common ancestr y. Therefore, it was possible to estimate the number of common precurs or cells (PC) based on binomial distribution and covariance analysis o f pairs of different hematopoietic cell populations. Our results obtai ned from hematopoietic cells at 15.5 to 18.5 days of gestation indicat ed the presence of 15 to 18 lymphoid and 18 to 22 myeloid/lymphoid spe cific precursor cells. Statistical analysis of the precursor cell numb ers showed a trend of increasing numbers that was highly significant, The precursor cell number was inversely related to maturity of the cel l populations analyzed; ie, the lowest number of lymphoid and lymphoid /myeloid precursors was calculated when the most mature CD3(+) T-cell population was used for comparison. Determination of PC numbers can th erefore be used to assess the relative maturity and developmental pote ntial of individual cell populations. (C) 1996 by The American Society of Hematology.