Fetal liver abnormalities are observed in Ts1Cje mice. (A) The proportion of HSCs in the Ts1Cje FL is slightly reduced. n = 5 disomic and 4 Ts1Cje embryos. (B) Ts1Cje FL HSCs cannot compete with disomic competitor cells, showing less than 2% contribution in the peripheral blood. n = 2 disomic and 6 Ts1Cje embryos, donor cells from each embryo injected into 2 recipient mice each. (C) CFU-S day 12 colonies. Ts1Cje FL-derived HSCs show a reduced capacity to form spleen colonies in recipient mice. Recipient mice receiving Ts1Cje FL donor cells had smaller spleens and fewer visible colonies than those mice receiving disomic FL donor cells. Cells from 3 donors of each genotype were injected into 3 recipients each. (D) Ts1Cje FL progenitor cells have an impaired ability to form colonies under IL-3/SCF/EPO stimulation: (i) Ts1Cje cultures had reduced numbers of each type of colony (G) granulocyte, (GM) granulocyte/macrophage, (Mixed) mix of different cell types, (Meg) megakaryocytic, (Meg/Eryth) megakaryocytic, and (BFU-E) erythroid; (ii) colonies formed in Ts1Cje cultures were significantly smaller than disomic cultures (original magnification ×20); (iii) fewer colonies were visible macroscopically (typically defined by the presence of > 1000 cells). n = 3 disomic and 4 Ts1Cje embryos. **P < .01; ***P < .001. Error bars represent SEM.