AGM HSCs are unaffected by the JAK2V617F mutation. (A) E11.5 AGM cells from embryos with the indicated genotypes were directly plated in methylcellulose, and colonies were counted 7 days later. n = 5 for Jak2^+/+; n = 9 for Jak2^+/VF; n = 4 for Jak2^VF/VF. **P < .01. (B) E11.5 AGM cells from embryos with the indicated genotypes were directly transplanted as 1 embryo equivalent, and donor cell contribution to the peripheral blood of the recipients was determined at 4 months. Dotted line represents 5% threshold. Twenty-one recipients for Jak2^+/+; 28 recipients for Jak2^+/VF; 24 recipients for Jak2^VF/VF. (C) Secondary transplants were performed with total BM cells from 3 primary recipients of Jak2^+/+ AGM cells and 2 primary recipients of Jak2^VF/VF AGM cells. Two to 3 million total BM cells were injected per secondary recipient with the amount adjusted to the repopulation levels in the primary recipient. Donor cell contribution to the peripheral blood was determined at 4 months after transplantation. Dotted line represents 5% threshold. Thirteen recipients for Jak2^+/+; 9 recipients for Jak2^VF/VF. Donor contribution within individual (D) primary and (E) secondary recipients was analyzed with respect to myeloid and lymphoid proportion. (F-I) Blood counts were performed on primary recipients at 4 months after transplantation. Error bars indicate standard deviation. (J) Donor LSK cells were sorted from secondary recipients of Jak2^+/+ and Jak2^VF/VF AGMs and stained for γ-H2A.X foci. The number of foci were counted in 200 to 300 cells per genotype. n = 2. (K) cDNA was prepared from sorted wild-type AGM HSCs (ckit⁺CD34⁺CD45⁺) and wild-type BM HSCs (CD45⁺CD48⁻CD150⁺EPCR⁺) and analyzed for the expression of Jak-Stat pathway components using the Qiagen Jak/Stat Signaling Pathway RT2 Profiler PCR Array. Differentially expressed genes with P < .05 and a fold change >2 are shown. n = 3.