Functional analysis of Dicer1^Δ/Δ primary mouse Lin⁻ BM cells. (A) CFU-GM assay and replating of mouse Lin⁻ BM progenitors. Cells were plated in triplicate at densities of 1 × 10⁴ cells per dish in 1 mL of methylcellulose medium containing GM-CSF (100 ng/mL). Cells were isolated from dishes, counted, and replated under the same conditions. Colonies consisting of more than 50 cells were counted after 7 days of growth. Significance was calculated by comparing Dicer1^Δ/Δ and Dicer1^wt/Δ with Dicer1^wt controls using the Mann-Whitney test (asymptotic significance [2-tailed]). *P < .05. (B) Average differential cell counts (of at least 100 cells and 3 independent experiments), blast, granulocyte (-like), and macrophages. Dicer1 control plating 1 (blasts 1%, SD = 0; granulocytes 2%, SD = 1; and macrophages 97%, SD = 1). Dicer1^Δ/Δ plating 1 (blasts 27%, SD = 4.7; granulocyte-like 39%, SD = 3.5; and macrophages 34%, SD = 8.1). Dicer1^Δ/Δ third and fourth replatings (blasts 74%, SD = 3.6; granulocyte-like 16%, SD = 3.2; and macrophages 10%, SD = 4.6). (C) Micrographs showing cells isolated from a liquid culture of mouse Lin⁻ BM progenitors with GM-CSF for 7 days. Arrowhead indicates the pince-nez–shaped nucleus, a hallmark for the Pelger-Huët anomaly. Black bar indicates 10 μm. (D) Number of EYFP⁺;CD11C⁺ myeloid DCs per 2 × 10⁶ cells plated in liquid culture after 1 week of expansion (n = 3). *P < .05.