Figure 1.

Generation of a conditional Asxl1 allele and characterization of mice with constitutive Asxl1 loss. (A) Schematic depiction of the targeted Asxl1 allele. Exons 5–10 are targeted and flanked by LoxP sites upon Frt-mediated deletion of the Neo cassette. (B) Verification of correct homologous recombination of Asxl1-targeted allele using Southern blots on targeted ES cells. (C) Enumeration of offspring derived from mating EIIa-cre Asxl1^+/Δ parents. (D and E) Gross pathology (D) and tissue sections (E) of Asxl1^Δ/Δ mice at 14.5 and 18.5 d postcoitus (dpc). (F) Analysis of skeletal preparations from germline Asxl1-null mice surviving to E20.5 including hypoplastic mandibles (asterisk), lack of hyoid bone (arrowhead), and lower lumbar/sacral posterior homeotic transformations (arrow). (G) Gross phenotype of EIIa-cre Asxl1^+/Δ and littermate control mice on bilateral microphthalmia. Bars: (D) 2 mm; (E and F [top]) 1 mm; (F, bottom) 2.5 mm; (G) 0.5 cm. (H) Immunophenotyping of fetal liver at 14.5 dpc on relative frequency of LSK cells, MPP cells (LSK, CD48⁺, CD150⁻ cells), and LT-HSCs (LSK, CD48⁻, CD150⁺ cells) between mice with germline loss of 0, 1, or 2 copies of Asxl1. FACS analysis was performed with three to five independent fetal liver samples per genotype. (I) FACS analysis of fetal liver at 14.5 dpc reveals relative frequency of CD71⁺ single-positive, CD71/Ter119 double-positive, or Ter119 single-positive cells with constitutive loss of Asxl1. Antibody stainings are as indicated, and cells were gated on live cells in the parent gate. Error bars represent ±SD.