Figure 3. Homozygous female Utx mutant embryos have mid-gestational developmental delay.

(A) Compared to controls (A-i and A-v), homozygous female E10.5 X^UtxGT1 X^UtxGT1 (A-ii) and X^UtxGT2Δ X^UtxGT2Δ (A-vi) embryos have some developmental delay including smaller size, underdeveloped hearts (white arrows), and open neural tube in the head (arrowheads). More severe embryos resemble the size and features of E9.5 embryos with cardiac abnormalities and peri-cardial edema (A-iii, vii, red arrows). Hemizygous male X^UtxGT1 Y^Uty+ embryos appear phenotypically normal at this stage (A-iv). The X^UtxGT1 and X^UtxGT2Δ alleles fail to complement as female X^UtxGT1 X^UtxGT2Δ embryos have identical phenotypes to homozygotes (A-viii). (B) At E10.5, homozygous X^UtxGT1 X^UtxGT1 female embryos exhibit either normal yolk sac vasculature with a reduction in red blood cells (B-ii) or have a completely pale yolk sac with unremodeled vascular plexus (B-iii).