Gata1 DNA binding level–dependent myeloid expansion. Lateral views of whole embryos with the head to the right and dorsal to the top. (A) Expression pattern of the myeloid markers l-plastin and mpo in 24-26 hpf gata1^T301K/vlt (l-plastin, n = 9/9; mpo, n = 5/5), gata1^vlt/vlt (l-plastin, n = 2/2; mpo, n = 5/5), and wild-type embryos (l-plastin, n = 6/6; mpo, n = 7/7) showing an expansion of l-plastin expression in the gata1 mutant embryos. (B) Double in situ hybridization showing l-plastin (purple staining, indicated by purple arrows) and mpo (orange staining, indicated by orange arrows) in the ICM/AGM regions of 26-30 hpf gata1^T301K/vlt (n = 4/4), gata1^vlt/vlt (n = 12/12) and wild-type (n = 12/12) embryos. Original magnifications ×50 (A) and ×115 (B). Individual embryos were imaged and genotyped by PCR followed by Taq1 digestion (vlt) or sequencing (T301K).