Fgd5 is required for embryonic development but is dispensable for definitive HSC formation and function. (A) Primary (1°) and (B) secondary (2°) transplantation of whole BM cells from Fgd5^mCherry/+ (red) and Fgd5^+/+ (black) mice showing total donor reconstitution (left) over the time course of transplantation and lineage breakdown of donor cells at 16 (1°) and 20 (2°) wk after transplant (right). Number of recipients: n = 9 and 5 (Fgd5^mCherry/+) and 8 and 4 (Fgd5^+/+) for 1° and 2° transplants, respectively, error bars indicate SD. (C) Table summarizing genotypes Fgd5^+/+ (WT), Fgd5^mCherry/+ (Het), and Fgd5^{mCherry/mCherry} (null) and number of embryos recovered at indicated time points of embryonic development from Fgd5^+/mCherry X Fgd5^+/mCherry crosses. * indicates the presence of one or more morphologically abnormal embryos. (D) Dissecting microscope images of E12.0 embryos derived from Fgd5^mCherry/+ X Fgd5^mCherry/+ timed matings showing genotype and gross morphology of the embryos. (E) Histological sections showing the mCherry signal at the aorta gonad mesonephros (AGM) region of E11.5 embryos derived from Fgd5^mCherry/+ X Fgd5^+/+ timed matings stained with FITC-Isolectin (for endothelial cells) and counterstained with DAPI. Figure shows separate channels and overlay of a representative Fgd5^+/+ (top) and Fgd5^mCherry/+ (bottom) embryos (bars, 100 µm). (F) Schematic of experimental strategy for AGM-explants and transplantation. (G) Primary (1°) and (H) secondary (2°) transplantation of AGM explants derived from Fgd5^+/+ (black), Fgd5^mCherry/+ (red), and Fgd^{mCherry/mCherry} (blue) embryos showing total donor reconstitution (top) over the time course of transplantation and lineage breakdown of donor cells in individual recipient at 16 wk after transplant (bottom). Granulocytes (GN), macrophage/monocytes (M), B cells, and T cells are indicated by color. Data are shown for all embryos transplanted in primary and secondary recipients.