The Big Picture
What do both Rhodes (2008) and Ferrara (1996) study in common?
A) Neuronal patterning
B) Embryonic vascular and hematopoietic development
C) Organ regeneration in adults
D) Muscle tissue formation
B) Embryonic vascular and hematopoietic development
The development and function of embryonic blood vessels and their link to hematopoiesis.
What genetic model did Rhodes use to visualize hematopoietic sites?
A) GFP transgene
B) Runx1-lacZ reporter mouse
C) Cre-Lox conditional knockout
D) Zebrafish model
B) Runx1-lacZ reporter mice (blue β-gal staining).
Where was Runx1-lacZ expression found in Figure 1 (Rhodes)?
A) Only in liver cells
B) In the chorioallantoic mesenchyme and placental vessels
C) Exclusively in trophoblasts
D) In yolk sac endoderm
B) In the chorioallantoic mesenchyme and placental vessels
What molecule in Ferrara’s paper indirectly supports the vascular niche idea explored by Rhodes?
A) VEGF
B) Notch
C) Sox17
D) HoxB4
A) VEGF — essential for endothelial health and vessel structure.
If VEGF were blocked in the placenta, what would happen?
A) Enhanced hematopoiesis
B) Failure of vascular and hematopoietic emergence
C) Increased blood flow
D) No change
B) Rhodes-like HSC emergence would likely fail — no vascular niche to support Runx1+ cells.
What transcription factor did Rhodes et al. use as a reporter to track hematopoietic sites?
A) VEGF
B) Sox17
C) Runx1
D) GATA1
C) Runx1 (using Runx1-lacZ reporter mice).
What knockout model did Rhodes use to eliminate circulation?
A) Runx1−/−
B) VEGF−/−
C) Ncx1−/−
D) HoxB4−/−
C) Ncx1−/− (sodium-calcium exchanger knockout) embryos.
In Figure 4 (Rhodes), what did coculture with OP9 cells show?
A) Only primitive erythropoiesis
B) Formation of definitive myeloid, erythroid, and lymphoid cells
C) Loss of all hematopoietic potential
D) No difference from controls
B) Formation of definitive myeloid, erythroid, and lymphoid cells
Placental cells could produce myeloid, erythroid, and lymphoid lineages — proving definitive HSC potential.
Without VEGF (Ferrara), what cellular environment fails — affecting processes like those in Rhodes?
A) Neural crest niche
B) Vascular microenvironment
C) Amniotic cavity
D) Hepatic bud
B) Endothelial networks and vascular microenvironments.
If Ncx1−/− embryos also lacked VEGF, predict the outcome:
A) Normal HSC formation
B) Excess blood vessels
C) Complete failure of both circulation and vasculature
D) Only partial loss of HSCs
C) No blood flow + no vasculature → total loss of both vascular and hematopoietic systems.
What key growth factor did Ferrara’s team target to study embryonic vascular development?
A) Notch1
B) FGF2
C) VEGF
D) BMP4
C) Vascular Endothelial Growth Factor (VEGF).
What three methods did Ferrara use to study VEGF’s role?
A) Western blot, FACS, RNA-seq
B) H&E, CD34 immunostaining, in situ hybridization
C) PCR, flow cytometry, Northern blot
D) EM imaging, ELISA, ISH
B) H&E, CD34 immunostaining, and in situ hybridization.
In Ferrara’s Fig.4, what phenotype was seen in VEGF+/− embryos?
A) Extra blood vessels
B) Neural hypertrophy
C) Loss of vascularization and apoptotic neuroepithelium
D) Increased hematopoiesis
C) Loss of vascularization and increased apoptosis in neuroepithelium.
How does Runx1 expression link to VEGF function?
A) Runx1 activates VEGF in neurons
B) Runx1+ endothelial cells require VEGF-supported vasculature to become HSCs
C) Runx1 represses VEGF expression
D) No connection
B) Runx1+ endothelial cells need a VEGF-supported vasculature to transition into hematopoietic cells.
How could VEGF+/− defects affect HSC migration?
A) Improved migration
B) Impaired vascular channels prevent HSC trafficking
C) More HSCs reach the liver
D) HSCs bypass circulation entirely
B) Impaired vascular channels prevent HSC trafficking Disrupted vessels → impaired delivery of HSCs to the liver or fetal circulation.
Why was the placenta chosen as a focus in Rhodes et al., 2008?
A) It’s an immune organ.
B) It was suspected to generate or host hematopoietic stem cells.
C) It’s easy to isolate.
D) It replaces the fetal liver.
B) It’s a vascular organ suspected to generate or support hematopoietic stem cells.
What does CD34 immunostaining label? which cell type?
A) Trophoblasts
B) Endothelial cells
C) Neurons
D) Fibroblasts
B) Endothelial cells — a marker of blood vessel formation.
How did Ferrara verify decreased VEGF expression?
A) PCR of VEGF cDNA
B) Antisense ISH showing weaker hybridization in heterozygotes
C) Western blotting
D) GFP fluorescence
B) Antisense ISH showing weaker hybridization in heterozygotes
In situ hybridization showed weaker antisense signal in VEGF+/− embryos.
What organ is central to both studies?
A) Brain
B) Placenta
C) Kidney
D) Heart
B) The placenta — as a vascular and developmental hub.
Which modern experiment could bridge both studies?
A) Overexpress VEGF in neurons
B) Inhibit VEGF signaling in Runx1-reporter placentas
C) Knock out Runx1 in brain tissue
D) Block Notch in neuroepithelium
B) Inhibit VEGF signaling in Runx1-reporter placentas
What concept unites both studies conceptually?
A) Hematopoiesis and angiogenesis occur independently.
B) The vasculature acts as a developmental niche for stem cells.
C) Blood vessels form only after hematopoiesis.
D) Neither involves signaling pathways.
B) That vascular development (angiogenesis) and hematopoietic emergence are developmentally intertwined — the vasculature acts as a stem cell niche.
What is the function of the sense probe in Ferrara’s ISH?
A) To amplify signal strength
B) To visualize apoptosis
C) To confirm probe specificity (negative control)
D) To detect protein level
C) Antisense probe detects VEGF mRNA; sense probe is the negative control for specificity.
What major conclusion did Rhodes reach about circulation?
A) It is required for HSC emergence.
B) HSCs emerge in the placenta even without blood flow.
C) Circulation drives Runx1 expression.
D) Hematopoiesis occurs only in the liver.
B) HSCs can emerge in the placenta even without blood flow, proving intrinsic hematopoietic initiation.
What developmental principle unites both?
A) Hematopoiesis and vasculogenesis are coupled processes.
B) Hematopoiesis occurs before vascularization.
C) VEGF is unrelated to stem cell formation.
D) Runx1 blocks vessel formation.
A) Blood and vessel formation co-develop — the vasculature is both the structure and the source of hematopoiesis.
What is the clinical implication of combining these insights?
A) HSCs can be regenerated only in adults
B) To make functional blood, you must rebuild the vascular microenvironment
C) Stem cells develop independently of the endothelium
D) VEGF and Runx1 have unrelated functions
B) To make functional blood, you must rebuild the vascular microenvironment To regenerate blood systems, we must also recreate their vascular microenvironments — stem cells and endothelial cells co-develop.