The document discusses cellular barcoding, a technique that tags individual cells with unique identifiers, particularly focusing on lymphoid-primed multipotent progenitor (LMPP) dendritic cells. It highlights findings that a significant proportion of LMPPs are biased toward generating dendritic cells and proposes that dendritic cells should be considered a distinct lineage in hematopoiesis. The research also raises questions about the mechanisms behind lineage output and suggests further investigations into hematopoietic pathways.

1. ‘Not far away day when pipette will be replaced by your iPhone’

2. • Cellular barcoding involves the tagging of individual cells of
interest with unique genetic heritable identifiers or barcodes
and is emerging as a powerful tool.
Lymphoid-Primed Multipotent Progenitor
Dendritic Cells

3. How would the results look like?
Three major groups; the dendritic cell
subtypes, the myeloid cell types and B cells
PCA – Principle
component analysis

4. LMPP’s and HSC’s contribution to the cell types
Almost one-half of the LMPPs were classified as dendritic-cell biased, 10% of the
progenitors contributed primarily to B cells, 10% primarily to myeloid cells, and just 3%
of the LMPPs were multi-outcome progenitors.
Many LMPPs produced dendritic cells without generating detectable lymphoid and
myeloid output, leading the authors to propose that dendritic cells should be
considered a separate lineage of hematopoiesis.

5. Snapshot of the output (Limitations)

6. Regular barcoding experiments cannot distinguish between the influence of the
environment in which a progenitor deposits, a stochastic fate choice after
transfer, and a pre-existing intrinsic fate preference of that progenitor

7. Restricted Lineage Output of LMPPs
• The question is whether this lineage output is
imprinted, or determined stochastically or by the
microenvironment after cell transfer.
Authors found that the distribution of cell types generated by
LMPPs was statistically consistent across mice, suggesting that
the hematopoietic pathway is mouse independent.

8. Summary
• A large number of LMPPs gave rise to dendritic cells!
• Authors have proposed the existence of additional branches to the
hematopoietic tree, such as a direct branch from LMPPs to dendritic cells
only!
• Although some HSCs were found to contribute to all the cell types
analyzed, some HSCs were biased toward output in the myeloid or
lymphoid lineage.
• Heritable lineage imprinting is initiated as early as at the HSC level and
progressively increases throughout haematopoiesis.

9. Pros-and-cons
• Looking at specific branch with known or
suspected outcome.
• Snapshot
• Irradiation
• Transplantation
• In-vitro manipulations
• Sorting bias