Clonal Hematopoiesis of Indeterminate Potential (CHIP) occurs when a blood stem cell acquires a somatic mutation and produces a clone of cells all carrying that mutation. Whole genome sequencing tracks the Variant Allele Frequency (VAF) — what percentage of blood cells carry each mutation.
Reading this chart
Y-axis shows Variant Allele Frequency (VAF) — what fraction of blood cells carry a specific mutation. The flat line at ~0.032 across ALL timepoints is actually good news: it means 3 days of space radiation didn't cause dangerous clone expansion. For longer missions, this might look very different.
If a CHIP clone expands during spaceflight, radiation may be driving dangerous mutations. The I4 finding was reassuring: pre-existing CHIP clones remained stable, suggesting 3 days of radiation exposure didn't measurably accelerate clonal expansion. However, longer missions may differ.
Variant Allele Frequency (VAF) — percentage of sequencing reads carrying the mutation (0-50% for heterozygous). Compare VAF at each timepoint. Stable VAF = clone not expanding. Increasing VAF = clone growing (concerning).
All AP-level math. No differential equations, no ML required. With n=4, descriptive statistics are more honest than hypothesis testing.
Pre-existing CHIP clones remained stable through mission
No evidence of radiation-induced new clone emergence
Reassuring for short-duration civilian missions
Longer missions may show different patterns (open question)
Part of DNA Damage Response domain. CHIP stability is a 'green flag' — include it as a reassuring indicator. For longer hypothetical missions, you could model projected clone growth rates.