Twin genomes trace a rare tumour’s passage before birth
A peer-reviewed study of one pair of newborn twins reconstructed evidence that a rare sarcoma began in one child and passed to the other before birth. Mutations in tumours, normal tissues and the placenta helped trace its path. The findings also illuminate early twin development, while their timing depends on a genetic model.
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Shared mutations trace a tumour from one twin
A single peer-reviewed study reconstructed the prenatal path of a rare sarcoma in one pair of identical female twins. Both infants had tumours associated with an MN1::ZNF341 fusion and died shortly after birth. Comparing mutations in tumours, normal tissues and placenta helped distinguish separate tumour origins from transmission. The pattern supports an origin in twin A’s cells, most likely in a facial mass. The tumour diversified and spread within A before a late, probably single transfer to twin B.[1]
Early cell lineages also distinguish the twins
Embryonic mutations persist in later cell generations, providing a way to trace their ancestry. The team analysed 23 normal samples, ten tumour samples and twelve additional laser-microdissected placental trophoblast samples. Twenty developmental mutations identified contributions from three early cell lineages. Different early lineages supplied most of each twin’s cells. Placental samples mainly contained cells from the lineage that contributed to B. This arrangement links the tumour reconstruction to the earlier division of cells during twin development; the entire placenta could not be sampled.[1]
The timing remains a genetic reconstruction
Mutation accumulation underpins the timing model: it places tumour onset towards the first trimester’s close, followed by transfer in the latter part of the second trimester. Those times were inferred rather than observed as the pregnancy progressed. The authors describe the transfer as rare, not inevitable. One pair cannot establish a general pattern for all twins, a population cancer risk or a screening method. The case instead supplies a detailed reconstruction of how tumour cells and early developmental lineages moved within this particular pregnancy.[1]
