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New Study Details Somatic Mutations in the Early Embryo

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Review of “Somatic mutations reveal asymmetric cellular dynamics in the early human embryo” from Nature by Stuart P. Atkinson

The study of early human embryos has indicated that gross chromosomal abnormalities are a common occurrence [1]; however, we understand less regarding the prevalence of potentially influential somatic mutations. To fill this knowledge gap, researchers from the laboratory of Sir Michael R. Stratton (Wellcome Trust Sanger Institute, Hinxton, UK) have applied whole genome sequencing of adult genomes to reveal how each embryo developed. Their findings now reveal important details regarding the prevalence of early mutations and how these somatic mutations may skew the developmental potential of cells of the early embryo [2].

As a starting point, the study sequenced the genomes of 241 adults from normal blood samples and identified 163 embryonic mutations with characteristics that identified them as arising during early human embryogenesis. As a validation step, the study also analyzed breast cancer cells from the same patients; as a tumor grows from a single cell, the proposed embryonic mutation should be present or not in every cell of the tumor.

Sophisticated analysis then allowed the authors to estimate that each cell doubling during embryogenesis generated three mutation events and highlight the fact that certain daughter cells become dominant due to these mutations and contributed to a greater extent to adult tissues (blood) than other daughter cells. Altogether, these data suggest that mutations at this early stage can greatly affect early human development.

This study, which many have likened to an archaeological dig, provides great insight into early human embryogenesis; however, the authors do note that their conclusions, based on statistical reconstruction, will require larger, more detailed studies for corroboration. Of note, studies on these mutations will also permit researchers to create cell lineage trees in humans in a similar manner to previous attempts in mice [3].

To hear more about early mutations and embryo development, stay tuned to the Stem Cells Portal.

References

  1. Vanneste E, Voet T, Le Caignec C, et al. Chromosome instability is common in human cleavage-stage embryos. Nat Med 2009;15:577-583.
  2. Ju YS, Martincorena I, Gerstung M, et al. Somatic mutations reveal asymmetric cellular dynamics in the early human embryo. Nature 2017;543:714-718.
  3. Behjati S, Huch M, van Boxtel R, et al. Genome sequencing of normal cells reveals developmental lineages and mutational processes. Nature 2014;513:422-425.