Diffusible signals and epigenetic timing cooperate in late proximo-distal limb patterning

Alberto Rosello-Diez, Carlos G. Arques, Irene Delgado, Giovanna Giovinazzo, Miguel Torres

Research output: Contribution to journalArticleResearchpeer-review

50 Citations (Scopus)


Developing vertebrate limbs initiate proximo-distal patterning by interpreting opposing gradients of diffusible signaling molecules. We report two thresholds of proximo-distal signals in the limb bud: a higher threshold that establishes the upper-arm to forearm transition; and a lower one that positions a later transition from forearm to hand. For this last transition to happen, however, the signal environment seems to be insufficient, and we show that a timing mechanism dependent on histone acetylation status is also necessary. Therefore, as a consequence of the time dependence, the lower signaling threshold remains cryptic until the timing mechanism reveals it. We propose that this timing mechanism prevents the distal transition from happening too early, so that the prospective forearm has enough time to expand and form a properly sized segment. Importantly, the gene expression changes provoked by the first transition further regulate proximo-distal signal distribution, thereby coordinating the positioning of the two thresholds, which ensures robustness. This model is compatible with the most recent genetic analyses and underscores the importance of growth during the time-dependent patterning phase, providing a new mechanistic framework for understanding congenital limb defects.

Original languageEnglish
Pages (from-to)1534-1543
Number of pages10
Issue number7
Publication statusPublished - 1 Apr 2014
Externally publishedYes


  • Chick
  • Epigenetics
  • FGF
  • Hox
  • Meis
  • Mouse
  • Patterning
  • Proximo-distal
  • Retinoic acid
  • Vertebrate limb

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