Molecular basis of left-right asymmetry

Koji Tamura*, Sayuri Yonei-Tamura, Juan Carlos Izpisúa Belmonte

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

29 Scopus citations


In vertebrates visceral asymmetry is conserved along the left-right axis within the body. Only a small percentage of randomization (situs ambiguus), or complete reversal (situs inversus) of normal internal organ position and structural asymmetry is found in humans. A breakdown in left-right asymmetry is occasionally associated with severe malformations of the organs, clearly indicating that the regulated asymmetric patterning could have an evolutionary advantage over allowing random placement of visceral organs. Genetic, molecular and cell transplantation experiments in humans, mice, zebrafish, chick and Xenopus have advanced our understanding of how initiation and establishment of left-right asymmetry occurs in the vertebrate embryo. In particular, the chick embryo has served as an extraordinary animal model to manipulate genes, cells and tissues. This chick model system has enabled us to reveal the genetic pathways that occur during left-right development. Indeed, genes with asymmetric expression domains have been identified and well characterized using the chick as a model system. The present review summarizes the molecular and experimental studies employed to gain a better understanding of left-right asymmetry pattern formation from the first split of symmetry in embryos, to the exhibition of asymmetric morphologies in organs.

Original languageEnglish (US)
Pages (from-to)645-656
Number of pages12
JournalDevelopment Growth and Differentiation
Issue number6
StatePublished - 1999
Externally publishedYes


  • Asymmetry
  • Cardiogenesis
  • Gene expression
  • Left-right
  • Pitx2

ASJC Scopus subject areas

  • Developmental Biology
  • Cell Biology


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