A molecular pathway determining left-right asymmetry in chick embryogenesis.
While significant progress has been made in understanding the molecular events underlying the early specification of the antero-posterior and dorso-ventral axes, little information is available regarding the cellular or molecular basis for left-right (LR) differences in animal morphogenesis. We describe the expression patterns of three genes involved in LR determination in chick embryos: activin receptor IIa, Sonic hedgehog (Shh), and cNR-1 (related to the mouse gene nodal). These genes are expressed asymmetrically during and after gastrulation and regulate the expression of one another in a sequential pathway. Moreover, manipulation of the sidedness of either activin protein or Shh expression alters heart situs. Together, these observations identify a cascade of molecular asymmetry in that determines morphological LR asymmetry in the chick embryo.
Levin
M
M
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Johnson
R L
RL
Stern
C D
CD
Kuehn
M
M
Tabin
C
C
D028341:Activins; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology*; D002642:Chick Embryo / Q000502:physiology*; D004627:Embryonic Induction / Q000502:physiology; D007839:Functional Laterality / Q000235:genetics; D005775:Gastrula / Q000502:physiology; D015870:Gene Expression / Q000502:physiology; D006321:Heart / Q000196:embryology; D053823:Hedgehog Proteins; D017403:In Situ Hybridization; D007265:Inhibins / Q000502:physiology; D011506:Proteins / Q000502:physiology; D015534:Trans-Activators; D016212:Transforming Growth Factor beta / Q000502:physiology
D053823:Hedgehog Proteins; D011506:Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D028341:Activins; D007265:Inhibins