Breaking leftright symmetry in early embryos:

1
Breaking left-right symmetry in early embryos
chirality and handedness choice in C.
elegans Bill Wood, Stephanie Schonegg, and Tony
Hyman MPI-CBG, Dresden, Germany MCD Biology,
Univ. of Colorado, Boulder
Int'l Worm Mtg.
June 2005
2
C. elegans normally exhibit an invariant dextral
anatomical handedness throughout development
Right
Left
defined arbitrarily as anterior
gonad on the animals right
Ventral view
3
C. elegans embryos are L-R asymmetric
dextral 8-cell embryo
(ventral views)
4
L-R-reversed (sinistral) embryos, produced by
micromanipulation, develop into sinistral adults
successful operation
sinistral embryo
dextral embryo
control
(ventral views)
Wood, Nature 349 536 (1991)
5
A
P
Rotation is always in the same direction
(n gt 200)
6
Par-2 embryos exhibit abnormal symmetries and
variable cell placements
A
P
7
Distinguishing handedness by relative positions
of ABal, ABar and MS, E
sinistral 8-cell embryo
dextral 8-cell embryo
L
L
al
MS
E
P
P
A
A
al
ar
E
MS
ar
R
R