Article Abstract:
Roles in left-right (L-R) development attributed to various molecules and embryological structures in the four common vertebrate model systems are reviewed and compared. Conserved and divergent mechanisms in LR axis formation are discussed. In the most recent 5 years much progress has been made in understanding of the embryological and molecular mechanisms underlying development of laterality in various vertebrates. It is still not clear whether many of the means used in one group of vertebrates are used in others or not. Nodal and downstream signaling, the midline as barrier or repressor, early events and the initial break in symmetry and other topics are discussed. Some of the mechanisms underlying L-R laterality are universal.
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Article Abstract:
Truncation of zebrafish Gli2 proteins causes Hedgehog (Hh) signaling needed for differentiation and axon guidance in the ventral forebrain to be disrupted. Zebrafish you-too (yot) mutations interfere with Hedgehog (Hh) signaling during embryogenesis and yot has been isolated as a zinc finger transcription factor homologous to the Hh target gli2. A comparative synteny approach was used. Two alleles of yot have nonsense mutations and carboxy terminally truncated proteins result. Mutations interfere with ventral forebrain and anterior pituitary differentiation. They also cause ectopic lens formation in the ventral diencephalon.
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Article Abstract:
The article discusses initial specification of the left-right (L-R) axis in the vertebrate embryo during late stages of gastrulation and morphological L-R asymmetry developing in the late fetal period. Gene disruption experiments to determine the biological function of Cryptic mutant embryos, and experiments with oep mutant embryos to demonstrate that mRNA injection rescues the development of all essential organs, are described.
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