Heads or tails? Retinoic acid will decide

Article Abstract:

Author's Abstract: COPYRIGHT 1999, John Wiley & Sons, Inc. A recent study (niederreither et al. Nat Genet 1999;21:444-448[ref.1] describes the phenotype of a gene knockout for an enzyme, retinaldehyde dehydrogenase 2 (RALDH-2), that synthesises retinoic acid (RA) in the early embro. The effects generated by this single enzyme mutation are remarkably similar tothose previously described in vitamin A-deprivation studies and compound retinoic acid receptor knockouts, which involve multiple systems of the embryo. With other data on the distribution of RA, its role in axial specification of the early embryo is considerably clarified. Surprisingly, it seems that head development is unaffected in these RALDH-2 knockout embryos; thus, the anterior of the embryo does not require RA, despite the observations that the hindbrain seems exquisitely sensitive to RA pertubation. Head development may be realised by a cytochrome P450 enzyme (CYP26), which has been discribed recently. Between those two opposing forces, the hindbrain develops.

Physiological aspects, Tretinoin

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Genes controlling specific cell fates in C. elegans embryos

Article Abstract:

Patterning in early embryogenic stages is determined by maternal and embryogenic gene activities. Analysis of maternal-effect embryonic lethal mutations have identified three genes, skn-1, mex-1 and pie-1, as regulating development of particular blastomeres in the 8-cell embryo. The maternal gene products and the early blastomere maternal factors interact to determine individual founder cell types in C. elegans embryos.

Cell differentiation, Caenorhabditis elegans

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Set down in bone

Article Abstract:

Researchers discussed the molecular aspects of skeleton development at a meeting in London in November, 1999. Most bones of the skeleton are laid down as cartilage first, which forms from undifferentiated mesenchyme.

Skeleton

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