Late effects of retinoic acid on neural crest and aspects of rhombomere

TY - JOUR

T1 - Late effects of retinoic acid on neural crest and aspects of rhombomere

AU - Gale, E

AU - Prince, V

AU - Lumsden, A

AU - Clarke, J

AU - Holder, N

AU - Maden, M

PY - 1996/3

Y1 - 1996/3

N2 - We exposed st.10 chicks to retinoic acid (RA), both globally, and locally to individual rhombomeres, to look at its role in specification of various aspects of hindbrain derived morphology. Previous studies have looked at RA exposure at earlier stages, during axial specification. Stage 10 is the time of morphological segmentation of the hindbrain and is just prior to neural crest migration. Rhombomere 4 localised RA injections result in specific alterations of pathways some crest cells that normally migrate to sites of differentiation of neurogenic derivatives. The r4 crest cells that give rise to mesenchymal derivatives are unaffected. In addition, r4 gene expression is also partially altered by RA; within 6 hours of r4 exposure to RA, ectopic expression of Krox-20 is seen in r4 and Hoxb-1 expression is lost while Hoxa-2 expression continues normally. When we examined these RA-treated animals later in development, they showed an anterior displacement of the facial ganglion in addition to a mis-direction of the extensions of its distal axons and a dramatic decrease in the number of contralateral vestibuloacoustic neurons normally seen in r4. Only this r4-specific neuronal type is affected in r4; the motor neuron projections seem normal in experimental animals. The specificity of this result, combined with the loss of Hoxb-1 expression in r4 and the work by Krumlauf and co-workers showing gain of contralateral neurons co-localised with ectopic Hoxb-1 expression, indicates a role for Hoxb-1 and RA in the specification of this cell type in normal development. These results suggest that RA, at st.10, is able to affect some aspects of segment identity while leaving others unchanged.

AB - We exposed st.10 chicks to retinoic acid (RA), both globally, and locally to individual rhombomeres, to look at its role in specification of various aspects of hindbrain derived morphology. Previous studies have looked at RA exposure at earlier stages, during axial specification. Stage 10 is the time of morphological segmentation of the hindbrain and is just prior to neural crest migration. Rhombomere 4 localised RA injections result in specific alterations of pathways some crest cells that normally migrate to sites of differentiation of neurogenic derivatives. The r4 crest cells that give rise to mesenchymal derivatives are unaffected. In addition, r4 gene expression is also partially altered by RA; within 6 hours of r4 exposure to RA, ectopic expression of Krox-20 is seen in r4 and Hoxb-1 expression is lost while Hoxa-2 expression continues normally. When we examined these RA-treated animals later in development, they showed an anterior displacement of the facial ganglion in addition to a mis-direction of the extensions of its distal axons and a dramatic decrease in the number of contralateral vestibuloacoustic neurons normally seen in r4. Only this r4-specific neuronal type is affected in r4; the motor neuron projections seem normal in experimental animals. The specificity of this result, combined with the loss of Hoxb-1 expression in r4 and the work by Krumlauf and co-workers showing gain of contralateral neurons co-localised with ectopic Hoxb-1 expression, indicates a role for Hoxb-1 and RA in the specification of this cell type in normal development. These results suggest that RA, at st.10, is able to affect some aspects of segment identity while leaving others unchanged.

KW - Cell Movement

KW - Rhombencephalon

KW - Animals

KW - Homeodomain Proteins

KW - Chick Embryo

KW - DNA-Binding Proteins

KW - Neural Crest

KW - Morphogenesis

KW - RNA, Messenger

KW - Phenotype

KW - Genes, Homeobox

KW - Base Sequence

KW - Transcription Factors

KW - DNA Primers

KW - Molecular Sequence Data

KW - Tretinoin

KW - Early Growth Response Protein 2

KW - Trans-Activators

KW - Gene Expression Regulation, Developmental

M3 - Article

C2 - 8631256

SN - 0950-1991

VL - 122

SP - 783

EP - 793

JO - Development (Cambridge): for advances in developmental biology and stem cells

JF - Development (Cambridge): for advances in developmental biology and stem cells

IS - 3

ER -