Retinoic acid, midkine, and defects of secondary neurulation
| Autor: | M, Griffith, M H, Zile |
|---|---|
| Rok vydání: | 2000 |
| Předmět: |
Tail
Time Factors Dose-Response Relationship Drug Reverse Transcriptase Polymerase Chain Reaction Terpenes Vitamin A Deficiency Acyclic Monoterpenes Midkine Abnormalities Drug-Induced Tretinoin Chick Embryo Immunohistochemistry Keratolytic Agents Teratogens Monoterpenes Animals Cytokines Nerve Growth Factors Neural Tube Defects RNA Messenger Carrier Proteins In Situ Hybridization |
| Zdroj: | Teratology. 62(2) |
| ISSN: | 0040-3709 |
| Popis: | Retinoic acid (RA) is necessary for normal differentiation of the tail bud into the secondary neural tube. Excess RA, however, is teratogenic and causes neural tube defects (NTDs). The way in which RA modulates secondary neurulation is unclear but probably involves RA-regulated downstream genes such midkine (MK), which encodes a growth factor implicated in tail bud mesenchymal-neuroepithelial conversion. Our objective was to determine whether RA-deficiency would produce similar defects and if MK is involved.Citral, a drug that blocks endogenous RA formation, as well as a neutralizing antibody, were used to block RA activity in chick embryos. Immunohistochemistry and in situ hybridization were used to localize RA and MK in the tail bud. Competitive RT-PCR was used to examine the effects of excess RA and RA deficiency due to citral on the expression of MK mRNA.Citral-induced NTDs displayed a morphological resemblance to those caused by excess RA. However, citral treatment did not significantly increase embryonic mortality, and RA rescue of citral-treated embryos proved unsuccessful. MK mRNA was detected in the differentiating tail bud by in situ hybridization. Competitive RT-PCR showed that excess RA decreased MK expression by 60%. Doses of citral that caused a comparable incidence of defects, however, caused only a 25% decrease.The results show that excess RA and RA deficiency both cause defects of secondary neurulation. While excess RA decreased MK expression, RA deficiency had minimal effects. However, whether or not MK is an intermediary in the developmental phenomena regulated physiologically or pathologically by RA remains to be elucidated. |
| Databáze: | OpenAIRE |
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