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Interaction between the splotch mutation and retinoic acid in mouse neural tube defects in vitro
1Department of Biology, McGill University, Montreal, Quebec, Canada.
Abstract:
The interaction between the splotch gene (Sp) and all-trans retinoic acid (RA) was investigated using cytogenetically marked Sp/+ and +/+ mouse embryos cultured in the presence of RA. Retinoic acid retarded the development of and had a teratogenic effect on mouse embryos in culture. In particular, RA had seemingly opposite effects on the posterior neural tube, inducing abnormally early fusion in some embryos and causing a dose-dependent delay in others. When the effects of RA on identified Sp/+ and +/+ embryos were compared, the only observed difference in their responses was in the degree of the delay in posterior neuropore (PNP) closure. At the end of the culture period, among the untreated control embryos, the Sp heterozygotes showed retardation of PNP closure compared to +/+ embryos. In addition, the RA treatment was found to have induced a greater delay in posterior neural tube closure in Sp/+ than in +/+ embryos. The basis for this difference in response to RA is presumed to be the retardation of PNP closure that is caused by the Sp gene in heterozygous form. The effects of the gene and the teratogen are additive and the gene carriers thus have greater mean PNP lengths at the end of culture. Since the length of the PNP is an indication of an embryo's likelihood of developing spina bifida, this provides an explanation for the observation that Sp/+ embryos are more sensitive to the spina bifida-causing effects of RA than are +/+ embryos.
Insights
The splotch gene (Sp) and all-trans retinoic acid (RA) interact to affect embryonic development. Sp heterozygous embryos show increased sensitivity to RA, leading to a greater delay in posterior neuropore closure and higher risk of spina bifida.
Area of Science:
- Developmental biology
- Genetics
- Teratology
Background:
- The splotch gene (Sp) is crucial for normal embryonic development.
- All-trans retinoic acid (RA) is a known teratogen that can cause developmental abnormalities.
- Understanding gene-teratogen interactions is vital for predicting birth defects.
Purpose of the Study:
- To investigate the interaction between the splotch gene (Sp) and all-trans retinoic acid (RA) on mouse embryonic development.
- To determine if Sp heterozygous embryos exhibit altered sensitivity to RA-induced teratogenesis.
- To elucidate the mechanisms underlying RA's effects on posterior neural tube closure.
Main Methods:
- Culturing cytogenetically marked Sp/+ and +/+ mouse embryos in the presence of varying concentrations of RA.
- Assessing developmental retardation and teratogenic effects, particularly on the posterior neural tube.
- Comparing the delay in posterior neuropore (PNP) closure between Sp/+ and +/+ embryos under RA exposure.
Main Results:
- RA caused developmental retardation and teratogenic effects in both Sp/+ and +/+ embryos.
- RA induced a dose-dependent delay in posterior neural tube closure, with opposite effects observed in some cases.
- Sp/+ embryos exhibited a significantly greater delay in PNP closure compared to +/+ embryos, both in controls and RA-treated groups.
- The teratogenic effects of RA and the developmental retardation caused by the Sp gene were found to be additive.
Conclusions:
- The splotch gene in heterozygous form exacerbates the teratogenic effects of all-trans retinoic acid on posterior neural tube closure.
- Sp/+ embryos are more sensitive to RA's spina bifida-inducing effects due to an additive interaction between the gene and the teratogen.
- This study provides a molecular explanation for the increased risk of neural tube defects in embryos carrying the splotch gene when exposed to RA.