Gene-teratogen interaction in insulin-induced mouse exencephaly

Area of Science:

• Developmental biology
• Genetics
• Teratology

Background:

• Mutant genes crooked (Cd) and rib fusion (Rf) in mice cause minor skeletal defects.
• Teratogens, such as insulin, can induce birth defects.

Purpose of the Study:

• To investigate the interaction between heterozygous mutant genes and insulin teratogenicity.
• To determine if mutant heterozygotes exhibit increased sensitivity to insulin-induced exencephaly.

Main Methods:

• Crossed mutant mouse strains (Cd or Rf) with A/J or SWV strains.
• Treated pregnant mothers with teratogenic doses of insulin.
• Analyzed F1 offspring for skeletal defects and exencephaly.
• Performed dose-response curves and probit regression analysis.
• Examined embryonic turning, neural tube closure, and cell proliferation histologically.

Main Results:

• Mutant heterozygotes exposed to insulin showed significantly higher rates of exencephaly compared to nonmutants.
• Gene-teratogen interaction was confirmed by nonparallel probit regression lines.
• Insulin delayed embryonic turning and neural tube closure, particularly in exencephalic embryos.
• Reduced neurectoderm cell proliferation and mitotic index were observed in exencephalic embryos.

Conclusions:

• Heterozygous mutant genes confer increased sensitivity to insulin-induced exencephaly.
• Delayed embryonic turning may be a mechanical factor in the failure of neural tube closure.
• Insulin impacts neurectoderm development, leading to exencephaly in susceptible embryos.