Exogenous retinoic acid induces digit reduction in opossums (Monodelphis domestica) by disrupting cell death and...

Area of Science:

• Developmental biology
• Toxicology
• Genetics

Background:

• Retinoic acid (RA), a vitamin A derivative, is known to cause congenital limb malformations (CLMs) across various species.
• Observed CLMs include oligodactyly and long-bone hypoplasia, with mechanisms in mammals largely unelucidated.
• Previous studies primarily focused on mouse models, leaving gaps in understanding RA's impact on mammalian limb development.

Purpose of the Study:

• To investigate the cellular and molecular effects of exogenous retinoic acid on limb development in the opossum (Monodelphis domestica).
• To compare the susceptibility of opossum limb development to RA-induced disruptions versus that of mice.
• To elucidate the mechanisms underlying RA-induced CLMs in a non-rodent mammalian model.

Main Methods:

• Exposing developing opossums to exogenous retinoic acid.
• Analyzing cellular changes, including cell death and proliferation, within the developing limb mesenchyme.
• Examining the expression patterns of key developmental genes, such as Shh and Fgf8, in response to RA exposure.

Main Results:

• RA exposure significantly increased cell death in the limb mesenchyme, particularly in the zone of polarizing activity.
• A notable reduction in cell proliferation was observed throughout the limb mesenchyme following RA exposure.
• Disrupted expression of Shh (in the zone of polarizing activity) and Fgf8 (in the apical ectodermal ridge) was detected, along with alterations in other limb development-related genes.

Conclusions:

• RA induces CLMs in opossum limbs by disrupting the signaling functions of the apical ectodermal ridge and zone of polarizing activity.
• The observed increase in cell death and reduction in cell proliferation in the limb mesenchyme are key mechanisms of RA teratogenicity.
• Opossums exhibit heightened susceptibility to RA-induced limb developmental disruptions compared to mice, highlighting their utility as a model for studying CLMs.