Sonic hedgehog expression in Gli3 depressed mouse embryo, Pdn/Pdn

Area of Science:

• Developmental biology
• Genetics
• Molecular biology

Background:

• The polydactyly/arhinencephaly mouse (Pdn/Pdn) exhibits a phenotype similar to Greig cephalopolysyndactyly syndrome (GCPS).
• GCPS is linked to mutations in the GLI3 gene, and Gli3 expression is suppressed in Pdn/Pdn mice.
• A transposon insertion in intron 3 of the Gli3 gene was identified as the cause of the Pdn/Pdn phenotype.

Purpose of the Study:

• To characterize the genetic basis of the Pdn/Pdn mouse model.
• To analyze the expression patterns of Gli3 and related genes in Pdn/Pdn embryos.
• To investigate the relationship between Gli3 and sonic hedgehog (Shh) signaling in this model.

Main Methods:

• Genotyping of Pdn embryos using PCR with primers targeting the transposon insertion.
• Quantitative real-time PCR to analyze Gli3, Shh, Bmp-2, Bmp-4, and ptc-1 gene expression.
• Whole-mount in situ hybridization to visualize Gli3 and Shh expression in embryonic tissues.

Main Results:

• Gli3 gene expression was significantly suppressed in Pdn/Pdn (20-30%) and Pdn/+ (approx. 60%) embryos compared to wild-type (+/+).
• Shh expression showed genotype-dependent differences only on day 9 of gestation, with no ectopic expression observed.
• Gli3 expression was absent in the neuroectoderm of Pdn/Pdn embryos, while Shh expression patterns in notochord and floor plate remained similar to wild-type.

Conclusions:

• The Pdn/Pdn mouse model provides a valuable tool for studying the role of Gli3 in development and GCPS.
• Suppressed Gli3 expression directly impacts neuroectoderm development.
• The interaction between Gli3 and Shh signaling warrants further investigation in the context of Pdn/Pdn.