Spina bifida occulta in homozygous Patch mouse embryos

Area of Science:

• Developmental Biology
• Genetics
• Skeletal Biology

Background:

• Platelet-derived growth factor A (PDGF A) and its receptor PDGFR alpha are expressed in embryonic tissues involved in skeletal development.
• The Patch (Ph) mutant mouse lacks the Pdgfra gene due to a large deletion, impacting skeletal formation.

Purpose of the Study:

• To investigate the role of PDGF A signaling in axial skeletal development.
• To characterize the specific vertebral and ribcage deformities in Patch mutant embryos.
• To determine the underlying cause of spina bifida in Ph/Ph embryos.

Main Methods:

• Analysis of Pdgfra gene expression patterns in normal embryos.
• Detailed examination of skeletal morphology in homozygous Patch (Ph/Ph) mutant mouse embryos.
• Histological analysis to assess vertebral and neural arch development.

Main Results:

• Ph/Ph embryos exhibit severe deformities in the spine and ribcage, including occult spina bifida affecting the entire spinal column.
• Vertebral components are present in late-gestation Ph/Ph embryos, but neural arches are misshapen.
• Neural tube closure appears normal, suggesting the defect originates in the somitic mesoderm.

Conclusions:

• PDGF A signaling is essential for the correct positioning of neural arch condensations during axial skeletal development.
• Spina bifida in Patch homozygotes is primarily caused by abnormalities in the somitic mesoderm, not neural tube defects.
• These findings highlight the critical role of PDGF signaling in craniofacial and axial skeletal patterning.