Key pathways regulated by HoxA9,10,11/HoxD9,10,11 during limb development

Area of Science:

• Developmental Biology
• Genetics
• Molecular Biology

Background:

• Mammalian Hox genes exhibit complex functional overlap, necessitating the study of multiple gene combinations.
• Understanding Hox gene regulation is critical for defining their roles in limb development.
• Downstream molecular pathways controlled by Hox genes during limb development are not fully understood.

Purpose of the Study:

• To define the developmental roles of six specific Hox genes (Hoxa9,10,11 and Hoxd9,10,11) by creating compound mutations.
• To investigate the downstream molecular pathways regulated by these Hox genes during mouse limb development.
• To characterize gene expression changes in specific limb compartments using RNA-Seq.

Main Methods:

• Generation of compound mutant mice with frameshift mutations in Hoxa9,10,11 and Hoxd9,10,11 using a novel recombineering technique.
• Analysis of limb development in mutant mice, including skeletal measurements and gene expression analysis (Shh, Fgf8).
• Laser capture microdissection coupled with RNA-Seq to profile gene expression in distinct cellular compartments of developing limbs.

Main Results:

• Compound Hoxa9,10,11 (-/-) /Hoxd9,10,11 (-/-) mutant mice displayed severe limb defects, confirming roles in zeugopod and stylopod development.
• Mutant mice showed significantly reduced Shh and Fgf8 expression, indicating Hox gene regulation of key signaling centers.
• RNA-Seq identified altered expression of multiple genes involved in bone formation (e.g., Gdf5, Bmp7, Lef1) in mutant limbs.

Conclusions:

• The developed recombineering method provides a valuable resource for studying overlapping Hox gene functions.
• The study confirms and extends previous findings on Hox gene roles in limb patterning and skeletal development.
• RNA-Seq analysis delineated key downstream pathways regulated by Hoxa9,10,11 and Hoxd9,10,11 during limb development.