Combinatorial effects on gene expression at the Lbx1/Fgf8 locus resolve split-hand/foot malformation type 3

Area of Science:

• Genetics
• Developmental Biology
• Molecular Biology

Background:

• Split-Hand/Foot Malformation type 3 (SHFM3) is a congenital limb defect linked to the LBX1/FGF8 gene locus.
• The precise molecular mechanisms driving SHFM3 pathogenesis remain unclear.

Purpose of the Study:

• To investigate how SHFM3-associated genomic rearrangements impact chromatin conformation and gene expression.
• To elucidate the disease mechanism of SHFM3 using a mouse model.

Main Methods:

• Generation of transgenic mice modeling SHFM3-associated duplication and inversion.
• Analysis of chromatin architecture and gene expression patterns in developing limbs.
• Investigating the role of AER-specific enhancers in gene misregulation.

Main Results:

• The Lbx1/Fgf8 locus comprises two interacting regulatory domains.
• SHFM3-associated rearrangements restructure chromatin, causing ectopic Lbx1 and Btrc gene activation in the apical ectodermal ridge (AER).
• This misexpression pattern mimics Fgf8 signaling and is driven by AER-specific enhancers.

Conclusions:

• SHFM3 arises from a combination of misexpressed genes during limb development.
• Genomic rearrangements can induce disease by altering chromatin structure and leading to aberrant gene expression.
• This study provides a framework for understanding SHFM3 molecular mechanisms and the impact of genomic alterations on development.