Distinct regulatory elements govern Fgf4 gene expression in the mouse blastocyst, myotomes, and developing limb

Area of Science:

• Developmental Biology
• Gene Regulation
• Molecular Biology

Background:

• Embryonic development relies on precisely regulated signaling molecules.
• Fgf4 is crucial for postimplantation development, growth, and limb patterning.
• Previous work identified Sox2 and Oct-3 regulation of Fgf4 in EC cells.

Purpose of the Study:

• To investigate Fgf4 gene regulation in vivo during embryonic development.
• To identify novel regulatory elements controlling Fgf4 expression.
• To understand stage- and tissue-specific Fgf4 expression patterns.

Main Methods:

• Generation and analysis of transgenic mouse embryos carrying Fgf4-LacZ reporter constructs.
• Mapping of cis-acting regulatory elements within the Fgf4 gene, particularly the 3' UTR.
• Identification of transcription factor binding sites within regulatory regions.

Main Results:

• Most Fgf4 embryonic regulatory elements are located in conserved regions of the 3' UTR.
• An EC cell-specific enhancer, dependent on Sox and Oct proteins, drives blastocyst ICM expression.
• Distinct enhancers control postimplantation expression in somitic myotomes (requiring bHLH factors) and limb bud AER.
• Positive and negative regulatory elements in the 3' UTR contribute to restricted AER expression.

Conclusions:

• Fgf4 gene expression is governed by multiple, distinct regulatory elements.
• These elements ensure precise, stage- and tissue-specific expression crucial for embryonic development.
• The 3' UTR is a key region for housing regulatory elements controlling Fgf4 expression.