A mesodermal factor, T, specifies mouse germ cell fate by directly activating germline determinants.

Area of Science:

• Developmental Biology
• Cell Biology
• Genetics

Background:

• Primordial germ cells (PGCs) are crucial for reproduction and heredity.
• The molecular mechanisms underlying PGC induction in mice by BMP4 and WNT3 signaling remain incompletely understood.

Purpose of the Study:

• To elucidate the signaling pathways and transcription factors involved in PGC specification.
• To determine the role of the mesodermal factor T (BRACHYURY) in activating key germline determinants.

Main Methods:

• Utilized an in vitro PGC specification system in epiblast-like cells.
• Investigated gene induction by WNT3 and BMP4 signaling.
• Performed transcription factor binding analysis for T, SMAD1, and TCF1 on regulatory elements of Blimp1 and Prdm14.

Main Results:

• WNT3 signaling, via β-CATENIN, induces mesodermal transcription factors in epiblast-like cells.
• The mesodermal factor T (BRACHYURY) is essential for robust activation of germline determinants Blimp1 and Prdm14.
• T directly binds and upregulates Blimp1 and Prdm14, defining the downstream PGC program.
• BMP4 acts permissively, preventing an alternative WNT3-induced program that inhibits T-mediated activation of Blimp1 and Prdm14.

Conclusions:

• Established a key signaling mechanism for mammalian PGC specification.
• Demonstrated a fundamental role for the mesodermal factor T in initiating the germline program.
• Highlighted the permissive role of BMP4 in conjunction with WNT3 for efficient PGC induction.