Lin28 proteins are required for germ layer specification in Xenopus

Area of Science:

• Developmental biology
• Stem cell biology
• Molecular genetics

Background:

• Lin28 family proteins, characterized by zinc knuckle and cold shock RNA-binding domains, are known regulators of developmental timing and pluripotency.
• The roles of Lin28 in early vertebrate embryonic development, particularly in response to mesoderm-inducing signals, remain incompletely understood.

Purpose of the Study:

• To investigate the function of the Lin28 family in early Xenopus tropicalis embryonic development.
• To determine the impact of global Lin28 inhibition on mesoderm formation and the response to key developmental signaling pathways.

Main Methods:

• Utilized Xenopus tropicalis as a model organism for studying early vertebrate embryogenesis.
• Employed knockdown (morphant) strategies to inhibit lin28a and lin28b gene function globally.
• Assessed mesoderm development, pluripotent cell responses to FGF and activin/nodal-like signals in vitro, and temporal regulation of signaling.

Main Results:

• Xenopus embryos possess two Lin28 genes, lin28a and lin28b, with distinct maternal and zygotic expression patterns.
• lin28a and lin28b are expressed in pluripotent cells and are enriched in mesoderm-responding cells.
• Lin28 inhibition severely disrupts axial and paraxial mesoderm development and compromises pluripotent cell responses to FGF and activin/nodal-like signals.

Conclusions:

• Xenopus Lin28 proteins are crucial for orchestrating pluripotent cell responses to germ layer specification signals during early embryogenesis.
• This early developmental role of Lin28 appears to be independent of its known function in let-7 microRNA biogenesis regulation.