Genomic imprinting in human placentation.

Area of Science:

• Epigenetics
• Developmental Biology
• Genetics

Background:

• Genomic imprinting (GI) is an epigenetic phenomenon unique to mammals, playing a role in placental evolution.
• Understanding GI is critical for comprehending mammalian reproductive strategies and placental development.

Purpose of the Study:

• To re-examine mouse placenta-specific GI genes using embryo transfer and trophoblast stem (TS) cells.
• To identify human placenta-specific GI genes and investigate their biological roles using human TS cells.

Main Methods:

• Utilized embryo transfer and trophoblast stem (TS) cells for mouse GI gene analysis.
• Isolated human cytotrophoblast cells and human TS cells for comprehensive analysis of human GI genes.
• Investigated biological roles of human GI genes in human TS cells.

Main Results:

• Identified potential false positives in previous mouse GI gene studies due to maternal cell contamination.
• Determined human placenta-specific GI genes, revealing incomplete germline DNA methylation erasure in the human placenta.
• Observed normal GI patterns in human TS cells, while complete hydatidiform mole-derived TS cells showed aberrant GI and enhanced proliferation, potentially linked to the p57KIP2 gene.
• Demonstrated the essential role of a primate-specific microRNA cluster on chromosome 19 in human TS cell self-renewal and differentiation.

Conclusions:

• Genomic imprinting plays significant roles in human placentation.
• Experimental evidence using TS cells indicates that maintaining GI is vital for normal human placental development.