Chronic replication stress-mediated genomic instability disrupts placenta development in mice

Area of Science:

• Reproductive Biology
• Genetics
• Developmental Biology

Background:

• Abnormal placentation is a significant cause of pregnancy complications and poor fetal outcomes.
• The molecular underpinnings of abnormal placentation remain incompletely understood.
• Replication stress is increasingly recognized as a factor in developmental pathologies.

Purpose of the Study:

• To investigate the role of persistent replication stress in placental development and embryo viability.
• To determine the impact of mutations in the MCM2-7 replicative helicase on placental structure and function.
• To explore the consequences of replication stress on trophoblast stem cell maintenance.

Main Methods:

• Generation of mouse models with mutations in the MCM2-7 replicative helicase.
• Analysis of embryonic and placental morphology, focusing on the junctional zone (JZ) and labyrinth zone (LZ).
• Assessment of cell proliferation in placental tissues and trophoblast stem cells (TSCs).
• Evaluation of the impact of FANCM deficiency on placental development.

Main Results:

• MCM2-7 deficient embryos showed normal morphology but severely diminished placental junctional zones.
• JZ cell proliferation was significantly reduced in MCM-deficient placentae, while labyrinth zone proliferation was unaffected.
• MCM2-7 deficient trophoblast stem cells lost stemness, indicating an impact on the progenitor cell pool.
• Female mice deficient for FANCM also exhibited diminished junctional zones, supporting the role of DNA repair in placentation.

Conclusions:

• Persistent replication stress, caused by MCM2-7 mutations, disrupts mouse placentation and reduces embryo viability.
• Replication stress preferentially impairs the developing junctional zone by affecting trophoblast stem cell maintenance.
• Genomic instability arising from replication stress compromises embryo development through impaired placentation.