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

Area of Science:

• Developmental biology
• Genetics
• Reproductive medicine

Background:

• Abnormal placentation is a significant cause of pregnancy complications and poor fetal outcomes.
• The molecular underpinnings of abnormal placentation remain insufficiently understood.
• Replication stress is implicated in various developmental processes and diseases.

Purpose of the Study:

• To investigate the role of persistent replication stress in abnormal placentation and embryo viability.
• To determine the molecular mechanisms by which replication stress impacts placental development.
• To explore the consequences of MCM2-7 helicase mutations on trophoblast stem cells and placental formation.

Main Methods:

• Utilized mouse models with mutations in the MCM2-7 replicative helicase.
• Analyzed placental morphology, focusing on the junctional zone (JZ) and labyrinth zone (LZ).
• Assessed cell proliferation in different placental compartments.
• Examined the stemness of trophoblast stem cells (TSCs) and pluripotency of embryonic stem cells (ESCs) under MCM deficiency.
• Investigated the role of FANCM, a DNA repair protein, in placental development.

Main Results:

• MCM2-7 deficient embryos showed normal morphology but severely diminished placental junctional zones.
• Cell proliferation was reduced in the JZ but not the LZ of MCM-deficient placentae.
• MCM2-7 deficient TSCs lost stemness, indicating an impact on early trophoblast progenitors.
• Mouse embryonic stem cells (ESCs) maintained pluripotency despite MCM2-7 deficiency.
• Deficiency in FANCM also led to a diminished JZ, suggesting a role for DNA repair in placentation.

Conclusions:

• Persistent replication stress, caused by MCM2-7 mutations, disrupts mouse placentation and reduces embryo viability.
• Replication stress preferentially affects the developing junctional zone by impacting trophoblast stem cell maintenance.
• Genomic instability arising from replication stress is a critical factor compromising embryo outcomes through impaired placentation.