The long-standing relationship between replication timing, gene expression, and chromatin accessibility is maintained...

Area of Science:

• Developmental Biology
• Genomics
• Epigenetics

Background:

• Replication timing (RT) governs genome duplication, 3D genome organization, and gene expression.
• The establishment of RT during early mammalian development remains poorly understood, with conflicting findings.
• Recent studies proposed divergent models for RT establishment, challenging established relationships with gene expression.

Purpose of the Study:

• To critically evaluate recent claims regarding the establishment of replication timing (RT) in mammalian zygotes.
• To reassess the relationship between RT, gene expression, and chromatin accessibility during early embryogenesis.
• To address methodological flaws in prior studies and provide a corrected understanding of RT establishment.

Main Methods:

• Critique and re-analysis of single-cell RT data from recent publications.
• Application of stage-matched controls from established studies for comparative analysis.
• Examination of computational methods and data processing artifacts impacting RT inference.

Main Results:

• Methodological flaws and artifacts in recent studies led to unreliable RT inference.
• The proposed inverse correlation between RT and gene expression is an artifact of flawed methodology.
• Re-analysis confirms that RT is established in the zygote and maintains its canonical relationship with gene expression and chromatin accessibility.

Conclusions:

• Replication timing is established in the zygote, contradicting recent claims of later establishment.
• The canonical relationship between replication timing, transcriptional activity, and chromatin accessibility is conserved during early mammalian embryogenesis.
• Corrected analysis refutes erroneous conclusions and reaffirms established principles in developmental genomics.