KAS-seq profiling captures transcription dynamics during oocyte maturation.

Area of Science:

• Developmental Biology
• Molecular Biology
• Genomics

Background:

• Oocyte transcriptional silencing is inferred but lacks direct genomic evidence.
• Previous methods relied on indirect measures like chromosome condensation and immunofluorescence.

Purpose of the Study:

• To directly investigate genome-wide transcriptional activity during mammalian oocyte meiotic maturation.
• To provide a dynamic readout of transcription using a novel sequencing approach.

Main Methods:

• Utilized kethoxal-assisted single-stranded DNA sequencing (KAS-seq) to map single-stranded DNA (ssDNA).
• Analyzed ssDNA landscape across different oocyte maturation stages (NSN, SN, mature).
• Performed integrative genomics analysis to dissect transcriptional dynamics.

Main Results:

• High transcriptional activity observed in non-surrounded nucleolus (NSN) oocytes via robust KAS-seq signals.
• Persistent, albeit weaker, KAS-seq signals in surrounded nucleolus (SN) oocytes indicate ongoing transcription.
• Gradual decrease in transcriptional activity and global repression detected in mature oocytes.

Conclusions:

• Directly demonstrates dynamic transcriptional changes during mouse oocyte meiotic maturation.
• KAS-seq provides a sensitive method to assess genome-wide transcription in oocytes.
• Reveals a transition from active transcription to global silencing as oocytes mature.