Retrotransposons regulate host genes in mouse oocytes and preimplantation embryos

Area of Science:

• Reproductive biology
• Genomics
• Developmental biology

Background:

• Transposable elements (TEs) are mobile genetic sequences comprising a significant portion of mammalian genomes.
• Their role in oogenesis and early embryogenesis is not fully understood.
• Maternal factors are crucial for the initial stages of embryonic development.

Purpose of the Study:

• To comprehensively analyze the expression of transposable elements (TEs) in mammalian oocytes and early embryos.
• To investigate the contribution of TEs to the maternal transcriptome.
• To explore the regulatory role of TEs in host gene expression during early development.

Main Methods:

• Analysis of transposable element expression in mammalian oocytes and cleavage-stage embryos.
• Quantification of TE-derived transcripts in the maternal mRNA pool.
• Identification of TEs acting as alternative promoters or first exons for host genes.

Main Results:

• LTR class III retrotransposons are unexpectedly abundant in the maternal mRNA pool of oocytes and persist in early embryos.
• The mouse transcript (MT) retrotransposon family is the most abundant TE transcript in mouse oocytes.
• TEs function as alternative promoters and first exons, regulating the expression of multiple host genes in a developmentally regulated manner.
• This represents the first documented instance of TEs coordinating synchronous gene expression in mammals.

Conclusions:

• Differential TE expression plays a critical role in regulating gene expression during the oocyte-to-embryo transition.
• TEs are key players in the sequential reprogramming of the embryonic genome in preimplantation embryos.
• TEs contribute significantly to the maternal transcriptome and influence early mammalian development.