The majority of the mammalian genome is composed of noncoding sequences. One important composition is transposons, which are mobile DNA sequences in the genome. During evolution, they continuously diversify and contribute to the rearrangement of the host genome. They are classified as DNA transposons or retrotransposons based on their manner of transposition.

Currently, DNA transposons are used as genetic tools in genome manipulation of stem cells whereas retrotransposons are dynamically expressed during development and actively participate in the functions of stem cells. Like protein-coding genes, the expression of transposons is cell type-specific and tightly controlled. The specific expression of transposons allows them to act as promoters, enhancers, long noncoding RNAs, form chimeric transcripts with protein-coding genes, and take part in self-renewal and differentiation of stem cells. Their specific expression is regulated by transcription factors, epigenetic regulators, and post-transcriptional pathways. Improper activation of transposons can cause aberrant gene expression, DNA transpositions, and instability of the host genome. Hence, the accurate control of transposon expression and function is key to the maintenance of stem cell fate and genome stability. However, given the importance of transposons in stem cells, many questions remain to be answered concerning the functions and expression regulation of transposons.

This Special Issue welcomes both original research and review articles that promote the understanding of the function and regulation of transposons in stem cells. We are interested in articles related to the novel function and application of transposons, transcriptional/epigenetic repression, and activation of transposons, as well as other mechanisms to control transposon expression in stem cells.

Potential topics include but are not limited to the following:

• Novel molecular mechanisms that repress transposition in stem cells
• Transcriptional regulation of transposons in stem cells
• Epigenetic regulation of transposons in stem cells
• Mechanisms of post-transcriptional regulation of transposons in stem cells
• New insights into the function of transposons in stem cells
• Recent developments of methods for studying transposons in stem cells
• Recent applications of transposons in genome manipulation of stem cells
• Stem cell systems and animal models in studying transposons
• Roles of transposons in mammalian development