G-quadruplex in animal development: Contribution to gene expression and genomic heterogeneity.

During animal development, gene expression is orchestrated by specific and highly evolutionarily conserved mechanisms that take place accurately, both at spatial and temporal levels. The last decades have provided compelling evidence showing that chromatin state plays essential roles in orchestrating most of the stages of development. The DNA molecule can adopt alternative structures different from the helical duplex architecture. G-rich DNA sequences can fold as intrastrand quadruple helix structures called G-quadruplexes or G4-DNA. G4 can also be formed in RNA molecules, such as mRNA, lncRNA and pre-miRNA. Emerging evidences suggest that G4s have crucial roles in a variety of biological processes, including transcription, recombination, replication, translation and chromosome stability. In this review, we have collected recent information gathered by various laboratories showing the important role of G4 DNA and RNA structures in several steps of animal development.