The genetic code was deciphered more than 50 years ago, but we are only now becoming aware of a second, hidden code. It is the concept of “codon optimality” that enters the scene of developmental and homeostatic gene expression, linking translation rates, mRNA stability, and tRNA abundance. Both at the biological and methodological levels, work by Giraldez and colleagues in this issue of The EMBO Journal paves the way for further analyses of such key regulatory mechanisms.
See also: AA Bazzini et al
Maternal‐to‐zygote transition in early embryonic development requires clearance of thousands of maternal mRNAs, illustrating the ability of a cell to carefully regulate gene expression by affecting the stability of its mRNAs. The general mechanisms of how this is achieved, however, remain largely mysterious. Pioneering work from Antonio Giraldez and Alexander Schier characterized the role of microRNAs (miRs), in particular miR‐430, in degrading maternal mRNAs during the zygotic program in zebrafish (Giraldez et al, 2006). Other groups reported similar observations in Drosophila (Bushati et al, 2008) and Xenopus (Lund et al, 2009). Notwithstanding their importance, miRNAs are only responsible for the degradation of a subset of mRNAs.
In a large‐scale, comparative analysis, Giraldez and coworkers now show that maternal mRNA clearance in early vertebrate embryogenesis as well …