Discovery of a dedicated, maternal-specific translation system in early zebrafish embryogenesis

Cellular translation relies heavily on several types of non-coding RNAs. Our studies focused on these non-coding RNAs (rRNAs, snoRNAs, snRNAs, tRNAs, RNase P and SRP RNA), which cover several basic cellular complexes, such as the ribosome and the spliceosome.
Using next generation sequencing, we find that specific non-coding RNA variants are active exclusively during the early oogenesis and embryogenesis in zebrafish. The abundance of these variants is progressively reduced during embryogenesis, and is virtually absent in somatic tissues. We refer to these variants as ‘maternal’ and ‘somatic’.
For each type of non-coding RNA we observe numerous sequence differences between the somatic variant and the maternal variant. These differences are also found in the catalytic domains of these RNAs, which is remarkable, given the high degree of evolutionary conservation. We also found that the maternal type genes characteristically occur in large gene clusters throughout the genome, whereas their somatic counterparts are often found in solitary genes. This difference can be explained by the activity of specific retrotransposons. The discovery of these maternal non-coding RNA variants hints on an intriguing dual translation system in zebrafish development.