Temporal transitions in post-mitotic neurons throughout the C. elegans nervous system

The nervous system of animals is functional at early postembryonic stages but undergoes extensive anatomical and functional changes throughout postembryonic development to eventually form a fully mature nervous system at adulthood. The molecular changes in post-mitotic neurons across post-embryonic development and the genetic programs that control these temporal transitions are not well understood. Using the model organism C. elegans, we comprehensively characterized the distinct functional states (locomotor behavior) and corresponding distinct molecular states (transcriptome) of the post-mitotic nervous system across temporal transitions from early post-embryonic periods to adulthood. We observed pervasive changes in gene expression, many of which controlled by the conserved heterochronic miRNA lin-4/mir-125 and its target, the transcription factor lin-14. The functional relevance of these molecular, lin-4/lin-14 controlled transitions are exemplified by a novel neuropeptide, nlp-45, which confers temporally controlled anti-exploratory activities. Our studies provide new insights into a perhaps generalizable regulatory mechanism that alters neuron-type specific gene batteries to modulate distinct behaviors states, and also provides a rich atlas of post-embryonic molecular changes to uncover additional regulatory mechanisms. Immunoprecipitation of neuronal nuclei, at 4 post-embryonic stages: 3 larval stages (L1, L2, and L4) and one adult (A) stage in control animals as well as in heterochronic mutants (lin-4 null, lin-14 gain of function, and lin-28 gain of function)