Gere regulatory networks in multicellular eukaryotes operate in a dosage dependent manner. Defects in managing transcriptional output of key regulatory genes, even by a subtle factor of two, can induce catastrophic effects during development. This is especially true in the gene regulatory networks that control stage-specific patterns of gene expression. Recently, we demonstrated that the conserved pioneer factor BLMP-1 modulates the transcriptional output of many cyclically expressed target genes during C. elegans development; including several heterochronic microRNAs that program temporal patterning. At the molecular level, BLMP-1 is constitutively bound to its target genes where it functions to increase chromatin accessibility and promote robust transcriptional output. To determine which features of cyclical transcription BLMP-1 modulates (i.e., burst amplitude, duration or frequency), we have combined a novel microfluidics-based imaging platform with an MS2/MCP-GFP based RNA-localization approach to continuously measure transcriptional dynamics of heterochronic microRNA genes in developing lava. These efforts have revealed an unanticipated coordination of precise transcriptional patterns in somatic cell-types across the animal. Specifically,
lin-4 transcriptional induction occurs in diverse cell types for 45 min to 1 hour at specific phases of each molting cycle. In addition to in intriguing spatial relationship to firing patterns of specific cell types, we will discuss how mutations in
blmp-1 modulate transcriptional output and also demonstrate how this chromatin remodeling-based mechanism counteracts the activity of the C. elegans Period ortholog, LIN-42, to modulate transcriptional dosage in different environments.