miRNA miRNA ancient form of regulation. Protection against viral pathogens Quick regulation and turnover of mRNA.
Drosophila Development: Genetics at work!
Development of Drosophila
Closer look at Early Development of Drosophila.
Cellularization
Gastrulation and Segmentation
Anterior-Posterior Polarity in Oocyte Starts during oogenesis Gurken mRNA transferred to oocyte. Signal sent back to oocyte post Gurken/Torpedo interaction. Par-1 mediated organization of microtubules to posterior side of oocyte via Oskar. Minus end (posterior) and plus end (anterior).
Dorsal-Ventral Patterning in Oocyte.
Dorsal Gradient
Anterior-Posterior Polarity in Embryo
Syncytial Specification in Drosophila
Anterior-Posterior Polarity in Embryo
Translational Regulation Stored oocyte mRNAs- selective inhibition of translation. Genes turned on quickly post-fertilization. Relies on the recruitment of proteins involved in making a polyA tail. Drosophila Bicoid gene product.
Gap Genes Role in early segmentation Transcriptional regulators
Pair-rule Genes Another set of Transcriptional Regulators. Develops the precursors for the actual segments. Zebra-stripe pattern of expression. Stripe position determined by which enhancer is bound.
Pair-rule Genes
Segment Polarity Genes Wingless (Wnt) and Hedgehog signal pathway proteins. Paracrine signaling maintains segmentation.
Homeotic Selector Genes (Hox) Regulated by Pair-rule and Gap genes. Antennapedia Complex and bithorax complex. AbdA and AbdB repressed by Hunchback and Kruppel. Repression maintained by Polycomb, activation maintained by Trithorax.
Epigenetic Memory Trithorax- keeps genes active. Counteract Polycombs Modify nucleosomes Keep H3K4 trimethylated Polycomb- keeps genes inactivated. H3K27 methylase Bind meH3 tails
Hox Genes in Other Species Mouse Limb development- deletion of Hoxd11, Hoxd12, Hoxd13 causes polydactyly Zebra fish, loss of H3K27 demethylase activity and subsequent Hox gene disregulation- poor tail development