Presentation on theme: "Developmental Genetics Overview of gene structure Mechanisms of gene regulation Drosophila: Genetics model for Developmental Biology."— Presentation transcript:
Developmental Genetics Overview of gene structure Mechanisms of gene regulation Drosophila: Genetics model for Developmental Biology
What is a gene? CDS Regulatory Promoter Core Promoter UTR AAAAAA AUG UAA
Developmental Genetics Differentiation of cells requires regulation of specific genes. Timing of Gene Regulation can determine when a tissue develops or when cells undergo Apoptosis. How can we regulate gene expression?
Histone Code: Modification of Histone tails. Acetylation, methylation, and phosphorylation. Charged residues in tail.
Histone Methylation Methylation of residues on H3 tail Methylation of H3K4(meH3K4) + high acetylation of H3/H4 tails)= active transcription. meH3K9+low acetylation of H3/H4= highly repressed meH3K9, meH3K27, meH4K20 =highly repressed.
Example: Hox genes Hox genes are responsible for determining the fate of segments along the anterior-posterior axis. Trimethylation of H3K27 represses Hox genes. Demethylase for me3H3K27 is recruited in differentiated cells to open up the promoters for Hox genes.
Methylation of DNA Once gene is turned on and needs to stay on CpG-usually associated with repression. -globin promoter. Methylation status of promoter can change during development. Ex. Embryonic hemoglobin ( -globin) fetal hemoglobin ( -globin)
Methylation and Transcriptional repression Can block transcription factor binding Recruit Histone methylases and acetylases Ex. MeCP2 Dnmt3 and Dnmt1 result in the heritability of methylated DNA regions in progeny cells. Methylation can inactivate entire chromosomes.
Transcriptional regulation cis factors trans factors
Promoters/enhancers Core promoter RNA Pol II binds to this region. Directly upstream of transcription start site. Regulatory Promoter Region upstream of core promoter Contains enhancers/regulatory binding sites Highly modular.
Promoter fusions Identifying new enhancers Reporter genes: -gal and GFP
Enhancer Modulation Multiple transcription factors can bind to a single Promoter region. Pax6 enhancer region- differential transcription factor binding for different tissue types. Pax6 1 Core promoter 123 4
Pay it forward Pax6 is a transcriptional regulator. Pax6 works with Sox2 and L -Maf to regulate the crystallin gene. Pax6 also regulates Pancreas related genes Insulin, glucagon, and somatostatin Pax6 regulates itself!
Transcription Factors Core Promoter TFIID/TBP stabilized by TFIIA TFIIH binds, RNA Pol II with TFIIE/TFIIF binds subsequently. TFIIH phosphroylates RNA Pol II CTD. Regulatory Promoter Wide array of factors bind to enhancer regions. (Pax6 regulation).
Transcription Factor Domains. DNA binding domain Transactivating Domain Protein-Protein Interaction domain. MITF Transcription Factor- Ear development And Pigment production
Gene Silencing Neural restrictive silencer element (NRSE) found represses neural genes in non-neural cells. NRSF binds to this element. L1 is critical for brain development. Transgene reporter with NRSE= neural tissue expression only Transgene reporter without NRSE= all tissues.
Regulation of mRNA mRNA must undergo splicing for protein to be made. Regulation of mRNA Determination of which transcripts get translated Splicing combinations to make new protein.
Splicing: different gene products from one gene. Bcl-x transcript. Bcl-x L and Bcl-x S Tropomysin Leads to multiple proteins that differ in function and location. Splicing enhancers-found in specific tissues. Splicing can silence as well- splice excludes an exon from mRNA.
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.
miRNA miRNA ancient form of regulation. Protection against viral pathogens Quick regulation and turnover of mRNA.
Drosophila Development: Genetics at work!
Development of Drosophila
Anterior-Posterior Polarity 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. Minus end (posterior) and plus end (anterior).