Molecular Biology Faculty
Paul Schedl
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 (609) 258-4979 |
 Moffet Lab, 228 |
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Lab (609) 258-5003 |
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Faculty Assistant
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Rebecca I Khaitman
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(609) 258-2683 |
Research Focus
Control of gene expression and early development in Drosophila melanogaster
The goal of our research is to understand how genetic regulatory mechanisms impact on the elaboration of developmental pathways—how are developmental pathways chosen and how is this choice of a pathway subsequently remembered. We have examined the mechanisms controlling pathway choice and pathway maintenance in three different D. melanogaster developmental systems.
Sex determination
Research on sex determination focuses on the binary switch gene Sex-lethal (Sxl). Sxl plays a pivotal role in the development of sexual dimorphism in the fruit fly. The special importance of Sxl may be understood by considering three of the central themes in development: 1) Pathway initiation: What mechanisms enable a cell to choose between alternative developmental programs? 2) Determination: Once that choice has been made, what mechanisms ensure that that cells remain committed to the correct pathway? 3) Differentiation: What mechanisms ensure the proper elaboration of the developmental program? Sxl is unusual in that it functions in all three of these processes. Additionally Sxl is of interest because its\' developmental functions are controlled by both transcriptional and post-transcriptional regulatory mechanisms. Pathway initiation depends upon a counting system that assess the X chromosome to autosome ratio and regulates the activity of the Sxl-establishment promoter, Sxl-Pe. The Sxl-Pe promoter is turned on female (2X/2A) cells while its kept off in male (1X/2A) cells. Protein products from the Sxl-Pe transcripts in females induce the permanent activation of the Sxl gene by directing the female-specific splicing of transcripts from the Sxl-maintenance promoter, Sxl-Pm. Once activated, the Sxl gene ensures that the female determined state is remembered during the rest development. The memory mechanism is an autoregulatory feed back loop in which Sxl proteins promote their own synthesis by directing the female splicing of Sxl-Pm pre-mRNAs. Finally Sxl orchestrates female differentiation by regulating several gene cascades at the level of splicing and translation.
Chromatin structure and developmental control mechanism
Research on chromatin structure focuses on the regulation of the homeotic Abd-B gene from BX-C. An elaborate cis-regulatory region is responsible for generating parasegment-specific expression of Abd-B. The region controls Abd-B expression in parasegments (PS)10-13 and is subdivided into 4 cis-regulatory domains: iab-5 (PS10), iab-6 (PS11), iab-7 (PS12) and iab-8 (PS13). Abd-B expression is divided into two phases: an initiation phase in which the gap and pair-rule segmentation genes activate the appropriate cis-regulatory domain and a memory phase in which Polycomb group and trithorax group genes maintain the parasegment specific cis-regulatory domains in the correct state, on or off. Each domain contains a unique set of initiator elements that respond to gap/pair-rule genes, and a set of maintenance elements that are targets for the Polycomb and trithorax group proteins. Critical to the functional autonomy of the cis-regulatory domains are chromatin boundary elements that insulate one domain from the adjacent domain. Studies underway are focused on one of the maintenance elements, the iab-7 Polycomb Response Element (PRE), and on two boundary elements Fab-7 and Fab-8 which flank the iab-7 cis-regulatory domain, insulating it from iab-7 and iab-8 respectively. Proteins that are critical for PRE or boundary function have been identified, and we are currently attempting to understand how these proteins contribute to either PRE or boundary activity. In related studies on chromatin structure we have shown that the zw5 gene encodes a protein component of the scs boundary. Multimerized binding sites for the Zw5 protein have boundary activity in vivo, and this activity is dependent on the zw5 gene.
Establishment of polarity in egg and embryo
mRNA localization plays a central role in the establishment of polarity axes in the Drosophila egg and embryo. A key component of the mRNA localization system is encoded by the orb gene. orb is essential for determining both the A-P and D-V axes of the developing egg chamber, and mutations in orb are found to prevent the proper localization of mRNAs required for these polarity axes such as osk, Bic-D, K(10), and gurken. orb encodes a germ-line specific RRM type RNA binding protein which is homologous to the Xenopus CPEB protein. In Xenopus, the CPEB protein controls the translation of masked mRNAs in developing oocytes. We have found that localized mRNAs such as osk, K(10) and Bic-D are not translated in orb mutant ovaries. In favor of a direct role in regulating the localization/translation of these mRNAs, we have found that Orb protein binds to their 3\'UTRs both in vivo and in vitro. One of the mRNAs bound by Orb protein in vivo is orb itself. Recent results indicate that Orb protein autoregulates its own on site expression by binding to localized orb mRNA and activating translation. The orb gene is weakly haploinsufficient and we taken advantage of this haploinsufficiency to devise genetic screens for other genes involved either in orb autoregulation or in the establishment of polarity.
Selected Publications
Aoki T, Sarkeshik A, Yates J, Schedl P. (2012) Elba, a novel developmentally regulated chromatin boundary factor is a hetero-tripartite DNA binding complex. elife. 1:e00171. Pubmed
Deshpande G, Spady E, Goodhouse J, Schedl P. (2012) Maintaining sufficient nanos is a critical function for polar granule component in the specification of primordial germ cells. G3 (Bethesda). 2: 1397-403. Pubmed
Wong LC, Schedl P. (2011) Cup blocks the precocious activation of the orb autoregulatory loop. PLoS One. 6: e28261. Pubmed
Hafer N, Xu S, Bhat KM, Schedl P. (2011) The Drosophila CPEB protein Orb2 has a novel expression pattern and is important for asymmetric cell division and nervous system function. Genetics. 189: 907-921. PubMed
Wong LC, Costa A, McLeod I, Sarkeshik A, Yates J 3rd, Kyin S, Perlman D, Schedl P. (2011) The functioning of the Drosophila CPEB protein Orb is regulated by phosphorylation and requires casein kinase 2 activity. PLoS One. 6: e24355. PubMed
Graham PL, Yanowitz JL, Penn JK, Deshpande G, Schedl P. (2011) The translation initiation factor eIF4E regulates the sex-specific expression of the master switch gene Sxl in Drosophila melanogaster. PLoS Genet. 7: e1002185. PubMed
Gohl D, Aoki T, Blanton J, Shanower G, Kappes G, Schedl P. (2011) Mechanism of chromosomal boundary action: Roadblock, sink or loop? Genetics. 187: 731-748. PubMed
Kappes G, Deshpande G, Mulvey BB, Horabin JI, Schedl P. (2011) The Drosophila Myc gene, diminutive, is a positive regulator of the Sex-lethal establishment promoter, Sxl-Pe. Proc Natl Acad Sci 108: 1543-1548. PubMed
Deshpande G, Godishala A, Schedl P. (2009) Ggamma1, a downstream target for the hmgcr-isoprenoid biosynthetic pathway, is required for releasing the Hedgehog ligand and directing germ cell migration. PLoS Genet. 5: e1000333. PubMed
Tan L, Schedl P, Song HJ, Garza D, Konsolaki M. (2008) The Toll-->NFkappaB signaling pathway mediates the neuropathological effects of the human Alzheimer's Abeta42 polypeptide in Drosophila. PLoS ONE. 3: e3966. PubMed
Penn JK, Graham P, Deshpande G, Calhoun G, Chaouki AS, Salz HK, Schedl P. (2008) Functioning of the Drosophila Wilms'-tumor-1-associated protein homolog, Fl(2)d, in Sex-lethal-dependent alternative splicing. Genetics 178: 737-748. PubMed
Aoki T, Schweinsberg S, Manasson J, Schedl P. (2007) A stage-specific factor confers Fab-7 boundary activity during early embryogenesis in Drosophila. Mol Cell Biol. 28: 1047-1060. PubMed
Deshpande G, Sethi N, Schedl P (2007). toutvelu (ttv), a regulator of heparan sulphate proteoglycan biosynthesis, controls guidance cues for germ cell migration. Genetics 176: 905-912. PubMed
Penn JK, Schedl P (2007). The master switch gene Sex-lethal promotes female development by negatively regulating the N-signaling pathway. Dev Cell 12: 275-286. PubMed
Desphande G, Calhoun G, Schedl P (2006). The Drosophila Fragile X protein, dFMR1, is required during early embryogenesis for pole cell formation and the rapid nuclear division cycles. Genetics 174: 1287-1298. PubMed
Shanower GA, Muller M, Blanton JL, Honti V, Gyurkovics H, Schedl P (2005). Characterization of the grappa gene, the Drosophila histone H3 lysine 79 methyltransferase. Genetics 169: 173-184. PubMed
Costa A, Wang Y, Dockendorff TC, Erdjument-Bromage H, Tempst P, Schedl P, Jongens TA (2005). The Drosophila fragile X protein functions as a negative regulator in the orb autoregulatory pathway. Dev Cell 8: 331-342. PubMed
Deshpande G and Schedl P (2005). HMGCoA reductase potentiates hedgehog signaling in Drosophila melanogaster. Dev Cell 9: 629-638. PubMed
Deshpande G, Calhoun G, Schedl P (2005). Drosophila argonaute-2 is required early in embryogenesis for the assembly of centric/centromeric heterochromatin, nuclear division, nuclear migration, and germ-cell formation. Genes Dev 19: 1680-1685. PubMed
Deshpande G, Calhoun G, Jinks TM, Polydorides AD and Schedl P (2005). Nanos downregulates transcription and modulates CTD phosphorylation in the soma of early Drosophila embryos. Mech Dev 122: 645-657. PubMed
Costa A, Wang Y, Dockendorff TC, Erdjument-Bromage H, Tempst P, Schedl P, Jongens TA (2005). The Drosophila fragile X protein functions as a negative regulator in the orb autoregulatory pathway. Dev Cell 8: 331-342. PubMed
Schweinsberg SE and Schedl P (2004). Developmental modulation of Fab-7 boundary function. Development 131: 4743-4749. PubMed
Schweinsberg S, Hagstrom K, Gohl D, Schedl P, Kumar RP, Mishra R, Karch F (2004). The enhancer-blocking activity of the Fab-7 boundary from the Drosophila bithorax complex requires GAGA-factor-binding sites. Genetics 168: 1371-1384. PubMed
Deshpande G, Calhoun G and Schedl P (2004). Overlapping mechanisms function to establish transcriptional quiescence in the embryonic Drosophila germline. Development 131: 1247-1257. PubMed
Blanton J, Gaszner M and Schedl P (2003). Protein:protein interactions and the pairing of boundary elements in vivo. Genes Dev 17: 664-675. PubMed
Schedl P and Broach JR (2003). Making good neighbors: the right fence for the right job. Nat Struct Biol 10: 241-243. PubMed
Tan L, Chang JS, Costa A and Schedl P (2001). An autoregulatory feedback loop directs the localized expression of the Drosophila CPEB protein Orb in the developing oocyte. Development 128: 1159-1169. PubMed
Deshpande G, Swanhart L, Chiang P and Schedl P (2001). Hedgehog signaling in germ cell migration. Cell 106: 759-769. PubMed
Chang JS, Tan L, Wolf MR and Schedl P (2001). Functioning of the Drosophila orb gene in gurken mRNA localization and translation. Development 128: 3169-3177. PubMed
Jinks TM, Polydorides AD, Calhoun G and Schedl P (2000). The JAK/STAT signaling pathway is required for the initial choice of sexual identity in Drosophila melanogaster. Mol Cell 5: 581-587. PubMed
Barges S, Mihaly J, Galloni M, Hagstrom K, Muller M, Shanower G, Schedl P, Gyurkovics H, Karch F (2000). The Fab-8 boundary defines the distal limit of the bithorax complex iab-7 domain and insulates iab-7 from initiation elements and a PRE in the adjacent iab-8 domain. Development 127: 779-790. PubMed
Yanowitz JL, Deshpande G, Calhoun G and Schedl PD (1999). An N-terminal truncation uncouples the sex-transforming and dosage compensation functions of sex-lethal. Mol Cell Biol 19: 3018-3028. PubMed
Gaszner M, Vazquez J and Schedl P (1999). The Zw5 protein, a component of the scs chromatin domain boundary, is able to block enhancer-promoter interaction. Genes Dev 13: 2098-2107. PubMed
Chang JS, Tan L and Schedl P (1999). The Drosophila CPEB homolog, orb, is required for oskar protein expression in oocytes. Dev Biol 215: 91-106. PubMed
