Hereditary Hemochromatosis

Transcription

1 Hereditary Hemochromatosis The HFE gene Becky Reese

2 What is hereditary hemochromatosis? Recessively inherited Iron overload disorder Inability to regulate iron absorption No cure

3 Image: What gene is associated with hereditary hemochromatosis? HFE H63D S65C C282Y Transmembrane 348aa Molecular Function Gene Ontology Cellular Component Biological Processes Receptor binding Cellular Iron Homeostasis

4 How does HFE function in iron uptake?

5 How well conserved is HFE? H. sapiens HFE P. troglodytes HFE M. mulatta HFE B. taurus HFE R. norvegicus HFE M. musculus HFE D. rerio UXA2 D. melanogaster Malvolio C. elegans DRAG-1 S. cerevisiae Aft1p Arabidopsis IRT1 RGM_N AFT RGM_C Transmembrane 348aa 348aa 348aa 356aa 360aa 359aa 350aa Nramp Zip 345aa 596aa 408aa 690aa

6 Approach: Clustal Omega HFE Phylogeny Fruit flies have blood Vertebrates Average distance using BLOSUM62 Blood cell:

7 Where are the mutations in HFE? H63D S65C C282Y Transmembrane 348aa

8 Differences in HFE mutations lead to iron uptake variability S65C H63D Low Risk C282Y High Risk

9 H63D S65C C282Y Knowledge Gap Is the domain of HFE important for iron uptake? Hypothesis The domain of HFE is important for iron uptake

10 Specific Aim 1: Mutation conservation

11 Aim: To determine how conserved the known mutation sites in human HFE are between vertebrates and invertebrates. Knowledge Gap: Why do H63D and S65C result in hereditary hemochromatosis? Hypothesis: The mutations in will be conserved, indicating the importance of these sites and in HFE s regulation of iron uptake Approach: Sequence alignment using Clustal Omega

12 H. sapiens HFE P. troglodytes HFE M. mulatta HFE B. taurus HFE R. norvegicus HFE M. musculus HFE D. rerio UXA2 348aa 348aa 348aa 356aa 360aa 359aa 350aa Vertebrates Invertebrates D. melanogaster Malvolio C. elegans DRAG-1 RGM_N Nramp RGM_C 596aa 408aa S. cerevisiae Aft1p AFT 690aa Arabidopsis IRT1 Zip 345aa

13 H63D S65C C282Y Approach: Clustal Omega IGc 1 C282Y site Summary: C282Y is highly conserved

14 H63D S65C C282Y Approach: Clustal Omega IGc 1 H63D site Summary: H63D is not conserved across vertebrates or invertebrates

15 Future Direction H63D site Fe? Serine (S) Histidine (H) Zebrafish:

16 H63D S65C C282Y Approach: Clustal Omega IGc 1 S65C site Summary: S65D is conserved in a variety of species

17 Future Direction S65C site Fe? Serine (S) Cysteine (C) C. elegans:

18 Overall Conclusions Cysteine is highly conserved at position 282 Histidine is somewhat conserved across vertebrates at position 63 Serine is conserved in a variety of species in position 65

19 Specific Aim 2: Identify drugs that target HFE

20 Aim: To identify drugs that can modify HFE protein function and lower iron levels Knowledge Gap: What drugs interact with HFE? Hypothesis: Drugs that interact with the domain of HFE will lower iron levels Approach: Chemical genetics

21 Chemical Genetics Diversity Oriented Library C. elegans RGM_N 408aa RGM_C C. elegans: Library: Stockwell,B.R.(2004).Exploring biology with small organic molecules. Nature.

22 Color detection assay to determine iron levels Chemical Treatment Lyse worms Spectrophotometry quantification C. elegans: Ferrozine: Detection Ferrozine

23 C. elegans: Expected Results DRAG-1 = HFE Homologue Chemical interacts with nonfunctional DRAG-1 Control Functional DRAG-1 Chemical does not interact with nonfunctional DRAG-1

24 Future Directions Take chemicals that interact with DRAG-1 and test them in an organism that has the domain in their HFE homologue

25 References 1. Allen, K.J., Gurrin, L.C., Constantine, C.C., Osborne, N.J., Delatycki, M.B., Nicoll, A.J., McLaren, C.E., Bahlo, M., Nisselle, A.E., Vulpe,C.D., Anderson, G.J., Southey, M.C., Giles, G.G., English, D.R., Hopper, J.L., Olynyk, J.K., Powell, L.W., Gertig, D.M. (2008). Iron-overload-related disease in HFE hereditary hemochromatosis. New England Journal of Medicine, 358(3): doi: /NEJMoa Hemochromatosis Information Society: 3. Swinkels, D.W., Janssen, M.C., Bergmans, J., Marx, J.J. (2006). Hereditary hemochromatosis: genetic complexity and new diagnostic approaches. Clinical Chemistry, 52(6): Gao, J., Chen, J., Kramer, M., Tsukamoto, H., Zhang, A., Enns, C.A. (2009). Interaction of the hereditary hemochromatosis protein HFE with transferrin receptor 2 is required for transferrininduced hepcidin expression. Cell Metabolism, 9: doi: /j.cmet Cha on, U., Valmas, N., Collins, P.J., Reilly, P.E.B., Hammock, B.D., and Ebert, P.R. (2007). Disruption of iron homeostasis increases phosphone toxicity in Caenorhabditis elegans. Toxicological Sciences, 96(1): doi: /toxsci/kfl Eide, D., Broderius, M., Fett, J., and Guerinot, M.L. (1996). A novel iron-regulated metal transporter from plants identitfied by functional expression in yeast. Proc. Natl. Acad. Sci. 93: Yamaguichi-Iwai, Y., Stearman, R., Dancis, A., and Klausner, R.D. (1996). Iron-regulated DNA binding by the AFT1 protein controls the iron regulon in yeast. The EMBO Journal. 15(13):

26 Questions?