Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Having -c- – wherein x is chalcogen – bonded directly to...
Reexamination Certificate
2000-11-28
2003-09-02
Padmanabhan, Sreeni (Department: 1617)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Having -c-, wherein x is chalcogen, bonded directly to...
C514S444000, C514S438000, C514S252010, C514S256000, C514S317000, C514S319000, C514S320000
Reexamination Certificate
active
06613798
ABSTRACT:
BACKGROUND OF THE INVENTION
Pattern formation is the activity by which embryonic cells form ordered spatial arrangements of differentiated tissues. The physical complexity of higher organisms arises during embryogenesis through the interplay of cell-intrinsic lineage and cell-extrinsic signaling. Inductive interactions are essential to embryonic patterning in vertebrate development from the earliest establishment of the body plan, to the patterning of the organ systems, to the generation of diverse cell types during tissue differentiation (Davidson, E., (1990)
Development
108: 365-389; Gurdon, J. B., (1992)
Cell
68: 185-199; Jessell, T. M. et al., (1992)
Cell
68: 257-270). The effects of developmental cell interactions are varied. Typically, responding cells are diverted from one route of cell differentiation to another by inducing cells that differ from both the uninduced and induced states of the responding cells (inductions). Sometimes cells induce their neighbors to differentiate like themselves (homeogenetic induction); in other cases a cell inhibits its neighbors from differentiating like itself. Cell interactions in early development may be sequential, such that an initial induction between two cell types leads to a progressive amplification of diversity. Moreover, inductive interactions occur not only in embryos, but in adult cells as well, and can act to establish and maintain morphogenetic patterns as well as induce differentiation (J. B. Gurdon (1992)
Cell
68:185-199).
Members of the Hedgehog family of signaling molecules mediate many important short- and long-range patterning processes during invertebrate and vertebrate development. In the fly, a single hedgehog gene regulates segmental and imaginal disc patterning. In contrast, in vertebrates, a hedgehog gene family is involved in the control of left-right asymmetry, polarity in the CNS, somites and limb, organogenesis, chondrogenesis and spermatogenesis.
The first hedgehog gene was identified by a genetic screen in the fruitfly Drosophila melanogaster (Nüsslein-Volhard, C. and Wieschaus, E. (1980)
Nature
287, 795-801). This screen identified a number of mutations affecting embryonic and larval development. In 1992 and 1993, the molecular nature of the Drosophila hedgehog (hh) gene was reported (C. F., Lee et al. (1992)
Cell
71, 33-50), and since then, several hedgehog homologues have been isolated from various vertebrate species. While only one hedgehog gene has been found in Drosophila and other invertebrates, multiple Hedgehog genes are present in vertebrates.
The vertebrate family of hedgehog genes includes at least four members, e.g., paralogs of the single drosophila hedgehog gene. Exemplary hedgehog genes and proteins are described in PCT publications WO 95/18856 and WO 96/17924. Three of these members, herein referred to as Desert hedgehog (Dhh), Sonic hedgehog (Shh) and Indian hedgehog (Ihh), apparently exist in all vertebrates, including fish, birds, and mammals. A fourth member, herein referred to as tiggie-winkle hedgehog (Thh), appears specific to fish. Desert hedgehog (Dhh) is expressed principally in the testes, both in mouse embryonic development and in the adult rodent and human; Indian hedgehog (Ihh) is involved in bone development during embryogenesis and in bone formation in the adult; and, Shh, which as described above, is primarily involved in morphogenic and neuroinductive activities. Given the critical inductive roles of hedgehog polypeptides in the development and maintenance of vertebrate organs, the identification of hedghog interacting proteins is of paramount significance in both clinical and research contexts.
The various Hedgehog proteins consist of a signal peptide, a highly conserved N-terminal region, and a more divergent C-terminal domain. In addition to signal sequence cleavage in the secretory pathway (Lee, J. J. et al. (1992)
Cell
71:33-50; Tabata, T. et al. (1992)
Genes Dev.
2635-2645; Chang, D. E. et al. (1994)
Development
120:3339-3353), Hedgehog precursor proteins undergo an internal autoproteolytic cleavage which depends on conserved sequences in the C-terminal portion (Lee et al. (1994)
Science
266:1528-1537; Porter et al. (1995)
Nature
374:363-366). This autocleavage leads to a 19 kD N-terminal peptide and a C-terminal peptide of 26-28 kD (Lee et al. (1992) supra; Tabata et al. (1992) supra; Chang et al. (1994) supra; Lee et al. (1994) supra; Bumcrot, D. A., et al. (1995)
Mol. Cell. Biol.
15:2294-2303; Porter et al. (1995) supra; Ekker, S. C. et al. (1995)
Curr. Biol.
5:944-955; Lai, C. J. et al. (1995)
Development
121:2349-2360). The N-terminal peptide stays tightly associated with the surface of cells in which it was synthesized, while the C-terminal peptide is freely diffusible both in vitro and in vivo (Porter et al. (1995)
Nature
374:363; Lee et al. (1994) supra; Bumcrot et al (1995) supra, Mart', E. et al. (1995)
Development
121:2537-2547; Roelink, H. et al. (1995)
Cell
81:445-455). Interestingly, cell surface retention of the N-terminal peptide is dependent on autocleavage, as a truncated form of HH encoded by an RNA which terminates precisely at the normal position of internal cleavage is diffusible in vitro (Porter et al. (1995) supra) and in vivo (Porter, J. A. et al. (1996)
Cell
86, 21-34). Biochemical studies have shown that the autoproteolytic cleavage of the HH precursor protein proceeds through an internal thioester intermediate which subsequently is cleaved in a nucleophilic substitution. It is likely that the nucleophile is a small lipophilic molecule which becomes covalently bound to the C-terminal end of the N-peptide (Porter et al. (1996) supra), tethering it to the cell surface. The biological implications are profound. As a result of the tethering, a high local concentration of N-terminal Hedgehog peptide is generated on the surface of the Hedgehog producing cells. It is this N-terminal peptide which is both necessary and sufficient for short- and long-range Hedgehog signaling activities in Drosophila and vertebrates (Porter et al. (1995) supra; Ekker et al. (1995) supra; Lai et al. (1995) supra; Roelink, H. et al. (1995)
Cell
81:445-455; Porter et al. (1996) supra; Fietz, M. J. et al. (1995)
Curr. Biol.
5:643-651; Fan, C. -M. et al. (1995)
Cell
81:457-465; Mart', E., et al. (1995)
Nature
375:322-325; Lopez-Martinez et al. (1995)
Curr. Biol
5:791-795; Ekker, S. C. et al. (1995)
Development
121:2337-2347; Forbes, A. J. et al.(1996)
Development
122:1125-1135).
HH has been implicated in short- and long-range patterning processes at various sites during Drosophila development. In the establishment of segment polarity in early embryos, it has short-range effects which appear to be directly mediated, while in the patterning of the imaginal discs, it induces long range effects via the induction of secondary signals.
In vertebrates, several hedgehog genes have been cloned in the past few years. Of these genes, Shh has received most of the experimental attention, as it is expressed in different organizing centers which are the sources of signals that pattern neighboring tissues. Recent evidence indicates that Shh is involved in these interactions.
The expression of Shh starts shortly after the onset of gastrulation in the presumptive midline mesoderm, the node in the mouse (Chang et al. (1994) supra; Echelard, Y. et al. (1993)
Cell
75:1417-1430), the rat (Roelink, H. et al. (1994)
Cell
76:761-775) and the chick (Riddle, R. D. et al. (1993)
Cell
75:1401-1416), and the shield in the zebrafish (Ekker et al. (1995) supra; Krauss, S. et al.(1993)
Cell
75:1431-1444). In chick embyros, the Shh expression pattern in the node develops a left-right asymmetry, which appears to be responsible for the left-right situs of the heart (Levin, M. et al. (1995)
Cell
82:803-814).
In the CNS, Shh from the notochord and the floorplate appears to induce ventral cell fates. When ectopically expressed, Shh leads to a ventralization of large regions of the mid- and hindbrain in mouse (Echelard et al. (1993) supra
Baxter Anthony David
Boyd Edward Andrew
Guicherit Oivin M.
Porter Jeffrey
Price Stephen
Curis, Inc.
Jiang S.
Padmanabhan Sreeni
Ropes & Gray
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