Hedgehog


TRANSPARENCY
M. Murone et al., Hedgehog signal transduction: From flies to Vertebrates, Exp. Cell. Res. 253, 25-33, 1999
Drosophila segment polarity gene
Shh (one of several in mammals) controls patterning and is involved in left-right
if gene is missing, cyclopia and many structural defects
cleavage to active 19 kDa N-terminal segment by catalysis by 26-28 kDa C-terminal peptide
N-terminal is palmitoylated at N-terminus and has cholesterol at C-terminus
Patched (Ptc)(12 transmembrane) negative regulator
Smoothened (Smo) positive regulator but it does not bind Shh
Smo is like Frizzled (Wnt/Wingless receptor)
Hh binds to Ptc, Ptc stops repressing Smo
Cubitus interruptus Ci/Gli is a downstream zinc finger transcription factor
target genes: ptc, wb and dpp (decapentaplegic)
Ci-155 active or N-terminal cleaved Ci-75 repressor

PWIngham, Transducing hedgehog: the story so far, EMBO Journal 17, 3505-3511, 1998, on line
Another figure to show the same thing

Steven Dickman, The left-handed gene, Discover 17-8, 70-75, August, 1996.
development from embryonic limb bud
1968 John Sanders showed that transplanted tissue has signal to make digits and polartiy comes from region ZPA (zone of polarizing activity)
Christiane Nusslein-Volhard & Eric Wieschaus 1980-> work on Drosophila
hedgehog - embryo lacking hh is porcupine-like
signal that maintains polarity in segments
Cliff Tabin - Sonic hedgehog is ZPA signal in chicken (because that lab likes loud music)
there's olts of vertebrate hedgehogs like tidiwinkle (who was a hedgehog)
More Sonic on left than right. Change distribution by transplantation, heart not necessarily on left

Mark Peifer, The two faces of hedgehog, Science 266, 1492-1493, 1994
Christiane Nusslein-Volhard & Eric Wieschaus late 1970's did their work which results in the following run-down of types of developmental molecules:
signal - wingless like vertebrate Wnt
receptors - DER Drosophila EGF receptor
transcription factors - Paired like vertebrate Pax
Hedgehog is segment polarity signal

S. S. Blair, Hedgehog digs up an old friend (News and views - Developmental Biology), Nature 373 656-657, 1995
diffusable morphogen
reception via cAMP -> PKA
clones lacking PKA have phenotype like clones expressing hh
expression in posterior cells controls gene expression to the anterior
vertebrate who's who of inducers: notochord, ZPA, floor plate express hh
receptors poorly understood:
Patched (Ptc) in Drosophila transmembrane protein is a candidate
TRANSPARENCY
hh posterior -> anterior Dpp (TGF-beta family) (compartments and eye)
Wingless (Wnt family)

R. L. Johnson & C. Tabin, The long and the short of hedgehog signalling (Minireview), Cell 81 313-316, 1995
morphogens organize cell fates relative to discrete inducing tissue
hh found in 1980 by Nusslein-Volhard and Wieschaus
over short range induce cells to secrete dpp which can act over long range
SHH D - V patterning of neural tube
A - P axis of limb bud
non-cell autonomous consistent with secreted
Processing (1) signal sequence cleavage
(2) self-cleaving into N-terminal (local active) & C-terminal (distance proteolysis)
maybe lower dose for distant effects of second messenger
polarizing activity P limb bud transplanted to anterior limb bud->mirror image extra
SHH mimics ZPA activity (both long and short range

M. Dominguez et al., Sending and receiving the Hedgehog signal: Control by the Drosophila Gli protein Cubitus interruptus, Science 272 1621-1625, 1996
E. Pennisi, Gene linked to commonist cancer (Research News) Science 272 1583-1584, 1996
[Ed. by P. Ssuromi, A patched path to cancer (This Week in Science) Science 272 1561, 1996]
basal cell carcinoma most common cancer:
sporatic in middle age
basal cell nevus syndrome mutant in human homologue of patched gene
Drosophila patched is transmembrane protein which down-regulates
growth factor genes
TRANSPARENCY
GLI (oncogene in rare brain tumor in human) = Ci
cubitus interruptus is a transcription factor
protein from Wnt1 (mice) = Drosophila wg stimulates Hedgehog production
cause mammary tumors when overactive

W. Roush, Hedgehog's patterning call is patched through, smoothly (Developmental biology), Science 274, 1996, 1304-1305
Patched works by interrupting the Smo (smoothened) signal
with Shh, the Smo signal gets through

G. Martin, Pass the butter... (Perspectives), Science 274, 203-204, 1996
hedgehog acts in short and long rang signalling
NH2-terminal (Hh-N) has signalling activity
COOH-terminal (Hh-C) has determinants for autoprocessing
processing is to cleave Hh-N from Hh-C and to attach lipid which, oddly, is cholesterol
It is thought that the cholesterol form, by sticking to membranes would work for short range signalling while a non-modified form would go further

D.I.Lewin, A single gene may tell the embryo left from right (News), Journal of NIH Research, 9 (January), 32- 33, 1997
dorsal-ventral and anterior-posterior better studied than left right in bilaterally "symetric" animals
refers to C. Tabin's work on how there is an asymmetry of shh
maternal mRNA from vegetal 1 (Vg1), in TGF-beta superfamily of diffusable growth factors, processed differently in left and right
also an asymmetry in Xenopus nodal-related 1 (Xnr-1), another maternal mRNA
injection of modified Vg1 containing processing region of bone morphogenic protein 2 (BVg1 mRNA) reverses symmetry
thus symmetry is from differing processings of Vg1 protein
thus there is something like TGF-beta working
chicken nodal-related (cNR), like the mouse nodal required for primitive streak in early embryo, are in TGF-beta family
iv=situs inversus viscerum - regulates Nodal, also:
inv=inversion of embryonic turning (inv)- if mutant mice are reversed for Nodal expression
lefty codes TGF-beta homologue expressed on the left, on right in inv mutant
thus inv important in regulating right-left

K. Hopkin, Wnt world: A window on gastrulation, development, and cancer (News) Journal of NIH Research, 9 (June) 21-23, 1997
TRANSPARENCY
Only last year do they know that frizzled is membrane receptor (fly bristles look unkempt)
has 7 transmembrane domains and a cysteine rich domain that binds Wnts
FRPs Frzb's (frizzled related proteins) antagonize Wnt by competitively binding Wnt outside cell
have cysteine rich domains but lack the membran anchoring
in melanomas and colon cancers, beta-catenin accumulates upon Wnt activation
there are lots (>16) different Wnts in different developmental pathways
there are also lots of frizzled receptors
See figure for involvement of APC and GSG which phosphorylate beta-catenin to mark it for ubiquitinization for degradation by the proteasome
otherwise, beta-catenin helps transcription by a factor called Tcf-Lef
Armidillo is fly beta-catenin

Notch (named after notch in wing)

S, Artavanis-Tsakonas et al., Notch signalling, Science 268 225-232, 1995
Here's the scheme:
Multicellular development: sequential action of genes
maternal-effect: (1) anterior, (2) posterior, (3) terminal, (4) dorso-ventral
zygotic: (1) gap, (2) pair rule, (3)segment polarity
then homeotic assigns segments
Specification
(1) lineage
(2) regulation by cell interaction
(i) "lateral" specification if cells were initially equivalent
(ii) ""Inductive" if nonequivalent
Notch in Drosophila and homologues in vertebrates
also lin-12 and glp-1 in C. elegans
TRANSPARENCY 300 kD w/ 36 EGF (epidermal growth factor) repeats
3 cysteine rich Notch/Lin-12 repeats
6 Ankyrin repeats
1 PEST (signal sequence for ubiquitinization)
ectoderm -> neuroblasts (delaminate)
dermmblasts
pro-neural express achaete-scute transcription factors
without Notch, all ectodermal cells continue to express
So Notch was called "neurogenic" but that does injustice to its multitude effects
Participates in both lateral and inductive signalling
in C. elegans, participates in anchor cell, uterine precursor & vulval precursor
vertebrate throughout development and in certain neoplasms
ligands shown in figure
some question about scabrous product involved in R8 spacing
also possibility of wingless product related to Wnt-1 proto-oncoprotein
pathway (TRANSPARENCY)
deltex encodes 737 a.a. cytoplasmic protein binds to ankyrin repeats
Suppressor of Hairless - product like several transcription factors
does detex multimerize Notch to interfere with Su(H)?
Hairless (novel basic protein) vs its supressor - adult sensory
Enhancer of split "complex" - 7 bHLH and another protein
mastermind shows up in modifier screens

J. D. Axelrod et al. Interaction between Wingless and Notch signalling pathways mediated by disheveled, Science 371 1826-1832, 1996
S.S.Blair, Notch and Wingless signals collide Science 371 1822-1823, 1996
ed. by P. Szuromi Inhibited by cross talk (This week in Science) Science 371 1785, 1996
The last paper was cautious in implicating wingless, here it is shown
TRANSPARENCY
dishevelled (dsh) protein of unknown protein
zeste-white 3 (zw3) = shaggy serine-threonine kinases
armadillo (arm) homologue of b-catenin (intracellular attachment protein)
(hooks membrane things to actin)
wingless signal is not known
Dsh inhibits Notch
Sgg-Zw3 phosphorylates and inactivates Arm

H. Kramer, RIPping notch apart: a new role for endocytosis in signal transduction? Science's STKE
DSL = Delta Serrate (Drosophila) Lag-2 (C. elegans
RIP = regulated intramembrane proteolysis
CSL = CBF1, Su(H), Lag-1 [CSL is a family of DNA binding proteins]
S1 cleavage makes notch receptor, S2 cuts off all but 12 a.a's on outside, S3 releases intracellular transcriptionally active domain (ICD)
S3 cut made by enzyme like gamma-secretase (Presenilin) thaty cuts APP (amyloid precursor protein) to make beta-amyloid that contributes to extracellular plaques


References:

M. Murone et al., Hedgehog signal transduction: From flies to Vertebrates, Exp. Cell. Res. 253, 25-33, 1999

PWIngham, Transducing hedgehog: the story so far, EMBO Journal 17, 3505-3511, 1998, on line


Steven Dickman, The left-handed gene, Discover 17-8, 70-75, August, 1996

Mark Peifer, The two faces of hedgehog, Science 266, 1492-1493, 1994

S. S. Blair, Hedgehog digs up an old friend (News and views - Developmental Biology), Nature 373 656-657, 1995

R. L. Johnson & C. Tabin, The long and the short of hedgehog signalling (Minireview), Cell 81 313-316, 1995

M. Dominguez et al., Sending and receiving the Hedgehog signal: Control by the Drosophila Gli protein Cubitus interruptus, Science 272 1621-1625, 1996

W. Roush, Hedgehog's patterning call is patched through, smoothly (Developmental biology), Science 274, 1996, 1304-1305

G. Martin, Pass the butter... (Perspectives), Science 274, 203-204, 1996

D.I.Lewin, A single gene may tell the embryo left from right (News), Journal of NIH Research, 9 (January), 32- 33, 1997

J. D. Axelrod et al. Interaction between Wingless and Notch signalling pathways mediated by disheveled, Science 371 1826-1832, 1996

Notch

S, Artavanis-Tsakonas et al., Notch signalling, Science 268 225-232, 1995

J. D. Axelrod et al. Interaction between Wingless and Notch signalling pathways mediated by disheveled, Science 371 1826-1832, 1996

S.S.Blair, Notch and Wingless signals collide Science 371 1822-1823, 1996

ed. by P. Szuromi Inhibited by cross talk (This week in Science) Science 371 1785, 1996

H. Kramer, RIPping notch apart: a new role for endocytosis in signal transduction? Science's STKE


This page was last updated on January 25, 2002

Return to Stark home page
Return to Signal Transduction Syllabus