McLellan JS, Zheng X, Hauk G, Ghirlando R, Beachy PA, Leahy DJ.. The mode of Hedgehog binding to Ihog homologues is not conserved across different phyla. Nature 455: 979-983

Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Nature (Impact Factor: 41.46). 10/2008; 455(7215):979-83. DOI: 10.1038/nature07358
Source: PubMed


Hedgehog (Hh) proteins specify tissue pattern in metazoan embryos by forming gradients that emanate from discrete sites of expression and elicit concentration-dependent cellular differentiation or proliferation responses. Cellular responses to Hh and the movement of Hh through tissues are both precisely regulated, and abnormal Hh signalling has been implicated in human birth defects and cancer. Hh signalling is mediated by its amino-terminal domain (HhN), which is dually lipidated and secreted as part of a multivalent lipoprotein particle. Reception of the HhN signal is modulated by several cell-surface proteins on responding cells, including Patched (Ptc), Smoothened (Smo), Ihog (known as CDO or CDON in mammals) and the vertebrate-specific proteins Hip (also known as Hhip) and Gas1 (ref. 11). Drosophila Ihog and its vertebrate homologues CDO and BOC contain multiple immunoglobulin and fibronectin type III (FNIII) repeats, and the first FNIII repeat of Ihog binds Drosophila HhN in a heparin-dependent manner. Surprisingly, pull-down experiments suggest that a mammalian Sonic hedgehog N-terminal domain (ShhN) binds a non-orthologous FNIII repeat of CDO. Here we report biochemical, biophysical and X-ray structural studies of a complex between ShhN and the third FNIII repeat of CDO. We show that the ShhN-CDO interaction is completely unlike the HhN-Ihog interaction and requires calcium, which binds at a previously undetected site on ShhN. This site is conserved in nearly all Hh proteins and is a hotspot for mediating interactions between ShhN and CDO, Ptc, Hip and Gas1. Mutations in vertebrate Hh proteins causing holoprosencephaly and brachydactyly type A1 map to this calcium-binding site and disrupt interactions with these partners.

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Available from: Xiaoyan Zheng, Dec 17, 2014
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    • "More recently, a number of co-receptors for Shh have been identified in the mouse, which include the GPI-linked membrane glycoprotein Growth arrest-specific 1 (Gas1) (Martinelli and Fan, 2007) and the closely related Ig/fibronectin single-pass membrane-spanning cell adhesion proteins Cdon (cell adhesion associated, oncogene regulated) and Boc (Boc cell adhesion associated, oncogene regulated) (Kang et al., 1997; Kang et al., 2002). Gas1, Cdon and Boc are able to interact directly with Shh (Lee et al., 2001a; Martinelli and Fan, 2007; McLellan et al., 2008; Okada et al., 2006; Tenzen et al., 2006) and form high-affinity individual complexes with Ptch1 on the surface of receiving cells (Bae et al., 2011; Izzi et al., 2011). Collectively, these three co-receptors demonstrate a co-operative and obligatory role during Shh signaling. "
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    ABSTRACT: Holoprosencephaly is a heterogeneous developmental malformation of the central nervous system characterized by impaired forebrain cleavage, midline facial anomalies and wide phenotypic variation. Indeed, microforms represent the mildest manifestation, associated with facial anomalies but an intact central nervous system. In many cases, perturbations in sonic hedgehog signaling are responsible for holoprosencephaly. Here, we have elucidated the contribution of Gas1 and an additional hedgehog co-receptor, Boc during early development of the craniofacial midline, by generating single and compound mutant mice. Significantly, we find Boc has an essential role in the etiology of a unique form of lobar holoprosencephaly that only occurs in conjunction with combined loss of Gas1. Whilst Gas1(-/-) mice have microform holoprosencephaly characterized by a single median maxillary central incisor, cleft palate and pituitary anomalies, Boc(-/-) mice have a normal facial midline. However, Gas1(-/-); Boc(-/-) mutants have lobar holoprosencephaly associated with clefting of the lip, palate and tongue, secondary to reduced sonic hedgehog transduction in the central nervous system and face. Moreover, maxillary incisor development is severely disrupted in these mice, arresting prior to cellular differentiation as a result of apoptosis in the odontogenic epithelium. Thus, Boc and Gas1 retain an essential function in these tooth germs, independent of their role in midline development of the central nervous system and face. Collectively, this phenotype demonstrates both redundancy and individual requirements for Gas1 and Boc during sonic hedgehog transduction in the craniofacial midline and suggests BOC as a potential digenic locus for lobar holoprosencephaly in human populations.
    Full-text · Article · Jul 2014 · Biology Open
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    • "GAS1 induces cell arrest and apoptosis because of its molecular similarity with the receptors for the glial cell-line derived neurotrophic factor (GDNF) family of ligands (GFRαs), which allows GAS1 to inhibit the intracellular survival signaling evoked by GDNF (Schueler- Furman et al. 2006; Lopez-Ramirez et al. 2008; Zarco et al. 2012; Dominguez-Monzon et al. 2011). However, there is also evidence for the interaction of GAS1 with sonic hedgehog (SHH) and Indian hedgehog (IHH), related hedgehog (HH) proteins (McLellan et al. 2008). This interaction was originally interpreted as antagonistic, but more recent work indicates this to be a cooperative effect between these two molecules (Lee, Buttitta, and Fan 2001; Allen, Tenzen, and McMahon 2007; Martinelli and Fan 2007; Allen et al. 2011; Izzi et al. 2011). "
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    ABSTRACT: Growth arrest specific 1 (GAS1) is a pleiotropic protein that induces apoptosis and cell arrest in different tumors, but it is also involved in the development of the nervous system and other tissues and organs. This dual ability is likely caused by its capacity to interact both by inhibiting the intracellular signaling cascade induced by glial cell-line derived neurotrophic factor and by facilitating the activity of the sonic hedgehog pathway. The presence of GAS1 mRNA has been described in adult mouse brain, and here we corroborated this observation. We then proceeded to determine the distribution of the protein in the adult central nervous system (CNS). We detected, by western blot analysis, expression of GAS1 in olfactory bulb, caudate-putamen, cerebral cortex, hippocampus, mesencephalon, medulla oblongata, cerebellum, and cervical spinal cord. To more carefully map the expression of GAS1, we performed double-label immunohistochemistry and noticed expression of GAS1 in neurons in all brain areas examined. We also observed expression of GAS1 in astroglial cells, albeit the pattern of expression was more restricted than that seen in neurons. Briefly, in the present article, we report the widespread distribution and cellular localization of the GAS1 native protein in adult mammalian CNS.
    Full-text · Article · Jun 2013 · Journal of Histochemistry and Cytochemistry
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    • "Of these, boi, in particular, stands out. boi, and its paralog, interference hedgehog (ihog, FBgn0031872) have recently been shown to encode proteins critical for Hedgehog (Hh) signaling during Drosophila wing development [52]–[59]. Currently, neither has been implicated in leg development. However, since Hh signaling is critical in the legs, it is reasonable that these genes could play a part in leg development and that SNPs in these genes could contribute to quantitative variation in leg phenotypes. "
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    ABSTRACT: The adult Drosophila melanogaster body develops from imaginal discs, groups of cells set-aside during embryogenesis and expanded in number during larval stages. Specification and development of Drosophila imaginal discs have been studied for many years as models of morphogenesis. These studies are often based on mutations with large developmental effects, mutations that are often lethal in embryos when homozygous. Such forward genetic screens can be limited by factors such as early lethality and genetic redundancy. To identify additional genes and genetic pathways involved in leg imaginal disc development, we employed a Genome Wide Association Study utilizing the natural genetic variation in leg proportionality found in the Drosophila Genetic Reference Panel fly lines. In addition to identifying genes already known to be involved in leg development, we identified several genes involved in pathways that had not previously been linked with leg development. Several of the genes appear to be involved in signaling activities, while others have no known roles at this time. Many of these uncharacterized genes are conserved in mammals, so we can now begin to place these genes into developmental contexts. Interestingly, we identified five genes which, when their function is reduced by RNAi, cause an antenna-to-leg transformation. Our results demonstrate the utility of this approach, integrating the tools of quantitative and molecular genetics to study developmental processes, and provide new insights into the pathways and networks involved in Drosophila leg development.
    Full-text · Article · Apr 2013 · PLoS ONE
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