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Preaxial polydactyly caused by Gli3 haploinsufficiency is rescued by Zic3 loss of function in mice

Division of Molecular Cardiovascular Biology, Cincinnati Children’s Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA.
Human Molecular Genetics (Impact Factor: 6.68). 01/2012; 21(8):1888-96. DOI: 10.1093/hmg/dds002
Source: PubMed

ABSTRACT Limb anomalies are important birth defects that are incompletely understood genetically and mechanistically. GLI3, a mediator of hedgehog signaling, is a genetic cause of limb malformations including pre- and postaxial polydactyly, Pallister-Hall syndrome and Greig cephalopolysyndactyly. A closely related Gli (glioma-associated oncogene homolog)-superfamily member, ZIC3, causes X-linked heterotaxy syndrome in humans but has not been investigated in limb development. During limb development, post-translational processing of Gli3 from activator to repressor antagonizes and posteriorly restricts Sonic hedgehog (Shh). We demonstrate that Zic3 and Gli3 expression overlap in developing limbs and that Zic3 converts Gli3 from repressor to activator in vitro. In Gli3 mutant mice, Zic3 loss of function abrogates ectopic Shh expression in anterior limb buds, limits overexpression in the zone of polarizing activity and normalizes aberrant Gli3 repressor/Gli3 activator ratios observed in Gli3+/- embryos. Zic3 null;Gli3+/- neonates show rescue of the polydactylous phenotype seen in Gli3+/- animals. These studies identify a previously unrecognized role for Zic3 in regulating limb digit number via its modifying effect on Gli3 and Shh expression levels. Together, these results indicate that two Gli superfamily members that cause disparate human congenital malformation syndromes interact genetically and demonstrate the importance of Zic3 in regulating Shh pathway in developing limbs.

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Available from: Stephanie M Ware, Aug 02, 2015
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    • "A polyalanine tract expansion in one of these patients [Wessels et al., 2010] is particularly intriguing as similar tract expansions have been associated with a variety of human genetic disorders, including holoprosencephaly caused by mutations in ZIC2 [Messaed and Rouleau, 2009]. Both the complexity of ZIC3-associated phenotypes and its broad expression during embryogenesis [McMahon and Merzdorf, 2010; Nagai et al., 1997; Quinn et al., 2012] are indicative of diversity in ZIC3 developmental function, including recognized roles in neural and neural crest development [Nakata et al., 1997; Klootwijk et al., 2000], limb bud digitation [Quinn et al., 2012], cardiac morphogenesis , and L–R patterning [Jiang et al., 2013; Kitaguchi et al., 2000; Purandare et al., 2002; Sutherland et al., 2013; Ware et al., 2004, 2006a, 2006b; Zhu et al., 2007a, 2007b]. Studies utilizing Zic3-null mice suggest that Zic3 is required for progression into and through gastrulation [Ware et al., 2006a; Cast et al., 2012] and that it acts upstream of Nodal signaling at the embryonic node [Purandare et al., 2002; Ware et al., 2006b]. "
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    ABSTRACT: Mutations in zinc-finger in cerebellum 3 (ZIC3) result in heterotaxy or isolated congenital heart disease (CHD). The majority of reported mutations cluster in zinc-finger domains. We previously demonstrated that many of these lead to aberrant ZIC3 subcellular trafficking. A relative paucity of N- and C-terminal mutations has, however, prevented similar analyses in these regions. Notably, an N-terminal polyalanine expansion was recently identified in a patient with VACTERL, suggesting a potentially distinct function for this domain. Here, we report ZIC3 sequencing results from 440 unrelated patients with heterotaxy and CHD, the largest cohort yet examined. Variants were identified in 5.2% of sporadic male cases. This rate exceeds previous estimates of 1% and has important clinical implications for genetic testing and risk-based counseling. Eight of 11 were novel, including 5 N-terminal variants. Subsequent functional analyses included 4 additional reported but untested variants. Aberrant cytoplasmic localization and decreased luciferase transactivation were observed for all zinc-finger variants, but not for downstream or in-frame upstream variants, including both analyzed polyalanine expansions. Collectively, these results expand the ZIC3 mutational spectrum, support a higher than expected prevalence in sporadic cases, and suggest alternative functions for terminal mutations, highlighting a need for further study of these domains. This article is protected by copyright. All rights reserved.
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    • "Aberrations in Gli3 are known to cause craniofacial dysmorphisms in both human and mice models. One result of altered Gli3 sequence is Greig cephalopolysyndactly syndrome, which causes metopic synostosis and is characterized by polydactyly and hypertelorism (Hui and Joyner, 1993; Quinn et al., 2012; Veistinen et al., 2012). Another caused by mutations in the Gli3 effector is Pallister-Hall Syndrome, with common craniofacial findings including disrupted midline development and abnormalities such as a short nose with flat nasal bridge, and cleft palate (Kuo et al., 1999; Naruse et al., 2010). "
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