Human Molecular Genetics Advance Access originally published online on April 7, 2008
Human Molecular Genetics 2008 17(14):2118-2131; doi:10.1093/hmg/ddn110
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Published by Oxford University Press 2008
A sensitized mutagenesis screen identifies Gli3 as a modifier of Sox10 neurocristopathy
1 Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA 2 Laboratorio di Genetica Molecolare, Instituto G. Gaslini, Genova, Italy
* To whom correspondence should be addressed at: Mouse Embryology Section, Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Building 49, Room 4A82, 49 Convent Drive, Bethesda, MD 20892-4472, USA. Tel: +1 3014967584; Fax: +1 3014022170; Email: bpavan{at}mail.nih.gov
Received January 25, 2008; Revised March 5, 2008; Accepted April 2, 2008
Haploinsufficiency for the transcription factor SOX10 is associated with the pigmentary deficiencies of Waardenburg syndrome (WS) and is modeled in Sox10 haploinsufficient mice (Sox10LacZ/+). As genetic background affects WS severity in both humans and mice, we established an N-ethyl-N-nitrosourea (ENU) mutagenesis screen to identify modifiers that increase the phenotypic severity of Sox10LacZ/+ mice. Analysis of 230 pedigrees identified three modifiers, named modifier of Sox10 neurocristopathies (Mos1, Mos2 and Mos3). Linkage analysis confirmed their locations on mouse chromosomes 13, 4 and 3, respectively, within regions distinct from previously identified WS loci. Positional candidate analysis of Mos1 identified a truncation mutation in a hedgehog(HH)-signaling mediator, GLI-Kruppel family member 3 (Gli3). Complementation tests using a second allele of Gli3 (Gli3Xt-J) confirmed that a null mutation of Gli3 causes the increased hypopigmentation in Sox10LacZ/+;Gli3Mos1/+ double heterozygotes. Early melanoblast markers (Mitf, Sox10, Dct, and Si) are reduced in Gli3Mos1/Mos1 embryos, indicating that loss of GLI3 signaling disrupts melanoblast specification. In contrast, mice expressing only the GLI3 repressor have normal melanoblast specification, indicating that the full-length GLI3 activator is not required for specification of neural crest to the melanocyte lineage. This study demonstrates the feasibility of sensitized screens to identify disease modifier loci and implicates GLI3 and other HH signaling components as modifiers of human neurocristopathies.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.