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Hum Mol Genet. 2015 Jul 15;24(14):3994-4005. doi: 10.1093/hmg/ddv137. Epub 2015 Apr 15.

Novel Jbts17 mutant mouse model of Joubert syndrome with cilia transition zone defects and cerebellar and other ciliopathy related anomalies.

Author information

1
Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
2
Department of Cell and Developmental Biology and.
3
Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA and.
4
Sainte-Justine Hospital Research Center, Montreal H3T1C5, Canada.
5
Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA, cel36@pitt.edu.

Abstract

Recent studies identified a previously uncharacterized gene C5ORF42 (JBTS17) as a major cause of Joubert syndrome (JBTS), a ciliopathy associated with cerebellar abnormalities and other birth defects. Here we report the first Jbts17 mutant mouse model, Heart Under Glass (Hug), recovered from a forward genetic screen. Exome sequencing identified Hug as a S235P missense mutation in the mouse homolog of JBTS17 (2410089e03rik). Hug mutants exhibit multiple birth defects typical of ciliopathies, including skeletal dysplasia, polydactyly, craniofacial anomalies, kidney cysts and eye defects. Some Hug mutants exhibit congenital heart defects ranging from mild pulmonary stenosis to severe pulmonary atresia. Immunostaining showed JBTS17 is localized in the cilia transition zone. Fibroblasts from Hug mutant mice and a JBTS patient with a JBTS17 mutation showed ciliogenesis defects. Significantly, Hug mutant fibroblasts showed loss of not only JBTS17, but also NPHP1 and CEP290 from the cilia transition zone. Hug mutants exhibited reduced ciliation in the cerebellum. This was associated with reduction in cerebellar foliation. Using a fibroblast wound-healing assay, we showed Hug mutant cells cannot establish cell polarity required for directional cell migration. However, stereocilia patterning was grossly normal in the cochlea, indicating planar cell polarity is not markedly affected. Overall, we showed the JBTS pathophysiology is replicated in the Hug mutant mice harboring a Jbts17 mutation. Our findings demonstrate JBTS17 is a cilia transition zone component that acts upstream of other Joubert syndrome associated transition zone proteins NPHP1 and CEP290, indicating its importance in the pathogenesis of Joubert syndrome.

PMID:
25877302
PMCID:
PMC4476446
DOI:
10.1093/hmg/ddv137
[Indexed for MEDLINE]
Free PMC Article

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