Transposon mutagenesis with coat color genotyping identifies an essential role for Skor2 in sonic hedgehog signaling and cerebellum development

Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030, USA.
Development (Impact Factor: 6.46). 10/2011; 138(20):4487-97. DOI: 10.1242/dev.067264
Source: PubMed


Correct development of the cerebellum requires coordinated sonic hedgehog (Shh) signaling from Purkinje to granule cells. How Shh expression is regulated in Purkinje cells is poorly understood. Using a novel tyrosinase minigene-tagged Sleeping Beauty transposon-mediated mutagenesis, which allows for coat color-based genotyping, we created mice in which the Ski/Sno family transcriptional co-repressor 2 (Skor2) gene is deleted. Loss of Skor2 leads to defective Purkinje cell development, a severe reduction of granule cell proliferation and a malformed cerebellum. Skor2 is specifically expressed in Purkinje cells in the brain, where it is required for proper expression of Shh. Skor2 overexpression suppresses BMP signaling in an HDAC-dependent manner and stimulates Shh promoter activity, suggesting that Skor2 represses BMP signaling to activate Shh expression. Our study identifies an essential function for Skor2 as a novel transcriptional regulator in Purkinje cells that acts upstream of Shh during cerebellum development.

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    • "Mice that lack the extracellular matrix protein SLIT3 develop a central form of CDH and have a high rate of renal agenesis [29], [30]. To determine if Frem1 and Slit3 interact genetically in the development of CDH, renal agenesis and/or lung lobulation defects, we crossed Frem1eyes2/eyes2 mice to mice in which one copy of the Slit3 gene has been disrupted by insertion of a Sleeping Beauty-tyrosinase transposon (Slit3+/−) [46]. Mice that are homozygous for this Slit3 allele have renal agenesis and CDH and usually die at birth or shortly thereafter. "
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    ABSTRACT: The FRAS1-related extracellular matrix 1 (FREM1) gene encodes an extracellular matrix protein that plays a critical role in the development of multiple organ systems. In humans, recessive mutations in FREM1 cause eye defects, congenital diaphragmatic hernia, renal anomalies and anorectal malformations including anteriorly placed anus. A similar constellation of findings-microphthalmia, cryptophthalmos, congenital diaphragmatic hernia, renal agenesis and rectal prolapse-have been described in FREM1-deficient mice. In this paper, we identify a homozygous Frem1 missense mutation (c.1687A>T, p.Ile563Phe) in an N-ethyl-N-nitrosourea (ENU)-derived mouse strain, crf11, with microphthalmia, cryptophthalmos, renal agenesis and rectal prolapse. This mutation affects a highly conserved residue in FREM1's third CSPG domain. The p.Ile563Phe change is predicted to be deleterious and to cause decreased FREM1 protein stability. The crf11 allele also fails to complement the previously described eyes2 allele of Frem1 (p.Lys826*) providing further evidence that the crf11 phenotype is due to changes affecting Frem1 function. We then use mice bearing the crf11 and eyes2 alleles to identify lung lobulation defects and decreased anogenital distance in males as novel phenotypes associated with FREM1 deficiency in mice. Due to phenotypic overlaps between FREM1-deficient mice and mice that are deficient for the retinoic acid-responsive transcription factor GATA4 and the extracellular matrix protein SLIT3, we also perform experiments to look for in vivo genetic interactions between the genes that encode these proteins. These experiments reveal that Frem1 interacts genetically with Gata4 in the development of lung lobulation defects and with Slit3 in the development of renal agenesis. These results demonstrate that FREM1-deficient mice faithfully recapitulate many of the phenotypes seen in individuals with FREM1 deficiency and that variations in GATA4 and SLIT3 expression modulate some FREM1-related phenotypes in mice.
    Full-text · Article · Mar 2013 · PLoS ONE
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    • "Mouse mutants were generated at Baylor College of Medicine (Houston, TX) as previously described [18]. Female transgenic mice containing a Sleeping Beauty transposon-based coat color gene trap construct pT2. "
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    Full-text · Article · Oct 2012 · PLoS ONE
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    • "Significant levels of conservation for both neural-specific expression and amino acid sequence for CORL proteins suggest that the function of CORL in TGF/Activin signaling (facilitation of Smad2 activity) and CORL developmental roles (tissue-specific activation of gene expression) will be conserved in vertebrates. This hypothesis is supported by a recent paper describing a loss-of-function phenotype for mouse Corl2 in mice (Wang et al., 2011). In addition to gross cerebellar defects, homozygous mouse Corl2 mutant mice lack sonic hedgehog expression in Purkinje cells. "
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    ABSTRACT: CORL proteins (FUSSEL/SKOR proteins in humans) are related to Sno/Ski oncogenes but their developmental roles are unknown. We have cloned Drosophila CORL and show that its expression is restricted to distinct subsets of cells in the central nervous system. We generated a deletion of CORL and noted that homozygous individuals rarely survive to adulthood. Df(4)dCORL adult escapers display mushroom body (MB) defects and Df(4)dCORL larvae are lacking Ecdysone Receptor (EcR-B1) expression in MB neurons. This is phenocopied in CORL-RNAi and Smad2-RNAi clones in wild-type larvae. Furthermore, constitutively active Baboon (type I receptor upstream of Smad2) cannot stimulate EcR-B1 MB expression in Df(4)dCORL larvae, which demonstrates a formal requirement for CORL in Smad2 signaling. Studies of mouse Corl1 (Skor1) revealed that it binds specifically to Smad3. Overall, the data suggest that CORL facilitates Smad2 activity upstream of EcR-B1 in the MB. The conservation of neural expression and strong sequence homology of all CORL proteins suggests that this is a new family of Smad co-factors.
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