- Newkirk, DA;
- Chen, YY;
- Flowers, E;
- Zeng, X;
- Kong, X;
- Yao, C;
- Ball, A;
- Kawauchi, S;
- Santos, R;
- Calof, AL;
- Lander, AD;
- Shi, Y;
- Xie, X;
- Yokomori, K
Cornelia de Lange Syndrome (CdLS) is a severe developmental
disorder frequently associated with heterozygous loss-of-function
NIPBL mutations. NIPBL loads cohesin onto chromatin. Cohesin
mediates sister chromatid cohesion important for mitosis, but is
also increasingly being recognized as a regulator of gene expression.
In CdLS patient cells and animal models, the presence of multiple
gene expression changes with little or no cohesion defect suggests
that disruption of gene regulation underlies this disorder. However,
the effect of NIP BL haploinsufficiency on cohesin binding, and how
this relates .to the clinical presentation of CdLS, has not been fully
investigated. We examined genome-wide cohesin binding and its
relationship to gene expression using mouse embryonic fibroblasts
(MEFs) from Nipbl +I- mice that recapitulate the CdLS phenotype.
We found a global decrease in cohesin binding, including
those at CTCF sites and repeat regions. Cohesin-bound genes are
enriched for H3K4me3 at the promoters and are mostly downregulated
in Nipbl mutant MEFs with evidence for reduced promoter-
enhancer interaction, suggesting that gene activation is the
primary co he sin function sensitive to Nip bl reduction. Over 50% of
genes affected in mutant MEFs are cohesin target genes, including
those involved in adipogenesis, indicating their direct contributions
to the Nipbl haploinsufficiency-induced CdLS phenotype.
Interestingly, mutations in several cohesin subunit genes exhibit
mild and somewhat distinct phenotypes compared to that of NIP BL
haploinsufficiency, raising the possibility that NIPBL may have
unique functions independent of cohesin. We will discuss our
recent findings that su11port the notion that the cohesin-independent
role ofNIPBL also contributes to the CdLS pathogenesis. This
work was supported in part by NIH grants P01-HD052860 and R21
HD062951.