Constitutive activation of Wnt/β-catenin inhibits oligodendrocyte myelination. Tcf7l2/Tcf4, a β-catenin transcriptional partner, is required for oligodendrocyte differentiation. How Tcf7l2 modifies β-catenin signalling and controls myelination remains elusive. Here we define a stage-specific Tcf7l2-regulated transcriptional circuitry in initiating and sustaining oligodendrocyte differentiation. Multistage genome occupancy analyses reveal that Tcf7l2 serially cooperates with distinct co-regulators to control oligodendrocyte lineage progression. At the differentiation onset, Tcf7l2 interacts with a transcriptional co-repressor Kaiso/Zbtb33 to block β-catenin signalling. During oligodendrocyte maturation, Tcf7l2 recruits and cooperates with Sox10 to promote myelination. In that context, Tcf7l2 directly activates cholesterol biosynthesis genes and cholesterol supplementation partially rescues oligodendrocyte differentiation defects in Tcf712 mutants. Together, we identify stage-specific co-regulators Kaiso and Sox10 that sequentially interact with Tcf7l2 to coordinate the switch at the transitions of differentiation initiation and maturation during oligodendrocyte development, and point to a previously unrecognized role of Tcf7l2 in control of cholesterol biosynthesis for CNS myelinogenesis.

Complex I deficiency, the most common respiratory chain defect, is genetically heterogeneous: mutations in 8 nuclear and 7 mitochondrial DNA genes encoding complex I subunits have been described. However, these genes account for disease in only a minority of complex I-deficient patients. We investigated whether there may be an unknown common gene by performing functional complementation analysis of cell lines from 10 unrelated patients. Two of the patients were found to have mitochondrial DNA mutations. The other 8 represented 7 different (nuclear) complementation groups, all but 1 of which showed abnormalities of complex I assembly. It is thus unlikely that any one unknown gene accounts for a large proportion of complex I cases. The 2 patients sharing a nuclear complementation group had a similar abnormal complex I assembly profile and were studied further by homozygosity mapping, chromosome transfers, and microarray expression analysis. NDUFS6, a complex I subunit gene not previously associated with complex I deficiency, was grossly underexpressed in the 2 patient cell lines. Both patients had homozygous mutations in this gene, one causing a splicing abnormality and the other a large deletion. This integrated approach to gene identification offers promise for identifying other unknown causes of respiratory chain disorders.

T-cell infiltration into tumors represents a critical bottleneck for immune-mediated control of cancer. We previously showed that this bottleneck can be overcome by depleting immunosuppressive Foxp3+ regulatory T cells (Tregs), a process which can increase frequencies of tumor-infiltrating lymphocytes (TILs) through promoting development of specialized portals for lymphocyte entry, namely high endothelial venules (HEVs). In this paper, we used a carcinogen-induced tumor model, that allows for co-evolution of the tumor microenvironment and the immune response, to demonstrate that Treg depletion not only results in widespread disruption to HEV networks in lymph nodes (LNs) but activates CD8+ T cells, which then drive intratumoral HEV development. Formation of these vessels contrasts with ontogenic HEV development in LNs in that the process is dependent on TNF receptor and independent of lymphotoxin β receptor-mediated signaling. These intratumoral HEVs do not express the chemokine CCL21, revealing a previously undescribed intratumoral blood vessel phenotype. We propose a model where Treg depletion enables a self-amplifying loop of T-cell activation, which promotes HEV development, T-cell infiltration, and ultimately, tumor destruction. The findings point to a need to test for HEV development as part of ongoing clinical studies in patients with cancer.

The methyl-CpG binding proteins (MBPs) interpret the methylation of DNA and its components. The number of MBPs in the human body currently stands at 15, which are split into 3 branches, a reflection of the intricate mechanisms of gene regulation. Each branch utilizes a different mechanism for interacting with methylated DNA or its components. These interactions function to direct gene expression and maintain or alter DNA architecture. It is these functions that are commonly exploited in human disease. For this review, we will focus on each protein and any roles it may have in initiating, promoting, progressing, or inhibiting cancer. This will highlight common threads in the roles of these proteins, which will allow us to speculate on potentially productive directions for future research.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by mutations in either the TSC1 or the TSC2 genes and characterized by the development of benign hamartomatous growths in multiple organ systems. We have inactivated Tsc1 in the mouse germ line by gene targeting in ES cells and confirmed that the mutant allele (Tsc1-) has a recessive embryonic lethal phenotype. We found that a significant number (approximately 27%) of heterozygous (Tsc1+/-) mice on the C57BL/6 background died before weaning (P = 0.014) and show that these mice die in the post-natal period (P = 0.033), normally at 1-2 days, from unknown causes. Forty-four percent (7/16) of Tsc1+/- mice on a C3H background developed macroscopically visible renal lesions as early as 3-6 months, increasing to 95% (37/39) by 15-18 months. Renal lesions progressed from cysts through cystadenomas to solid carcinomas. Eighty percent (16/20) of Tsc1+/- mice on a Balb/c background exhibited solid renal cell carcinomas (RCC) by 15-18 months and in 41%, RCCs were > or = 5 mm, resulting in grossly deformed kidneys. Some RCCs had a sarcomatoid morphology of spindle cells in whorled patterns and metastasized to the lungs. We detected loss of the wild-type Tsc1 allele and elevated levels of p-mTOR and p-S6 in lesions from Tsc1+/- mice. This new murine model of hamartin deficiency exhibits a more severe phenotype than existing models.