SUMMARY The activity of keratinocytes in the hair follicle is regulated by signals from a specialized mesenchymal niche, the dermal papilla. Here, mice expressing cre recombinase in the dermal papilla were developed to probe the interaction between follicular keratinocyte populations and the dermal papilla in vivo. Inactivation of the β-catenin gene within the dermal papilla of fully developed hair follicles results in dramatically reduced proliferation of the progenitors and their immediate progeny that generate the hair shaft and, subsequently, premature induction of the destructive phase of the hair cycle (catagen). It also prevents regeneration of the cycling follicle from stem cells resident in the permanent portion of the follicle. Gene expression analysis reveals that β-catenin activity in the dermal papilla regulates at least two signaling pathways, FGF and IGF, that can mediate the inductive effects of the DP on keratinocytes. This study reveals a reciprocal signaling loop that employs Wnt/β-catenin signaling in both epithelial progenitor cells and their mesenchymal niche to govern and coordinate the interactions that are essential for the function of these two compartments.

While HLA-B*1502 is unlikely to be associated with carbamazepine-related or aromatic anti-epileptic agent-related SJS/TEN, HLA-B*5801 was significantly associated with allopurinol-related SJS/TEN in Japanese.

Cell fate decisions depend on the interplay between chromatin regulators and transcription factors. Here we show that activity of the Mi-2β nucleosome remodeling and deacetylase (NuRD) complex was controlled by the Ikaros family of lymphoid-lineage determining proteins. Ikaros, an integral component of the NuRD complex in lymphocytes, tethered this complex to active lymphoid differentiation genes. Loss in Ikaros DNA binding activity caused a local increase in Mi-2β chromatin remodeling and histone deacetylation and suppression of lymphoid gene expression. The NuRD complex also redistributed to transcriptionally poised non-Ikaros gene targets, involved in proliferation and metabolism, inducing their reactivation. Thus, release of NuRD from Ikaros regulation blocks lymphocyte maturation and mediates progression to a leukemic state by engaging functionally opposing epigenetic and genetic networks.