NFI transcription factors provide chromatin access to maintain stem cell identity while preventing unintended lineage fate choices.

Tissue homeostasis and regeneration rely on resident stem cells (SCs), whose behaviour is regulated through niche-dependent crosstalk. The mechanisms underlying SC identity are still unfolding. Here, using spatiotemporal gene ablation in murine hair follicles, we uncover a critical role for the transcription factors (TFs) nuclear factor IB (NFIB) and IX (NFIX) in maintaining SC identity. Without NFI TFs, SCs lose their hair-regenerating capability, and produce skin bearing striking resemblance to irreversible human alopecia, which also displays reduced NFIs. Through single-cell transcriptomics, ATAC-Seq and ChIP-Seq profiling, we expose a key role for NFIB and NFIX in governing super-enhancer maintenance of the key hair follicle SC-specific TF genes. When NFIB and NFIX are genetically removed, the stemness epigenetic landscape is lost. Super-enhancers driving SC identity are decommissioned, while unwanted lineages are de-repressed ectopically. Together, our findings expose NFIB and NFIX as crucial rheostats of tissue homeostasis, functioning to safeguard the SC epigenome from a breach in lineage confinement that otherwise triggers irreversible tissue degeneration.

Clinicopathologic characteristics of early-onset Becker's nevus in Korean children and adolescents.

BACKGROUND: Becker's nevus (BN) presents as a hairy patch or plaque with or without proliferation of the dermal smooth muscles. BN has been described as acquired as found in a similar entity, congenital smooth muscle hamartoma (CSMH). This study was aimed at evaluating the clinicopathological aspects of BN in Korean cases in differential diagnosis with CSMH. METHODS: We performed a retrospective study of 103 patients histopathologically diagnosed as having BN or CSMH. The cases included 40 cases diagnosed with BN or CSMH before the age of 10 years who had clinical monitoring and a second skin biopsy after puberty to determine the disease course. RESULTS: Among cases of children to adolescents (<18 years), we observed a slight male predominance. Among children aged <14 years, sex ratio converged at 1:1. Early-onset BN showed a female predominance and hyperpigmented skin lesions. All BN cases showed hyperpigmentation, and face and neck involvement tended to make severe cosmetic concerns. In contrast, hypertrichosis was more frequent in CSMH. Either skin-colored lesion or pseudo-Darier's sign was not seen in early-onset BN. BN showed less dermal smooth muscle than CSMH. CONCLUSIONS: Androgens themselves do not seem to be related to the development of BN but play only an aggravating role especially in male patients. Considering high occurrence in exposed areas, BN may distress patients severely. As early laser treatment may be helpful in some patients with BN, early-onset BN in comparison to CSMH should be diagnosed appropriately.

Metastatic Crohn disease clinically reminiscent of erythema nodosum on the right leg.

Cutaneous manifestations are well-recognized complications of Crohn disease (CD) that can be divided into disease-specific and reactive conditions. One of the most common reactive conditions is erythema nodosum (EN), which presents as subcutaneous tender nodules most often on the legs. On the other hand, metastatic Crohn disease (MCD) is a rare cutaneous manifestation of CD defined as the presence of noncaseating granulomas that are not contiguous with the gastrointestinal (GI) tract. The clinical presentation of MCD is variable; however, lesions often are located on the legs and genital region. We report the case of a 21-year-old woman with a 6-year history of CD who presented with MCD clinically simulating EN.