Nfatc1 orchestrates aging in hair follicle stem cells
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2013; 110 (51): E4950-E4959
NFIB is a governor of epithelial-melanocyte stem cell behaviour in a shared niche
2013; 495 (7439): 98-102
Hair production is fueled by stem cells (SCs), which transition between cyclical bouts of rest and activity. Here, we explore why hair growth wanes with age. We show that aged hair follicle SCs (HFSCs) in mice exhibit enhanced resting and abbreviated growth phases and are delayed in response to tissue-regenerating cues. Aged HFSCs are poor at initiating proliferation and show diminished self-renewing capacity upon extensive use. Only modestly restored by parabiosis, these features are rooted in elevated cell-intrinsic sensitivity and local elevation in bone morphogenic protein (BMP) signaling. Transcriptional profiling presents differences consistent with defects in aged HFSC activation. Notably, BMP-/calcium-regulated, nuclear factor of activated T-cell c1 (NFATc1) in HFSCs becomes recalcitrant to its normal down-regulating cues, and NFATc1 ChIP-sequencing analyses reveal a marked enrichment of NFATc1 target genes within the age-related signature. Moreover, aged HFSCs display more youthful levels of hair regeneration when BMP and/or NFATc1 are inhibited. These results provide unique insights into how skin SCs age.
View details for DOI 10.1073/pnas.1320301110
View details for Web of Science ID 000328548600006
View details for PubMedID 24282298
Sarm1, a negative regulator of innate immunity, interacts with syndecan-2 and regulates neuronal morphology
JOURNAL OF CELL BIOLOGY
2011; 193 (4): 769-784
Adult stem cells reside in specialized niches where they receive environmental cues to maintain tissue homeostasis. In mammals, the stem cell niche within hair follicles is home to epithelial hair follicle stem cells and melanocyte stem cells, which sustain cyclical bouts of hair regeneration and pigmentation. To generate pigmented hairs, synchrony is achieved such that upon initiation of a new hair cycle, stem cells of each type activate lineage commitment. Dissecting the inter-stem-cell crosstalk governing this intricate coordination has been difficult, because mutations affecting one lineage often affect the other. Here we identify transcription factor NFIB as an unanticipated coordinator of stem cell behaviour. Hair follicle stem-cell-specific conditional targeting of Nfib in mice uncouples stem cell synchrony. Remarkably, this happens not by perturbing hair cycle and follicle architecture, but rather by promoting melanocyte stem cell proliferation and differentiation. The early production of melanin is restricted to melanocyte stem cells at the niche base. Melanocyte stem cells more distant from the dermal papilla are unscathed, thereby preventing hair greying typical of melanocyte stem cell differentiation mutants. Furthermore, we pinpoint KIT-ligand as a dermal papilla signal promoting melanocyte stem cell differentiation. Additionally, through chromatin-immunoprecipitation with high-throughput-sequencing and transcriptional profiling, we identify endothelin 2 (Edn2) as an NFIB target aberrantly activated in NFIB-deficient hair follicle stem cells. Ectopically induced Edn2 recapitulates NFIB-deficient phenotypes in wild-type mice. Conversely, endothelin receptor antagonists and/or KIT blocking antibodies prevent precocious melanocyte stem cell differentiation in the NFIB-deficient niche. Our findings reveal how melanocyte and hair follicle stem cell behaviours maintain reliance upon cooperative factors within the niche, and how this can be uncoupled in injury, stress and disease states.
View details for DOI 10.1038/nature11847
View details for Web of Science ID 000316039800047
View details for PubMedID 23389444
Atg19 mediates a dual interaction cargo sorting mechanism in selective autophagy
MOLECULAR BIOLOGY OF THE CELL
2007; 18 (3): 919-929
Dendritic arborization is a critical neuronal differentiation process. Here, we demonstrate that syndecan-2 (Sdc2), a synaptic heparan sulfate proteoglycan that triggers dendritic filopodia and spine formation, regulates dendritic arborization in cultured hippocampal neurons. This process is controlled by sterile α and TIR motif-containing 1 protein (Sarm1), a negative regulator of Toll-like receptor 3 (TLR3) in innate immunity signaling. We show that Sarm1 interacts with and receives signal from Sdc2 and controls dendritic arborization through the MKK4-JNK pathway. In Sarm1 knockdown mice, dendritic arbors of neurons were less complex than those of wild-type littermates. In addition to acting downstream of Sdc2, Sarm1 is expressed earlier than Sdc2, which suggests that it has multiple roles in neuronal morphogenesis. Specifically, it is required for proper initiation and elongation of dendrites, axonal outgrowth, and neuronal polarization. These functions likely involve Sarm1-mediated regulation of microtubule stability, as Sarm1 influenced tubulin acetylation. This study thus reveals the molecular mechanism underlying the action of Sarm1 in neuronal morphogenesis.
View details for DOI 10.1083/jcb.201008050
View details for Web of Science ID 000290677500017
View details for PubMedID 21555464
Autophagy is a catabolic membrane-trafficking mechanism conserved in all eukaryotic cells. In addition to the nonselective transport of bulk cytosol, autophagy is responsible for efficient delivery of the vacuolar enzyme Ape1 precursor (prApe1) in the budding yeast Saccharomyces cerevisiae, suggesting the presence of a prApe1 sorting machinery. Sequential interactions between Atg19-Atg11 and Atg19-Atg8 pairs are thought responsible for targeting prApe1 to the vesicle formation site, the preautophagosomal structure (PAS), and loading it into transport vesicles, respectively. However, the different patterns of prApe1 transport defect seen in the atg11Delta and atg19Delta strains seem to be incompatible with this model. Here we report that prApe1 could not be targeted to the PAS and failed to be delivered into the vacuole in atg8Delta atg11Delta double knockout cells regardless of the nutrient conditions. We postulate that Atg19 mediates a dual interaction prApe1-sorting mechanism through independent, instead of sequential, interactions with Atg11 and Atg8. In addition, to efficiently deliver prApe1 to the vacuole, a proper interaction between Atg11 and Atg9 is indispensable. We speculate that Atg11 may elicit a cargo-loading signal and induce Atg9 shuttling to a specific PAS site, where Atg9 relays the signal and recruits other Atg proteins to induce vesicle formation.
View details for DOI 10.1091/mbc.E06-08-0683
View details for Web of Science ID 000244761500022
View details for PubMedID 17192412