Sox9 marks limbal stem cells and is required for asymmetric cell fate switch in the corneal epithelium.

Adult tissues with high cellular turnover require a balance between stem cell renewal and differentiation, yet the mechanisms underlying this equilibrium are unclear. The cornea exhibits a polarized lateral flow of progenitors from the peripheral stem cell niche to the center; attributed to differences in cellular fate. To identify genes that are critical for regulating the asymmetric fates of limbal stem cells and their transient amplified progeny in the central cornea, we utilized an in vivo cell cycle reporter to isolate proliferating basal cells across the anterior ocular surface epithelium and performed single-cell transcriptional analysis. This strategy greatly increased the resolution and revealed distinct basal cell identities with unique expression profiles of structural genes and transcription factors. We focused on Sox9; a transcription factor implicated in stem cell regulation across various organs. Sox9 was found to be differentially expressed between limbal stem cells and their progeny in the central corneal. Lineage tracing analysis confirmed that Sox9 marks long-lived limbal stem cells and conditional deletion led to abnormal differentiation and squamous metaplasia in the central cornea. These data suggest a requirement for Sox9 for the switch to asymmetric fate and commitment toward differentiation, as transient cells exit the limbal niche. By inhibiting terminal differentiation of corneal progenitors and forcing them into perpetual symmetric divisions, we replicated the Sox9 loss-of-function phenotype. Our findings reveal an essential role for Sox9 for the spatial regulation of asymmetric fate in the corneal epithelium that is required to sustain tissue homeostasis.

Nasopharyngeal carcinoma with non-squamous phenotype may be a variant of nasopharyngeal squamous cell carcinoma after inhibition of EGFR/PI3K/AKT/mTOR pathway.

Nasopharyngeal carcinoma (NPC) is a cancerous tumor that develops in the nasopharynx epithelium and typically has squamous differentiation. The squamous phenotype is evident in immunohistochemistry, with diffuse nuclear positivity for p63 and p40. Nonetheless, a few NPCs have been identified by clinicopathological diagnosis that do not exhibit the squamous phenotype; these NPCs are currently referred to as non-squamous immunophenotype nasopharyngeal carcinomas (NSNPCs). In a previous work, we have revealed similarities between the histological appearance, etiology, and gene alterations of NSNPC and conventional NPC. According to ultrastructural findings, NSNPC still falls under the category of non-keratinized squamous cell carcinoma that is undifferentiated. NSNPC has an excellent prognosis and a low level of malignancy, according to a retrospective investigation. Based on prior research, we investigated the molecular mechanism of NSNPC not expressing the squamous phenotype and its biological behavior. IHC was used to determine the expression of EGFR, PI3K, AKT, p-AKT, mTOR, p-mTOR, Notch, STAT3 and p-STAT3 in a total of 20 NSNPC tissue samples and 20 classic NPC tissue samples. We obtained human NPC cell lines (CNE-2,5-8F) and used EGFR overexpression plasmid and shRNAs to transfect them. To find out whether mRNA and proteins were expressed in the cells, we used Western blotting and qRT-PCR. Cell biological behavior was discovered using the CCK-8 assay, cell migration assay, and cell invasion assay. EGFR, PI3K, p-AKT and p-mTOR proteins were lowly expressed in NSNPC tissues by immunohistochemistry, compared with classical NPC. In the classical NPC cell lines CNE-2 and 5-8F, overexpression EGFR can up-regulate the expression of p63 through the PI3K/AKT/mTOR pathway, and promote the proliferation, migration, and invasion of nasopharyngeal carcinoma cells. At the same time, knockout of EGFR can down-regulate p63 expression through the PI3K/AKT/mTOR pathway, and inhibit the proliferation, migration, and invasion of nasopharyngeal carcinoma cells. The lack of p63 expression in NSNPC was linked with the inhibition of the EGFR/PI3K/AKT/mTOR pathway, and NSNPC may be a variant of classical NPC.

Clinicopathologic Analysis of Kikuchi-Fujimoto Disease and Etiologic Exploration Using Metagenomic Next-Generation Sequencing.

CONTEXT.­: Kikuchi-Fujimoto lymphadenitis, also known as Kikuchi-Fujimoto disease (KFD), is a self-limited lymphoproliferative disease, with no definitive causative agent confirmed by traditional methods. OBJECTIVES.­: To further explore the clinicopathologic features of KFD and clarify related pathogenic factors. DESIGN.­: A retrospective analysis was performed in a collection of KFD cases to review the clinical and histopathologic features, and metagenomic next-generation sequencing (mNGS) was used in 64 formalin-fixed, paraffin-embedded (FFPE) tissues from patients with KFD. RESULTS.­: One hundred five of the 170 patients with KFD (61.8%) were female; 10 patients had autoimmune diseases. Four pathologic subtypes were classified: necrotic (45.9%, 78 of 170), phagocytic (32.4%, 55 of 170), proliferative (17.1%, 29 of 170), and xanthomatous (4.7%, 8 of 170). Patients younger than 40 years with unilateral cervical lymphadenopathy and small vessel fibrinous degeneration accounted for significant differences among the 4 pathologic subtypes (P < .05). Among 64 patients with KFD, 9 had detectable bacterial or viral DNA-of 6 bacterial cases, 1 involved Chlamydia psittaci; while of 3 viral cases, 1 involved human beta herpesvirus 6B and 2 involved Epstein-Barr virus. No significant relationships were found between the pathologic subtypes and specific pathogens. CONCLUSIONS.­: Only a small proportion of patients with KFD had autoimmune diseases or infections from specific pathogens, suggesting that KFD is likely a reactive lesion of lymph nodes to various circumstances. To our knowledge, this is the first and the largest study to detect pathogens with the use of mNGS on FFPE samples in KFD. Our study also further confirms that mNGS can be used on FFPE samples to detect potentially infectious agents in clinical settings.

Lgr6 marks epidermal stem cells with a nerve-dependent role in wound re-epithelialization.

Stem cells support lifelong maintenance of adult organs, but their specific roles during injury are poorly understood. Here we demonstrate that Lgr6 marks a regionally restricted population of epidermal stem cells that interact with nerves and specialize in wound re-epithelialization. Diphtheria toxin-mediated ablation of Lgr6 stem cells delays wound healing, and skin denervation phenocopies this effect. Using intravital imaging to capture stem cell dynamics after injury, we show that wound re-epithelialization by Lgr6 stem cells is diminished following loss of nerves. This induces recruitment of other stem cell populations, including hair follicle stem cells, which partially compensate to mediate wound closure. Single-cell lineage tracing and gene expression analysis reveal that the fate of Lgr6 stem cells is shifted toward differentiation following loss of their niche. We conclude that Lgr6 epidermal stem cells are primed for injury response and interact with nerves to regulate their fate.

Two-photon live imaging of single corneal stem cells reveals compartmentalized organization of the limbal niche.

The functional heterogeneity of resident stem cells that support adult organs is incompletely understood. Here, we directly visualize the corneal limbus in the eyes of live mice and identify discrete stem cell niche compartments. By recording the life cycle of individual stem cells and their progeny, we directly analyze their fates and show that their location within the tissue can predict their differentiation status. Stem cells in the inner limbus undergo mostly symmetric divisions and are required to sustain the population of transient progenitors that support corneal homeostasis. Using in situ photolabeling, we captured their progeny exiting the niche before moving centripetally in unison. The long-implicated slow-cycling stem cells are functionally distinct and display local clonal dynamics during homeostasis but can contribute to corneal regeneration after injury. This study demonstrates how the compartmentalized organization of functionally diverse stem cell populations supports the maintenance and regeneration of an adult organ.

Mutational characteristics of gastrointestinal stromal tumors: A single-center analysis of 302 patients.

Gastrointestinal stromal tumors (GISTs) represent a spectrum of tumors characterized by variable behaviors and activating mutations in KIT proto-oncogene, receptor tyrosine kinase (KIT) or platelet derived growth factor receptor α (PDGFRA) genes. However, whether genotype analysis should be regarded as a prognostic indicator remains unclear. In the present study, clinicopathological data and the mutation phenotypes of KIT and PDGFRA genes were assessed in a series of 302 patients with GISTs at a single center. Univariate and multivariate Cox regression analyses were performed to identify the clinicopathological and mutational factors associated with relapse-free survival (RFS) in patients who had undergone complete primary GIST resection. KIT and PDGFRA mutations were identified in 233 (77.2%) and 30 (9.9%) cases, respectively. The following clinicopathological parameters were significantly associated with a shorter RFS: Male, non-gastric tumor origin, larger tumor size (>5 cm), high mitotic activity (>5/50 high-power fields), necrosis and epithelioid morphology. Tumors at non-gastric sites, with high National Institutes of Health risk classification, high World Health Organization (WHO) grade and KIT deletion involving codons 557/558/559 exhibited a significantly higher risk of progression. In the Cox regression model, KIT deletion involving codons 557/558/559, non-gastric origin and high WHO grade were independent indicators of RFS. The adverse prognosis associated with KIT deletions involving codons 557/558/559 was also observed for gastric GISTs. Conversely, spindle morphology, KIT exon 11 substitution and PDGFRA exon 18 mutation were associated with a longer RFS and lower rate of relapse. Furthermore, the coexistence of KIT exon 11 deletion and exon 13 duplication was observed in one tumor, with adverse prognostic features. Heterogeneity affecting morphology, immunostaining and genotype was identified in 4 cases. In addition, the presence of succinate dehydrogenase-deficient GIST was found in 5 cases (3.6%). In conclusion, the tumor genotype with regard to KIT and PDGFRA mutations exhibited prognostic significance for the risk of GIST progression and may be helpful for the optimization of tailored adjuvant therapy.

Histo- and clinico-pathological analysis of a large series of triple-negative breast cancer in a single center in China: Evidences on necessity of histological subtyping and grading.

OBJECTIVE: To investigate histo-pathological distribution and clinico-pathological significance in a large Chinese triple-negative breast cancer (TNBC) patients serials based on the latest understanding of its clinico-pathological diversity, and to provide more information to clinicians to improve precision of individualized treatment of TNBC. METHODS: A retrospective analysis was performed on patients with TNBC at Breast Disease Center, Peking University First Hospital between January 2010 and December 2019. Histo- and clinico-pathological characteristics were analyzed by Chi-square test and Student's t-test, and prognoses were calculated using Kaplan-Meier method and a Cox proportionate hazards model. Bonferroni correction was used to correct for multiple comparison. RESULTS: Conventional type of TNBC (cTNBC) were identified in 73.7% of 582 TNBC, while special type of TNBC (sTNBC) were 26.3%, including 71 apocrine carcinoma, 20 medullary carcinoma, 31 metaplastic carcinoma, 18 invasive lobular carcinoma, 7 invasive micropapillary carcinoma, 5 adenoid cystic carcinoma and 1 acinic cell carcinoma. Compared to sTNBC, cTNBC was associated with high histologic grade (P<0.001) and lower androgen receptor (AR) expression (P<0.001). TNM stage of low-grade cTNBC was significantly lower than that of high-grade cTNBC (P=0.002). Although no significant difference, there was a trend that the rate of 5-year disease-free survival (DFS) and 5-year overall survival (OS) were longer in high-grade cTNBC than in high-grade sTNBC (P=0.091 and 0.518), and were longer in low-grade sTNBC than in high-grade sTNBC (P=0.051 and 0.350). Metaplastic carcinomas showed larger tumor size (P=0.008) and higher proliferative Ki67 index (P=0.004) than cTNBCs. CONCLUSIONS: Results from our cohort imply that sub-categorization or subtyping and histological grading could be meaningful in pathological evaluation of TNBC, and need to be clarified in more large collections of TNBC.

The Psychology of Gray Hair.

Stress has long been associated with hair graying, yet there is little evidence to substantiate this claim. In a recent issue of Nature, Zhang et al. (2020) show that stress induces the release of noradrenaline from sympathetic nerves, which depletes the stem cells that give hair their color.

Foxp1 controls brown/beige adipocyte differentiation and thermogenesis through regulating ß3-AR desensitization.

ß-Adrenergic receptor (ß-AR) signaling is a pathway controlling adaptive thermogenesis in brown or beige adipocytes. Here we investigate the biological roles of the transcription factor Foxp1 in brown/beige adipocyte differentiation and thermogenesis. Adipose-specific deletion of Foxp1 leads to an increase of brown adipose activity and browning program of white adipose tissues. The Foxp1-deficient mice show an augmented energy expenditure and are protected from diet-induced obesity and insulin resistance. Consistently, overexpression of Foxp1 in adipocytes impairs adaptive thermogenesis and promotes diet-induced obesity. A robust change in abundance of the ß3-adrenergic receptor (ß3-AR) is observed in brown/beige adipocytes from both lines of mice. Molecularly, Foxp1 directly represses ß3-AR transcription and regulates its desensitization behavior. Taken together, our findings reveal Foxp1 as a master transcriptional repressor of brown/beige adipocyte differentiation and thermogenesis, and provide an important clue for its targeting and treatment of obesity.

Prognostic impact of diffuse large B-cell lymphoma with extra copies of MYC, BCL2 and/or BCL6: comparison with double/triple hit lymphoma and double expressor lymphoma.

BACKGROUND: The poor outcome of high-grade B-cell lymphoma, with rearrangements of MYC, BCL2 and/or BCL6, also known as double-hit lymphoma or triple-hit lymphoma (DHL or THL), has been well documented, while the clinical significance of extra copies of MYC, BCL2 or BCL6 are still less well known. METHODS: In total, 130 cases of diffuse large B-cell lymphoma, not otherwise specified (DLBCL-NOS) were included in our study. Fluorescence in situ hybridization and immunohistochemistry were performed in all cases to evaluate the genetic status and protein expression levels of MYC, BCL2 and BCL6. RESULTS: Among the 130 cases of DLBCL, the prevalence rates of extra copies of MYC, BCL2 and BCL6 were 10.8, 20.0 and 14.6%, respectively, and the corresponding rates of gene rearrangement were 10.0, 14.6 and 16.9%, respectively. In total, 7.7% (10/130) of patients were DHL/THL; 9.2% (12/130) of patients were DLBCL with MYC and BCL2 and/or BCL6 gene abnormalities including rearrangements or extra copies, while excluded DHL/THL. The positive protein expression rates of MYC, BCL2 and BCL6 were 46.9% (61), 75.4% (98) and 70.0% (91), respectively. Among the 51 cases with MYC/BCL2 co-expression, 14 cases showed concurrence of MYC, BCL2 and/or BCL6 genetic abnormalities, and the remaining 37 cases were classified as double-expressor lymphoma (DEL). MYC and BCL2 rearrangement and BCL2 extra copies were all associated with upregulated protein expression. Cases with concurrence of MYC, BCL2 and/or BCL6 genetic abnormalities were both associated with MYC/BCL2 co-expression. Patients with concurrence of MYC, BCL2 and/or BCL6 genetic abnormalities excluded DHL/THL had shorter OS (P < 0.001) than patients with DLBCL with no genetic change, and showed no statistical different with patients with DHL/THL (P = 0.419). Extra copies of MYC was independent prognostic factors for DLBCL. CONCLUSIONS: Patients with MYC and BCL2 and/or BCL6 gene extra copies might show a trend towards poor prognosis, and the detection of extra copies of MYC, BCL2 and BCL6 might deserve more attention.

Comparison of PD-L1 detection assays and corresponding significance in evaluation of diffuse large B-cell lymphoma.

The expression of programmed cell death ligand 1 (PD-L1) is a biomarker for immunotherapy, but approved detection method is absent in diffuse large B-cell lymphoma (DLBCL). Here, we performed three methods including immunohistochemistry (IHC) (clone SP263 and SP142), RNAscope, and fluorescence in situ hybridization (FISH) to evaluate PD-L1 status on a cohort of DLBCL including 94 of DLBCL-NOS, 25 of primary mediastinal large B-cell lymphoma (PMBCL) and 7 of double-hit lymphoma (DHL). SP263 with 25% for immune cell (IC) or combined cell and SP142 with 10% for tumor cell (TC), 20% for both of IC and combined cell were proved to have corresponding survival prognostic. Combined+ showed comparable prognostic value with TC+ and IC+ . SP263 and SP142 showed strong concordance (k = 0.788) with combined+ rates of 33.3% (42/126) and 34.9% (44/126), respectively. In DLBCL-NOS, TC+ by SP263 preferred to non-GCB and immunoblastic variant DLBCL-NOS (P = 0.029 and P = 0.004). Combined+ (SP263 and SP142) were associated with more than one extranodal site involved (P = 0.006, P = 0.042), higher ECOG PS scores (P = 0.001, P < 0.001), high IPI risk (P = 0.012, P = 0.005), and poor treatment response (P = 0.095, P = 0.002). IC+ by SP263 and SP142 were both independent risk factors (P = 0.027, P = 0.037). 9p24.1 locus amplification and gain were identified in 4.3% and 7.6% DLBCL-NOS and indicated shorter overall survival (P = 0.004). Positive rate of PD-L1 by RNAscope was 36.5%, while no clinical significance shown. PD-L1 positive rates were all higher in PMBCL and DHL than in DLBCL-NOS by SP263, SP142, RNAscope, and FISH (P = 0.001, P < 0.001, P = 0.005 and P < 0.001, respectively). In conclusion, combined PD-L1 expression by IHC was potentially reliable and convenient as a predicting biomarker. SP263 staining was easier to evaluate and recognized more PD-L1-stained cells, but SP142 presented a better prognostic indicator. FISH and RNAscope could be used as supplementary assays. PMBCL itself was a sensitive cohort for immunotherapy.

Low expression of SPARC in gastric cancer-associated fibroblasts leads to stemness transformation and 5-fluorouracil resistance in gastric cancer.

BACKGROUND: The aim of the present study was to clarify the correlations between SPARC expression in gastric cancer-associated fibroblasts (GCAFs) and the prognosis of patients with gastric cancer and to elucidate the role of GCAF-derived SPARC in stemness transformation and 5-fluorouracil resistance in gastric cancer. METHODS: One hundred ninety-two patients were enrolled in the present study. SPARC expression levels were evaluated by immunohistochemical staining. Primary GCAFs were obtained and cultured from cancer patients for in vitro study, and a lentivirus infection method was employed to knock down SPARC expression in GCAFs. The stemness phenotype and 5-fluorouracil (5-FU) response of gastric cancer cells were assessed via a 3D co-culture model. The apoptotic status and stemness alterations were monitored by flow cytometry and western blotting. Additionally, label-free quantification proteomics was used to identify the differentially expressed proteins and potential pathways in gastric cancer cells treated with GCAF-derived SPARC. RESULTS: Low expression of GCAF-derived SPARC was associated with decreased differentiation and reduced 5-year overall survival and was an independent predictive factor for prognosis in gastric cancer. The 3D tumour growth and 5-FU resistance abilities of gastric cancer cells were elevated after treatment with GCAFs with SPARC knockdown relative to these abilities in negative control cells. Additionally, suppressing SPARC expression in GCAFs facilitated the phenotypic alteration of gastric cancer cells towards CD44+/CD24- cancer stem cell (CSC)-like cells. Quantification proteomics analysis revealed that the differentially expressed proteins in gastric cancer cells were mainly involved in the AKT/mTOR and MEK/ERK signalling pathways. CONCLUSIONS: SPARC expression in GCAFs is a useful prognostic factor in patients with gastric cancer. Low expression of GCAF-derived SPARC can lead to CSC transformation and 5-FU resistance. Additionally, the AKT/mTOR and MEK/ERK signalling pathways may participate in the malignant process.

JAK3/STAT3 oncogenic pathway and PRDM1 expression stratify clinicopathologic features of extranodal NK/T­cell lymphoma, nasal type.

The inactivation of tumor suppressor gene positive regulatory domain containing I (PRDM1) and activation of signal transducer and activator of transcription 3 (STAT3) have been detected in the majority of extranodal NK/T­cell lymphoma, nasal type (EN­NK/T­NT) cases. In the present study, their association with and effects on the clinicopathologic features of EN­NK/T­NT are described. PRDM1 was revealed to be expressed in 19 out of 58 patients (32.8%) with EN­NK/T­NT, and phosphorylated STAT3 was overexpressed in 42 out of 58 (72.4%). Oncogenic pathways were investigated by NanoString encounter technology in 5 PRDM1(+) and 5 PRDM1(­) EN­NK/T­NT specimens. Multiple oncogenic pathways involved in cell apoptosis, cellcycle (CC) and angiogenesis were discriminately activated in EN­NK/T­NT cases, and in PRDM1(+) cases in particular. The sustained activation of the Janus kinase 3 (JAK)/STAT3 pathway was more pronounced. In addition, missense mutations in the SRC homology 2 domain of STAT3 were detected in 7 out of 37 EN­NK/T­NT cases (18.92%), and the acquired mutation was related to the activation of the JAK3/STAT3 pathway. The downregulation of PRDM1 and upregulation of phospho­STAT3 (Tyr705) were associated with angiocentric infiltration of EN­NK/T­NT (P=0.039). Notably, the prognosis of patients in the PRDM1(+)/STAT3 [mutated (mut­)] group was considerably improved than that of patients in the STAT3(mut+)/PRDM(­) group (P=0.037). In addition, the inhibition of NK/T cell lymphoma cell lines by Stattic and tofacitinib could suppress cell proliferation by inducing cell apoptosis or arresting the CC. The present results revealed that the JAK3/STAT3 oncogenic pathway and PRDM1 expression could stratify clinicopathologic features of EN­NK/T­NT. The inhibition of the JAK3/STAT3 pathway may serve as a treatment option for EN­NK/T­NT.

Aberrant differential expression of EZH2 and H3K27me3 in extranodal NK/T-cell lymphoma, nasal type, is associated with disease progression and prognosis.

Enhancer of zeste homolog 2 (EZH2), an H3K27-specific histone methyltransferase, has been shown to be frequently overexpressed in various human cancers including lymphoma. Here we investigate the expression and functionality of EZH2 and H3K27me3 in extranodal NK/T-cell lymphoma, nasal type (ENKTL). Results of NanoString analysis revealed that EZH2 and related histone H3 families were up-regulated genes in ENKTL tissues. Results of immunohistochemistry demonstrated that EZH2 and trimethylation of Lys-27 in histone (H3K27me3) were highly expressed in 55.2% and 78.0% of patients with ENKTL, respectively. EZH2 overexpression was significantly associated with higher tumor cell proliferation (r = 0.582, P = .000), advanced stage (P = .012), and predicted poorer overall survival (P = .016) in ENKTL. H3K27me3-positive expression was correlated with lower tumor cell proliferation (r = -0.623, P = .036), earlier stage (P = .043), and predicted better overall survival (P = .020). In addition, EZH2 and H3K27me3 showed inverse correlations (r = -0.652, P = .002) in clinical samples by immunohistochemistry. Furthermore, inhibition of EZH2 by 3-deazaneplanocin A significantly suppressed tumor cell growth. Interestingly, pharmacologic suppression of the JAK3/STAT3 pathway effectively reduced EZH2 and enhanced H3K27me3 in NK/T tumor cell lines. Our data suggest that EZH2 and H3K27me3 are important prognostic markers and potential therapeutic targets in ENKTL.

Fluorescence in situ hybridisation as an ancillary tool in the diagnosis of acral melanoma: a review of 44 cases.

Acral melanoma is associated with outcomes which are more unfavourable than those of other melanoma subtypes, and acral melanoma has higher mortality. However, histological distinction of acral melanoma from acral naevi may be difficult. Fluorescence in situ hybridisation (FISH) targeting specific genes has been used as an ancillary method for differential diagnosis of melanocytic tumours, but most previous studies have focused on non-acral lesions which may have genetic alterations different from acral lesions. We evaluated use of multi-site FISH in the diagnosis of acral melanoma in a series of 82 acral melanocytic tumours. Two probe groups were applied. Probe set 1 involved a 4-probe FISH targeting 6p25 (RREB1), CEP6 (centromere 6), 6q23 (MYB) and 11q13 (CCND1). Probe set 2 involved a 3-probe FISH targeting 8q24 (MYC), 9p21 (CDKN2A) and CEP9 (centromere 9). In 44 primary acral melanomas, sensitivity was 70.5% (31/44) using probe set 1 alone, and 59.1% (26/44) using probe set 2 alone. When both probe sets were combined, sensitivity increased to 88.6% (39/44). The frequency of each gene alteration was as follows: MYC gain in 54.5% cases (24/44), RREB1 gain in 52.3% cases (23/44), CCND1 gain in 45.4% cases (20/44), MYB loss relative to CEP6 in 25.0% cases (11/44), and CDKN2A homozygous deletion in 20.5% cases (9/44). For lesions with both in situ and invasive disease, FISH findings in these two components were similar. No gene alterations were detected in any of 36 benign acral naevi. In this study FISH exhibited sensitivity and specificity in diagnosis of acral melanoma which allows its application as an auxiliary diagnostic test in acral melanocytic tumours.

Two-photon microscopy for intracutaneous imaging of stem cell activity in mice.

The adult skin is a typical example of a highly regenerative tissue. Terminally differentiated keratinocytes are shed from the external layers of the epidermis or extruded from the skin as part of the growing hair shaft on a daily basis. These are effectively replenished through the activity of skin-resident stem cells. Precise regulation of stem cell activity is critical for normal skin homoeostasis or wound healing and irregular stem cell proliferation or differentiation can lead to skin disease. The scarcity and dynamic nature of stem cells presents a major challenge for elucidating their mechanism of action. To address this, we have recently established a system for visualizing stem cell activity, in real time or long term, in the intact skin of live mice using two-photon microscopy. The purpose of this review was to provide essential information to researchers who wish to incorporate two-photon microscopy and live imaging into their experimental toolbox for studying aspects of skin and stem biology in the mouse model. We discuss fundamental principles of the method, instrumentation and basic experimental approaches to interrogate stem cell activity in the interfollicular epidermis and hair follicle.

"Secretory" Carcinoma of the Skin Mimicking Secretory Carcinoma of the Breast: Case Report and Literature Review.

Secretory carcinoma is a unique kind of adenocarcinoma. It has distinct histological features and a special genetic change, that is, t (12; 15) (p13; q25) translocation which leads to the expression of the ETV6-NTRK3 fusion gene. Secretory carcinoma has been found to occur both in the breast and salivary gland. Here the authors present a case of 22-year-old woman with a unique cutaneous neoplasm located at the axilla. The tumor was characterized histologically with the formation of round to ovoid microcysts and papillary structure, which was similar to the secretory carcinoma of the breast and salivary gland. Furthermore, the gene sequence analysis of reverse-transcription polymerase chain reaction products demonstrated the expression of the ETV6-NTRK3 fusion gene. To the authors' knowledge, this is the first case of secretory carcinoma from the skin which has the same genetic change as those from the breast and salivary gland. Local excision was performed on this patient. She had been followed up for nearly 1 year. No recurrence or metastasis was found yet.

Involvement of epithelial Wntless in the regulation of postnatal hair follicle morphogenesis.

The roles of the Wnt cargo receptor Wntless (Wls) during hair follicle (HF) induction and postnatal HF cycling in skin have been elucidated. However, whether Wls regulates postnatal HF morphogenesis remains unclear. In this study, we found that Wls is expressed in developing HF during the morphogenesis stage after birth. By knocking out Wls in mouse skin epithelia with hypomorphic K14-cre, we found that Wls is required for normal HF morphogenesis. Wls-deficient HFs prematurely regressed, which was possibly caused by abnormally activated TGF-ß/JNK pathway. Although Wls was reported to be a direct target of the Wnt/ß-catenin pathway, we found that epithelial ß-catenin was not necessary to maintain Wls expression. Therefore, other signals are involved in regulating Wls transcription in mouse skin.

Overexpression of Wnt5a in mouse epidermis causes no psoriasis phenotype but an impairment of hair follicle anagen development.

Increased Wnt5a expression has been observed in psoriatic plaques. However, whether Wnt5a overexpression directly causes psoriasis is unknown. In this study, we generated transgenic (TG) mice with epidermal Wnt5a overexpression under the control of the human K14 promoter. The skin of Wnt5a TG mice was not psoriatic, but characterized with normal proliferation and homeostasis of epidermis. Instead, these TG mice displayed impaired hair follicle transition from telogen to anagen, most likely due to impaired canonical Wnt signalling. These results suggest that increased Wnt5a expression alone is inadequate to induce psoriasis in the skin and possible involvement of Wnt5a in hair follicle cycling.

Constitutive activation of ectodermal ß-catenin induces ectopic outgrowths at various positions in mouse embryo and affects abdominal ventral body wall closure.

Vertebrate limbs originate from the lateral plate mesoderm (LPM) and the overlying ectoderm. While normal limb formation in defined regions has been well studied, the question of whether other positions retain limb-forming potential has not been fully investigated in mice. By ectopically activating ß-catenin in the ectoderm with Msx2-cre, we observed that local tissue outgrowths were induced, which either progressed into limb-like structure within the inter-limb flank or formed extra tissues in other parts of the mouse embryo. In the presumptive abdominal region of severely affected embryos, ectopic limb formation was coupled with impaired abdominal ventral body wall (AVBW) closure, which indicates the existence of a potential counterbalance of limb formation and AVBW closure. At the molecular level, constitutive ß-catenin activation was sufficient to trigger, but insufficient to maintain the ectopic expression of a putative limb-inducing factor, Fgf8, in the ectoderm. These findings provide new insight into the mechanism of limb formation and AVBW closure, and the crosstalk between the Wnt/ß-catenin pathway and Fgf signal.