Epimorphin acts to induce hair follicle anagen in C57BL/6 mice

Generation of iPS-derived model cells for analyses of hair shaft differentiation

Biological evaluation of hair growth/differentiation activity in vitro has been a formidable challenge, primarily due to the lack of relevant model cell systems. To solve this problem, we generated a stable model cell line in which successive differentiation via epidermal progenitors to hair components is easily inducible and traceable. Mouse induced pluripotent stem (iPS) cell–derived cells were selected to stably express a tetracycline (Tet)-inducible bone morphogenic protein-4 (BMP4) expression cassette and a luciferase reporter driven by a hair-specific keratin 31 gene (krt31) promoter (Tet-BMP4-KRT31-Luc iPS). While Tet- BMP4-KRT31-Luc iPS cells could be maintained as stable iPS cells, the cells differentiated to produce luciferase luminescence in the presence of all-trans retinoic acid (RA) and doxycycline (Dox), and addition of a hair differentiation factor significantly increased luciferase fluorescence. Thus, this cell line may provide a reliable cell-based screening system to evaluate drug candidates for hair differentiation activity.

Extracellularly Extruded Syntaxin-4 Binds to Laminin and Syndecan-1 to Regulate Mammary Epithelial Morphogenesis

Epithelial morphogenesis in the mammary gland proceeds as a consequence of complex cell behaviors including apoptotic cell death and epithelial-mesenchymal transition (EMT); the extracellular matrix (ECM) protein laminin is crucially involved. Syntaxins mediate intracellular vesicular fusion, yet certain plasmalemmal members have been shown to possess latent extracellular functions. In this study, the extracellular subpopulation of syntaxin-4, extruded in response to the induction of differentiation or apoptosis in mammary epithelial cells, was detected. Using a tetracycline-repressive transcriptional system and clonal mammary epithelial cells, SCp2, we found that the expression of cell surface syntaxin-4 elicits EMT-like cell behaviors. Intriguingly, these cells did not up-regulate key transcription factors associated with the canonical EMT such as snail, slug, or twist, and repressed translation of E-cadherin. Concurrently, the cells completely evaded the cellular aggregation/rounding triggered by a potent EMT blocker laminin-111. We found that the recombinant form of syntaxin-4 not only bound to laminin but also latched onto the glycosaminoglycan (GAG) side chains of syndecan-1, a laminin receptor that mediates epithelial morphogenesis. Thus, temporal extracellular extrusion of syntaxin-4 emerged as a novel regulatory element for laminin-induced mammary epithelial cell behaviors. J. Cell. Biochem. 118: 686-698, 2017. © 2016 Wiley Periodicals, Inc.

Krtap11-1, a hair keratin-associated protein, as a possible crucial element for the physical properties of hair shafts

BACKGROUND

The physical properties of the hair are predominantly determined by the assembly of keratin bundles. The keratin-associated proteins (Krtaps) are thought to be involved in keratin bundle assembly, however, the functional role of the individual member still remains largely unknown.

OBJECTIVE

The aim of this study is to clarify the role of a unique class of Krtaps, Krtap11-1, in the development and physical properties of the hair.

METHODS

The expression regulation of Krtap11-1 was analyzed and its binding partners in the hair cortex were determined. Also, the effects of the forcible expression of this protein on the hair follicle development were analyzed in culture.

RESULTS

The expression pattern of Krtap11-1 was concentrically asymmetric in the faulty hair that develops in Foxn1nu mice. In cultured keratinocytes, the expression of Krtap11-1 transgene product was strictly regulated by the keratinization process and proteasome-dependent protein elimination. While the association with keratin as well as the cohesive self-assembly of Krtap11-1 appeared to be stabilized by disulfide cross-links, the biotinylated Krtap11-1 probe enabled the adherence to certain type I keratins in the hair cortex, including K31, 33 and 34, in the absence of disulfide formation. When embryonic upper lip rudiments were forcibly introduced with Krtap11-1, the hair follicles formed irregularly arranged globular hair keratin-clumps surrounded by multilayered epithelial cells in culture.

CONCLUSION

Krtap11-1 may play an important role on keratin-bundle assembly in the hair cortex and this study provides insight into the physical properties of the hair shaft.

Epimorphin is a novel regulator of the progesterone receptor isoform-a

Epimorphin/syntaxin-2 is a membrane-tethered protein localized extracellularly (Epim) and intracellularly (Stx-2). The extracellular form Epim stimulates morphogenic processes in a range of tissues, including in murine mammary glands where its overexpression in luminal epithelial cells is sufficient to drive hyperplasia and neoplasia. We analyzed WAP-Epim transgenic mice to gain insight into how Epim promotes malignancy. Ectopic overexpression of Epim during postnatal mammary gland development led to early side-branching onset, precocious bud formation, and increased proliferation of mammary epithelial cells. Conversely, peptide-based inhibition of Epim function reduced side branching. Because increased side branching and hyperplasia occurs similarly in mice upon overexpression of the progesterone receptor isoform-a (Pgr-a), we investigated whether Epim exhibits these phenotypes through Pgr modulation. Epim overexpression indeed led to a steep upregulation of both total Pgr mRNA and Pgr-a protein levels. Notably, the Pgr antagonist RU486 abrogated Epim-induced ductal side branching, mammary epithelial cell proliferation, and bud formation. Evaluation of Epim signaling in a three-dimensional ex vivo culture system showed that its action was dependent on binding to its extracellular receptor, integrin-αV, and on matrix metalloproteinase 3 activity downstream of Pgr-a. These findings elucidate a hitherto unknown transcriptional regulator of Pgr-a, and shed light on how overexpression of Epim leads to malignancy.

Identification of the C-terminal tail domain of AHF/trichohyalin as the critical site for modulation of the keratin filamentous meshwork in the keratinocyte

BACKGROUND

AHF/trichohyalin is a large structural protein abundant in the inner root sheath (IRS) of anagenic hair follicles, which has been thought to mediate the keratin filamentous assembly. However, its functional mechanism is largely unknown.

OBJECTIVE

This study aimed at the identification of the key domain in AHF for keratin association and the establishment of a plausible mechanism for the modulation of the keratin meshwork.

METHODS

Several keratinocyte cell lines were introduced with the full length or several mutants of AHF, together with IRS-specific keratin krt31, and the profile of the AHF granules and the cellular behaviors were carefully analyzed.

RESULTS

Full length of AHF formed small round granules that clearly bound to and aligned on the exogenous keratin filaments in the keratinocytes, severely affected cellular growth, mobility and shape. Intriguingly, the removal of only 6 amino acids around the C-terminal tail of AHF resulted not only in the complete loss of its keratin adherent ability but also in a dramatic enlargement of the granules.

CONCLUSION

We propose a model for cytoskeletal modulation in the IRS of anagenic hair follicles: AHF latches onto the keratin bundles by its C-terminus and rearranges the keratin meshwork by intrinsic cohesive activity for the granule formation.

The mesenchymal component of hair follicle neogenesis: background, methods and molecular characterization

Hair follicle morphogenesis and regeneration occur by an extensive and collaborative crosstalk between epithelial and mesenchymal skin components. A series of pioneering studies, which revealed an indispensable role of follicular dermal papilla and dermal sheath cells in this crosstalk, has led workers in the field to study in detail the anatomical distribution, functional properties, and molecular signature of the trichogenic dermal cells. The purpose of this paper was to provide a practical summary of the development and recent advances in the study of trichogenic dermal cells. Following a short review of the relevant literature, the methods for isolating and culturing these cells are summarized. Next, the bioassays, both in vivo and in vitro, that enable the evaluation of trichogenic properties of tested dermal cells are described in detail. A list of trichogenic molecular markers identified by those assays is also provided. Finally, this methods review is completed by defining some of the major questions needing resolution.

Mesenchymal epimorphin is important for pancreatic duct morphogenesis

Epithelial-mesenchymal interactions are crucial for the proper development of many organs, including the pancreas. Within the pancreas, the ducts are thought to harbor stem/progenitor cells, and possibly to give rise to pancreatic ductal carcinoma. Little is known about the mechanism of formation of pancreatic ducts in the embryo. Pancreatic mesenchyme contains numerous soluble factors which help to sustain the growth and differentiation of exocrine and endocrine structures. Here, we report that one such morphoregulatory mesenchymal protein, epimorphin, plays an important role during pancreatic ductal proliferation and differentiation. We found that epimorphin is expressed in pancreatic mesenchyme during early stages of development, and at mesenchymal-epithelial interfaces surrounding the ducts at later stages. Strong upregulation of epimorphin expression was seen during in vitro pancreatic duct differentiation. Similarly, in vitro pancreatic duct formation was inhibited by a neutralizing antibody against epimorphin, whereas addition of recombinant epimorphin partially rescued duct formation. Together, our study demonstrates the role of epimorphin in pancreatic ductal morphogenesis.

Homology with vesicle fusion mediator syntaxin-1a predicts determinants of epimorphin/syntaxin-2 function in mammary epithelial morphogenesis

We have shown that branching morphogenesis of mammary ductal structures requires the action of the morphogen epimorphin/syntaxin-2. Epimorphin, originally identified as an extracellular molecule, is identical to syntaxin-2, an intracellular molecule that is a member of the extensively investigated syntaxin family of proteins that mediate vesicle trafficking. We show here that, although epimorphin/syntaxin-2 is highly homologous to syntaxin-1a, only epimorphin/syntaxin-2 can stimulate mammary branching morphogenesis. We construct a homology model of epimorphin/syntaxin-2 based on the published structure of syntaxin-1a, and we use this model to identify the structural motif responsible for the morphogenic activity. We identify four residues located within the cleft between helices B and C that differ between syntaxin-1a and epimorphin/syntaxin-2; through site-directed mutagenesis of these four amino acids, we confer the properties of epimorphin for cell adhesion, gene activation, and branching morphogenesis onto the inactive syntaxin-1a template. These results provide a dramatic demonstration of the use of structural information about one molecule to define a functional motif of a second molecule that is related at the sequence level but highly divergent functionally.

The TFIID subunit TAF4 regulates keratinocyte proliferation and has cell-autonomous and non-cell-autonomous tumour suppressor activity in mouse epidermis

The TAF4 subunit of transcription factor TFIID was inactivated in the basal keratinocytes of foetal and adult mouse epidermis. Loss of TAF4 in the foetal epidermis results in reduced expression of the genes required for skin barrier function, leading to early neonatal death. By contrast, TAF4 inactivation in adult epidermis leads to extensive fur loss and an aberrant hair cycle characterised by a defective anagen phase. Although the mutant epidermis contains few normal anagen-phase hair follicles, many genes expressed at this stage are strongly upregulated indicating desynchronised and inappropriate gene expression. The TAF4 mutant adult epidermis also displays interfollicular hyperplasia associated with a potent upregulation of several members of the EGF family of mitogens. Moreover, loss of TAF4 leads to malignant transformation of chemically induced papillomas and the appearance of invasive melanocytic tumours. Together, our results show that TAF4 is an important regulator of keratinocyte proliferation and has cell-autonomous and non-cell-autonomous tumour suppressor activity.

Non-classical export of epimorphin and its adhesion to alphav-integrin in regulation of epithelial morphogenesis

Epimorphin (also known as syntaxin 2) acts as an epithelial morphogen when secreted by stromal cells of the mammary gland, lung, liver, colon, pancreas and other tissues, but the same molecule functions within the cell to mediate membrane fusion. How this molecule, which lacks a signal sequence and contains a transmembrane domain at the C-terminus, translocates across the plasma membrane and is secreted to become a morphogen, and how it initiates morphogenic events is not clear. Here, we show that epimorphin is secreted through a non-classical mechanism, similar to that previously described for secretion of the leaderless protein FGF1, and we identify the key molecular elements responsible for translocation and secretion from the cell. We also show that secreted epimorphin binds to alphav-integrin-containing receptors on target epithelial cells, leading to activation of specific downstream signaling pathways and induction of epithelial morphogenesis. These findings provide key insight into how epimorphin functions as an epithelial morphogen.

Epimorphin acts extracellularly to promote cell sorting and aggregation during the condensation of vertebral cartilage

Formation of vertebrae occurs via endochondral ossification, a process involving condensation of precartilaginous cells. Here, we provide the first molecular evidence of mechanism that underlies initiation of this process by showing that the extracellular factor, Epimorphin, plays a role during early steps in vertebral cartilage condensation. Epimorphin mRNA is predominantly localized in the vertebral primordium. When provided exogenously in ovo, it causes precocious differentiation of chondrocytes, resulting in the formation of supernumerary vertebral cartilage in chicken embryos. To further analyze its mode of action, we used an in vitro co-culture system in which labeled 10T1/2 or sclerotomal prechondrogenic cells were co-cultured with unlabeled Epimorphin-producing cells. In the presence of Epimorphin, the labeled cells formed tightly packed aggregates, and sclerotomal cells displayed augmented accumulation of NCAM and other early markers of chondrocyte differentiation. Finally, we found that the Epimorphin expression is initiated during vertebrogenesis by Sonic hedgehog from the notochord mediated by Sox 9. We present a model in which successive action of Epimorphin in recruiting and stacking sclerotomal cells leads to a sequential elongation of a vertebral primordium.

Identification of soluble N-ethylmaleimide-sensitive factor attachment protein receptor exocytotic machinery in human plasma cells: SNAP-23 is essential for antibody secretion

Plasma cells (PC) are B-lymphocytes terminally differentiated in a postmitotic state, with the unique purpose of manufacturing and exporting Igs. Despite the importance of this process in the survival of vertebrates, no studies have been made to understand the molecular events that regulate Ig exocytosis by PC. The present study explores the possible presence of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) system in human PC, and examines its functional role in Ig secretion. Syntaxin-2, Syntaxin-3, Syntaxin-4, vesicle-associated membrane protein (VAMP)-2, VAMP-3, and synaptosome-associated protein (SNAP)-23 could be readily detected in normal human PC obtained from intestinal lamina propria and blood, as well as in human PC lines. Because SNAP-23 plays a central role in SNAREs complex formation, it was chosen to examine possible functional implications of the SNARE system in PC Ig secretion. When recombinant SNAP-23 fusion protein was introduced into the cells, a complete abolishment of Ig production was observed in the culture supernatants of PC lines, as well as in those of normal PC. These results provide insights, for the first time, into the molecular machinery of constitutive vesicular trafficking in human PC Ig secretion and present evidence indicating that at least SNAP-23 is essential for Ab production.

Structural optimization of pep7, a small peptide extracted from epimorphin, for effective induction of hair follicle anagen

Epimorphin is representative of a unique class of stromal membrane-anchored proteins that plays distinct functions depending on its membrane topology. When exposed extracellularly, this molecule acts as a morphoregulator for various tissues including hair follicle epithelia. Previous study identified its functional domain (the pep7 domain: SIEQSCDQDE) for hair follicular morphogenesis followed by the successful generation of a chemically modified active peptide. Here, we report optimization of this peptide by the introduction of sequential mutations and subsequent structural determination. We found that three residues from the C-terminus are dispensable, and alternation of the seventh amino acid to an Alanine residue enhanced activity. To favour the biologically active conformation, epsilon-Acp (NH(CH(2))(5)CO) linked to a Cysteine residue was connected at the N-terminus followed by the introduction of an intramolecular disulphide bridge, the modification process of which could be included in the peptide synthesis. The obtained modified peptide, termed 'EPM (epimorphin-derived) peptide', has a Mw of 950 Da and exerts an inductive effect on hair follicle regeneration at a concentration of approximately 0.00001% or even lower. The action of this EPM peptide was more apparent in mice treated with 1% minoxidil, suggesting its potential clinical benefit as a new type of hair-regenerating agent.

Regulation of embryo outgrowth by a morphogenic factor, epimorphin, in the mouse

Conceptus implantation to the uterine endometrium represents a complex series of events, including synchronized development of conceptus and uterus through up- and/or down-regulation of numerous gene products. In a previous study using the DNA microarray technique, we had discovered evidence that increase in a transcript for mesenchymal morphogen, epimorphin, was noted as the conceptus attached to the matrix in vitro (Qin et al., 2003). In the present study, the expression and potential function of epimorphin in developing conceptuses was investigated through the use of reverse transcription-polymerase chain reaction (RT-PCR), whole mount in situ hybridization/immunohistochemistry, and in vitro blastocyst culture. RT-PCR and in situ hybridization analysis revealed that epimorphin mRNA was expressed weakly in murine conceptuses during early developmental stages (1 cell to post-adhesion blastocyst stages) and higher levels of epimorphin transcripts were observed in both inner cell mass (ICM) and trophectoderm of outgrowing blastocysts. Immunohistochemical analysis confirmed that epimorphin was localized in outgrowing trophoblast cells and ICM. Treating blastocysts in culture with a 115 kDa form of recombinant epimorphin promoted trophoblast outgrowth (P < 0.05), but a 34 kDa form of recombinant epimorphin had no effect. Treatment with a function inhibitor, rat anti-mouse epimorphin IgM, reduced the number of embryos progressing to blastocyst outgrowth to the levels similar to those observed with plain culture medium. Reverse transcription-polymerase chain reaction (RT-PCR) analysis also revealed that epimorphin increased the expression of a trophoblast cell differentiation marker, placental lactogen-1 (PL-1), mRNA (P < 0.01). These results suggest that epimorphin is involved in trophoblast outgrowth, a process required for conceptus implantation into the endometrium.