Autoimmune amelogenesis imperfecta in patients with APS-1 and coeliac disease.

Ameloblasts are specialized epithelial cells in the jaw that have an indispensable role in tooth enamel formation-amelogenesis. Amelogenesis depends on multiple ameloblast-derived proteins that function as a scaffold for hydroxyapatite crystals. The loss of function of ameloblast-derived proteins results in a group of rare congenital disorders called amelogenesis imperfecta.

Epithelial TNF controls cell differentiation and CFTR activity to maintain intestinal mucin homeostasis.

The gastrointestinal tract relies on the production, maturation, and transit of mucin to protect against pathogens and to lubricate the epithelial lining. Although the molecular and cellular mechanisms that regulate mucin production and movement are beginning to be understood, the upstream epithelial signals that contribute to mucin regulation remain unclear. Here, we report that the inflammatory cytokine tumor necrosis factor (TNF), generated by the epithelium, contributes to mucin homeostasis by regulating both cell differentiation and cystic fibrosis transmembrane conductance regulator (CFTR) activity.

A Suite of Mouse Reagents for Studying Amelogenesis.

Amelogenesis, the formation of dental enamel, is driven by specialized epithelial cells called ameloblasts, which undergo successive stages of differentiation. Ameloblasts secrete enamel matrix proteins (EMPs), proteases, calcium, and phosphate ions in a stage-specific manner to form mature tooth enamel. Developmental defects in tooth enamel are common in humans, and they can greatly impact the well-being of affected individuals.

Early evolution of enamel matrix proteins is reflected by pleiotropy of physiological functions.

Highly specialized enamel matrix proteins (EMPs) are predominantly expressed in odontogenic tissues and diverged from common ancestral gene. They are crucial for the maturation of enamel and its extreme complexity in multiple independent lineages. However, divergence of EMPs occured already before the true enamel evolved and their conservancy in toothless species suggests that non-canonical functions are still under natural selection.

A DLG1-ARHGAP31-CDC42 axis is essential for the intestinal stem cell response to fluctuating niche Wnt signaling.

A central factor in the maintenance of tissue integrity is the response of stem cells to variations in the levels of niche signals. In the gut, intestinal stem cells (ISCs) depend on Wnt ligands for self-renewal and proliferation. Transient increases in Wnt signaling promote regeneration after injury or in inflammatory bowel diseases, whereas constitutive activation of this pathway leads to colorectal cancer.

SRSF1 governs progenitor-specific alternative splicing to maintain adult epithelial tissue homeostasis and renewal.

Alternative splicing generates distinct mRNA variants and is essential for development, homeostasis, and renewal. Proteins of the serine/arginine (SR)-rich splicing factor family are major splicing regulators that are broadly required for organ development as well as cell and organism viability. However, how these proteins support adult organ function remains largely unknown.

Inflation-collapse dynamics drive patterning and morphogenesis in intestinal organoids.

How stem cells self-organize to form structured tissues is an unsolved problem. Intestinal organoids offer a model of self-organization as they generate stem cell zones (SCZs) of typical size even without a spatially structured environment. Here we examine processes governing the size of SCZs.

Generation of Knockout Gene-Edited Human Intestinal Organoids.

We discuss a methodology to generate and study knockout gene-edited human intestinal organoids. We describe the generation of knockout human embryonic stem cell lines that we then differentiate into mature human intestinal organoid tissue in Matrigel using several growth factors. We also discuss a pair of assays that can be used to study the integrity of the intestinal epithelial barrier of the human intestinal organoids under inflammatory stress conditions.

A large pool of actively cycling progenitors orchestrates self-renewal and injury repair of an ectodermal appendage.

The classical model of tissue renewal posits that small numbers of quiescent stem cells (SCs) give rise to proliferating transit-amplifying cells before terminal differentiation. However, many organs house pools of SCs with proliferative and differentiation potentials that diverge from this template. Resolving SC identity and organization is therefore central to understanding tissue renewal.

Atoh1 secretory progenitors possess renewal capacity independent of Lgr5 cells during colonic regeneration.

During homeostasis, the colonic epithelium is replenished every 3-5 days by rapidly cycling stem cells. However, various insults can lead to depletion of stem cells, and colonic epithelium can be regenerated from negative cells. While studies in the small intestine have addressed the lineage identity of the negative regenerative cell population, in the colon this question has remained unanswered.

Cytotoxic activity of Kingella kingae RtxA toxin depends on post-translational acylation of lysine residues and cholesterol binding.

Kingella kingae is a member of the commensal oropharyngeal flora of young children. Improvements in detection methods have led to the recognition of K. kingae as an emerging pathogen that frequently causes osteoarticular infections in children and a severe form of infective endocarditis in children and adults.

Intrinsically disordered proteins drive enamel formation via an evolutionarily conserved self-assembly motif.

The formation of mineralized tissues is governed by extracellular matrix proteins that assemble into a 3D organic matrix directing the deposition of hydroxyapatite. Although the formation of bones and dentin depends on the self-assembly of type I collagen via the Gly-X-Y motif, the molecular mechanism by which enamel matrix proteins (EMPs) assemble into the organic matrix remains poorly understood. Here we identified a Y/F-x-x-Y/L/F-x-Y/F motif, evolutionarily conserved from the first tetrapods to man, that is crucial for higher order structure self-assembly of the key intrinsically disordered EMPs, ameloblastin and amelogenin.

Calcium-Driven Folding of RTX Domain β-Rolls Ratchets Translocation of RTX Proteins through Type I Secretion Ducts.

Calcium-binding RTX proteins are equipped with C-terminal secretion signals and translocate from the Ca(2+)-depleted cytosol of Gram-negative bacteria directly into the Ca(2+)-rich external milieu, passing through the "channel-tunnel" ducts of type I secretion systems (T1SSs). Using Bordetella pertussis adenylate cyclase toxin, we solved the structure of an essential C-terminal assembly that caps the RTX domains of RTX family leukotoxins. This is shown to scaffold directional Ca(2+)-dependent folding of the carboxy-proximal RTX repeat blocks into β-rolls.

Transmembrane segments of complement receptor 3 do not participate in cytotoxic activities but determine receptor structure required for action of Bordetella adenylate cyclase toxin.

Adenylate cyclase toxin-hemolysin (CyaA, ACT or AC-Hly) of the whooping cough agent Bordetella pertussis penetrates phagocytes expressing the integrin complement receptor 3 (CR3, CD11b/CD18, α(M)β(2) or Mac-1). CyaA translocates its adenylate cyclase (AC) enzyme domain into cell cytosol and catalyzes unregulated conversion of ATP to cAMP, thereby subverting cellular signaling. In parallel, CyaA forms small cation-selective membrane pores that permeabilize cells for potassium efflux, contributing to cytotoxicity of CyaA and eventually provoking colloid-osmotic cell lysis.

Quantification of potassium levels in cells treated with Bordetella adenylate cyclase toxin.

The aim of this study was to compare two methods for quantification of changes in intracellular potassium concentration (decrease from ∼140 to ∼20mM) due to the action of a pore-forming toxin, the adenylate cyclase toxin (CyaA) from the pathogenic bacterium Bordetella pertussis. CyaA was incubated with stably transfected K1 Chinese hamster ovary cells expressing the toxin receptor CD11b/CD18 and the decrease in potassium concentration in the cells was followed by inductively coupled plasma mass spectrometry (ICP-MS). It is shown that this method is superior in terms of sensitivity, accuracy, and temporal resolution over the method employing the potassium-binding benzofuran isophthalate-acetoxymethyl ester fluorescent indicator.

Intrinsically disordered enamel matrix protein ameloblastin forms ribbon-like supramolecular structures via an N-terminal segment encoded by exon 5.

Tooth enamel, the hardest tissue in the body, is formed by the evolutionarily highly conserved biomineralization process that is controlled by extracellular matrix proteins. The intrinsically disordered matrix protein ameloblastin (AMBN) is the most abundant nonamelogenin protein of the developing enamel and a key element for correct enamel formation. AMBN was suggested to be a cell adhesion molecule that regulates proliferation and differentiation of ameloblasts.

The Bordetella pertussis type III secretion system tip complex protein Bsp22 is not a protective antigen and fails to elicit serum antibody responses during infection of humans and mice.

The type III secretion system (T3SS) of pathogenic bordetellae employs a self-associating tip complex protein Bsp22. This protein is immunogenic during infections by Bordetella bronchiseptica and could be used as a protective antigen to immunize mice against B. bronchiseptica challenge.

Biophysical characterization of recombinant human ameloblastin.

Ameloblastin (AMBN) is a protein expressed mainly during dental hard tissue development. Biochemically, it is classified as an intrinsically disordered protein (IDP). Its biological role remains largely unknown; however, the question of AMBN function will undoubtedly be connected to its structural properties and its potential for protein-protein and protein-cell interactions.