Zebrafish prss59.1 is involved in chorion development.

The prss59.1 gene was identified as one of 11 genes that were highly upregulated during the induction of ovulation in zebrafish by using an in vivo ovulation assay. Previously, we conducted biochemical characterization of Prss59.1 and revealed it to be a trypsin-like proteolytic enzyme. In this study, we established a prss59.1 gene knockout strain using the CRISPR/Cas9 system. Phenotypic analysis of prss59.1 knockout fish showed that prss59.1 is associated with chorion elevation, a prominent event in egg activation during fertilization. The chorions of heterozygous and homozygous prss59.1 mutant zebrafish were smaller than those of the wild type. The results suggested that Prss59.1 is necessary for chorion expansion. The homozygous prss59.1 mutant strain, with a small chorion, showed an extremely low survival rate. Fiber-supported knob-like structures (KS) on the chorion showed an abnormal structure in prss59.1 mutants. Prss59.1 was detected in the KS on the chorion. The pores on the chorion were smaller in the prss59.1 mutants than in the wild type. Transmission electron microscopy (TEM) observations of the cross sections of the chorions showed abnormalities in the chorion structure in prss59.1 mutants. These results demonstrated that Prss59.1 is involved in chorion elevation and in proper formation of the chorion, which is necessary for embryo development.

Characterisation of dehydrated amnion chorion membranes and evaluation of fibroblast and keratinocyte responses in vitro.

The purpose of this study is to characterise the composition of a dehydrated amnion and chorion graft and investigate how factors released from this graft interact with cells important to the wound microenvironment using in vitro models. Characterisation was completed by proteomic analysis of growth factors and cytokines, evaluation of matrix components and protease inhibition, immunohistochemistry, and in vitro release of key growth factors and cytokines. To evaluate the effect of released factors on cells found within the microenvironment, in vitro assays including: cell proliferation, migration, gene expression, protein production, and intracellular pathway activation were used; additionally, responses of fibroblasts in the context of inflammation were measured. We found that released factors from dehydrated amnion/chorion membranes (dACM) stimulated cell proliferation, migration, and altered gene and protein expression profiles of cells important for wound repair in vitro. When cells were cultured in the presence of pro-inflammatory cytokines, the addition of releasate from dACM resulted in an altered production of cytokines, including a reduction of pro-inflammatory regulated on activation, normal T cell expressed and secreted (RANTES). In sum, the results presented here characterise the components of dACM, and in vitro studies were used to evaluate interactions of dACM with cell types important in wound healing.

Skin Integrity and Infection Prevention Las Vegas: don't bust on biofilm, bet on dHACM.

The 4th International Skin Integrity and Infection Prevention conference, hosted by the Journal of Wound Care and the University of Huddersfield, was held earlier this year in Las Vegas. A key theme was the impact of biofilm on wound healing. In the second of our sponsored symposia reports, the manner in which delayed healing can be reversed through effective biofilm management, and the introduction of regulatory proteins found in dehydrated human amnion chorion membrane allograft were explained.

Effects of L-carnitine on reproductive performance, milk composition, placental development and IGF concentrations in blood plasma and placental chorions in sows.

Recent studies have shown that L-carnitine supplementation of sows during pregnancy and lactation enhances their reproductive performance, but the underlying mechanisms are still needed to be further confirmed. This study was conducted to investigate the function of L-carnitine on placental development, milk nutrient content and release of hormones in sows. In this experiment, 40 multiparous crossbred sows (Yorkshire × Landrace) were allotted to two groups fed diets with or without a supplemental 50 mg/kg L-carnitine. The experimental diets were fed from d 1 post-coitus until d 21 post-partum. L-carnitine-treated sow had fewer weak piglets (p < 0.05) and a greater percentage of oestrus by 5 after 5-d post-partum (p < 0.05) than control sows. The percentage fat from colostrum was greater in L-carnitine-treated sow than control sows (p < 0.05). L-carnitine-treated sows had greater plasma concentrations of triglyceride and insulin-like growth factor (IGF)-1 and lesser plasma concentrations of glucose and IGF-binding protein (IGFBP-3) on day 60 of pregnancy (p < 0.05). A clearer structure of chorions, better-developed capillaries and absence of necrosis were observed in L-carnitine-treated sows compared with control sows. The protein abundance of IGF-1 and IGF-2 in placental chorions was greater in L-carnitine-treated sows compared with control sows (p < 0.05). This study suggests that sows fed an L-carnitine supplemented diet during pregnancy improved reproductive performance through enhancement of placental development and by increasing IGF concentrations in blood plasma and placental chorions.

Salinity-dependent toxicity of water-dispersible, single-walled carbon nanotubes to Japanese medaka embryos.

To investigate the effects of salinity on the behavior and toxicity of functionalized single-walled carbon nanotubes (SWCNTs), which are chemical modified nanotube to increase dispersibility, medaka embryos were exposed to non-functionalized single-walled carbon nanotubes (N-SWCNTs), water-dispersible, cationic, plastic-polymer-coated, single-walled carbon nanotubes (W-SWCNTs), or hydrophobic polyethylene glycol-functionalized, single-walled carbon nanotubes (PEG-SWCNTs) at different salinities, from freshwater to seawater. As reference nanomaterials, we tested dispersible chitin nanofiber (CNF), chitosan-chitin nanofiber (CCNF) and chitin nanocrystal (CNC, i.e. shortened CNF). Under freshwater conditions, with exposure to 10 mg l-1 W-SWCNTs, the yolk sacks of 57.8% of embryos shrank, and the remaining embryos had a reduced heart rate, eye diameter and hatching rate. Larvae had severe defects of the spinal cord, membranous fin and tail formation. These toxic effects increased with increasing salinity. Survival rates declined with increasing salinity and reached 0.0% in seawater. In scanning electron microscope images, W-SWCNTs, CNF, CCNF and CNC were adsorbed densely over the egg chorion surface; however, because of chitin's biologically harmless properties, only W-SWCNTs had toxic effects on the medaka eggs. No toxicity was observed from N-SWCNT and PEG-SWCNT exposure. We demonstrated that water dispersibility, surface chemistry, biomedical properties and salinity were important factors in assessing the aquatic toxicity of nanomaterials. Copyright © 2016 John Wiley & Sons, Ltd.

Prostaglandin pathway gene expression in human placenta, amnion and choriodecidua is differentially affected by preterm and term labour and by uterine inflammation.

BACKGROUND: Elucidation of the biochemical pathways involved in activation of preterm and term human labour would facilitate the development of effective management and inform judgements regarding the necessity for preterm tocolysis and post-term induction. Prostaglandins act at all stages of human reproduction, and are potentially activators of labour. METHODS: Expression of 15 genes involved in prostaglandin synthesis, transport and degradation was measured by qPCR using tissue samples from human placenta, amnion and choriodecidua at preterm and full-term vaginal and caesarean delivery. Cellular localisation of eight prostaglandin pathway proteins was determined by immunohistochemistry. RESULTS: Expression of prostaglandin pathway genes was differentially affected by factors including gestational age at delivery, and the incidence and duration of labour. Chorioamnionitis/deciduitis was associated with upregulation of PTGS2 (prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclooxygenase)), along with the inflammatory genes IL8 (interleukin 8), S100A8 (S100 calcium binding protein A8) and TLR2 (toll-like receptor 2), in amnion and choriodecidua, and with downregulation of CBR1 (carbonyl reductase 1) and HPGD (hydroxyprostaglandin dehydrogenase 15-(NAD)) in choriodecidua. Protein localisation differed greatly between the various maternal and fetal cell types. CONCLUSIONS: Preterm and term labour are associated with distinct prostaglandin pathway expression profiles; inflammation provokes specific changes, unrelated to the presence of labour; spontaneous and induced term labour are indistinguishable.

Comparison of cryopreserved amniotic membrane and umbilical cord tissue with dehydrated amniotic membrane/chorion tissue.

OBJECTIVE: To evaluate how the different processing methods cryopreservation and dehydration affect the structural integrity and biological composition of key signalling molecules within amniotic membrane and umbilical cord tissues. METHOD: We directly compared cryopreserved amniotic membrane (AM) and umbilical cord (UC) tissues with dehydrated amniotic membrane/chorion (dHACM) tissue using biochemical and functional assays including histological and histochemical staining, BCA, agarose gel electrophoresis, western blot, ELISA, and proliferation and cell death assays. RESULTS: Cryopreservation retains the native architecture of the AM/UC extracellular matrix and maintains the quantity and activity of key biological signals present in fresh AM/UC, including high molecular weight hyaluronic acid, heavy chain-HA complex, and pentraxin 3. In contrast, dehydrated tissues were structurally compromised and almost completely lacked these crucial components. CONCLUSION: The results presented here indicate that cryopreservation better preserves the structural and biological signaling molecules of foetal tissues.

[The related study of first pregnancy women with Cu-IUD on copper content of blood serum and decidua, chorion tissues].

OBJECTIVE: Through determine the copper content of decidua, chorion and blood serum of first pregnancy women with Cu-IUD, we offer date for security of offspring. METHODS: March 2010 to December 2010, in family planning clinics of the general hospital of Tianjin medical university, we selected twenty-five first pregnancy women with Cu-IUD who intended to terminate pregnancy to be experimental group and twenty-five normal first pregnancy women who intended to terminate pregnancy to be control group, and determined the copper content of decidua, chorion and blood serum in experimental group and control group. RESULTS: The copper content of decidua, chorion and blood serum in experimental group is (0.91 ± 0.51) mg/kg, (0.72 ± 0.50) mg/kg, (0.79 ± 0.15) mg/L; the copper content of decidua, chorion and blood serum in control group is (0.57 ± 0.21) mg/kg, (0.46 ± 0.21) mg/kg, (0.71 ± 0.15) mg/L. The copper content of blood serum has no significant difference between experimental group and control group (P > 0.05). The copper content of decidua, chorion of experimental group is higher than control group (P < 0.05). CONCLUSION: Copper ion released from Cu-IUD only has an influence on the uterus tissues, but having no influence on the copper metabolism all over the body. The effects of high copper content of chorion in first pregnancy women with Cu-IUD on the offspring security will be researched further.

Significance of eggshell morphology as an additional tool to distinguish species of sand flies (Diptera: Psychodidae: Phlebotominae).

Morphological characteristics of eggshells are important in sand fly ootaxonomy. In this study, eggshells from Phlebotomus stantoni Newstead, Sergentomyia khawi (Raynal), and Grassomyia indica (Theodor) sand flies collected in Chiang Mai province, Thailand were examined and characterized using light microscopy (LM) and scanning electron microscopy (SEM). Then, eggshell morphology of these three species was described for the first time. Each gravid female was forced to lay eggs by decapitation and the eggs were collected for SEM analysis. Egg laying females were identified by morphological examination and molecular typing using cytochrome b (Cytb) as a molecular marker. The chorionic sculpturing of Ph. stantoni eggs combines two patterns on the same egg: unconnected parallel ridges and reticular patterns. Sergentomyia khawi and Gr. indica have similar chorionic polygonal patterns, but their exochorionic morphology and aeropylar area are different. Results indicate that eggshell morphological characteristics such as chorionic pattern, exochorionic morphology, inter-ridge/boundary area, aeropylar area (including the number of aeropyles) and basal layer, can be useful to develop morphological identification keys of eggs. These can serve as an additional tool to distinguish species of sand flies. In addition, the chorionic sculpturing of the eggs of the three species of sand flies observed by LM is useful for species identification in gravid females with spermathecae obscured by eggs.

phytanoyl-CoA dioxygenase domain-containing protein 1 plays an important role in egg shell formation of silkworm (Bombyx mori).

Yun7Ge is a giant egg mutant found in the silkworm variety Yun7. In comparison with the giant mutant Ge, the eggs of Yun7Ge are larger. The number of laid eggs and hatching rate of Yun7Ge are reduced, which is not conducive to reproduction. In this work, the target gene controlling giant egg trait is located on the Z chromosome and was determined through genetic analysis. Transcriptome results showed that phytanoyl-CoA dioxygenase domain-containing protein 1 (PHYHD1) on the Z chromosome was silenced, and the 25 chorion genes on chromosome 2 were remarkably downregulated. Sequence analysis showed that the 73.5 kb sequence including the PHYHD1 was replaced by a ~3.0 kb sequence. After knocking out the PHYHD1 by using CRISPR/Cas9, the chorion genes were significantly downregulated. Hence, the silencing of PHYHD1 leads to the downregulation of many chorion protein genes, thus directly causing giant eggs.

Expression and regulation of prostaglandin receptors in the human placenta and fetal membranes at term and preterm.

Prostaglandins (PGs) play an important role in parturition in many species, including humans. The present study examined the distribution of PG receptor subtypes (EP1-4 and FP) in intrauterine tissues at term and preterm birth. Placentas and fetal membranes were collected from patients at term in labour (n = 12) or not in labour (n = 12). Preterm tissue was collected from three different groups of patients: (1) idiopathic preterm labour (PTL) without chorioamnionitis or betamethasone (BM) treatment (n = 9), (2) idiopathic PTL that received BM with no chorioamnionitis (PTL-BM; n = 9) and (3) pregnancies that were complicated with chorioamnionitis and had no BM (PTL-CHA; n = 6). EP1-4 and FP receptors were localised and levels of expression were determined by western blot analysis. All EP receptors and FP were localised to the amnion, placenta and choriodecidua. Moreover, isolated amnion mesenchymal, amnion epithelial, chorion trophoblast and syncytiotrophoblast cells in primary culture also expressed PG receptors. A significant increase was observed in EP1, EP3 and FP expression in placenta, chorion and amnion with labour. Maternal betamethasone treatment increased EP1, EP3 and FP receptor protein expression and chorioamnionitis decreased expression in all the receptor subtypes. These changes in PG receptors in the fetal membranes are consistent with the development of a feed-forwards cascade mediated through PG action that may contribute to the birth process.

Ability of polyurethane foams to support placenta-derived cell adhesion and osteogenic differentiation: preliminary results.

In bone tissue reconstruction, the use of engineered constructs created by mesenchymal stem cells (MSCs) that differentiate and proliferate into 3D porous scaffolds is an appealing alternative to clinical therapies. Human placenta represents a possible source of MSCs, as it is readily available without invasive procedures and because of the phenotypic plasticity of many of the cell types isolated from this tissue. The scaffold considered in this work is a slowly degradable polyurethane foam (EF PU foam), synthesized and characterized for morphology and in vitro interaction with chorion mesenchymal cells (CMCs). These cells were isolated from human term placenta and cultured onto the EF PU foam using two different culture media (EMEM and NH osteogenic differentiation medium). Synthesized EF PU foam showed homogeneous pore size and distribution, with 89% open porosity. In vitro tests showed CMCs scaffold colonization, as confirmed by Scanning Electron Microscopy (SEM) observations and hematoxylin-eosin staining. Alizarin Red staining revealed the presence of a small amount of calcium deposition for the samples treated with the osteogenic differentiation medium. Therefore, the proposed EF PU foam appears to stimulate cell adhesion in vitro, sustaining CMCs growth and differentiation into the osteogenic lineage.

Decellularized Human Chorion Membrane as a Novel Biomaterial for Tissue Regeneration.

Although some placenta-derived products are already used for tissue regeneration, the human chorion membrane (HCM) alone has been poorly explored. In fact, just one study uses decellularized HCM (dHCM) with native tissue architecture (i.e., without extracellular matrix (ECM) suspension creation) as a substrate for cell differentiation. The aim of this work is to fully characterize the dHCM for the presence and distribution of cell nuclei, DNA and ECM components. Moreover, mechanical properties, in vitro biological performance and in vivo biocompatibility were also studied. Our results demonstrated that the HCM was successfully decellularized and the main ECM proteins were preserved. The dHCM has two different surfaces, the reticular layer side and the trophoblast side; and is biocompatible both in vitro and in vivo. Importantly, the in vivo experiments demonstrated that on day 28 the dHCM starts to be integrated by the host tissue. Altogether, these results support the hypothesis that dHCM may be used as a biomaterial for different tissue regeneration strategies, particularly when a membrane is needed to separate tissues, organs or other biologic compartments.

Intermediate layer contribution in placental membrane allografts.

Placental membrane (PM) allografts are commonly used to treat chronic wounds. Native PM is composed of an amnion, chorion, and intermediate layer (IL) that contain matrix structures and regulatory components beneficial in wound healing. Historically, commercially available allografts were composed of only one or two layers of the PM. To maximize the conserved material in PM allografts, a dehydrated complete human placental membrane (dCHPM) allograft processed using the Clearify™ process was developed. Histological and proteomic characterization comparing dCHPM allografts with native PM demonstrated that the majority of matrix structures and regulatory proteins are retained in dCHPM allografts through processing. To evaluate the importance of maintaining the entire intact PM and the contribution of the IL, the structural and proteomic makeup of the IL was compared with that of dCHPM allografts. This is the first known characterization of regulatory proteins in the IL. Results demonstrate that the IL contains over 900 regulatory and signaling components, including chemokines, growth factors, interleukins, and protease inhibitors. These components are key regulators of angiogenesis, neurogenesis, osteogenesis, inflammation, tissue remodeling, and host defense. The results show that the proteomic composition of the IL is consistent with that of the entire dCHPM allograft. Although further investigation is required to fully understand the contribution of the IL in PM allografts, these results demonstrate that the IL contains structural and regulatory proteins that can enhance the barrier and wound healing properties of PM allografts.

Up-to-date role of the dehydrated human amnion/chorion membrane (AMNIOFIX) for wound healing.

INTRODUCTION: Chronic wounds pose a significant burden on patients, society, and the health-care setup. Higher costs, protracted clinical course, and increased risk of complications necessitate identifying novel treatment modalities that hasten healing and wound closure. AREAS COVERED: This article covers newer available treatment modalities for chronic wounds, namely the dehydrated amniotic membrane products, biological skin substitutes, and similar therapies aimed at the healing of chronic non-healing wounds. It presents product description for Amniofix (dehydrated human amniotic/chorionic membrane) and its efficacy, compared to other similar products. EXPERT OPINION: In our experience and review of available literature, we expect Amniofix to offer wound care specialists with a more effective, easy-to-use, and convenient treatment modality for chronic wounds. Amniofix and other dHACM (dehydrated human amniotic/chorionic membrane) therapies reported faster and complete healing with lower complication rates, when compared to other similar products. These features encourage the use of Amniofix in Diabetic foot ulcers and Venous Leg Ulcers, besides other conditions such as plantar fasciitis.

Visualization of replication initiation and elongation in Drosophila.

Chorion gene amplification in the ovaries of Drosophila melanogaster is a powerful system for the study of metazoan DNA replication in vivo. Using a combination of high-resolution confocal and deconvolution microscopy and quantitative realtime PCR, we found that initiation and elongation occur during separate developmental stages, thus permitting analysis of these two phases of replication in vivo. Bromodeoxyuridine, origin recognition complex, and the elongation factors minichromosome maintenance proteins (MCM)2-7 and proliferating cell nuclear antigen were precisely localized, and the DNA copy number along the third chromosome chorion amplicon was quantified during multiple developmental stages. These studies revealed that initiation takes place during stages 10B and 11 of egg chamber development, whereas only elongation of existing replication forks occurs during egg chamber stages 12 and 13. The ability to distinguish initiation from elongation makes this an outstanding model to decipher the roles of various replication factors during metazoan DNA replication. We utilized this system to demonstrate that the pre-replication complex component, double-parked protein/cell division cycle 10-dependent transcript 1, is not only necessary for proper MCM2-7 localization, but, unexpectedly, is present during elongation.

Variation in DNA methylation in the KvDMR1 (ICR2) region in first-trimester human pregnancies.

OBJECTIVE: To investigate the levels of DNA methylation in the KvDMR1 (KvLQT1 differentially methylated region 1) in embryonic and extra-embryonic tissues. DESIGN: Cross-sectional study. SETTING: University medical center and clinical hospital. PATIENT(S): Embryonic and/or extraembryonic tissues (umbilical cord, chorionic villus, chorion, decidua, and/or amnion) collected from 27 first-trimester pregnancies (up to 12 weeks of gestation, single embryos) from elective abortions, extravillous trophoblasts (EVTs) from the top of individual chorionic villi, and chorionic villi from 10 normal full-term placentas collected after birth. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): DNA methylation of the KvDMR1 region evaluated using quantitative analysis of DNA methylation followed by real-time polymerase chain reaction (qAMP) and bisulfite sequencing (bis-seq) analysis. RESULT(S): The results showed variability in KvDMR1 DNA methylation in different tissues from the same pregnancy. The average of DNA methylation was not different between the embryo, umbilical cord, amnion, and chorionic villi, despite the relatively low level of methylation observed in the amnion (33.50% ± 14.48%). Chorionic villi from term placentas showed a normal methylation pattern at KvDMR1 (42.60% ± 6.08%). The normal methylation pattern at KvDMR1 in chorionic villi (as well as in EVTs) from first-trimester placentas was confirmed by bis-seq. CONCLUSION(S): Our results highlight an existing heterogeneity in DNA methylation of the KvDMR1 region during first trimester and a consistent hypomethylation in the amnion in this period of gestation.

Human trophoblast cells express the immunomodulator progesterone-induced blocking factor.

Progesterone-induced blocking factor (PIBF) is an immunomoduatory factor with anti-abortive properties. In this study, we present evidence that PIBF is synthesized in the human placenta and determine its cellular source. Expression of PIBF was analysed with polyclonal rabbit anti-human PIBF antibodies against recombinant N-terminal 48kDa PIBF in first trimester and term placental tissues and in the choriocarcinoma cell line JAR by means of immunohistochemistry, confocal laser scanning microscopy of double immunofluorescence labelling, and Western blotting; RT-PCR was performed for analysis of PIBF mRNA in isolated trophoblast cells. PIBF protein is present in human first trimester and term placenta. Double immunofluorescence labelling localised PIBF to the extravillous cytotrophoblast. PIBF is also expressed heterogeneously by syncytiotrophoblast and part of the villous cytotrophoblast. Full-length PIBF mRNA encoded by exons 1-18 is present in isolated first trimester and term villous trophoblast and in the choriocarcinoma cell line JAR. The corresponding 90kDa protein is expressed by JAR cells, first trimester and term villous trophoblast cells. In addition, these cells express PIBF proteins of 50 and 34kDa. Trophoblast is a source of PIBF; its tissue distribution suggests a role both in systemic and local (decidual) immunoregulation.

[Extracellular matrix metalloproteases profile identification in chorioamniotic membranes of term and preterm pregnancies through soluble microarrays]. / Identificación del perfil de metaloproteasas de matriz extracelular en membranas corioamnióticas de embarazos a término y pretérmino mediante microarreglos solubles.

BACKGROUND: Physiological and pathological membrane rupture is a complex phenomenon with different biochemical processes; it is known that collagenolitic activity rises and collagen content diminishes within term tissue membranes in comparison to preterm membranes. Identification of these processes within rupture mechanism allows to suggest that fetal membranes and decidua can respond to biochemical and mechanical stimulus alike, and to produce mediators that degrade matrix of intracellular membranes. OBJECTIVE: To identify simultaneously, whit a soluble microarray, different matrix metalloproteinases in extracts from amniochorion of pregnancies at term and preterm. PATIENTS AND METHODS: Biomedical experimental study where amniochorion explants were obtained from four women groups. Group 1: at term with spontaneous labor; group 2: at term without labor; group 3: at term with premature rupture of membranes, and group 4: preterm labor. Explants were cultured for 24 h and then homogenated in their own culture media to obtain cell free extracts. MMP were identified in these extracts using a soluble microarray for MMPs that included: MMP-1, -2, -3, -7, -8, -9, -12 and -13. RESULTS: MMP-8 and -2 were the enzymes most abundant in all the extracts of amniochorion. However, the concentration of MMP-8 in the extracts of group 3 (PROM) was significantly greater in comparison with the extracts of groups 1 and 2 (p = 0.01). The MMP-8 also was in greater concentration in the extracts of group 4 (preterm labor) in comparison with in the extracts of group 1 (p = 0.01). CONCLUSION: Activation of cellular processes that lead to the degradation of connective tissue in the MCA under physiological conditions seems to defer in originating tissues from cases with PROM or preterm labor, and this activation is characterized by an increase in the concentration of MMP-8.

Hexapeptide Tandem Repeats Dictate the Formation of Silkmoth Chorion, a Natural Protective Amyloid.

Silkmoth chorion is a fibrous structure composed mainly of two major protein classes, families A and B. Both families of silkmoth chorion proteins present a highly conserved, in sequence and in length, central domain, consisting of Gly-rich tandem hexapeptide repetitive segments, flanked by two more variable N-terminal and C-terminal arms. Primary studies identified silkmoth chorion as a functional protective amyloid by unveiling the amyloidogenic properties of the central domain of both protein families. In this work, we attempt to detect the principal source of amyloidogenicity of the central domain by focusing on the role of the tandem hexapeptide sequence repeats. Concurrently, we discuss a possible mechanism for the self-assembly of class A protofilaments, suggesting that the aggregation-prone hexapeptide building blocks may fold into a triangle-shaped ß-helical structure.