Cytoplasmic intermediate filaments revealed as dynamic and multipurpose scaffolds

Keratin Variants in Pyoderma Gangrenosum: Pathogenetic Insights from a Whole-Exome Sequencing-Based Bioinformatic Analysis

Pyoderma gangrenosum (PG) is an inflammatory skin disorder that belongs to the group of neutrophilic dermatoses. Clinically, it is typified by cutaneous ulcers with distinctive erythematoviolaceous borders and may occur alone or in association with other inflammatory, autoinflammatory, or neoplastic conditions. Although its pathophysiology remains incompletely understood, mounting evidence points toward a predisposing genetic background and dysregulation of both the innate and adaptive immune responses, with follicular or epidermal structures as putative initial targets. To investigate the genetic factors associated with PG susceptibility and severity (arbitrarily defined as unilesional or multilesional), whole-exome sequencing was performed on 11 unrelated patients with PG. Eight carried at least 1 variant of the keratin-encoding genes, including keratin (K)18 gene K18, K20, K23, K32, and K33B. Strikingly, a recurrent variant (rs77999286) of the K18 gene was identified in 5 of 6 patients with multilesional PG and 1 of 5 of those with unilesional PG. AlphaFold modeling and mutation analysis revealed the destabilizing effect of the K18 rs77999286 variant on protein structure. Furthermore, immunohistochemistry revealed undetectable K18 staining in lesional skin compared with that in healthy control skin. Overall, these findings suggest that keratin variants may play a role in PG pathogenesis and indicate that the K18 rs77999286 variant is a potential genetic factor linked to multilesional disease.

Improving molecular subtypes and prognosis of pancreatic cancer through multi group analysis and machine learning

BACKGROUND

Pancreatic cancer (PAC) has a complex tumor immune microenvironment, and currently, there is a lack of accurate personalized treatment. Establishing a novel consensus machine learning driven signature (CMLS) that offers a unique predictive model and possible treatment targets for this condition was the goal of this study.

METHODS

This study integrated multiple omics data of PAC patients, applied ten clustering techniques and ten machine learning approaches to construct molecular subtypes for PAC, and created a new CMLS.

RESULTS

Using multi-omics clustering, we discovered two cancer subtypes (CSs) associated with prognosis, among which CS1 exhibited poor prognostic outcomes. Subsequently, 13 central genes were identified through screening, constituting CMLS with a significant prognostic ability. The low CMLS group had a better prognosis and was more likely to possess a "hot" tumor phenotype. The prognosis for the high CMLS group was dismal. Still, the tumor mutation burden (TMB) and tumor neoantigen burden (TNB) levels in this group of patients were higher than in the low CMLS group, which were more favorable for immune therapy response.

CONCLUSION

This study emphasizes that CMLS provides a beneficial instrument for early prediction of patient prognosis and screening of probable patients appropriate for immunotherapy and has broad implications for clinical practice.

m1A-regulated DIAPH3 promotes the invasiveness of colorectal cancer via stabilization of KRT19

BACKGROUND

In recent years, the emphasis has shifted to understanding the role of N1-methyladenosine (m1A) in tumor progression as little is known about its regulatory effect on mRNA and its role in the metastasis of colorectal cancer (CRC).

METHODS

We performed methylated RNA immunoprecipitation sequencing of tumor tissues and tumor-adjacent normal tissues from three patients with CRC to determine the m1A profile of mRNA in CRC. The expression of diaphanous-related formin 3 (DIAPH3) and its correlation with clinicopathological characteristics of CRC were evaluated using immunohistochemistry and online datasets. The role of DIAPH3 in the migration and invasion of CRC cells was evaluated using wound healing assay, Transwell assay and xenograft metastatic model. The downstream targets of DIAPH3 were screened using mass spectrometry. By co-transfecting DIAPH3 siRNA and a keratin 19 (KRT19) ectopic plasmid into CRC cells, the role of DIAPH3-KRT19 signaling axis was confirmed.

RESULTS

The mRNA level of DIAPH3 and its m1A modifications increased simultaneously in the CRC tissues. In addition, high DIAPH3 expression in CRC tissues is significantly associated with metastasis and progression to an advanced stage. After the knockdown of DIAPH3, the migration and invasion capabilities of CRC cells suffered a notable decline, which could be rescued by overexpressing KRT19. In addition, the proteasome inhibitor MG132 could block the degradation of KRT19 induced by DIAPH3 silencing.

CONCLUSIONS

Our study reveals that DIAPH3 mRNA was modified in CRC cells by m1A methylation. Silencing DIAPH3 suppresses the migration and invasion of CRC cells, potentially through the proteasome-dependent degradation of downstream KRT19.

The Type III Intermediate Filament Protein Peripherin Regulates Lysosomal Degradation Activity and Autophagy

Peripherin belongs to heterogeneous class III of intermediate filaments, and it is the only intermediate filament protein selectively expressed in the neurons of the peripheral nervous system. It has been previously discovered that peripherin interacts with proteins important for the endo-lysosomal system and for the transport to late endosomes and lysosomes, such as RAB7A and AP-3, although little is known about its role in the endocytic pathway. Here, we show that peripherin silencing affects lysosomal abundance but also positioning, causing the redistribution of lysosomes from the perinuclear area to the cell periphery. Moreover, peripherin silencing affects lysosomal activity, inhibiting EGFR degradation and the degradation of a fluorogenic substrate for proteases. Furthermore, we demonstrate that peripherin silencing affects lysosomal biogenesis by reducing the TFEB and TFE3 contents. Finally, in peripherin-depleted cells, the autophagic flux is strongly inhibited. Therefore, these data indicate that peripherin has an important role in regulating lysosomal biogenesis, and positioning and functions of lysosomes, affecting both the endocytic and autophagic pathways. Considering that peripherin is the most abundant intermediate filament protein of peripheral neurons, its dysregulation, affecting its functions, could be involved in the onset of several neurodegenerative diseases of the peripheral nervous system characterized by alterations in the endocytic and/or autophagic pathways.

Adapting cytoskeleton-mitochondria patterning with myocyte differentiation by promyogenic PRR33

Coordinated cytoskeleton-mitochondria organization during myogenesis is crucial for muscle development and function. Our understanding of the underlying regulatory mechanisms remains inadequate. Here, we identified a novel muscle-enriched protein, PRR33, which is upregulated during myogenesis and acts as a promyogenic factor. Depletion of Prr33 in C2C12 represses myoblast differentiation. Genetic deletion of Prr33 in mice reduces myofiber size and decreases muscle strength. The Prr33 mutant mice also exhibit impaired myogenesis and defects in muscle regeneration in response to injury. Interactome and transcriptome analyses reveal that PRR33 regulates cytoskeleton and mitochondrial function. Remarkably, PRR33 interacts with DESMIN, a key regulator of cytoskeleton-mitochondria organization in muscle cells. Abrogation of PRR33 in myocytes substantially abolishes the interaction of DESMIN filaments with mitochondria, leading to abnormal intracellular accumulation of DESMIN and mitochondrial disorganization/dysfunction in myofibers. Together, our findings demonstrate that PRR33 and DESMIN constitute an important regulatory module coordinating mitochondrial organization with muscle differentiation.

An endometrial biomimetic extracellular matrix (ECM) for enhanced endometrial regeneration using hyaluronic acid hydrogel containing recombinant human type III collagen

Endometrial injury poses a significant challenge in tissue regeneration, with type III collagen (COL III) playing a pivotal role in maintaining endometrial integrity and facilitating repair. Our study explored the utility of recombinant human type III collagen (RHC) as an intervention for endometrial damage. To address the challenges associated with the inherent instability and rapid degradation of COL III in vivo, we developed an RHC-HA hydrogel by conjugating RHC with hyaluronic acid (HA), thus ensuring a more stable and sustained delivery. Our findings suggested that the RHC-HA hydrogel significantly promoted endometrial regeneration and restored fertility. The hydrogel facilitated prolonged retention of RHC in the uterus, leading to a substantial improvement in the repair process. The synergistic interaction between RHC and HA greatly enhances cell proliferation and adhesion, surpassing the efficacy of HA or RHC alone. Additionally, the RHC-HA hydrogel demonstrated notable anti-fibrotic effects, which are crucial for preventing abnormalities during endometrial healing. These findings suggested that the RHC-HA hydrogel presented a therapeutic strategy in the treatment of uterine endometrial injuries, which may improve female reproductive health.

Endocrine-disrupting compounds and their impact on human placental function: evidence from placenta organ-on-chip studies

The effects of endocrine-disrupting compounds (EDCs) on the placenta, a critical gestational organ for xenobiotic protection, are well reported; however, models to determine the role of EDCs in placental disruption are limited. An advanced 2nd-trimester human placenta organ-on-chip model (2TPLA-OOC) was developed and validated, with six representative cells of the maternal and the fetal interface interconnected with microchannels. Various EDCs (150 ng mL-1 each of bisphenol A, bisphenol S, and polybrominated diphenyl ethers-47 and -99) were gradually propagated across the chip for 72 hours, and their various effects were determined. Cigarette smoke extract (CSE), an environmental risk factor, was used as a positive control. EDCs produced overall oxidative stress in the placental/decidual cells, induced cell-specific endocrine effects, caused limited (<10%) apoptosis/necrosis in trophoblasts and mesenchymal cells, induced localized inflammation but an overall anti-inflammatory shift, did not change immune cell migration from stroma to decidua, and did not affect placental nutrient transport. Overall, (1) the humanized 2TPLA-OOC recreated the placental organ and generated data distinct from the trophoblast and other cells studied in isolation, and (2) at doses associated with adverse pregnancies, EDCs produced limited and localized insults, and the whole organ compensated for the exposure.

Low-input lipidomics reveals lipid metabolism remodelling during early mammalian embryo development

Lipids are indispensable for energy storage, membrane structure and cell signalling. However, dynamic changes in various categories of endogenous lipids in mammalian early embryonic development have not been systematically characterized. Here we comprehensively investigated the dynamic lipid landscape during mouse and human early embryo development. Lipid signatures of different developmental stages are distinct, particularly for the phospholipid classes. We highlight that the high degree of phospholipid unsaturation is a conserved feature as embryos develop to the blastocyst stage. Moreover, we show that lipid desaturases such as SCD1 are required for in vitro blastocyst development and blastocyst implantation. One of the mechanisms is through the regulation of unsaturated fatty-acid-mediated fluidity of the plasma membrane and apical proteins and the establishment of apical-basal polarity during development of the eight-cell embryo to the blastocyst. Overall, our study provides an invaluable resource about the remodelling of the endogenous lipidome in mammalian preimplantation embryo development and mechanistic insights into the regulation of embryogenesis and implantation by lipid unsaturation.

Single-cell RNA sequencing-guided fate-mapping toolkit delineates the contribution of yolk sac erythro-myeloid progenitors

Erythro-myeloid progenitors of the yolk sac that originates during early embryo development has been suggested to generate tissue-resident macrophage, mast cell, and even endothelial cell populations from fetal to adult stages. However, the heterogeneity of erythro-myeloid progenitors (EMPs) is not well characterized. Here, we adapt single-cell RNA sequencing to dissect the heterogeneity of EMPs and establish several fate-mapping tools for each EMP subset to trace the contributions of different EMP subsets. We identify two primitive and one definitive EMP subsets from the yolk sac. In addition, we find that primitive EMPs are decoupled from definitive EMPs. Furthermore, we confirm that primitive and definitive EMPs give rise to microglia and other tissue-resident macrophages, respectively. In contrast, only Kit+ Csf1r- primitive EMPs generate endothelial cells transiently during early embryo development. Overall, our results delineate the contribution of yolk sac EMPs more clearly based on the single-cell RNA sequencing (scRNA-seq)-guided fate-mapping toolkit.

E3 ubiquitin ligase RNF187 promotes growth of spermatogonia via lysine 48-linked polyubiquitination-mediated degradation of KRT36/KRT84

Ubiquitination is the most common post-translational modification and is essential for various cellular regulatory processes. RNF187, which is known as RING domain AP1 coactivator-1, is a member of the RING finger family. RNF187 can promote the proliferation and migration of various tumor cells. However, whether it has a similar role in regulating spermatogonia is not clear. This study explored the role and molecular mechanism of RNF187 in a mouse spermatogonia cell line (GC-1). We found that RNF187 knockdown reduced the proliferation and migration of GC-1 cells and promoted their apoptosis. RNF187 overexpression significantly increased the proliferation and migration of GC-1 cells. In addition, we identified Keratin36/Keratin84 (KRT36/KRT84) as interactors with RNF187 by co-immunoprecipitation and mass spectrometry analyses. RNF187 promoted GC-1 cell growth by degrading KRT36/KRT84 via lysine 48-linked polyubiquitination. Subsequently, we found that KRT36 or KRT84 overexpression significantly attenuated proliferation and migration of RNF187-overexpressing GC-1 cells. In summary, our study explored the involvement of RNF187 in regulating the growth of spermatogonia via lysine 48-linked polyubiquitination-mediated degradation of KRT36/KRT84. This may provide a promising new strategy for treating infertility caused by abnormal spermatogonia development.

Omics Views of Mechanisms for Cell Fate Determination in Early Mammalian Development

During mammalian preimplantation development, a totipotent zygote undergoes several cell cleavages and two rounds of cell fate determination, ultimately forming a mature blastocyst. Along with compaction, the establishment of apicobasal cell polarity breaks the symmetry of an embryo and guides subsequent cell fate choice. Although the lineage segregation of the inner cell mass (ICM) and trophectoderm (TE) is the first symbol of cell differentiation, several molecules have been shown to bias the early cell fate through their inter-cellular variations at much earlier stages, including the 2- and 4-cell stages. The underlying mechanisms of early cell fate determination have long been an important research topic. In this review, we summarize the molecular events that occur during early embryogenesis, as well as the current understanding of their regulatory roles in cell fate decisions. Moreover, as powerful tools for early embryogenesis research, single-cell omics techniques have been applied to both mouse and human preimplantation embryos and have contributed to the discovery of cell fate regulators. Here, we summarize their applications in the research of preimplantation embryos, and provide new insights and perspectives on cell fate regulation.

Transcriptomic analysis reveals partial epithelial-mesenchymal transition and inflammation as common pathogenic mechanisms in hypertensive nephrosclerosis and Type 2 diabetic nephropathy

Hypertensive nephrosclerosis (HN) and Type 2 diabetic nephropathy (T2DN) are the leading causes of chronic kidney disease (CKD). To explore shared pathogenetic mechanisms, we analyzed transcriptomes of kidney biopsies from patients with HN or T2DN. Total RNA was extracted from 10 μm whole kidney sections from patients with HN, T2DN, and normal controls (Ctrl) (n = 6 for each group) and processed for RNA sequencing. Differentially expressed (log2 fold change >1, adjusted p < 0.05) genes (DEG) and molecular pathways were analyzed, and selected results were validated by immunohistochemistry (IHC). ELISA on serum samples was performed on a related cohort consisting of patients with biopsy-proven HN (n = 13) and DN (n = 9), and a normal control group (n = 14). Cluster analysis on RNA sequencing data separated diseased and normal tissues. RNA sequencing revealed that 88% (341 out of 384) of DEG in HN were also altered in T2DN, while gene set enrichment analysis (GSEA) showed that over 90% of affected molecular pathways, including those related to inflammation, immune response, and cell-cycle regulation, were similarly impacted in both HN and T2DN samples. The increased expression of genes tied to interleukin signaling and lymphocyte activation was more pronounced in HN, while genes associated with extracellular matrix organization were more evident in T2DN. Both HN and T2DN tissues exhibited significant upregulation of genes connected with inflammatory responses, T-cell activity, and partial epithelial to mesenchymal transition (p-EMT). Immunohistochemistry (IHC) further confirmed T-cell (CD4+ and CD8+ ) infiltration in the diseased tissues. Additionally, IHC revealed heightened AXL protein expression, a key regulator of inflammation and p-EMT, in both HN and T2DN, while serum analysis indicated elevated soluble AXL levels in patients with both conditions. These findings underline the shared molecular mechanisms between HN and T2DN, hinting at the potential for common therapeutic strategies targeting both diseases.

Intermediate filament proteins are reliable immunohistological biomarkers to help diagnose multiple tissue-specific diseases

Cytoskeletal networks are proteins that effectively maintain cell integrity and provide mechanical support to cells by actively transmitting mechanical signals. Intermediate filaments, which are from the cytoskeleton family and are 10 nanometres in diameter, are unlike actin and microtubules, which are highly dynamic cytoskeletal elements. Intermediate filaments are flexible at low strain, harden at high strain and resist breaking. For this reason, these filaments fulfil structural functions by providing mechanical support to the cells through their different strain-hardening properties. Intermediate filaments are suitable in that cells both cope with mechanical forces and modulate signal transmission. These filaments are composed of fibrous proteins that exhibit a central α-helical rod domain with a conserved substructure. Intermediate filament proteins are divided into six groups. Type I and type II include acidic and basic keratins, type III, vimentin, desmin, peripheralin and glial fibrillary acidic protein (GFAP), respectively. Type IV intermediate filament group includes neurofilament proteins and a fourth neurofilament subunit, α-internexin proteins. Type V consists of lamins located in the nucleus, and the type VI group consists of lens-specific intermediate filaments, CP49/phakinin and filen. Intermediate filament proteins show specific immunoreactivity in differentiating cells and mature cells of various types. Various carcinomas such as colorectal, urothelial and ovarian, diseases such as chronic pancreatitis, cirrhosis, hepatitis and cataract have been associated with intermediate filaments. Accordingly, this section reviews available immunohistochemical antibodies to intermediate filament proteins. Identification of intermediate filament proteins by methodological methods may contribute to the understanding of complex diseases.

KRT18 regulates trophoblast cell migration and invasion which are essential for embryo implantation

Female infertility is a worldwide concern that impacts the quality of life and well-being of affected couples. Failure of embryo implantation is a major cause of early pregnancy loss and is precisely regulated by a programmed molecular mechanism. Recent studies have shown that proper trophoblast adhesion and invasion are essential for embryo implantation. However, the potential regulatory mechanism involved in trophoblast adhesion and invasion has yet to be fully elucidated. KRT18 has been reported to play a critical role in early embryonic development, but its physiological function in embryo implantation remains unclear. In the present study, we revealed that KRT18 was highly expressed in trophoblast cells and that knockdown of KRT18 in mouse embryos inhibited embryo adhesion and implantation. In vitro experiments further showed that silencing KRT18 disturbed trophoblast migration and invasion. More importantly, we provide evidence that KRT18 directly binds to and stabilizes cell surface E-cadherin in trophoblast cells through microscale thermophoresis (MST) analysis and molecular biology experiments. In brief, our data reveal that KRT18, which is highly expressed in trophoblast cells, plays an important role in the regulation of trophoblast invasion and adhesion during embryo implantation by directly binding to E-cadherin.

A programmed cell death-related model based on machine learning for predicting prognosis and immunotherapy responses in patients with lung adenocarcinoma

Background

lung adenocarcinoma (LUAD) remains one of the most common and lethal malignancies with poor prognosis. Programmed cell death (PCD) is an evolutionarily conserved cell suicide process that regulates tumorigenesis, progression, and metastasis of cancer cells. However, a comprehensive analysis of the role of PCD in LUAD is still unavailable.

Methods

We analyzed multi-omic variations in PCD-related genes (PCDRGs) for LUAD. We used cross-validation of 10 machine learning algorithms (101 combinations) to synthetically develop and validate an optimal prognostic cell death score (CDS) model based on the PCDRGs expression profile. Patients were classified based on their median CDS values into the high and low-CDS groups. Next, we compared the differences in the genomics, biological functions, and tumor microenvironment of patients between both groups. In addition, we assessed the ability of CDS for predicting the response of patients from the immunotherapy cohort to immunotherapy. Finally, functional validation of key genes in CDS was performed.

Results

We constructed CDS based on four PCDRGs, which could effectively and consistently stratify patients with LUAD (patients with high CDS had poor prognoses). The performance of our CDS was superior compared to 77 LUAD signatures that have been previously published. The results revealed significant genetic alterations like mutation count, TMB, and CNV were observed in patients with high CDS. Furthermore, we observed an association of CDS with immune cell infiltration, microsatellite instability, SNV neoantigens. The immune status of patients with low CDS was more active. In addition, CDS could be reliable to predict therapeutic response in multiple immunotherapy cohorts. In vitro experiments revealed that high DNA damage inducible transcript 4 (DDIT4) expression in LUAD cells mediated protumor effects.

Conclusion

CDS was constructed based on PCDRGs using machine learning. This model could accurately predict patients' prognoses and their responses to therapy. These results provide new promising tools for clinical management and aid in designing personalized treatment strategies for patients with LUAD.

What about the Cytoskeletal and Related Proteins of Tapeworms in the Host's Immune Response? An Integrative Overview

Recent advances have increased our understanding of the molecular machinery in the cytoskeleton of mammalian cells, in contrast to the case of tapeworm parasites, where cytoskeleton remains poorly characterized. The pertinence of a better knowledge of the tapeworm cytoskeleton is linked to the medical importance of these parasitic diseases in humans and animal stock. Moreover, its study could offer new possibilities for the development of more effective anti-parasitic drugs, as well as better strategies for their surveillance, prevention, and control. In the present review, we compile the results of recent experiments on the cytoskeleton of these parasites and analyze how these novel findings might trigger the development of new drugs or the redesign of those currently used in addition to supporting their use as biomarkers in cutting-edge diagnostic tests.

Lamin Filament Assembly Derived from the Atomic Structure of the Antiparallel Four-Helix Bundle

The nucleoskeletal protein lamin is primarily responsible for the mechanical stability of the nucleus. The lamin assembly process requires the A11, A22, and ACN binding modes of the coiled-coil dimers. Although X-ray crystallography and chemical cross-linking analysis of lamin A/C have provided snapshots of A11 and ACN binding modes, the assembly mechanism of the entire filament remains to be explained. Here, we report a crystal structure of a coil 2 fragment, revealing the A22 interaction at the atomic resolution. The structure showed detailed structural features, indicating that two coiled-coil dimers of the coil 2 subdomain are separated and then re-organized into the antiparallel-four-helix bundle. Furthermore, our findings suggest that the ACN binding mode between coil 1a and the C-terminal part of coil 2 when the A11 tetramers are arranged by the A22 interactions. We propose a full assembly model of lamin A/C with the curvature around the linkers, reconciling the discrepancy between the in situ and in vitro observations. Our model accounts for the balanced elasticity and stiffness of the nuclear envelopes, which is essential in protecting the cellular nucleus from external pressure.

Th2 Cytokines Affect the Innate Immune Barrier without Impairing the Physical Barrier in a 3D Model of Normal Human Skin

(1) Background: Atopic dermatitis is one of the most common inflammatory skin diseases characterized by T helper (Th) 2 and Th22 cells producing interleukin (IL)-4/IL-13 and IL-22, respectively. The specific contribution of each cytokine to the impairment of the physical and the immune barrier via Toll-like receptors (TLRs) is poorly addressed concerning the epidermal compartment of the skin. (2) Methods: The effect of IL-4, IL-13, IL-22, and the master cytokine IL-23 is evaluated in a 3D model of normal human skin biopsies (n = 7) at the air-liquid interface for 24 and 48 h. We investigated by immunofluorescence the expressions of (i) claudin-1, zonula occludens (ZO)-1 filaggrin, involucrin for the physical barrier and (ii) TLR2, 4, 7, 9, human beta-defensin 2 (hBD-2) for the immune barrier. (3) Results: Th2 cytokines induce spongiosis and fail in impairing tight junction composition, while IL-22 reduces and IL-23 induces claudin-1 expression. IL-4 and IL-13 affect the TLR-mediated barrier largely than IL-22 and IL-23. IL-4 early inhibits hBD-2 expression, while IL-22 and IL-23 induce its distribution. (4) Conclusions: This experimental approach looks to the pathogenesis of AD through molecular epidermal proteins rather than cytokines only and paves the way for tailored patient therapy.

Multiset multicover methods for discriminative marker selection

Markers are increasingly being used for several high-throughput data analysis and experimental design tasks. Examples include the use of markers for assigning cell types in scRNA-seq studies, for deconvolving bulk gene expression data, and for selecting marker proteins in single-cell spatial proteomics studies. Most marker selection methods focus on differential expression (DE) analysis. Although such methods work well for data with a few non-overlapping marker sets, they are not appropriate for large atlas-size datasets where several cell types and tissues are considered. To address this, we define the phenotype cover (PC) problem for marker selection and present algorithms that can improve the discriminative power of marker sets. Analysis of these sets on several marker-selection tasks suggests that these methods can lead to solutions that accurately distinguish different phenotypes in the data.

Calpain-mediated proteolysis of vimentin filaments is augmented in giant axonal neuropathy fibroblasts exposed to hypotonic stress

Giant Axonal Neuropathy (GAN) is a pediatric neurodegenerative disease caused by loss-of-function mutations in the E3 ubiquitin ligase adaptor gigaxonin, which is encoded by the KLHL16 gene. Gigaxonin regulates the degradation of multiple intermediate filament (IF) proteins, including neurofilaments, GFAP, and vimentin, which aggregate in GAN patient cells. Understanding how IFs and their aggregates are processed under stress can reveal new GAN disease mechanisms and potential targets for therapy. Here we tested the hypothesis that hypotonic stress-induced vimentin proteolysis is impaired in GAN. In both GAN and control fibroblasts exposed to hypotonic stress, we observed time-dependent vimentin cleavage that resulted in two prominent ∼40-45 kDa fragments. However, vimentin proteolysis occurred more rapidly and extensively in GAN cells compared to unaffected controls as both fragments were generated earlier and at 4-6-fold higher levels. To test enzymatic involvement, we determined the expression levels and localization of the calcium-sensitive calpain proteases-1 and -2 and their endogenous inhibitor calpastatin. While the latter was not affected, the expression of both calpains was 2-fold higher in GAN cells compared to control cells. Moreover, pharmacologic inhibition of calpains with MDL-28170 or MG-132 attenuated vimentin cleavage. Imaging analysis revealed striking colocalization between large perinuclear vimentin aggregates and calpain-2 in GAN fibroblasts. This colocalization was dramatically altered by hypotonic stress, where selective breakdown of filaments over aggregates occurred rapidly in GAN cells and coincided with calpain-2 cytoplasmic redistribution. Finally, mass spectrometry-based proteomics revealed that phosphorylation at Ser-412, located at the junction between the central "rod" domain and C-terminal "tail" domain on vimentin, is involved in this stress response. Over-expression studies using phospho-deficient and phospho-mimic mutants revealed that Ser-412 is important for filament organization, solubility dynamics, and vimentin cleavage upon hypotonic stress exposure. Collectively, our work reveals that osmotic stress induces calpain- and proteasome-mediated vimentin degradation and IF network breakdown. These effects are significantly augmented in the presence of disease-causing KLHL16 mutations that alter intermediate filament organization. While the specific roles of calpain-generated vimentin IF fragments in GAN cells remain to be defined, this proteolytic pathway is translationally-relevant to GAN because maintaining osmotic homeostasis is critical for nervous system function.

Keratin 8 is a scaffolding and regulatory protein of ERAD complexes

Early recognition and enhanced degradation of misfolded proteins by the endoplasmic reticulum (ER) quality control and ER-associated degradation (ERAD) cause defective protein secretion and membrane targeting, as exemplified for Z-alpha-1-antitrypsin (Z-A1AT), responsible for alpha-1-antitrypsin deficiency (A1ATD) and F508del-CFTR (cystic fibrosis transmembrane conductance regulator) responsible for cystic fibrosis (CF). Prompted by our previous observation that decreasing Keratin 8 (K8) expression increased trafficking of F508del-CFTR to the plasma membrane, we investigated whether K8 impacts trafficking of soluble misfolded Z-A1AT protein. The subsequent goal of this study was to elucidate the mechanism underlying the K8-dependent regulation of protein trafficking, focusing on the ERAD pathway. The results show that diminishing K8 concentration in HeLa cells enhances secretion of both Z-A1AT and wild-type (WT) A1AT with a 13-fold and fourfold increase, respectively. K8 down-regulation triggers ER failure and cellular apoptosis when ER stress is jointly elicited by conditional expression of the µs heavy chains, as previously shown for Hrd1 knock-out. Simultaneous K8 silencing and Hrd1 knock-out did not show any synergistic effect, consistent with K8 acting in the Hrd1-governed ERAD step. Fractionation and co-immunoprecipitation experiments reveal that K8 is recruited to ERAD complexes containing Derlin2, Sel1 and Hrd1 proteins upon expression of Z/WT-A1AT and F508del-CFTR. Treatment of the cells with c407, a small molecule inhibiting K8 interaction, decreases K8 and Derlin2 recruitment to high-order ERAD complexes. This was associated with increased Z-A1AT secretion in both HeLa and Z-homozygous A1ATD patients' respiratory cells. Overall, we provide evidence that K8 acts as an ERAD modulator. It may play a scaffolding protein role for early-stage ERAD complexes, regulating Hrd1-governed retrotranslocation initiation/ubiquitination processes. Targeting K8-containing ERAD complexes is an attractive strategy for the pharmacotherapy of A1ATD.

Development of a Highly Sensitive Neurofilament Light Chain Assay on an Automated Immunoassay Platform

Background

Neurofilament light chain (NfL) is an axonal cytoskeletal protein that is released into the extracellular space following neuronal or axonal injury associated with neurological conditions such as multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and other diseases. NfL is detectable in the cerebrospinal fluid (CSF) and blood. Numerous studies on MS have demonstrated that NfL is correlated with disease activity, predicts disease progression, and is reduced by treatment with MS disease-modifying drugs, making NfL an attractive candidate to supplement existing clinical and imaging measures in MS. However, for NfL to achieve its potential as a clinically useful biomarker for clinical decision-making or drug development, a standardized, practical, and widely accessible assay is needed. Our objective was to develop a novel NfL assay on an automated, globally available immunoassay platform and validate its performance.

Methods

A prototype NfL assay was first developed and evaluated on the ADVIA Centaur® XP immunoassay system from Siemens Healthineers. The lower limit of quantitation (LLoQ), within-lab precision, assay range, cross-reactivity with neurofilament medium and heavy chains, and effect of interfering substances were determined. NfL assay values in serum and CSF were compared with radiological and clinical disease activity measures in patients with MS and ALS, respectively. This assay was further optimized to utilize serum, plasma, and CSF sample types on the Atellica® IM system and transferred to Siemens' CLIA laboratory where it was analytically validated as a laboratory-developed test (LDT).

Results

In this study, an LLoQ of 1.85 pg/mL, within-lab precision <6%, and an assay range of up to 646 pg/mL were demonstrated with the serum prototype assay. Cross-reactivity of <0.7% with the neurofilament medium and heavy chains was observed. Serum and CSF NfL assay values were associated with radiological and clinical disease activity measures in patients with MS and ALS, respectively. The optimized version of the NfL assay demonstrated specimen equivalence with additional plasma tube types and was analytically validated as an LDT.

Conclusion

The analytical performance of the NfL assay fulfilled all acceptance criteria; therefore, we suggest that the assay is acceptable for use in both research and clinical practice settings to determine elevated NfL levels in patients.

Identification and prognostic analysis of biomarkers to predict the progression of pancreatic cancer patients

BACKGROUND

Pancreatic cancer (PC) is a malignancy with a poor prognosis and high mortality. Surgical resection is the only "curative" treatment. However, only a minority of patients with PC can obtain surgery. Improving the overall survival (OS) rate of patients with PC is still a major challenge. Molecular biomarkers are a significant approach for diagnostic and predictive use in PCs. Several prediction models have been developed for patients newly diagnosed with PC that is operable or patients with advanced and metastatic PC; however, these models require further validation. Therefore, precise biomarkers are urgently required to increase the efficiency of predicting a disease-free survival (DFS), OS, and sensitivity to immunotherapy in PC patients and to improve the prognosis of PC.

METHODS

In the present study, we first evaluated the highly and selectively expressed targets in PC, using the GeoMxTM Digital Spatial Profiler (DSP) and then, we analyzed the roles of these targets in PCs using TCGA database.

RESULTS

LAMB3, FN1, KRT17, KRT19, and ANXA1 were defined as the top five upregulated targets in PC compared with paracancer. The TCGA database results confirmed the expression pattern of LAMB3, FN1, KRT17, KRT19, and ANXA1 in PCs. Significantly, LAMB3, FN1, KRT19, and ANXA1 but not KRT17 can be considered as biomarkers for survival analysis, univariate and multivariate Cox proportional hazards model, and risk model analysis. Furthermore, in combination, LAMB3, FN1, KRT19, and ANXA1 predict the DFS and, in combination, LAMB3, KRT19, and ANXA1 predict the OS. Immunotherapy is significant for PCs that are inoperable. The immune checkpoint blockade (ICB) analysis indicated that higher expressions of FN1 or ANXA1 are correlated with lower ICB response. In contrast, there are no significant differences in the ICB response between high and low expression of LAMB3 and KRT19.

CONCLUSIONS

In conclusion, LAMB3, FN1, KRT19, and ANXA1 are good predictors of PC prognosis. Furthermore, FN1 and ANXA1 can be predictors of immunotherapy in PCs.

Transcriptional Feedback Loops in the Caprine Circadian Clock System

The circadian clock system is based on interlocked positive and negative transcriptional and translational feedback loops of core clock genes and their encoded proteins. The mammalian circadian clock system has been extensively investigated using mouse models, but has been poorly investigated in diurnal ruminants. In this study, goat embryonic fibroblasts (GEFs) were isolated and used as a cell model to elucidate the caprine circadian clock system. Real-time quantitative PCR analysis showed that several clock genes and clock-controlled genes were rhythmically expressed in GEFs over a 24 h period after dexamethasone stimulation. Immunofluorescence revealed that gBMAL1 and gNR1D1 proteins were expressed in GEFs, and western blotting analysis further verified that the proteins were expressed with circadian rhythmic changes. Diurnal changes in clock and clock-controlled gene expression at the mRNA and protein levels were also observed in goat liver and kidney tissues at two representative time points in vivo. Amino acid sequences and tertiary structures of goat BMAL1 and CLOCK proteins were found to be highly homologous to those in mice and humans. In addition, a set of goat representative clock gene orthologs and the promoter regions of two clock genes of goats and mice were cloned. Dual-luciferase reporter assays showed that gRORα could activate the promoter activity of the goat BMAL1, while gNR1D1 repressed it. The elevated pGL4.10-gNR1D1-Promoter-driven luciferase activity induced by mBMAL1/mCLOCK was much higher than that induced by gBMAL1/gCLOCK, and the addition of gCRY2 or mPER2 repressed it. Real-time bioluminescence assays revealed that the transcriptional activity of BMAL1 and NR1D1 in goats and mice exhibited rhythmic changes over a period of approximately 24 h in NIH3T3 cells or GEFs. Notably, the amplitudes of gBMAL1 and gNR1D1 promoter-driven luciferase oscillations in NIH3T3 cells were higher than those in GEFs, while mBMAL1 and mNR1D1 promoter-driven luciferase oscillations in NIH3T3 cells had the highest amplitude. In sum, transcriptional and translational loops of the mammalian circadian clock system were found to be broadly conserved in goats and not as robust as those found in mice, at least in the current experimental models. Further studies are warranted to elucidate the specific molecular mechanisms involved.

Unbiased peptoid cell screen identifies a peptoid targeting newly appeared cell surface vimentin on tumor transformed early lung cancer cells

To identify potential new reagents and biomarkers for early lung cancer detection we combined the use of a novel preclinical isogenic model of human lung epithelial cells comparing non-malignant cells with those transformed to full malignancy using defined oncogenic changes and our on-bead two color (red and green stained cells) (OBTC) peptoid combinatorial screening methodology. The preclinical model used normal parent lung epithelial cells (HBEC3-KT, labeled with green dye) and isogenic fully malignant transformed derivatives (labeled with a red dye) via the sequential introduction of key genetic alterations of p53 knockdown, oncogenic KRAS and overexpression of cMYC (HBEC3^{p53, KRAS, cMYC}). Using the unbiased OBTC screening approach, we tested 100,000 different peptoids and identified only one (named JM3A) that bound to the surface of the HBEC3^{p53, KRAS, cMYC} cells (red cells) but not HBEC3-KT cells (green cells). Using the JM3A peptoid and proteomics, we identified the protein bound as vimentin using multiple validation approaches. These all confirmed the cell surface expression of vimentin (CSV) on transformed (HBEC3^{p53, KRAS, cMYC}) but not on untransformed (HBEC3-KT) cells. JM3A coupled with fluorophores was able to detect and stain cell surface vimentin on very early stage lung cancers but not normal lung epithelial cells in a fashion comparable to that using anti-vimentin antibodies. We conclude: using a combined isogenic preclinical model of lung cancer and two color screening of a large peptoid library, we have identified differential expression of cell surface vimentin (CSV) after malignant transformation of lung epithelial cells, and developed a new peptoid reagent (JM3A) for detection of CSV which works well in staining of early stage NSCLCs. This new, highly specific, easy to prepare, CSV detecting JM3A peptoid provides an important new reagent for identifying cancer cells in early stage tumors as well as a resource for detection and isolating of CSV expressing circulating tumor cells.

Pluripotency state of mouse ES cells determines their contribution to self-organized layer formation by mesh closure on microstructured adhesion-limiting substrates

Assembly of pluripotent stem cells to initiate self-organized tissue formation on engineered scaffolds is an important process in stem cell engineering. Pluripotent stem cells are known to exist in diverse pluripotency states, with heterogeneous subpopulations exhibiting differential gene expression levels, but how such diverse pluripotency states orchestrate tissue formation is still an unrevealed question. In this study, using microstructured adhesion-limiting substrates, we aimed to clarify the contribution to self-organized layer formation by mouse embryonic stem cells in different pluripotency states: ground and naïve state. We found that while ground state cells as well as sorted REX1-high expression cells formed discontinuous cell layers with limited lateral spread, naïve state cells could successfully self-organize to form a continuous layer by progressive mesh closure within 3 days. Using sequential immunofluorescence microscopy to examine the mesh closure process, we found that KRT8+ cells were particularly localized around unfilled holes, occasionally bridging the holes in a manner suggestive of their role in the closure process. These results highlight that compared with ground state cells, naïve state cells possess a higher capability to contribute to self-organized layer formation by mesh closure. Thus, this study provides insights with implications for the application of stem cells in scaffold-based tissue engineering.

Increased circulating cytokeratin 19 fragment levels in preterm neonates receiving mechanical ventilation are associated with poor outcome

Invasive mechanical ventilation and oxygen toxicity are postnatal contributors to chronic lung disease of prematurity, also known as bronchopulmonary dysplasia (BPD). Cyfra 21-1 is a soluble fragment of cytokeratin 19, which belongs to the cytoskeleton stabilizing epithelial intermediate filaments. As a biomarker of structural integrity, Cyfra 21-1 might be associated with airway injury and lung hypoplasia in neonates. Serum Cyfra 21-1 concentrations for 80 preterm and 80 healthy term newborns were measured within 48 h after birth. Preterm infants with the combined endpoint BPD/mortality had significantly higher Cyfra 21-1 levels compared with those without fulfilling BPD/mortality criteria (P = 0.01). Also, severe RDS (>grade III) was associated with higher Cyfra levels (P = 0.01). Total duration of oxygen therapy was more than five times longer in neonates with high Cyfra 21-1 levels (P = 0.01). Infants with higher Cyfra 21-1 values were more likely to receive mechanical ventilation (50% vs. 17.5%). However, the duration of mechanical ventilation was similar between groups. The median Cyfra value was 1.93 ng/mL (IQR: 1.68-2.53 ng/mL) in healthy term neonates and 8.5 ng/mL (IQR: 3.6-16.0 ng/mL) in preterm infants. Using ROC analysis, we calculated a Cyfra cutoff > 8.5 ng/mL to predict BPD/death with an AUC of 0.795 (P = 0.004), a sensitivity of 88.9%, and a specificity of 55%. Mortality was predicted with a cutoff > 17.4 ng/mL (AUC: 0.94; P = 0.001), a sensitivity of 100%, and a specificity of 84%. These findings suggest that Cyfra 21-1 concentration might be useful to predict poor outcome in premature infants.

Translational control of stem cell function

Stem cells are characterized by their ability to self-renew and differentiate into many different cell types. Research has focused primarily on how these processes are regulated at a transcriptional level. However, recent studies have indicated that stem cell behaviour is strongly coupled to the regulation of protein synthesis by the ribosome. In this Review, we discuss how different translation mechanisms control the function of adult and embryonic stem cells. Stem cells are characterized by low global translation rates despite high levels of ribosome biogenesis. The maintenance of pluripotency, the commitment to a specific cell fate and the switch to cell differentiation depend on the tight regulation of protein synthesis and ribosome biogenesis. Translation regulatory mechanisms that impact on stem cell function include mTOR signalling, ribosome levels, and mRNA and tRNA features and amounts. Understanding these mechanisms important for stem cell self-renewal and differentiation may also guide our understanding of cancer grade and metastasis.

A novel role of snail in regulating tuberin/AMPK pathways to promote renal fibrosis in the new mouse model of type II diabetes

Epithelial-mesenchymal transition (EMT) plays an important role in tissue fibrosis following chronic exposure to hyperglycemia. This study investigates the role of chronic diabetes in regulating tuberin/snail/AMPK to enhance EMT and increase renal fibrosis. A new mouse model of db/db/TSC2 ^+/- was generated by backcrossing db/db mice and TSC2 ^+/- mice. Wild type (WT), db/db, TSC2 ^+/- and dbdb/TSC2 ^+/- mice were sacrificed at ages 6 and 8 months old. Tuberin protein level was significantly decreased in kidneys from diabetic compared to WT mice at both ages. In addition, tuberin and E-cadherin protein levels were significantly decreased in dbdb/TSC2 ^+/- compared to TSC2 ^+/- and db/db mice. In contrast, p-PS6K, NFkB, snail, vimentin, fibronectin, and α-SMA protein levels were significantly increased in dbdb/TSC2 ^+/- compared to db/db and TSC2 ^+/- mice at ages 6 and 8 months. Both downregulation of AMPK by DN-AMPK and downregulation of tuberin by siRNA resulted in increased NFkB, snail, and fibronectin protein expression and decreased E-cadherin protein expression in mouse primary renal proximal tubular cells. Interestingly, downregulation of snail by siRNA increased tuberin expression via feedback through activation of AMPK and reversed the expression of epithelial proteins such as E-cadherin as well as mesenchymal proteins such as fibronectin, NF-KB, vimentin, and α-SMA in mouse primary renal proximal tubular cells isolated from kidneys of four mice genotypes. The data show that chronic diabetes significantly decreases tuberin expression and that provides strong evidence that tuberin is a major key protein involved in regulating EMT. These data also demonstrated a novel role for snail in regulating of AMPK/tuberin to enhance EMT and renal cell fibrosis in diabetes.

Roles for Ndel1 in keratin organization and desmosome function

Keratin intermediate filaments form dynamic polymer networks that organize in specific ways dependent on the cell type, the stage of the cell cycle, and the state of the cell. In differentiated cells of the epidermis, they are organized by desmosomes, cell–cell adhesion complexes that provide essential mechanical integrity to this tissue. Despite this, we know little about how keratin organization is controlled and whether desmosomes locally regulate keratin dynamics in addition to binding preassembled filaments. Ndel1 is a desmosome-associated protein in the differentiated epidermis, though its function at these structures has not been examined. Here, we show that Ndel1 binds directly to keratin subunits through a motif conserved in all intermediate filament proteins. Further, Ndel1 was necessary for robust desmosome–keratin association and sufficient to reorganize keratins at distinct cellular sites. Lis1, a Ndel1 binding protein, was required for desmosomal localization of Ndel1, but not for its effects on keratin filaments. Finally, we use mouse genetics to demonstrate that loss of Ndel1 results in desmosome defects in the epidermis. Our data thus identify Ndel1 as a desmosome-associated protein that promotes local assembly/reorganization of keratin filaments and is essential for robust desmosome formation.

Molecular Mechanisms Underlying the Anti-Breast Cancer Stem Cell Activity of Pterocladia capillacea and Corallina officinalis Polysaccharides

OBJECTIVE

This study aimed to appraise the activity of Pterocladia capillacea and Corallina officinalis polysaccharides against breast cancer stem cells (BCSCs). P. capillacea and C. officinalis polysaccharides were characterized to be sulfated polysaccharide-protein complexes.

METHODS

Cytotoxicity of the polysaccharides against MDA-MB-231 and MCF-7 cell lines along with their impact on CD44+/CD24- and aldehyde dehydrogenase 1(ALDH1) positive BCSC population were determined. Their effect on gene expression of CSC markers, Wnt/β-catenin and Notch signaling pathways was evaluated.

RESULTS

P. capillacea and C. officinalis polysaccharides inhibited the growth of breast cancer cells and reduced BCSC subpopulation. P. capillacea polysaccharides significantly down-regulated OCT4, SOX2, ALDH1A3 and vimentin in MDA-MB-231 as well as in MCF-7 cells except for vimentin that was up-regulated in MCF-7 cells. C. officinalis polysaccharides exhibited similar effects except for OCT4 that was up-regulated in MDA-MB-231 cells. Significant suppression of Cyclin D1 gene expression was noted in MDA-MB-231 and MCF-7 cells treated with P. capillacea or C. officinalis polysaccharides. β-catenin and c-Myc genes were significantly down-regulated in MDA-MB-231 cells treated with C. officinalis and P. capillacea polysaccharides, respectively, while being up-regulated in MCF-7 cells treated with either of them. Additionally, P. capillacea and C. officinalis polysaccharides significantly down-regulated Hes1 gene in MCF-7 cells despite increasing Notch1 gene expression level. However, significant down-regulation of Notch1 gene was observed in MDA-MB-231 cells treated with P. capillacea polysaccharides.

CONCLUSION

Collectively, this study provides evidence for the effectiveness of P. capillacea and C. officinalis polysaccharides in targeting BCSCs through interfering with substantial signaling pathways contributing to their functionality.

KRT18 Modulates Alternative Splicing of Genes Involved in Proliferation and Apoptosis Processes in Both Gastric Cancer Cells and Clinical Samples

Keratin 18 (KRT18), one of the most abundant keratins in epithelial and endothelial cells, has been reported to be aberrantly expressed in many malignancies and extensively regarded as a biomarker and important regulator in multiple cancers, including gastric cancer (GC). But the molecular regulatory mechanisms of KRT18 in GC patients and cells are largely unknown. In the present study, we analyzed the expression level of KRT18 in 450 stomach adenocarcinoma tissue samples from TCGA database and found a significantly higher expression level in tumor tissues. We then explored the potential functions of KRT18 in AGS cells (human gastric adenocarcinoma cell line) by KRT18 knockdown using siRNA and whole transcriptome RNA-seq analysis. Notably, KRT18 selectively regulates expression of cell proliferation and apoptotic genes. Beyond this, KRT18 affects the alternative splicing of genes enriched in apoptosis, cell cycle, and other cancer-related pathways, which were then validated by reverse transcription-quantitative polymerase chain reaction approach. We validated KRT18-KD promoted apoptosis and inhibited proliferation in AGS cells. We then used RNA-seq data of GC samples to further demonstrate the modulation of KRT18 on alternative splicing regulation. These results together support the conclusion that KRT18 extensively modulates diverse alternative splicing events of genes enriched in proliferation and apoptosis processes. And the dysregulated splicing factors at transcriptional or posttranscriptional level by KRT18 may contribute to the alternative splicing change of many genes, which expands the functional importance of keratins in apoptotic and cell cycle pathways at the posttranscriptional level in GC.

BBLN-1 is essential for intermediate filament organization and apical membrane morphology

Epithelial tubes are essential components of metazoan organ systems that control the flow of fluids and the exchange of materials between body compartments and the outside environment. The size and shape of the central lumen confer important characteristics to tubular organs and need to be carefully controlled. Here, we identify the small coiled-coil protein BBLN-1 as a regulator of lumen morphology in the C. elegans intestine. Loss of BBLN-1 causes the formation of bubble-shaped invaginations of the apical membrane into the cytoplasm of intestinal cells and abnormal aggregation of the subapical intermediate filament (IF) network. BBLN-1 interacts with IF proteins and localizes to the IF network in an IF-dependent manner. The appearance of invaginations is a result of the abnormal IF aggregation, indicating a direct role for the IF network in maintaining lumen homeostasis. Finally, we identify bublin (BBLN) as the mammalian ortholog of BBLN-1. When expressed in the C. elegans intestine, BBLN recapitulates the localization pattern of BBLN-1 and can compensate for the loss of BBLN-1 in early larvae. In mouse intestinal organoids, BBLN localizes subapically, together with the IF protein keratin 8. Our results therefore may have implications for understanding the role of IFs in regulating epithelial tube morphology in mammals.

New roles for desmin in the maintenance of muscle homeostasis

Desmin is the primary intermediate filament (IF) of cardiac, skeletal, and smooth muscle. By linking the contractile myofibrils to the sarcolemma and cellular organelles, desmin IF contributes to muscle structural and cellular integrity, force transmission, and mitochondrial homeostasis. Mutations in desmin cause myofibril misalignment, mitochondrial dysfunction, and impaired mechanical integrity leading to cardiac and skeletal myopathies in humans, often characterized by the accumulation of protein aggregates. Recent evidence indicates that desmin filaments also regulate proteostasis and cell size. In skeletal muscle, changes in desmin filament dynamics can facilitate catabolic events as an adaptive response to a changing environment. In addition, post-translational modifications of desmin and its misfolding in the heart have emerged as key determinants of homeostasis and disease. In this review, we provide an overview of the structural and cellular roles of desmin and propose new models for its novel functions in preserving the homeostasis of striated muscles.

Hyaluronic Acid Treatment Improves Healing of the Tenorrhaphy Site by Suppressing Adhesions through Extracellular Matrix Remodeling in a Rat Model

Due to the limited supply of vessels and nerves, acute or chronic tendon injuries often result in significant and persistent complications, such as pain and sprains, as well as the loss of joint functions. Among these complications, tendon adhesions within the surrounding soft tissue have been shown to significantly impair the range of motion. In this study, to elucidate the effects of a hyaluronic acid (HA) injection at the site of tenorrhaphy on tendon adhesion formation, we used a full transection model of a rat’s Achilles tendon to investigate the anti-adhesive function of HA. Our initial findings showed that significantly lower adhesion scores were observed in the HA-treated experimental group than in the normal saline-treated control group, as determined by macroscopic and histological evaluations. Hematoxylin and eosin, as well as picrosirius red staining, showed denser and irregular collagen fibers, with the larger number of infiltrating inflammatory cells in the control group indicating severe adhesion formation. Furthermore, we observed that the expression of tendon adhesion markers in operated tendon tissue, such as collagen type I, transforming growth factor-β1, and plasminogen activator inhibitor-1, was suppressed at both the gene and protein levels following HA treatment. These results suggest that HA injections could reduce tendon adhesion formation by significantly ameliorating inflammatory-associated reactions.

Type I IFNs and CD8 T cells increase intestinal barrier permeability after chronic viral infection

Intestinal barrier leakage constitutes a potential therapeutic target for many inflammatory diseases and represents a disease progression marker during chronic viral infections. However, the causes of altered gut barrier remain mostly unknown. Using murine infection with lymphocytic choriomeningitis virus, we demonstrate that, in contrast to an acute viral strain, a persistent viral isolate leads to long-term viral replication in hematopoietic and mesenchymal cells, but not epithelial cells (IECs), in the intestine. Viral persistence drove sustained intestinal epithelial barrier leakage, which was characterized by increased paracellular flux of small molecules and was associated with enhanced colitis susceptibility. Type I IFN signaling caused tight junction dysregulation in IECs, promoted gut microbiome shifts and enhanced intestinal CD8 T cell responses. Notably, both type I IFN receptor blockade and CD8 T cell depletion prevented infection-induced barrier leakage. Our study demonstrates that infection with a virus that persistently replicates in the intestinal mucosa increases epithelial barrier permeability and reveals type I IFNs and CD8 T cells as causative factors of intestinal leakage during chronic infections.

Diagnostic and prognostic impact of cytokeratin 18 expression in human tumors: a tissue microarray study on 11,952 tumors

BACKGROUND

Cytokeratin 18 (CK18) is an intermediate filament protein of the cytokeratin acidic type I group and is primarily expressed in single-layered or "simple" epithelial tissues and carcinomas of different origin.

METHODS

To systematically determine CK18 expression in normal and cancerous tissues, 11,952 tumor samples from 115 different tumor types and subtypes (including carcinomas, mesenchymal and biphasic tumors) as well as 608 samples of 76 different normal tissue types were analyzed by immunohistochemistry in a tissue microarray format.

RESULTS

CK18 was expressed in normal epithelial cells of most organs but absent in normal squamous epithelium. At least an occasional weak CK18 positivity was seen in 90 of 115 (78.3%) tumor types. Wide-spread CK18 positivity was seen in 37 (31.9%) of tumor entities, including adenocarcinomas of the lung, prostate, colon and pancreas as well as ovarian cancer. Tumor categories with variable CK18 immunostaining included cancer types arising from CK18 positive precursor cells but show CK18 downregulation in a fraction of cases, tumor types arising from CK18 negative precursor cells occasionally exhibiting CK18 neo-expression, tumors derived from normal tissues with variable CK18 expression, and tumors with a mixed differentiation. CK18 downregulation was for example seen in renal cell cancers and breast cancers, whereas CK18 neo-expression was found in squamous cell carcinomas of various origins. Down-regulation of CK18 in invasive breast carcinomas of no special type and clear cell renal cell carcinomas (ccRCC) was related to adverse tumor features in both tumors (p ≤ 0.0001) and poor patient prognosis in ccRCC (p = 0.0088). Up-regulation of CK18 in squamous cell carcinomas was linked to high grade and lymph node metastasis (p < 0.05). In summary, CK18 is consistently expressed in various epithelial cancers, especially adenocarcinomas.

CONCLUSIONS

Down-regulation or loss of CK18 expression in cancers arising from CK18 positive tissues as well as CK18 neo-expression in cancers originating from CK18 negative tissues is linked to cancer progression and may reflect tumor dedifferentiation.

Serum CYFRA 21.1 Level Predicts Disease Course in Thyroid Cancer with Distant Metastasis

Simple Summary

The role of serum Cyfra 21.1 as a biomarker in thyroid cancer has yet to be validated. This study investigated the diagnostic or prognostic role of serum Cyfra 21.1 in thyroid cancer. In the present analysis, we found that serum Cyfra 21.1 was increased in thyroid cancer with distant metastasis compared with thyroid cancer without metastasis. Furthermore, in progressive disease when thyroglobulin was undetectable or thyroglobulin monitoring was useless because of thyroglobulin antibody, serial follow-up based on serum Cyfra 21.1 levels might be used as an alternative biomarker for disease monitoring.

Abstract

Background: Serum Cyfra 21.1, the soluble fragment of CK19, has been used as a prognostic tumor marker in various cancers, indicating poor tumor differentiation and increased metastasis. Methods: We analyzed the serum Cyfra 21.1 level in 51 consecutive patients with thyroid cancer manifesting distant metastasis treated with prior total thyroidectomy. Serum Cyfra 21.1 levels of 26 thyroid cancer patients without metastasis and 50 healthy individuals were used for comparison. Results: Higher serum Cyfra 21.1 levels were detected in thyroid cancer patients with distant metastasis compared with healthy subjects and thyroid cancer patients without metastasis (p = 0.012). Serum Cyfra 21.1 levels were significantly increased in patients with positive BRAF V600E mutation (p = 0.019), undergoing Tyrosine Kinase Inhibitor (TKI) therapy (p = 0.008), with radioiodine-refractory status (p = 0.047), and in disease progression compared with those manifesting stable disease (p = 0.007). In progressive disease with undetectable or unmonitored thyroglobulin because of thyroglobulin antibody, serum Cyfra 21.1 was useful as a biomarker for follow-up of disease course. Conclusion: Serum Cyfra 21.1 in thyroid cancer patients might represent an alternative biomarker predicting tumor progression, especially in cases not associated with serum Tg levels.

Intracellular and Extracellular Markers of Lethality in Osteogenesis Imperfecta: A Quantitative Proteomic Approach

Osteogenesis imperfecta (OI) is a heritable disorder that mainly affects the skeleton. The inheritance is mostly autosomal dominant and associated to mutations in one of the two genes, COL1A1 and COL1A2, encoding for the type I collagen α chains. According to more than 1500 described mutation sites and to outcome spanning from very mild cases to perinatal-lethality, OI is characterized by a wide genotype/phenotype heterogeneity. In order to identify common affected molecular-pathways and disease biomarkers in OI probands with different mutations and lethal or surviving phenotypes, primary fibroblasts from dominant OI patients, carrying COL1A1 or COL1A2 defects, were investigated by applying a Tandem Mass Tag labeling-Liquid Chromatography-Tandem Mass Spectrometry (TMT LC-MS/MS) proteomics approach and bioinformatic tools for comparative protein-abundance profiling. While no difference in α1 or α2 abundance was detected among lethal (type II) and not-lethal (type III) OI patients, 17 proteins, with key effects on matrix structure and organization, cell signaling, and cell and tissue development and differentiation, were significantly different between type II and type III OI patients. Among them, some non-collagenous extracellular matrix (ECM) proteins (e.g., decorin and fibrillin-1) and proteins modulating cytoskeleton (e.g., nestin and palladin) directly correlate to the severity of the disease. Their defective presence may define proband-failure in balancing aberrances related to mutant collagen.

Prognostic significance of KRT19 in Lung Squamous Cancer

Backgroud: Keratin 19 (KRT19) is the intermediate filament that constitutes the cytoskeleton and regulates cell-cycle and cell death. Objective: We aimed to assess whether KRT19 was involved in lung cancer development. Methods: The expression of KRT19 in lung cancer was evaluated from mRNA expression on open databse and protein abundance on tumor tissue array. Results: Using open microarray gene expression datasets and differential expression analysis, we found that KRT19 was upregulated in lung cancer compared with normal tissue. Further analysis suggested that KRT19 mRNA expression was correlated with tumor progression and overall survival in lung cancer patients. As KRT19 was overexpressed in adenocarcinoma (AC) and squamous cell carcinoma (SCC), we examined the prognostic value of KRT19 protein abundance by tissue microarray (TMA). The results suggested that protein expression of KRT19 was significantly associated with overall survival of SCC. Conclusions: Giving the prognostic role of KRT19 in lung cancer, KRT19 could be considered as an potential molecular marker in lung cancer, especially in SCC.

Radiologic Features of Resected Lung Adenocarcinoma With Epithelial-Mesenchymal Transition

BACKGROUND

Epithelial-mesenchymal transition plays a crucial role in cancer progression and is a significant prognosticator for postoperative survival in patients with lung cancer. Predicting epithelial-mesenchymal transition preoperatively using computed tomography may help to determine the optimal surgical strategy.

METHODS

We performed an immunohistochemical analysis of E-cadherin and vimentin expressions using tumor specimens from resected primary lung adenocarcinoma and classified the results into 3 subgroups according to the expressions: epithelial, intermediate, and mesenchymal. The intermediate and mesenchymal groups were classified as the epithelial-mesenchymal transition conversion group. We analyzed the association between epithelial-mesenchymal transition and radiologic characteristics, especially computed tomographic features.

RESULTS

The epithelial-mesenchymal transition conversion group comprised 162 patients (49.1%). Computed tomography revealed that tumors with epithelial-mesenchymal transition conversion showed a high consolidation/tumor ratio compared with those without conversion. Univariate analysis demonstrated that tumors with epithelial-mesenchymal transition were significantly associated with bronchial and/or vascular convergence (P < .001) and notching (P = .028). When the cutoff value for the consolidation/tumor ratio was set by the receiver operating characteristic curve, independent predictive factors for epithelial-mesenchymal transition by multivariate analysis were high ratio (>0.7946; P < .001) and the presence of convergence (P = .05). Tumors with a high consolidation/tumor ratio and convergence had a 4-fold higher odds ratio for epithelial-mesenchymal transition, and patients had significantly poorer survival.

CONCLUSIONS

Convergence and a high consolidation/tumor ratio were independently associated with epithelial-mesenchymal transition conversion. These preoperative radiologic results will help to predict epithelial-mesenchymal transition conversion in lung adenocarcinoma.

Cerebrospinal Fluid Biomarkers in Relation to MRZ Reaction Status in Primary Progressive Multiple Sclerosis

The MRZ reaction (MRZR) comprises the three antibody indices (AIs) against measles, rubella, and varicella zoster virus, reflecting an intrathecal polyspecific B cell response highly specific for multiple sclerosis (MS). Thus, MRZR can be used to confirm a diagnosis of primary progressive MS (PPMS) but its pathophysiological and wider clinical relevance is unclear. This study aimed to investigate whether PPMS patients with a positive MRZR (MRZR+) differ from those with a negative MRZR (MRZR-) according to cerebrospinal fluid (CSF) biomarkers of B cell activity, neuroaxonal damage or glial activity, and clinical features. (1) Methods: In a multicenter PPMS cohort (n = 81) with known MRZR status, we measured B cell-activating factor (BAFF), chemokine CXC ligand 13 (CXCL-13), soluble B cell maturation antigen (sBCMA), soluble transmembrane activator and CAML interactor (sTACI), and chitinase-3-like protein 1 (CHI3L1) in the CSF with enzyme-linked immunosorbent assays (ELISAs). Glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) were detected in serum and CSF using single molecule array (SIMOA) technology. (2) Results: MRZR+ patients (45.7% of all PPMS patients) revealed higher levels of NfL in CSF compared to MRZR- patients (54.3%). There were positive correlations between each of sBCMA, sTACI, and intrathecal immunoglobin G (IgG) synthesis. Additionally, NfL concentrations in serum positively correlated with those in CSF and those of GFAP in serum. However, MRZR+ and MRZR- patients did not differ concerning clinical features (e.g., age, disease duration, Expanded Disability Status Scale (EDSS) at diagnosis and follow-up); CSF routine parameters; CSF concentrations of BAFF, CXCL-13, sBCMA, sTACI, CHI3L1, and GFAP; or serum concentrations of GFAP and NfL. (3) Conclusions: In PPMS patients, MRZR positivity might indicate a more pronounced axonal damage. Higher levels of the soluble B cell receptors BCMA and transmembrane activator and CAML interactor (TACI) in CSF are associated with a stronger intrathecal IgG synthesis in PPMS.

Long-term myofibroblast persistence in the capsular bag contributes to the late spontaneous in-the-bag intraocular lens dislocation

Late spontaneous in-the-bag intraocular lens (IOL) dislocation is a complication presenting 6 months or later after cataract surgery. We aimed to characterize the cells in the lens capsules (LCs) of 18 patients with spontaneous late in-the-bag IOL dislocation. Patients' average age was 82.6 ± 1.5 years (range 72-98), and most of them had pseudoexfoliation syndrome (PEX). Cells from the LCs were positive for myofibroblast (αSMA), proliferation (Ki-67, PCNA), early lens development/lens progenitor (SOX2, PAX6), chemokine receptor (CXCR4), and transmembrane (N-cadherin) markers, while negative for epithelial (E-cadherin) marker. Moreover, the cells produced abundant fibronectin, type I and type V collagen in the nearby extracellular matrix (ECM). During ex vivo cultivation of dislocated IOL-LCs in toto, the cells proliferated and likely migrated onto the IOL's anterior side. EdU proliferation assay confirmed the proliferation potential of the myofibroblasts (MFBs) in dislocated IOL-LCs. Primary cultured lens epithelial cells/MFBs isolated from the LC of dislocated IOLs could induce collagen matrix contraction and continuously proliferated, migrated, and induced ECM remodeling. Taken together, this indicates that long-lived MFBs of dislocated IOLs might contribute to the pathogenic mechanisms in late in-the-bag IOL dislocation.

Single Cell Mechanotype and Associated Molecular Changes in Urothelial Cell Transformation and Progression

Cancer cell mechanotype changes are newly recognized cancer phenotypic events, whereas metastatic cancer cells show decreased cell stiffness and increased deformability relative to normal cells. To further examine how cell mechanotype changes in early stages of cancer transformation and progression, an in vitro multi-step human urothelial cell carcinogenic model was used to measure cellular Young's modulus, deformability, and transit time using single-cell atomic force microscopy, microfluidic-based deformability cytometry, and quantitative deformability cytometry, respectively. Measurable cell mechanotype changes of stiffness, deformability, and cell transit time occur early in the transformation process. As cells progress from normal, to preinvasive, to invasive cells, Young's modulus of stiffness decreases and deformability increases gradually. These changes were confirmed in three-dimensional cultured microtumor masses and urine exfoliated cells directly from patients. Using gene screening and proteomics approaches, we found that the main molecular pathway implicated in cell mechanotype changes appears to be epithelial to mesenchymal transition.

Spatial organization and crosstalk of vimentin and actin stress fibers regulate the osteogenic differentiation of human adipose-derived stem cells

Human adipose-derived stem cells (hASCs) are ideal seed cells for tissue engineering due to their multidirectional differentiation potential. Microfilaments, microtubules, and intermediate filaments are responsible for supporting the intracellular space. Vimentin, a type III intermediate filament protein that is specifically expressed in cells of mesenchymal origin, can function as a scaffold and endow cells with tension and shear stress resistance. Actin stress fibers (ASF) act as an important physical device in stress signal transduction, providing stiffness for cells, and promoting osteogenesis. Through direct physical contact, cross-linkers, and spatial interactions, vimentin and actin networks exist as intersecting entities. Spatial interactions occur in the overlapping area of cytoskeleton subsystems, which could affect cell morphology, cell mechanics, and cell fate. However, how does the spatial organization between the cytoskeletal subsystems changed during osteogenesis, especially between vimentin and ASF, is still not understood, and its mechanism effect on cell fate remains unclear. In our study, WB experiment was used to detect the expression changes in Vimentin, ASF, and other proteins. Cells were reconstructed by three-dimensional scanning with fluorescence microscope, and the spatial thickness of vimentin and ASF cytoskeletons and the thickness of the overlapping area between them were calculated, respectively, so as to observe the spatial reorganization of vimentin and ASF in cells. Cytochalasin D (an inhibitor of actin polymerization) and vimentin upregulated/downregulated cells were used to verify the change in the spatial organization between vimentin and ASF and its influence on osteogenesis. Then, heat shock protein 27 (HSP27) was downregulated to illuminate the regulatory mechanisms of spatial organization between vimentin and ASF during osteogenesis. The amounts and the spatial positions of vimentin and actin stress fiber exhibited opposite trends during osteogenesis. Through controlling the anchor sites on the nucleus, intermediate filaments vimentin can reduce the spatial proportion of actin stress fibers, which can be regulated by HSP27. In addition, depolymerization of actin stress fibers lead to lower osteogenic differentiation ability, resulting in osteogenesis and lipogenesis existed simultaneously, that can be resisted by vimentin. Our data indicate that the spatial reorganization of vimentin and actin stress fibers is a key factor in the regulation of the differentiation state of hASCs. And their spatial overlapping area is detrimental to hASCs osteogenesis, providing a new perspective for further exploring the mechanism underlying hASCs osteogenesis.

Keratins are asymmetrically inherited fate determinants in the mammalian embryo

To implant in the uterus, the mammalian embryo first specifies two cell lineages: the pluripotent inner cell mass that forms the fetus, and the outer trophectoderm layer that forms the placenta1. In many organisms, asymmetrically inherited fate determinants drive lineage specification2, but this is not thought to be the case during early mammalian development. Here we show that intermediate filaments assembled by keratins function as asymmetrically inherited fate determinants in the mammalian embryo. Unlike F-actin or microtubules, keratins are the first major components of the cytoskeleton that display prominent cell-to-cell variability, triggered by heterogeneities in the BAF chromatin-remodelling complex. Live-embryo imaging shows that keratins become asymmetrically inherited by outer daughter cells during cell division, where they stabilize the cortex to promote apical polarization and YAP-dependent expression of CDX2, thereby specifying the first trophectoderm cells of the embryo. Together, our data reveal a mechanism by which cell-to-cell heterogeneities that appear before the segregation of the trophectoderm and the inner cell mass influence lineage fate, via differential keratin regulation, and identify an early function for intermediate filaments in development.

Enzymatic Extraction of Bioactive and Self-Assembling Wool Keratin for Biomedical Applications

Keratin is widely recognized as a high-quality renewable protein resource for biomedical applications. Despite their extensive existence, keratin resources such as feathers, wool, and hair exhibit high stability and mechanical properties because of their high disulfide bond content. Consequently, keratin extraction is challenging and its application is greatly hindered. In this work, a biological extraction strategy is proposed for the preparation of bioactive keratin and the fabrication of self-assembled keratin hydrogels (KHs). Based on moderate and controlled hydrolysis by keratinase, keratin with a high molecular weight of approximately 45 and 28 kDa that retain its intrinsic bioactivities is obtained. The keratin products show excellent ability to promote cell growth and migration and are conferred with significant antioxidant ability because of their intrinsically high cysteine content. In addition, without the presence of any cross-linking agent, the extracted keratin can self-assemble into injectable hydrogels. The KHs exhibit a porous network structure and 3D culture ability, showing potential in promoting wound healing. This enzyme-driven keratin extraction strategy opens up a new approach for the preparation of keratin that can self-assemble into injectable hydrogels for biomedical engineering.

Muscle Cell Morphogenesis, Structure, Development and Differentiation Processes Are Significantly Regulated during Human Ovarian Granulosa Cells In Vitro Cultivation

Granulosa cells (GCs) have many functions and are fundamental for both folliculogenesis and oogenesis, releasing hormones and communicating directly with the oocyte. Long-term in vitro cultures of GCs show significant stem-like characteristics. In the current study, RNA of human ovarian granulosa cells was collected at 1, 7, 15 and 30 days of long-term in vitro culture. Understanding the process of differentiation of GCs towards different cell lineages, as well as the molecular pathways underlying these mechanisms, is fundamental to revealing other possible stemness markers of this type of cell. Identifying new markers of GC plasticity may help to understand the aetiology and recurrence of a wide variety of diseases and health conditions and reveal possible clinical applications of the ovarian tissue cells, affecting not only the reproductive ability but also sex hormone production. Granulosa cells were the subject of this study, as they are readily available as remnant material leftover after in vitro fertilisation procedures and exhibit significant stem-like characteristics in culture. The change in gene expression was investigated through a range of molecular and bioinformatic analyses. Expression microarrays were used, allowing the identification of groups of genes typical of specific cellular pathways. This candidate gene study focused on ontological groups associated with muscle cell morphogenesis, structure, development and differentiation, namely, “muscle cell development”, “muscle cell differentiation”, “muscle contraction”, “muscle organ development”, “muscle organ morphogenesis”, “muscle structure development”, “muscle system process” and “muscle tissue development”. The results showed that the 10 most upregulated genes were keratin 19, oxytocin receptor, connective tissue growth factor, nexilin, myosin light chain kinase, cysteine and glycine-rich protein 3, caveolin 1, actin, activating transcription factor 3 and tropomyosin, while the 10 most downregulated consisted of epiregulin, prostaglandin-endoperoxide synthase 2, transforming growth factor, interleukin, collagen, 5-hydroxytryptmine, interleukin 4, phosphodiesterase, wingless-type MMTV integration site family and SRY-box 9. Moreover, ultrastructural observations showing heterogeneity of granulosa cell population are presented in the study. At least two morphologically different subpopulations were identified: large, light coloured and small, darker cells. The expression of genes belonging to the mentioned ontological groups suggest the potential ability of GCs to differentiate and proliferate toward muscle lineage, showing possible application in muscle regeneration and the treatment of different diseases.

Vimentin plays an important role in the promotion of breast cancer cell migration and invasion by leucine aminopeptidase 3

Breast cancer is a common type of cancer in females. Our previous studies indicated that leucine aminopeptidase 3 (LAP3) promotes migration and invasion of breast cancer cells. Vimentin is a mesenchymal marker, and its upregulation represents the promotion of epithelial-mesenchymal transition. In this study, we found that LAP3 and vimentin were highly expressed in breast cancer tissues, and the overexpression of LAP3 in breast cancer cells promoted the expression of vimentin. Western blot analysis indicated that the overexpression of LAP3 upregulated the phosphorylation of Erk1/2. MEK inhibitor PD98059 downregulated the expression of vimentin, matrix metalloproteinase-2/9 (MMP-2/9), and fascin through the inhibition of Erk1/2 activity. We hypothesized that LAP3 promoted tumor migration and invasion by upregulating vimentin. The knockdown of vimentin resulted in the inhibited migration and invasion of MDA-MB-231 and MDA-MB-468 cells. The expression of MMP-2/9 and fascin could also be downregulated. In conclusion, vimentin might play an important role in the promotion of breast cancer metastasis by LAP3.

Comparative proteomics reveals genetic mechanisms underlying secondary hair follicle development in fine wool sheep during the fetal stage

The aim of this study was to investigate the genetic mechanisms underlying wool production by characterizing the skin protein profile and determining the proteomic changes that occur as a consequence of development in wool-producing sheep using a label-free proteomics approach. Samples were collected at four stages during gestation (87, 96, 102, and 138 days), and every two consecutive stages were statistically compared (87 versus 96, 96 versus 102, and 102 versus 138 days). We identified 227 specific proteins in the sheep proteome that were present in all four stages, and 123 differentially abundant proteins (DAPs). We also observed that the microstructure of the secondary follicles changed significantly during the development of the fetal skin hair follicle. The screened DAPs were strictly related to metabolic and skin development pathways, and were associated with pathways such as the glycolysis/gluconeogenesis. These analyses indicated that the wool production of fine wool sheep is regulated via a variety of pathways. These findings provide an important resource that can be used in future studies of the genetic mechanisms underlying wool traits in fine wool sheep, and the identified DAPs should be further investigated as candidate markers for predicting wool traits in sheep. SIGNIFICANCE: Wool quality (fiber diameter, length, etc.) is an important economic trait of fine wool sheep that is determined by secondary follicle differentiation and re-differentiation. Secondary follicles of fine wool sheep developed from a bud (87 days), and underwent differentiation (96 days) and rapid growth (102 days) until maturity (138 days) during gestation. Comparative analysis based on differential proteomics of these four periods could provide a better understanding of the wool growth mechanism of fine wool sheep and offer novel strategies for improving fine wool quality by breeding.