A 15-Inflammation-Related Gene Signature Predicts the Prognosis of Patients With Pancreatic Ductal Adenocarcinoma.

Chronic inflammation promotes the development of pancreatic ductal adenocarcinoma (PDAC) and PDAC-related inflammatory tumor microenvironment facilitates tumor growth and metastasis. Thus, we aimed to study the association between inflammatory response and prognosis in patients with PDAC. We conducted the whole transcriptomic sequencing using tissue samples collected from patients diagnosed with PDAC (n = 106) recruited from Shandong Cancer Hospital. We first constructed a prognostic signature using 15 inflammation-related genes in The Cancer Genome Atlas (TCGA) cohort (n = 177) and further validated it in an independent International Cancer Genome Consortium (ICGC) cohort (n = 90) and our in-house cohort. PDAC patients with a higher risk score had poorer overall survival (OS) (P < 0.001; HR, 3.02; 95% CI, 1.94-4.70). The association between the prognostic signature and OS remained significant in the multivariable Cox regression adjusting for age, sex, alcohol exposure, diabetes, and stage (P < 0.001; HR, 2.91; 95% CI, 1.73-4.89). This gene signature also robustly predicted prognosis in the ICGC cohort (P = 0.01; HR, 1.94; 95% CI, 1.14-3.30) and our cohort (P < 0.001; HR, 2.40; 95% CI, 1.45-3.97). Immune subtype C3 (inflammatory) was enriched and CD8+ T cells were higher in patients with a lower risk score (P < 0.05). Furthermore, PDAC patients with higher risk scores were more sensitive to chemotherapy, immunotherapy, and PARP inhibitors (P < 0.05). In sum, we identified a novel gene signature that was associated with inflammatory response for risk stratification, prognosis prediction, and therapy guidance in PDAC patients. Future studies are warranted to validate the clinical utility of the signature.

MAEL in human cancers and implications in prognostication and predicting benefit from immunotherapy over VEGFR/mTOR inhibitors in clear cell renal cell carcinoma: a bioinformatic analysis.

Maelstrom (MAEL), a novel cancer/testis-associated gene, may facilitate the initiation and progression of human malignancies, warranting comprehensive investigations. Single-cell and tissue-bulk transcriptomic data demonstrated higher MAEL expression in testis (spermatogonia/spermatocyte), kidney (proximal tubular cell), and brain (neuron/astrocyte), and corresponding cancers, including testicular germ cell tumor, glioma, papillary renal cell carcinoma, and clear cell renal cell carcinoma (ccRCC). Of these cancers, only in ccRCC did MAEL expression exhibit associations with both recurrence-free survival and overall survival. High MAEL expression was associated with an anti-inflammatory tumor immune microenvironment and VEGFR/mTOR activation in ccRCC tissues and high sensitivities to VEGFR/PI3K-AKT-mTOR inhibitors in ccRCC cell lines. Consistent with these, low rather than high MAEL expression indicated remarkable progression-free survival benefits from immune checkpoint inhibitor (ICI)-based immunotherapies over VEGFR/mTOR inhibitors in two large phase III trials (JAVELIN Renal 101 and CheckMate-025). MAEL is a biologically and clinically significant determinant with potential for prognostication after nephrectomy and patient selection for VEGFR/mTOR inhibitors and immunotherapy-based treatments.

Robotic hiatal hernia repair without mesh.

Background: Newer minimally invasive techniques have supplanted laparotomy and thoracotomy for management of hiatal hernias. Limited data exists on outcomes after robotic hiatal hernia repair without mesh despite the increasing popularity of this approach. We report our high-volume experience with durable robotic hiatal hernia repair with gastric fundoplication without mesh. Methods: A retrospective review was conducted on patients with type I-IV hiatal hernias who underwent an elective robotic-assisted repair from 2016 to 2019 using a novel technique of approximating the hiatus with running barbed absorbable (V-locTM) suture and securing it with interrupted silk sutures. Main outcomes included length of stay, readmission rate, and recurrence rate. Results: A total of 144 patients were reviewed. The average age of the patient was 61 years. Most of the patients were female [95 females (66%) to 49 males], and the average body mass index (BMI) was 29.96 kg/m2. The average operating time was 173 minutes (standard deviation 62 minutes). The average length of stay in the hospital was 2 days, and 89% of patients went home within the first 3 days. Ten patients (6.9%) were readmitted within 30 days, there were no mortalities in 30 days, and there were 6 (4.2%) recurrences on follow up requiring reoperation. Conclusions: Elective robotic hiatal hernia repair with fundoplication and primary closure of the hiatus with V-locTM and nonabsorbable suture without mesh is safe and effective. The robotic approach has similar operative times, lengths of stay, and complications compared to nationally published data on laparoscopic hiatal hernia repairs.

Notch activation defines immune-suppressive subsets of ccRCCs with unfavorable benefits from immunotherapy over VEGFR/mTOR inhibitors.

The evolutionarily conserved Notch pathway, involved in cancer stem cell capacity and cancer immunity, may predict the benefit from immune checkpoint inhibitors (ICIs) in clear cell renal cell carcinoma (ccRCC). In the TCGA dataset, mRNA expression of Notch pathway genes identified three clusters with different prognoses and molecular characteristics. Based on the differentially expressed Notch pathway genes between clusters, we constructed the Notch-score, correlated with Notch activation, angiogenesis, PI3K-AKT-mTOR activity, and sensitivities to VEGFR/mTOR inhibitors. A high Notch-score was linked with more "resting"/"anti-inflammatory" rather than "activated"/"pro-inflammatory" tumor-infiltrating immune cells, inactivated immune pathways, and scarce any benefits from ICI-based therapies over VEGFR/mTOR inhibitors in the JAVELIN Renal 101 (avelumab plus axitinib vs. sunitinib) and the CheckMate-009/010/025 trials (nivolumab vs. everolimus). For the Notch-activated ccRCCs, ICIs provide limited advantages and might not be strongly recommended, by which the cost-effectiveness of treatments in ccRCCs may be potentially improved.

Complement and coagulation cascades pathway-related signature as a predictor of immunotherapy in metastatic urothelial cancer.

BACKGROUND: Immune checkpoint inhibitors (ICIs) have shown efficacy in patients with metastatic urothelial cancer (mUC), however, only a small subset of patients could benefit from ICIs. Identifying predictive biomarkers of ICIs in patients with mUC is clinical meaningful for patient stratification and administration. METHODS: Clinical and transcriptomic data of mUC patients treated with ICIs from mUC cohort (IMvigor210 study) was utilized to explore the predictive biomarkers. LASSO Cox regression was performed to construct a predictive model. The predictive model was trained and tested in the mUC cohort, and then exploratively tested in clear cell renal cell carcinoma (ccRCC) and melanoma cohorts in which patients also received ICIs regimens. RESULTS: The differentially expressed genes (DEGs) in complement and coagulation cascades pathway (CCCP) were mainly enriched in non-responders of ICIs in the mUC cohort. A CCCP risk score was constructed based on the DEGs in CCCP. Patients with a low-risk score were more responsive to ICIs and had better overall survival (OS) than those with a high-risk score in the training set (HR, 0.38; 95%CI, 0.27-0.53, P<0.001) and the test set (HR, 0.34; 95%CI, 0.17-0.71, P=0.003). The association between the CCCP risk score and OS remained significant in the multivariable cox regression by adjusting PD-L1 expression and TMB (P<0.05). In addition, there was no difference for OS in the bladder cancer patients without ICIs (TCGA-BLCA cohort, HR, 0.76, 95%CI, 0.49-1.18, P=0.22), suggesting a predictive but not prognostic effect of the risk score. For the exploratory analysis, consistent results were observed that low-risk group showed superior OS in ccRCC cohort (HR, 0.52, 95%CI, 0.37-0.75, P<0.001) and melanoma cohort (HR, 0.27, 95%CI, 0.12-0.62, P=0.001). CONCLUSIONS: Our study showed that the CCCP risk score is an independent biomarker that predicts the efficacy of ICIs in mUC patients. The patients with a low-risk score tend to have a better response to ICIs and a longer life time probably due to the immune-activated TME. Further studies are needed to validate the clinical utility of the seven-gene signature.

Development and validation of an inflammatory response-related gene and clinical factor-based signature for predicting prognosis in gastric cancer.

Background: Gastric cancer (GC) is an aggressive disease that requires prognostic tools to aid in clinical management. The prognostic power of clinical features is unsatisfactory, which might be improved by combining mRNA-based signatures. Inflammatory response is widely associated with cancer development and treatment response. It is worth exploring the prognostic performance of inflammatory-related genes plus clinical factors in GC. Methods: An 11-gene signature was trained using the least absolute shrinkage and selection operator (LASSO) based on the messenger RNA (mRNA) and overall survival (OS) data of The Cancer Genome Atlas-stomach adenocarcinoma (TCGA-STAD) cohort. A nomogram was established using the signature and clinical factors with a significant linkage with OS and was validated in 3 independent cohorts (GSE15419, GSE13861, and GSE66229) via calculating the area under the receiver operator characteristic curve (AUC). The association between the signature and immunotherapy efficacy was explored in the ERP107734 cohort. Results: A high risk score was associated with shorter OS in both the training and the validation sets (the AUC for 1-, 3-, 5-year in TCGA-STAD cohort: 0.691, 0.644, and 0.707; GSE15459: 0.602, 0.602, and 0.650; GSE13861: 0.648, 0.611, and 0.647; GSE66229: 0.661, 0.630, and 0.610). Its prognostic power was improved by combining clinical factors including age, sex, and tumor stage (the AUC for 1-, 3-, 5-year in TCGA-STAD cohort: 0.759, 0.706, and 0.742; GSE15459: 0.773, 0.786, and 0.803; GSE13861: 0.749, 0.881, and 0.795; GSE66229: 0.773, 0.735, and 0.722). Moreover, a low-risk score was associated with a favorable response to pembrolizumab monotherapy in the advanced setting (AUC =0.755, P=0.010). Conclusions: In GCs, the inflammatory response-related gene-based signature was related to immunotherapy efficacy, and its risk score plus clinical features yielded robust prognostic power. With prospective validation, this model may improve the management of GC by enabling risk stratification and the prediction of response to immunotherapy.

Experimental Study and Modelling of Fresh Behaviours of Basalt Fibre-Reinforced Mortar Based on Average Water Film Thickness and Fibre Factor.

Though previous studies have indicated that the fresh behaviours of plain mortar/concrete are mainly governed by the average water film thickness (AWFT), whether the concept of AWFT is also applicable to fibrous mortar/concrete still needs to be explored. Furthermore, for fibrous mortar/concrete, it is obvious that the fibres added also have certain effects on the fresh behaviours. In two previous studies on basalt fibre-reinforced mortar (BFRM), the integral effects of the AWFT and fibre dosage as well as the integral effects of the AWFT and fibre length were individually investigated. In this study, a fibre factor (FF) defined as the fibre volume multiplied by the fibre aspect ratio was employed and 24 extra mortar groups were tested. A total of 68 mortar groups were applied in numerical analysis. The results of the regression analysis yielded good correlations of the workability, fluidity, cohesiveness, and adhesiveness of BFRM with the AWFT and FF, suggesting that the AWFT and FF are together the governing parameters controlling the fresh behaviours of BFRM. Hence, the AWFT and FF may be used to develop a model for the fresh properties of BFRM.

A DNA Damage Response Related Signature to Predict Prognosis in Patients with Acute Myeloid Leukemia.

The prognosis of acute myeloid leukemia (AML) is disappointing in most subtypes and varies widely. DNA damage response (DDR) is associated with prognosis and immunotherapy in multiple cancers. Here, we identify a signature of eight DDR-related genes associated with overall survival, which stratifies AML patients into high- and low-risk groups. Patients in low-risk group were more likely to respond to sorafenib. The signature could be an independent prognostic predictor for patients treated with ADE and ADE plus gemtuzumab ozogamicin. Therefore, this DDR prognostic signature might be applied to prognostic stratification and treatment selection in AML patients, which warrants further studies.

Impact of age on outcomes after transcatheter aortic valve implantation.

AIMS: Usage of transcatheter aortic valve implantation (TAVI) for treatment of severe aortic stenosis is increasing across age groups. However, literature on age-specific TAVI outcomes is lacking. The purpose of this study is to assess the risks of procedural complications, mortality, and readmission in patients undergoing TAVI across different age groups. METHODS AND RESULTS: The Nationwide Readmissions Database was used to identify 84 017 patients undergoing TAVI from 2016 to 2018. Patients were stratified into four age groups: younger than 70, 70-79, 80-89, and older than 90. Complications, mortality, and readmission rates were compared between groups in a proportional hazards regression model. Risk of post-procedural stroke, acute kidney injury, and pacemaker or implantable cardioverter defibrillator implantation increased with incremental age grouping. Compared with patients younger than 70, patients aged 70-79 had no significant difference in mortality, whereas patients aged 80-89 and older than 90 had an increased mortality risk [odds ratio (OR) 1.39, confidence interval (CI) 1.14-1.70, P = 0.001 and OR 1.68, CI 1.33-2.12, P < 0.001, respectively]. Patients aged 80-89 and older than 90 had increased overall readmission compared with patients younger than 70 (HR 1.09, CI 1.03-1.14, P = 0.001 and HR 1.33, CI 1.25-1.41, P < 0.001, respectively). Cardiac readmissions followed the same trend. CONCLUSION: Patients aged 80-89 and older than 90 undergoing TAVI have increased risk of readmission, complications, and mortality compared with patients younger than 70.

Suction-based catheter retrieval of right ventricular clot-in-transit.

Right ventricular clot-in-transit (CIT) is a rare finding in venous thromboembolic disease and carries a high mortality rate. Its optimal treatments have yet to be established in the literature. Here we describe the usage of a suction-based catheter, the INARI FlowTriever® system (INARI Medical Inc.) to successfully retrieve a CIT from the right ventricle of a patient with coronavirus disease 2019 acute respiratory distress syndrome on veno-veno extracorporeal membrane oxygenation.

Choice of DNA extraction method affects detection of bacterial taxa from retail chicken breast.

BACKGROUND: Sequence-based methods for the detection of bacteria such as 16S rRNA amplicon sequencing and metagenomics can provide a comprehensive view of the bacterial microbiome of food. These methods rely on the detection of gene sequences to indicate the presence of viable bacteria. This indirect form of detection can be prone to experimental artefacts. Sample handling and processing are key sources of variation that require standard approaches. Extracting sufficient quantities of high quality DNA from food matrices is challenging because target bacterial species are usually minor components of the microbiota and foods contain an array of compounds that are inhibitory to downstream DNA applications. Here, three DNA extraction methods are compared for their ability to extract high quality bacterial DNA from retail chicken breast rinses, with or without enrichment. Method performance was assessed by comparing ease of use, DNA yield, DNA quality, PCR amplicon yield, and the detection of bacterial taxa by 16S rRNA amplicon sequencing. RESULTS: All three DNA extraction methods yielded DNA of sufficient quantity and quality to perform quantitative PCR and 16S rRNA amplicon sequencing. The extraction methods differed in ease of use, with the two commercial kits (PowerFood, PowerSoil) offering considerable time and cost savings over a hybrid method that used laboratory reagents for lysis and commercial column based kits for further purification. Bacterial richness as determined by 16S rRNA amplicon sequencing was similar across the three DNA extraction methods. However, differences were noted in the relative abundance of bacterial taxa, with significantly higher abundance of Gram-positive genera detected in the DNA samples prepared using the PowerFood DNA extraction kit. CONCLUSION: The choice of DNA extraction method can affect the detection of bacterial taxa by 16S rRNA amplicon sequencing in chicken meat rinses. Investigators should be aware of this procedural bias and select methods that are fit for the purposes of their investigation.

Pre-hospital caloric deficits in surgical patients.

BACKGROUND: The timing, route, and amount of nutrition for surgical patients with substantial caloric deficits remain active areas of study. Current guidelines are based on in-hospital days NPO after admission to the hospital. This historic process neglects the multiple days of caloric deficit patients experience prior to hospital admission. AIM: To determine the impact of pre-hospital caloric deficit (PHCD) for surgical patients on their outcomes. METHODS: 313 patients admitted with a diagnosis of small bowel obstruction, pancreatitis, or diverticulitis were analyzed for their PHCD's. PHCD's were estimated using patient-reported days with significant emesis, and absent oral intake. Patients with PHCD's were compared to patients with no PHCD for length of stay, status on discharge, disposition, and 30-day readmission rate. RESULTS: There were 313 patients and 42% of the patients were male. The median age was 65 years. Median number of days sick prior to hospital admission was 1 (IQR: 1 to 2). Median PHCD was 1882 kcal (IQR: 1355 to 3650). Median number of days NPO while in-hospital was 3 (IQR: 2 to 5). Median in-hospital caloric deficit was 4268 kcal (IQR: 2825 to 6610). No significant association was observed between discharge disposition, complication rate, ambulatory status, 30-day readmission rate and PHCD. In-hospital caloric deficit was associated with complications after surgery (p < 0.0001). CONCLUSION: Small PHCD's in patients with SBO's, pancreatitis, or diverticulitis do not negatively affect their outcomes. Further research of patients with large PHCD's is needed to best treat surgical patients at risk for malnutrition.

Isolation of third generation cephalosporin resistant Enterobacteriaceae from retail meats and detection of extended spectrum beta-lactamase activity.

Various methods have been described to isolate third generation cephalosporin (3GC) resistant Enterobacteriaceae from foods, but it is not known how comparable they are between studies. Here, the performance of five enrichment broths and two selective agars are compared for their ability to isolate 3GC resistant Enterobacteriaceae from retail chicken, beef, pork, and veal samples. The results showed equivalence between Enterobacteriaceae enrichment broth (EE), lauryl sulfate broth (LST), and modified typtone soy broth (mTSB). Lower isolation rates were observed when LST and mTSB were supplemented with the 3GC antibiotic cefotaxime. The overall performance of MacConkey agar supplemented with cefotaxime and a proprietary selective agar (ESBL CHROMagar) was equivalent, although differences linked to the microbiota of specific meat commodities were noted. Regardless of the isolation method, further screening was required to confirm the taxonomy and resistance of the presumptive positive strains. Approximately 40% of confirmed 3GC resistant foodborne Enterobacteriaceae strains tested positive for extended spectrum beta-lactamase (ESBL) activity. Strains that were resistant to ceftriaxone and susceptible to cefoxitin were more likely to test positive for ESBL activity, as were strains that possessed either of two ESBL genes (blaSHV or blaTEM). Based on our results, we recommend using an antibiotic-free enrichment broth, two selective agars, and an isolate screening strategy to isolate 3GC resistant Enterobacteriaceae from retail meats. Antibiotic susceptibility testing and/or PCR screening for blaSHV or blaTEM can then be used to identify ESBL producing strains among the 3GC resistant meat isolates. The adoption of this approach by the research community will enable more effective monitoring of antibiotic resistance rates and trends among foodborne Enterobacteriaceae over time and across jurisdictions.

Field Identification of Matricaria chamomilla using a Portable qPCR System.

Quality control in botanical products begins with the raw material supply. Traditionally, botanical identification is performed through morphological assessment and chemical analytical methods. However, the lack of availability of botanists, especially in recent years, coupled with the need to enhance quality control to combat the stresses on the supply chain brought by increasing consumer demand and climate change, necessitates alternative approaches. The goal of this protocol is to facilitate botanical species identification using a portable qPCR system on the field or in any setting, where access to laboratory equipment and expertise is limited. Target DNA is amplified using dye-based qPCR, with DNA extracted from botanical reference materials serving as a positive control. The target DNA is identified by its specific amplification and matching its melting peak against the positive control. A detailed description of the steps and parameters, from hands-on field sample collection, to DNA extraction, PCR amplification, followed by data interpretation, has been included to ensure that readers can replicate this protocol. The results produced align with traditional laboratory botanical identification methods. The protocol is easy to perform and cost-effective, enabling quality testing on raw materials as close to the point of origin of the supply chain as possible.

Development and validation of a probe-based qPCR method to prevent parsley leaf material misidentification.

Parsley (Petroselinum crispum) leaf is an herb widely consumed for its health benefits. Due to similar morphological and chemical profiles, celery leaf may be a source of substitution in commercial parsley materials. In order to detect this substitution, the present work characterized parsley and celery leaf at the cultivar level by physical, chemical and DNA approaches. In contrast to the variations observed in physical appearances and chemical profiles that make verification of authenticity difficult, consistent differences observed between their DNA sequences are suitable for verifying parsley material authenticity. To identify parsley and detect celery simultaneously, a multiplex qPCR assay was developed and validated with respect to efficiency and specificity. Further testing indicated the assay can be used to detect 1% (w/w) celery in parsley materials with a probability of detection greater than 0.9. The developed method is well-suited for routine quality control to prevent parsley material misidentification in commercial trade.

Weight Gain in Infants With Pierre Robin Sequence in the First Year of Life.

OBJECTIVE: To compare growth trends among infants with Pierre Robin sequence (PRS) to normal World Health Organization (WHO) growth standards. STUDY DESIGN: Case series with chart review. SUBJECTS AND METHODS: Twenty-four infants with syndromic and nonsyndromic PRS (54% male) treated at an urban academic medical center between 2009 and 2017 were included. Infants with symptomatic hypoventilation underwent mandibular distraction osteogenesis (71%). Weights were recorded at roughly 1- to 3-month intervals from birth to 12 months, with ages adjusted for prematurity. The 50th percentile (P50) for this cohort was calculated and compared to WHO standards. RESULTS: In total, 135 weight entries for 24 subjects were included. The birth weight P50 was similar to the WHO standard (females: 0.09 kg above WHO [95% CI, -0.25 to +0.43; z score = 0.19]; males: 0.38 kg below WHO [95% CI, -0.77 to 0.00; z score = -0.79]). A slower growth rate was noted among female and male infants with PRS: in month 5, the PRS P50 among females was 1.42 kg below the WHO standard (95% CI, -1.77 to -1.07; z score = -1.64). Among males in month 3, the PRS P50 was 1.68 kg below the WHO standard (95% CI, -2.12 to -1.24; z score = -2.19). By month 12, weight deficiencies had resolved in both groups. CONCLUSION: Newborns with and without PRS may have similar birth weights, but the growth rate among male and female infants with PRS may lag behind that of unaffected infants, even when upper airway obstruction has been addressed in early infancy.

Effects of Maternal Voluntary Wheel Running During Pregnancy on Adult Hippocampal Neurogenesis, Temporal Order Memory, and Depression-Like Behavior in Adult Female and Male Offspring.

Research suggests that maternal exercise in pregnancy may have beneficial effects on the brain function of offspring. This study sought to determine if voluntary wheel running during pregnancy improves depression-like behavior, temporal order memory, and hippocampal neurogenesis in both female and male offspring mice. Pregnant mice were allowed to run voluntarily by introducing running wheels into the housing cages throughout the gestational period. Male and female mice offspring at the age of 8- to 9-week-old were then tested on the temporal order task and forced swim test, then euthanized for immunostaining for examining adult hippocampal cell proliferation and neuronal differentiation. Results showed that both male and female pups had reduced depression-like behavior, while only male offspring demonstrated improvement in temporal order memory. Immunostaining revealed that male offspring showed an increase in the number of immature neurons in the ventral hippocampus, whereas female offspring showed enhanced cell proliferation in the dorsal hippocampus. These findings indicate that maternal voluntary wheel running benefits both female and male offspring on reducing depression-like behavior, but with gender effect on promoting hippocampal cell proliferation, neuronal differentiation, and temporal order memory.

A spectroscopic and ab initio study of the hydrogen peroxide-formic acid complex: hindering the internal motion of H2O2.

The microwave spectrum of the hydrogen-bonded hydrogen peroxide-formic acid complex was measured in the range from 4 to 17 GHz. Assignment of transitions and analyses of the spectrum were supported by ab initio wavefunction and density functional calculations. The detected conformer features a seven-membered hydrogen-bonded ring, in which the H-atom of one hydroxyl group of H2O2 and the O-atom of the other OH group are a hydrogen bond donor and acceptor, respectively, to the carboxyl group of formic acid. The rotational transitions show a tunnelling splitting, which is attributed to a wagging-like motion of the free H-atom of H2O2 from above to below the heavy atom plane of formic acid. Transitions between tunneling states are driven by the change in dipole moment accompanying this motion and were measured and analyzed. Ab initio analyses of the tunneling path reveal an asymmetric potential, which reflects the (transiently) chiral nature of the complex.

Posttranslational Amelogenin Processing and Changes in Matrix Assembly during Enamel Development.

The extracellular tooth enamel matrix is a unique, protein-rich environment that provides the structural basis for the growth of long and parallel oriented enamel crystals. Here we have conducted a series of in vivo and in vitro studies to characterize the changes in matrix shape and organization that take place during the transition from ameloblast intravesicular matrices to extracellular subunit compartments and pericrystalline sheath proteins, and correlated these changes with stages of amelogenin matrix protein posttranslational processing. Our transmission electron microscopic studies revealed a 2.5-fold difference in matrix subunit compartment dimensions between secretory vesicle and extracellular enamel protein matrix as well as conformational changes in matrix structure between vesicles, stippled materials, and pericrystalline matrix. Enamel crystal growth in organ culture demonstrated granular mineral deposits associated with the enamel matrix framework, dot-like mineral deposits along elongating initial enamel crystallites, and dramatic changes in enamel matrix configuration following the onset of enamel crystal formation. Atomic force micrographs provided evidence for the presence of both linear and hexagonal/ring-shaped full-length recombinant amelogenin protein assemblies on mica surfaces, while nickel-staining of the N-terminal amelogenin N92 His-tag revealed 20 nm diameter oval and globular amelogenin assemblies in N92 amelogenin matrices. Western blot analysis comparing loosely bound and mineral-associated protein fractions of developing porcine enamel organs, superficial and deep enamel layers demonstrated (i) a single, full-length amelogenin band in the enamel organ followed by 3 kDa cleavage upon entry into the enamel layer, (ii) a close association of 8-16 kDa C-terminal amelogenin cleavage products with the growing enamel apatite crystal surface, and (iii) a remaining pool of N-terminal amelogenin fragments loosely retained between the crystalline phases of the deep enamel layer. Together, our data establish a temporo-spatial correlation between amelogenin protein processing and the changes in enamel matrix configuration that take place during the transition from intracellular vesicle compartments to extracellular matrix assemblies and the formation of protein coats along elongating apatite crystal surfaces. In conclusion, our study suggests that enzymatic cleavage of the amelogenin enamel matrix protein plays a key role in the patterning of the organic matrix framework as it affects enamel apatite crystal growth and habit.