The glycoproteins EDIL3 and MFGE8 regulate vesicle-mediated eggshell calcification in a new model for avian biomineralization

Genetic parameter estimation and molecular foundation of chicken egg-laying trait

The age of first egg (AFE) in chicken can affect early and even life-time egg production performance to some extent, and therefore is an important economic trait that affects production efficiency. To better understand the genetic patterns of AFE and other production traits including body weight at first egg (BWA), first egg weight (FEW), and total egg number from AFE to 58 wk of age (total-EN), we recorded the production performance of 2 widely used layer breeds, white leghorn (WL) and Rhode Island Red (RIR) and estimated genetic parameters based on pedigree and production data. The results showed that the heritability of AFE in both breeds ranged from 0.4 to 0.6, and AFE showed strong positive genetic and phenotypic correlations to BWA as well as FEW, while showing strong negative genetic and phenotypic correlations with total-EN. Furtherly, by genome-wide association analysis study (GWAS), we identified 12 and 26 significant SNPs to be related to AFE in the 2-layer breeds, respectively. A total of 18 genes were identified that could affect AFE based on the significant SNP annotations obtained, but there were no gene overlapped in the 2 breeds indicating the genetic foundation of AFE could differ from breed to breed. Our results provided a deeper understanding of genetic patterns and molecular basement of AFE in different breeds and could help in the selection of egg production traits.

Molecular genetic foundation of a sex-linked tailless trait in Hongshan chicken by whole genome data analysis

As a Chinese local chicken breed, Hongshan chickens have 2 kinds of tail feather phenotypes, normal and taillessness. Our previous studies showed that taillessness was a sex-linked dominant trait. Abnormal development of the tail vertebrae could be explained this phenomenon in some chicken breeds. However, the number of caudal vertebrae in rumpless Hongshan chickens was normal, so rumplessness in Hongshan chicken was not related to the development of the caudal vertebrae. Afterwards, we found that rumplessness in Hongshan was due to abnormal development of tail feather rather than abnormal development of caudal vertebrae. In order to understand the genetic foundation of the rumplessness of Hongshan chickens, we compared and reanalyzed 2 sets of data in normal and rumpless Hongshan chickens from our previous studies. By joint analysis of genome-wide selection signature analysis and genome-wide association approach, we found that 1 overlapping gene (EDIL3) and 16 peak genes (ENSGALG00000051843, ENSGALG00000053498, ENSGALG00000054800, KIF27, PTPRD, ENSGALG00000047579, ENSGALG00000041052, ARHGEF28, CAMK4, SERINC5, ENSGALG00000050776, ERCC8, MCC, ADAMTS19, ENSGALG00000053322, CHRNA8) located on the Z chromosome was associated with the rumpless trait. The results of this study furtherly revealed the molecular mechanism of the rumpless trait in Hongshan chickens, and identified the candidate genes associated with this trait. Our results will help to improve the shape of chicken tail feathers and to rise individual economic value in some specific market in China.

Inheritance of genomic regions and genes associated with number of oocytes and embryos in Gir cattle through daughter design

Over the past decades, daughter designs, including genotyped sires and their genotyped daughters, have been used as an approach to identify QTL related to economic traits. The aim of this study was to identify genomic regions inherited by Gir sire families and genes associated with number of viable oocytes (VO), total number of oocytes (TO), and number of embryos (EMBR) based on a daughter design approach. In total, 15 Gir sire families were selected. The number of daughters per family ranged from 26 to 395, which were genotyped with different SNP panels and imputed to the Illumina BovineHD BeadChip (777K) and had phenotypes for oocyte and embryo production. Daughters had phenotypic data for VO, TO, and EMBR. The search for QTL was performed through GWAS based on GBLUP. The QTL were found for each trait among and within families based on the top 10 genomic windows with the greatest genetic variance. For EMBR, genomic windows identified among families were located on BTA4, BTA5, BTA6, BTA7, BTA8, BTA13, BTA16, and BTA17, and they were most frequent on BTA7 within families. For VO, genomic windows were located on BTA2, BTA4, BTA5, BTA7, BTA17, BTA21, BTA22, BTA23, and BTA27 among families, being most frequent on BTA8 within families. For TO, the top 10 genomic windows were identified on BTA2, BTA4, BTA5, BTA7, BTA17, BTA21, BTA22, BTA26, and BTA27, being most frequent on BTA7 and BTA8 within families. Considering all results, the greatest number of genomic windows was found on BTA7, where the VCAN, XRCC4, TRNAC-ACA, HAPLN1, and EDIL3 genes were identified in the common regions. In conclusion, 15 Gir sire families with 26 to 395 daughters per family with phenotypes for oocyte and embryo production helped to identify the inheritance of several genomic regions, especially on BTA7, where the EDIL3, HAPLN1, and VCAN candidate genes were associated with number of oocytes and embryos in Gir cattle families.

EDIL3 as an Angiogenic Target of Immune Exclusion Following Checkpoint Blockade

Immune checkpoint blockade (ICB) has become the standard of care for several solid tumors. Multiple combinatorial approaches have been studied to improve therapeutic efficacy. The combination of antiangiogenic agents and ICB has demonstrated efficacy in several cancers. To improve the mechanistic understanding of synergies with these treatment modalities, we performed screens of sera from long-term responding patients treated with ipilimumab and bevacizumab. We discovered a high-titer antibody response against EGF-like repeats and discoidin I-like domains protein 3 (EDIL3) that correlated with favorable clinical outcomes. EDIL3 is an extracellular protein, previously identified as a marker of poor prognosis in various malignancies. Our Tumor Immune Dysfunction and Exclusion analysis predicted that EDIL3 was associated with immune exclusion signatures for cytotoxic immune cell infiltration and nonresponse to ICB. Cancer-associated fibroblasts (CAF) were predicted as the source of EDIL3 in immune exclusion-related cells. Furthermore, The Cancer Genome Atlas Skin Cutaneous Melanoma (TCGA-SKCM) and CheckMate 064 data analyses correlated high levels of EDIL3 with increased pan-fibroblast TGFβ response, enrichment of angiogenic signatures, and induction of epithelial-to-mesenchymal transition. Our in vitro studies validated EDIL3 overexpression and TGFβ regulation in patient-derived CAFs. In pretreatment serum samples from patients, circulating levels of EDIL3 were associated with circulating levels of VEGF, and like VEGF, EDIL3 increased the angiogenic abilities of patient-derived tumor endothelial cells (TEC). Mechanistically, three-dimensional microfluidic cultures and two-dimensional transmigration assays with TEC endorsed EDIL3-mediated disruption of the lymphocyte function-associated antigen-1 (LFA-1)-ICAM-1 interaction as a possible means of T-cell exclusion. We propose EDIL3 as a potential target for improving the transendothelial migration of immune cells and efficacy of ICB therapy.

Transcriptome profiling analysis of uterus during chicken laying periods

The avian eggshell is formed in the uterus. Changes in uterine function may have a significant effect on eggshell quality. To identify the vital genes impacting uterine functional maintenance in the chicken, uteri in three different periods (22W, 31W, 51W) were selected for RNA sequencing and bioinformatics analysis. In our study, 520, 706 and 736 differentially expressed genes (DEGs) were respectively detected in the W31 vs W22 group, W51 vs W31 group and W51 vs W22 group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated DEGs were enriched in the extracellular matrix, extracellular region part, extracellular region, extracellular matrix structural constituent, ECM receptor interaction, collagen-containing extracellular matrix and collagen trimer in the uterus (P < 0.05). Protein-protein interaction analysis revealed that FN1, LOX, THBS2, COL1A1, COL1A2, COL5A1, COL5A2, POSTN, MMP13, VANGL2, RAD54B, SPP1, SDC1, BTC, ANGPTL3 might be key candidate genes for uterine functional maintenance in chicken. This study discovered dominant genes and pathways which enhanced our knowledge of chicken uterine functional maintenance.

Comparative N-Glycoproteomic Investigation of Eggshell Cuticle and Mineralized Layer Proteins

The eggshell cuticle layer (ECL) and eggshell mineralized layer (EML) contain amounts of glycoproteins and proteoglycans. However, there were few comprehensive reports about the effect of post-translational modifications on protein structure and function which requires investigation. Therefore, we used comparative N-glycoproteomics to study glycoproteins in the ECL and EML. We identified a total of 272 glycoproteins in this experiment and found that glycoproteins located in EML were more than that in ECL. Moreover, they showed distinct functional difference between both layers. As N-glycosylation of ovocleidin-17 and ovocleidin-116 in the EML affected eggshell mineralization, some glycoproteins located in ECL, like ovotransferrin and ovostatin-like, possessed antibacterial activity. The several regulated glycoproteins in the EML may pertain to the regulation of mineralization, while glycosylated proteins in the ECL may contribute to molecular adhesion and defense against microbial invasion. This study provides new insights into the eggshell matrix protein contents of the ECL and EML.

Milk Fat Globule Epidermal Growth Factor VIII Fragment Medin in Age-Associated Arterial Adverse Remodeling and Arterial Disease

Medin, a small 50-amino acid peptide, is an internal cleaved product from the second discoidin domain of milk fat globule epidermal growth factor VIII (MFG-E8) protein. Medin has been reported as the most common amylogenic protein in the upper part of the arterial system, including aortic, temporal, and cerebral arterial walls in the elderly. Medin has a high affinity to elastic fibers and is closely associated with arterial degenerative inflammation, elastic fiber fragmentation, calcification, and amyloidosis. In vitro, treating with the medin peptide promotes the inflammatory phenotypic shift of both endothelial cells and vascular smooth muscle cells. In vitro, ex vivo, and in vivo studies demonstrate that medin enhances the abundance of reactive oxygen species and reactive nitrogen species produced by both endothelial cells and vascular smooth muscle cells and promotes vascular endothelial dysfunction and arterial stiffening. Immunostaining and immunoblotting analyses of human samples indicate that the levels of medin are increased in the pathogenesis of aortic aneurysm/dissection, temporal arteritis, and cerebrovascular dementia. Thus, medin peptide could be targeted as a biomarker diagnostic tool or as a potential molecular approach to curbing the arterial degenerative inflammatory remodeling that accompanies aging and disease.

Ancient proteins resolve controversy over the identity of Genyornis eggshell

The realization that ancient biomolecules are preserved in "fossil" samples has revolutionized archaeological science. Protein sequences survive longer than DNA, but their phylogenetic resolution is inferior; therefore, careful assessment of the research questions is required. Here, we show the potential of ancient proteins preserved in Pleistocene eggshell in addressing a longstanding controversy in human and animal evolution: the identity of the extinct bird that laid large eggs which were exploited by Australia's indigenous people. The eggs had been originally attributed to the iconic extinct flightless bird Genyornis newtoni (†Dromornithidae, Galloanseres) and were subsequently dated to before 50 ± 5 ka by Miller et al. [Nat. Commun. 7, 10496 (2016)]. This was taken to represent the likely extinction date for this endemic megafaunal species and thus implied a role of humans in its demise. A contrasting hypothesis, according to which the eggs were laid by a large mound-builder megapode (Megapodiidae, Galliformes), would therefore acquit humans of their responsibility in the extinction of Genyornis. Ancient protein sequences were reconstructed and used to assess the evolutionary proximity of the undetermined eggshell to extant birds, rejecting the megapode hypothesis. Authentic ancient DNA could not be confirmed from these highly degraded samples, but morphometric data also support the attribution of the eggshell to Genyornis. When used in triangulation to address well-defined hypotheses, paleoproteomics is a powerful tool for reconstructing the evolutionary history in ancient samples. In addition to the clarification of phylogenetic placement, these data provide a more nuanced understanding of the modes of interactions between humans and their environment.

Embryonic transcriptome unravels mechanisms and pathways underlying embryonic development with respect to muscle growth, egg production, and plumage formation in native and broiler chickens

Background: Muscle development, egg production, and plumage colors are different between native and broiler chickens. The study was designed to investigate why improved Aseel (PD4) is colorful, stronger, and grew slowly compared with the control broiler (CB).

Methods: A microarray was conducted using the 7th-day embryo (7EB) and 18th-day thigh muscle (18TM) of improved Aseel and broiler, respectively. Also, we have selected 24 Gallus gallus candidate reference genes from NCBI, and total RNA was isolated from the broiler, improved Aseel embryo tissues, and their expression profiles were studied by real-time quantitative PCR (qPCR). Furthermore, microarray data were validated with qPCR using improved Aseel and broiler embryo tissues.

Results: In the differential transcripts screening, all the transcripts obtained by microarray of slow and fast growth groups were screened by fold change ≥ 1 and false discovery rate (FDR) ≤ 0.05. In total, 8,069 transcripts were differentially expressed between the 7EB and 18TM of PD4 compared to the CB. A further analysis showed that a high number of transcripts are differentially regulated in the 7EB of PD4 (6,896) and fewer transcripts are differentially regulated (1,173) in the 18TM of PD4 compared to the CB. On the 7th^- and 18th-day PD4 embryos, 3,890, 3,006, 745, and 428 transcripts were up- and downregulated, respectively. The commonly up- and downregulated transcripts are 91 and 44 between the 7th- and 18th-day of embryos. In addition, the best housekeeping gene was identified. Furthermore, we validated the differentially expressed genes (DEGs) related to muscle growth, myostatin signaling and development, and fatty acid metabolism genes in PD4 and CB embryo tissues by qPCR, and the results correlated with microarray expression data.

Conclusion: Our study identified DEGs that regulate the myostatin signaling and differentiation pathway; glycolysis and gluconeogenesis; fatty acid metabolism; Jak-STAT, mTOR, and TGF-β signaling pathways; tryptophan metabolism; and PI3K-Akt signaling pathways in PD4. The results revealed that the gene expression architecture is present in the improved Aseel exhibiting embryo growth that will help improve muscle development, differentiation, egg production, protein synthesis, and plumage formation in PD4 native chickens. Our findings may be used as a model for improving the growth in Aseel as well as optimizing the growth in the broiler.

Evolution of EGF-like and Zona pellucida domains containing shell matrix proteins in mollusks

Several types of shell matrix proteins (SMPs) have been identified in molluskan shells. Their diversity is the consequence of various molecular processes, including domain shuffling and gene duplication. However, the evolutionary origin of most SMPs remains unclear. In this study, we investigated the evolutionary process EGF-like and zona pellucida (ZP) domains containing SMPs. Two types of the proteins (EGF-like protein (EGFL) and EGF-like and ZP domains containing protein (EGFZP)) were found in the pearl oyster, Pinctada fucata. In contrast, only EGFZP was identified in the gastropods. Phylogenetic analysis and genomic arrangement studies showed that EGFL and EGFZP formed a clade in bivalves, and their encoding genes were localized in tandem repeats on the same scaffold. In P. fucata, EGFL genes were expressed in the outer part of mantle epithelial cells are related to the calcitic shell formation. However, in both P. fucata and the limpet Nipponacmea fuscoviridis, EGFZP genes were expressed in the inner part of the mantle epithelial cells are related to aragonitic shell formation. Furthermore, our analysis showed that in P. fucata, the ZP domain interacts with eight SMPs that have various functions in the nacreous shell mineralization. The data suggest that the ZP domain can interact with other SMPs, and EGFL evolution in pterimorph bivalves represents an example of neo-functionalization that involves the acquisition of a novel protein through gene duplication.

Liquid-Liquid Phase Separation in Nucleation Process of Biomineralization

Biomineralization is a typical interdisciplinary subject attracting biologists, chemists, and geologists to figure out its potential mechanism. A mounting number of studies have revealed that the classical nucleation theory is not suitable for all nucleation process of biominerals, and phase-separated structures such as polymer-induced liquid precursors (PILPs) play essential roles in the non-classical nucleation processes. These structures are able to play diverse roles biologically or pathologically, and could also give inspiring clues to bionic applications. However, a lot of confusion and dispute occurred due to the intricacy and interdisciplinary nature of liquid precursors. Researchers in different fields may have different opinions because the terminology and current state of understanding is not common knowledge. As a result, our team reviewed the most recent articles focusing on the nucleation processes of various biominerals to clarify the state-of-the-art understanding of some essential concepts and guide the newcomers to enter this intricate but charming field.

Pathogenesis of Enamel-Renal Syndrome Associated Gingival Fibromatosis: A Proteomic Approach

The enamel renal syndrome (ERS) is a rare disorder featured by amelogenesis imperfecta, gingival fibromatosis and nephrocalcinosis. ERS is caused by bi-allelic mutations in the secretory pathway pseudokinase FAM20A. How mutations in FAM20A may modify the gingival connective tissue homeostasis and cause fibromatosis is currently unknown. We here analyzed conditioned media of gingival fibroblasts (GFs) obtained from four unrelated ERS patients carrying distinct mutations and control subjects. Secretomic analysis identified 109 dysregulated proteins whose abundance had increased (69 proteins) or decreased (40 proteins) at least 1.5-fold compared to control GFs. Proteins over-represented were mainly involved in extracellular matrix organization, collagen fibril assembly, and biomineralization whereas those under-represented were extracellular matrix-associated proteins. More specifically, transforming growth factor-beta 2, a member of the TGFβ family involved in both mineralization and fibrosis was strongly increased in samples from GFs of ERS patients and so were various known targets of the TGFβ signaling pathway including Collagens, Matrix metallopeptidase 2 and Fibronectin. For the over-expressed proteins quantitative RT-PCR analysis showed increased transcript levels, suggesting increased synthesis and this was further confirmed at the tissue level. Additional immunohistochemical and western blot analyses showed activation and nuclear localization of the classical TGFβ effector phospho-Smad3 in both ERS gingival tissue and ERS GFs. Exposure of the mutant cells to TGFB1 further upregulated the expression of TGFβ targets suggesting that this pathway could be a central player in the pathogenesis of the ERS gingival fibromatosis. In conclusion our data strongly suggest that TGFβ -induced modifications of the extracellular matrix contribute to the pathogenesis of ERS. To our knowledge this is the first proteomic-based analysis of FAM20A-associated modifications.

Advanced Nanotechnologies for Extracellular Vesicle-Based Liquid Biopsy

Extracellular vesicles (EVs) are emerging as a new source of biomarkers in liquid biopsy because of their wide presence in most body fluids and their ability to load cargoes from disease-related cells. Owing to the crucial role of EVs in disease diagnosis and treatment, significant efforts have been made to isolate, detect, and analyze EVs with high efficiency. A recent overview of advanced EV detection nanotechnologies is discussed here. First, several key challenges in EV-based liquid biopsies are introduced. Then, the related pivotal advances in nanotechnologies for EV isolation based on physical features, chemical affinity, and the combination of nanostructures and chemical affinity are summarized. Next, a summary of high-sensitivity sensors for EV detection and advanced approaches for single EV detection are provided. Later, EV analysis is introduced in practical clinical scenarios, and the application of machine learning in this field is highlighted. Finally, future opportunities for the development of next-generation nanotechnologies for EV detection are presented.

Transcriptome analysis reveals key genes and pathways associated with egg production in Nandan-Yao domestic chicken

BACKGROUND

Egg production is a very important economic trait in chicken breeding, but its molecular mechanism is unclear until now. Nandan-Yao chicken (Gallus gallus domesticus) is a native breed in Guangxi province, China, which is famous for good meet quality, but with low egg production.

METHODS

To explore the molecular regulation related to egg production, high egg production (HEP) and low egg production (LEP) were divided according to the total egg number at 55 weeks, and the concentration of serum sex hormones was tested to evaluate the physiological function of ovary and uterus. RNA sequencing (RNA-Seq) was used to explore the transcriptome from the ovary and uterus of Nandan-Yao chicken.

RESULTS

The levels of serum sex hormone showed that concentrations of estradiol (E2), follicle-stimulating hormone (FSH), and luteotropic hormone (LH) were significantly higher in HEP than those in LEP (P < 0.01), while the concentration of testosterone (T) was significantly lower in HEP (P < 0.01). RNA-Seq analysis identified 901 and 2763 differentially expressed genes (DEGs) in ovary and uterus, respectively. Enrichment analysis showed that DEGs were significantly involved in the regulation of tight junction in the ovary (P < 0.05), while in uterus, DEGs were mainly enriched in the phagosome, ECM-receptor interaction, cell adhesion molecules (CAMs), focal adhesion, cardiac muscle contraction, cytokine-cytokine receptor interaction, and the regulation of MAPK signaling pathway (P < 0.05). Protein network interaction and function analyses revealed that FN1, FGF7, SOX2 identified from the ovary, and UQCRH, COX5A, FN1 from the uterus might be key candidate genes for egg production in Nandan-Yao chicken.

CONCLUSIONS

Our study provided key candidate genes and pathways involved in the egg-laying process of Nandan-Yao chicken and could help to further understand the molecular mechanisms of chicken reproduction.

Biotechnological Applications of Eggshell: Recent Advances

The eggshell (ES) provides protection against pathogenic and physical insults while supplying essential metabolic and nutritional needs for the growing avian embryo. It is constituted mainly of calcium carbonate arranged as calcite crystals. The global chicken egg production in 2018 was over 76.7 million metric tons. In industrialized countries, about 30% of eggs are processed at breaker plants that produce liquid egg products and large quantities of solid ES waste. ES waste is utilized for a variety of low-value applications, or alternatively is disposed in landfill with associated economic and environmental burdens. The number of patents pertaining to ES applications has increased dramatically in recent years; of 673 patents granted in the last century, 536 (80%) were published in the last two decades. This review provides a snapshot of the most recent patents published between 2015 and 2020, with emphasis on different biotechnological applications of ES waste, and summarizes applications for biomedical, chemical, engineering, and environmental technologies. Biomedical technologies include the production of calcium lactate, calcium phosphate, and health-promoting products, while chemical technologies include plant growth promoters, food processing and production, and biodiesel oil catalysis along with active calcium, carbon, soluble proteins, organic calcium, and ultrafine calcium carbonate sources. Engineering technologies address material engineering and nanoparticle production, while environmental technologies pertain to production of biomass, solubilization of sludge as well as production of magnetic ES adsorbents and adsorption of heavy metals, organics, total nitrogen and fluoride, soil pollutants, and radioactive compounds. Although the number of ES-based patents has exponentially increased in the last decade, exploration of innovative top-down approaches and ES development as a physical platform are new endeavors that are expected to further increase the upscaling of ES waste exploitation.

Evolution of the Avian Eggshell Biomineralization Protein Toolkit - New Insights From Multi-Omics

The avian eggshell is a remarkable biomineral, which is essential for avian reproduction; its properties permit embryonic development in the desiccating terrestrial environment, and moreover, are critically important to preserve unfertilized egg quality for human consumption. This calcium carbonate (CaCO₃) bioceramic is made of 95% calcite and 3.5% organic matrix; it protects the egg contents against microbial penetration and mechanical damage, allows gaseous exchange, and provides calcium for development of the embryonic skeleton. In vertebrates, eggshell occurs in the Sauropsida and in a lesser extent in Mammalia taxa; avian eggshell calcification is one of the fastest known CaCO₃ biomineralization processes, and results in a material with excellent mechanical properties. Thus, its study has triggered a strong interest from the researcher community. The investigation of eggshell biomineralization in birds over the past decades has led to detailed characterization of its protein and mineral constituents. Recently, our understanding of this process has been significantly improved using high-throughput technologies (i.e., proteomics, transcriptomics, genomics, and bioinformatics). Presently, more or less complete eggshell proteomes are available for nine birds, and therefore, key proteins that comprise the eggshell biomineralization toolkit are beginning to be identified. In this article, we review current knowledge on organic matrix components from calcified eggshell. We use these data to analyze the evolution of selected matrix proteins and underline their role in the biological toolkit required for eggshell calcification in avian species. Amongst the panel of eggshell-associated proteins, key functional domains are present such as calcium-binding, vesicle-binding and protein-binding. These technical advances, combined with progress in mineral ultrastructure analyses, have opened the way for new hypotheses of mineral nucleation and crystal growth in formation of the avian eggshell, including transfer of amorphous CaCO₃ in vesicles from uterine cells to the eggshell mineralization site. The enrichment of multi-omics datasets for bird species is critical to understand the evolutionary context for development of CaCO₃ biomineralization in metazoans, leading to the acquisition of the robust eggshell in birds (and formerly dinosaurs).

Avian eggshell biomineralization: an update on its structure, mineralogy and protein tool kit

BACKGROUND

The avian eggshell is a natural protective envelope that relies on the phenomenon of biomineralization for its formation. The shell is made of calcium carbonate in the form of calcite, which contains hundreds of proteins that interact with the mineral phase controlling its formation and structural organization, and thus determine the mechanical properties of the mature biomaterial. We describe its mineralogy, structure and the regulatory interactions that integrate the mineral and organic constituents during eggshell biomineralization. Main Body. We underline recent evidence for vesicular transfer of amorphous calcium carbonate (ACC), as a new pathway to ensure the active and continuous supply of the ions necessary for shell mineralization. Currently more than 900 proteins and thousands of upregulated transcripts have been identified during chicken eggshell formation. Bioinformatic predictions address their functionality during the biomineralization process. In addition, we describe matrix protein quantification to understand their role during the key spatially- and temporally- regulated events of shell mineralization. Finally, we propose an updated scheme with a global scenario encompassing the mechanisms of avian eggshell mineralization.

CONCLUSION

With this large dataset at hand, it should now be possible to determine specific motifs, domains or proteins and peptide sequences that perform a critical function during avian eggshell biomineralization. The integration of this insight with genomic data (non-synonymous single nucleotide polymorphisms) and precise phenotyping (shell biomechanical parameters) on pure selected lines will lead to consistently better-quality eggshell characteristics for improved food safety. This information will also address the question of how the evolutionary-optimized chicken eggshell matrix proteins affect and regulate calcium carbonate mineralization as a good example of biomimetic and bio-inspired material design.

Characterization of the chalky layer-derived EGF-like domain-containing protein (CgELC) in the pacific oyster, Crassostrea gigas

The shells of the Pacific oyster Crassostrea gigas contain calcite crystals with three types of microstructures: prismatic, chalky, and foliated layers. Many shell matrix proteins were annotated from the shells of C. gigas; however, it is unclear which SMPs play important roles in their shell mineralization. The matrix proteins have never been reported from the chalky layer. In this study, we identified a chalky layer-derived EGF-like domain-containing protein (CgELC) from the chalky layer of C. gigas shells. The gene sequence of the CgELC was encoded under CGI_ 10,017,544 of the C. gigas genome database. Only peptide fragments in the N-terminal region of CGI_ 10,017,544 were detected by LC-MS/MS analyses, suggesting that CGI_ 10,017,544 was digested at the predicted protease digestion dibasic site by post-translational modification to become a mature CgELC protein. We produced three types of CgELC recombinant proteins, namely, the full length CgELC, as well as the N-terminal and C-terminal parts of CgELC (CgELC-N or -C, respectively), for in vitro crystallization experiments. In the presence of these recombinant proteins, the aggregation of polycrystalline calcite was observed. Some fibrous organic components seemed to be incorporated into the calcite crystals in the presence of the r-CgELC protein. We also noted different features in the crystallization between CgELC-N and CgELC-C; some crystals were inhibited crystal plane formation and contained many columnar prisms inside the crystals (CgELC-N) and formed numerous holes on their surfaces (CgELC-C). These results suggest that CgELC is involved in crystal aggregation and incorporated into calcite crystals.

Avian eggshell formation reveals a new paradigm for vertebrate mineralization via vesicular amorphous calcium carbonate

Amorphous calcium carbonate (ACC) is an unstable mineral phase, which is progressively transformed into aragonite or calcite in biomineralization of marine invertebrate shells or avian eggshells, respectively. We have previously proposed a model of vesicular transport to provide stabilized ACC in chicken uterine fluid where eggshell mineralization takes place. Herein, we report further experimental support for this model. We confirmed the presence of extracellular vesicles (EVs) using transmission EM and showed high levels of mRNA of vesicular markers in the oviduct segments where eggshell mineralization occurs. We also demonstrate that EVs contain ACC in uterine fluid using spectroscopic analysis. Moreover, proteomics and immunofluorescence confirmed the presence of major vesicular, mineralization-specific and eggshell matrix proteins in the uterus and in purified EVs. We propose a comprehensive role for EVs in eggshell mineralization, in which annexins transfer calcium into vesicles and carbonic anhydrase 4 catalyzes the formation of bicarbonate ions (HCO[Formula: see text]), for accumulation of ACC in vesicles. We hypothesize that ACC is stabilized by ovalbumin and/or lysozyme or additional vesicle proteins identified in this study. Finally, EDIL3 and MFGE8 are proposed to serve as guidance molecules to target EVs to the mineralization site. We therefore report for the first-time experimental evidence for the components of vesicular transport to supply ACC in a vertebrate model of biomineralization.