Giantin is required for coordinated production of aggrecan, link protein and type XI collagen during chondrogenesis

Mutation of the Thap4 gene causes dwarfism and testicular anomalies in rats and mice

The petit (pet) locus is associated with dwarfism, testicular anomalies, severe thymic hypoplasia, and high postnatal lethality, which are inherited in autosomal recessive mode of inheritance in rats with a Wistar strain genetic background. Linkage analysis localized the pet locus between 98.7 Mb and 101.2 Mb on rat chromosome 9. Nucleotide sequence analysis identified 2 bp deletion in exon 2 of the Thap4 gene as the causative mutation for pet. This deletion causes a frameshift and premature termination codon, resulting in a truncated THAP4 protein lacking approximately two-thirds of the C-terminal side. Thap4 is expressed in various organs, including the testis and thymus in rats. To elucidate the biological function of THAP4 in other species, we generated Thap4 knockout mice lacking exon 2 of the Thap4 gene through genome editing. Thap4 knockout mice also exhibited dwarfism and small testis but did not show high postnatal lethality. Thymus weights of adult Thap4 knockout male mice were significantly higher compared to wild-type male mice. Although Thap4 knockout male mice were fertile, their testis contained seminiferous tubules with spermatogenesis and degenerative seminiferous tubules lacking germ cells. Additionally, we observed vacuoles in seminiferous tubules, and clusters of cells in the lumen in seminiferous tubules in Thap4 knockout male mice. These results demonstrate that spontaneous mutation of Thap4 gene in rats and knockout of Thap4 gene in mice both cause dwarfism and testicular anomalies. Thap4 gene in rats and mice is essential for normal testicular development, maintaining spermatogenesis throughout the entire region of seminiferous tubules.

The factory, the antenna and the scaffold: the three-way interplay between the Golgi, cilium and extracellular matrix underlying tissue function

The growth and development of healthy tissues is dependent on the construction of a highly specialised extracellular matrix (ECM) to provide support for cell growth and migration and to determine the biomechanical properties of the tissue. These scaffolds are composed of extensively glycosylated proteins which are secreted and assembled into well-ordered structures that can hydrate, mineralise, and store growth factors as required. The proteolytic processing and glycosylation of ECM components is vital to their function. These modifications are under the control of the Golgi apparatus, an intracellular factory hosting spatially organised, protein-modifying enzymes. Regulation also requires a cellular antenna, the cilium, which integrates extracellular growth signals and mechanical cues to inform ECM production. Consequently, mutations in either Golgi or ciliary genes frequently lead to connective tissue disorders. The individual importance of each of these organelles to ECM function is well-studied. However, emerging evidence points towards a more tightly linked system of interdependence between the Golgi, cilium and ECM. This review examines how the interplay between all three compartments underpins healthy tissue. As an example, it will look at several members of the golgin family of Golgi-resident proteins whose loss is detrimental to connective tissue function. This perspective will be important for many future studies looking to dissect the cause and effect of mutations impacting tissue integrity.

Compartmentalized Proteomic Profiling Outlines the Crucial Role of the Classical Secretory Pathway during Recombinant Protein Production in Chinese Hamster Ovary Cells

Different cellular processes that contribute to protein production in Chinese hamster ovary (CHO) cells have been previously investigated by proteomics. However, although the classical secretory pathway (CSP) has been well documented as a bottleneck during recombinant protein (RP) production, it has not been well represented in previous proteomic studies. Hence, the significance of this pathway for production of RP was assessed by identifying its own proteins that were associated to changes in RP production, through subcellular fractionation coupled to shot-gun proteomics. Two CHO cell lines producing a monoclonal antibody with different specific productivities were used as cellular models, from which 4952 protein groups were identified, which represent a coverage of 59% of the Chinese hamster proteome. Data are available via ProteomeXchange with identifier PXD021014. By using SAM and ROTS algorithms, 493 proteins were classified as differentially expressed, of which about 80% was proposed as novel targets and one-third were assigned to the CSP. Endoplasmic reticulum (ER) stress, unfolded protein response, calcium homeostasis, vesicle traffic, glycosylation, autophagy, proteasomal activity, protein synthesis and translocation into ER lumen, and secretion of extracellular matrix components were some of the affected processes that occurred in the secretory pathway. Processes from other cellular compartments, such as DNA replication, transcription, cytoskeleton organization, signaling, and metabolism, were also modified. This study gives new insights into the molecular traits of higher producer cells and provides novel targets for development of new sub-lines with improved phenotypes for RP production.

Giantin is required for intracellular N-terminal processing of type I procollagen

Knockout of the golgin giantin leads to skeletal and craniofacial defects driven by poorly studied changes in glycosylation and extracellular matrix deposition. Here, we sought to determine how giantin impacts the production of healthy bone tissue by focusing on the main protein component of the osteoid, type I collagen. Giantin mutant zebrafish accumulate multiple spontaneous fractures in their caudal fin, suggesting their bones may be more brittle. Inducing new experimental fractures revealed defects in the mineralization of newly deposited collagen as well as diminished procollagen reporter expression in mutant fish. Analysis of a human giantin knockout cell line expressing a GFP-tagged procollagen showed that procollagen trafficking is independent of giantin. However, our data show that intracellular N-propeptide processing of pro-α1(I) is defective in the absence of giantin. These data demonstrate a conserved role for giantin in collagen biosynthesis and extracellular matrix assembly. Our work also provides evidence of a giantin-dependent pathway for intracellular procollagen processing.

The role of the Golgi apparatus in disease (Review)

The Golgi apparatus is known to underpin many important cellular homeostatic functions, including trafficking, sorting and modifications of proteins or lipids. These functions are dysregulated in neurodegenerative diseases, cancer, infectious diseases and cardiovascular diseases, and the number of disease-related genes associated with Golgi apparatus is on the increase. Recently, many studies have suggested that the mutations in the genes encoding Golgi resident proteins can trigger the occurrence of diseases. By summarizing the pathogenesis of these genetic diseases, it was found that most of these diseases have defects in membrane trafficking. Such defects typically result in mislocalization of proteins, impaired glycosylation of proteins, and the accumulation of undegraded proteins. In the present review, we aim to understand the patterns of mutations in the genes encoding Golgi resident proteins and decipher the interplay between Golgi resident proteins and membrane trafficking pathway in cells. Furthermore, the detection of Golgi resident protein in human serum samples has the potential to be used as a diagnostic tool for diseases, and its central role in membrane trafficking pathways provides possible targets for disease therapy. Thus, we also introduced the clinical value of Golgi apparatus in the present review.

Transcriptome for the breast muscle of Jinghai yellow chicken at early growth stages

Background

The meat quality of yellow feathered broilers is better than the quality of its production. Growth traits are important in the broiler industry. The exploration of regulation mechanisms for the skeletal muscle would help to increase the growth performance of chickens. At present, some progress has been made by researchers, but the molecular mechanisms of the skeletal muscle still remain unclear and need to be improved.

Methods

In this study, the breast muscles of fast- and slow-growing female Jinghai yellow chickens (F4F, F8F, F4S, F8S) and slow-growing male Jinghai yellow chickens (M4S, M8S) aged four and eight weeks were selected for transcriptome sequencing (RNA-seq). All analyses of differentially expressed genes (DEGs) and functional enrichment were performed. Finally, we selected nine DEGs to verify the accuracy of the sequencing by qPCR.

Results

The differential gene expression analysis resulted in 364, 219 and 111 DEGs (adjusted P-value ≤ 0.05) for the three comparison groups, F8FvsF4F, F8SvsF4S, and M8SvsM4S, respectively. Three common DEGs (ADAMTS20, ARHGAP19, and Novel00254) were found, and they were all highly expressed at four weeks of age. In addition, some other genes related to growth and development, such as ANXA1, COL1A1, MYH15, TGFB3 and ACTC1, were obtained. The most common DEGs (n = 58) were found between the two comparison groups F8FvsF4F and F8SvsF4S, and they might play important roles in the growth of female chickens. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway also showed some significant enrichment pathways, for instance, extracellular matrix (ECM)-receptor interaction, focal adhesion, cell cycle, and DNA replication. The two pathways that were significantly enriched in the F8FvsF4F group were all contained in that of F8SvsF4S. The same two pathways were ECM–receptor interaction and focal adhesion, and they had great influence on the growth of chickens. However, many differences existed between male and female chickens in regards to common DEGs and KEGG pathways. The results would help to reveal the regulation mechanism of the growth and development of chickens and serve as a guideline to propose an experimental design on gene function with the DEGs and pathways.

Circulating Exosomal miR-150-5p and miR-99b-5p as Diagnostic Biomarkers for Colorectal Cancer

Background: Circulating exosomal miRNAs are potential non-invasive biomarkers for colorectal cancer. The present study aimed to validate the novel sensitive and specific exosomal miRNA biomarkers for diagnosing colorectal cancer (CRC). Patients and Methods: Exosomes isolated from the serum of CRC patients and healthy donors by ultracentrifugation were characterized using TEM, qNano, and immunoblotting. The exosomes from 2 healthy donors and 4 CRC patients were subjected to RNA isolation and miRNA sequencing. The differently expressed miRNAs from 165 primary CRC patients and 153 healthy donors were substantiated by RT-qPCR. Results: The RNA-sequence data analysis revealed that 29 exosomal miRNAs (20 downregulated and 9 upregulated) with >1.5-fold difference between CRC patients and healthy donors were selected. The serum exosomal miR-99b-5p and miR-150-5p levels were significantly downregulated in CRC patients as compared to healthy donors (p < 0.0001 and p < 0.0001, respectively) and benign disease (p = 0.009 and p < 0.0001, respectively). The expression levels of exosomal miR-99b-5p and miR-150-5p were significantly decreased in early CRC patients as compared to healthy donors (p < 0.0001 and p < 0.0001, respectively). The expression levels of exosomal miR-99b-5p and miR-150-5p were significantly increased postoperatively (p = 0.0058 and p < 0.0001, respectively). Conclusions: The present study demonstrated that serum exosomal miRNAs are promising, sensitive, specific, and non-invasive diagnostic biomarkers for CRC. Impact: This is the first study to specifically identify exosomal miR-99b-5p and miR-150-5p associated with CRC. This study, therefore, might deepen the understanding of tumor-derived exosomes for CRC diagnosis.

The Golgin Protein Giantin Regulates Interconnections Between Golgi Stacks

Golgins are a family of Golgi-localized long coiled-coil proteins. The major golgin function is thought to be the tethering of vesicles, membranes, and cytoskeletal elements to the Golgi. We previously showed that knockdown of one of the longest golgins, Giantin, altered the glycosylation patterns of cell surfaces and the kinetics of cargo transport, suggesting that Giantin maintains correct glycosylation through slowing down transport within the Golgi. Giantin knockdown also altered the sizes and numbers of mini Golgi stacks generated by microtubule de-polymerization, suggesting that it maintains the independence of individual Golgi stacks. Therefore, it is presumed that Golgi stacks lose their independence following Giantin knockdown, allowing easier and possibly increased transport among stacks and abnormal glycosylation. To gain structural insights into the independence of Golgi stacks, we herein performed electron tomography and 3D modeling of Golgi stacks in Giantin knockdown cells. Compared with control cells, Giantin-knockdown cells had fewer and smaller fenestrae within each cisterna. This was supported by data showing that the diffusion rate of Golgi membrane proteins is faster in Giantin-knockdown Golgi, indicating that Giantin knockdown structurally and functionally increases connectivity among Golgi cisternae and stacks. This increased connectivity suggests that contrary to the cis-golgin tether model, Giantin instead inhibits the tether and fusion of nearby Golgi cisternae and stacks, resulting in transport difficulties between stacks that may enable the correct glycosylation of proteins and lipids passing through the Golgi.

Form and function of the Golgi apparatus: scaffolds, cytoskeleton and signalling

In addition to the classical functions of the Golgi in membrane transport and glycosylation, the Golgi apparatus of mammalian cells is now recognised to contribute to the regulation of a range of cellular processes, including mitosis, DNA repair, stress responses, autophagy, apoptosis and inflammation. These processes are often mediated, either directly or indirectly, by membrane scaffold molecules, such as golgins and GRASPs which are located on Golgi membranes. In many cases, these scaffold molecules also link the actin and microtubule cytoskeleton and influence Golgi morphology. An emerging theme is a strong relationship between the morphology of the Golgi and regulation of a variety of signalling pathways. Here, we review the molecular regulation of the morphology of the Golgi, especially the role of the golgins and other scaffolds in the interaction with the microtubule and actin networks. In addition, we discuss the impact of the modulation of the Golgi ribbon in various diseases, such as neurodegeneration and cancer, to the pathology of disease.

The Physiological Functions of the Golgin Vesicle Tethering Proteins

The golgins comprise a family of vesicle tethering proteins that act in a selective manner to tether transport vesicles at the Golgi apparatus. Tethering is followed by membrane fusion to complete the delivery of vesicle-bound cargo to the Golgi. Different golgins are localized to different regions of the Golgi, and their ability to selectively tether transport vesicles is important for the specificity of vesicle traffic in the secretory pathway. In recent years, our mechanistic understanding of golgin-mediated tethering has greatly improved. We are also beginning to appreciate how the loss of golgin function can impact upon physiological processes through the use of animal models and the study of human disease. These approaches have revealed that loss of a golgin causes tissue-restricted phenotypes, which can vary in severity and the cell types affected. In many cases, it is possible to attribute these phenotypes to a defect in vesicular traffic, although why certain tissues are sensitive to loss of a particular golgin is still, in most cases, unclear. Here, I will summarize recent progress in our understanding of golgins, focusing on the physiological roles of these proteins, as determined from animal models and the study of disease in humans. I will describe what these in vivo analyses have taught us, as well as highlight less understood aspects, and areas for future investigations.