Regulation of the COPII secretory machinery via focal adhesions and extracellular matrix signaling

Signaling pathways and regulatory networks in quail skeletal muscle development: insights from whole transcriptome sequencing

Quail, as an advantageous avian model organism due to its compact size and short reproductive cycle, holds substantial potential for enhancing our understanding of skeletal muscle development. The quantity of skeletal muscle represents a vital economic trait in poultry production. Unraveling the molecular mechanisms governing quail skeletal muscle development is of paramount importance for optimizing meat and egg yield through selective breeding programs. However, a comprehensive characterization of the regulatory dynamics and molecular control underpinning quail skeletal muscle development remains elusive. In this study, through the application of HE staining on quail leg muscle sections, coupled with preceding fluorescence quantification PCR of markers indicative of skeletal muscle differentiation, we have delineated embryonic day 9 (E9) and embryonic day 14 (E14) as the start and ending points, respectively, of quail skeletal muscle differentiation. Then, we employed whole transcriptome sequencing to investigate the temporal expression profiles of leg muscles in quail embryos at the initiation of differentiation (E9) and upon completion of differentiation (E14). Our analysis revealed the expression patterns of 12,012 genes, 625 lncRNAs, 14,457 circRNAs, and 969 miRNAs in quail skeletal muscle samples. Differential expression analysis between the E14 and E9 groups uncovered 3,479 differentially expressed mRNAs, 124 lncRNAs, 292 circRNAs, and 154 miRNAs. Furthermore, enrichment analysis highlighted the heightened activity of signaling pathways related to skeletal muscle metabolism and intermuscular fat formation, such as the ECM-receptor interaction, focal adhesion, and PPAR signaling pathway during E14 skeletal muscle development. Conversely, the E9 stage exhibited a prevalence of pathways associated with myoblast proliferation, exemplified by cell cycle processes. Additionally, we constructed regulatory networks encompassing lncRNA‒mRNA, miRNA‒mRNA, lncRNA‒miRNA-mRNA, and circRNA-miRNA‒mRNA interactions, thus shedding light on their putative roles within quail skeletal muscle. Collectively, our findings illuminate the gene and non-coding RNA expression characteristics during quail skeletal muscle development, serving as a foundation for future investigations into the regulatory mechanisms governing non-coding RNA and quail skeletal muscle development in poultry production.

First Case of a Dominant De Novo SEC23A Mutation with Neurological and Psychiatric Features: New Insights into Cranio-Lenticulo-Sutural Dysplasia with Literature Review

Cranio-lenticulo-sutural dysplasia (CLSD, OMIM #607812) is a rare genetic condition characterized by late-closing fontanels, skeletal defects, dysmorphisms, and congenital cataracts that are caused by bi-allelic or monoallelic variants in the SEC23A gene. Autosomal recessive inheritance (AR-CLSD) has been extensively documented in several cases with homozygous or compound heterozygous variants in SEC23A, whereas autosomal dominant inheritance (AD-CLSD) involving heterozygous inherited variants has been reported just in three patients. The SEC23A gene encodes for one of the main components of a protein coat complex known as coat-protein-complex II (COPII), responsible for the generation of the envelope of the vesicles exported from the endoplasmic reticulum (ER) toward the Golgi complex (GC). AR-CLSD and AD-CLSD exhibit common features, although each form also presents distinctive and peculiar characteristics. Herein, we describe a rare case of a 10-year-old boy with a history of an anterior fontanel that closed only at the age of 9. The patient presents with short proportionate stature, low weight, and neurological impairment, including intellectual disability, global developmental delay, abnormal coordination, dystonia, and motor tics, along with dysmorphisms such as a wide anterior fontanel, hypertelorism, frontal bossing, broad nose, high-arched palate, and micrognathia. Trio clinical exome was performed, and a de novo heterozygous missense variant in SEC23A (p.Arg716Cys) was identified. This is the first reported case of CLSD caused by a de novo heterozygous missense variant in SEC23A presenting specific neurological manifestations never described before. For the first time, we have conducted a comprehensive phenotype-genotype correlation using data from our patient and the eight most well-documented cases in the literature. Our work has allowed us to identify the main specific and characteristic signs of both forms of CLSD (AR-CLSD, AD CLSD), offering valuable insights that can guide physicians in the diagnostic process. Notably, detailed descriptions of neurological features such as intellectual disability, global developmental delay, and motor impairment have not been documented before. Furthermore, our literature overview is crucial in the current landscape of CLSD due to the absence of guidelines for the clinical diagnosis and proper follow-up of these patients, especially during childhood.

Nutrient deprivation alters the rate of COPII subunit recruitment at ER subdomains to tune secretory protein transport

Co-assembly of the multilayered coat protein complex II (COPII) with the Sar1 GTPase at subdomains of the endoplasmic reticulum (ER) enables secretory cargoes to be concentrated efficiently within nascent transport intermediates, which subsequently deliver their contents to ER-Golgi intermediate compartments. Here, we define the spatiotemporal accumulation of native COPII subunits and secretory cargoes at ER subdomains under differing nutrient availability conditions using a combination of CRISPR/Cas9-mediated genome editing and live cell imaging. Our findings demonstrate that the rate of inner COPII coat recruitment serves as a determinant for the pace of cargo export, irrespective of COPII subunit expression levels. Moreover, increasing inner COPII coat recruitment kinetics is sufficient to rescue cargo trafficking deficits caused by acute nutrient limitation. Our findings are consistent with a model in which the rate of inner COPII coat addition acts as an important control point to regulate cargo export from the ER.

Mechanobiology of organelles: illuminating their roles in mechanosensing and mechanotransduction

Mechanobiology studies the mechanisms by which cells sense and respond to physical forces, and the role of these forces in shaping cells and tissues themselves. Mechanosensing can occur at the plasma membrane, which is directly exposed to external forces, but also in the cell's interior, for example, through deformation of the nucleus. Less is known on how the function and morphology of organelles are influenced by alterations in their own mechanical properties, or by external forces. Here, we discuss recent advances on the mechanosensing and mechanotransduction of organelles, including the endoplasmic reticulum (ER), the Golgi apparatus, the endo-lysosmal system, and the mitochondria. We highlight open questions that need to be addressed to gain a broader understanding of the role of organelle mechanobiology.

Intrinsically disordered region-mediated condensation of IFN-inducible SCOTIN/SHISA-5 inhibits ER-to-Golgi vesicle transport

Newly synthesized proteins in the endoplasmic reticulum (ER) are sorted by coat protein complex II (COPII) at the ER exit site en route to the Golgi. Under cellular stresses, COPII proteins become targets of regulation to control the transport. Here, we show that the COPII outer coat proteins Sec31 and Sec13 are selectively sequestered into the biomolecular condensate of SCOTIN/SHISA-5, which interferes with COPII vesicle formation and inhibits ER-to-Golgi transport. SCOTIN is an ER transmembrane protein with a cytosolic intrinsically disordered region (IDR), which is required and essential for the formation of condensates. Upon IFN-γ stimulation, which is a cellular condition that induces SCOTIN expression and condensation, ER-to-Golgi transport was inhibited in a SCOTIN-dependent manner. Furthermore, cancer-associated mutations of SCOTIN perturb its ability to form condensates and control transport. Together, we propose that SCOTIN impedes the ER-to-Golgi transport through its ability to form biomolecular condensates at the ER membrane.

ER exit sites take the strain

Cells are able to adapt their growth to external mechanical strain. A recent study by Phuyal et al (2022) has shown that these responses depend on the heterodimerization of two small GTPases.