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Pancreatic organogenesis mapped through space and time
The spatial organization of cells within a tissue is dictated throughout dynamic developmental processes. We sought to understand whether cells geometrically coordinate with one another throughout development to achieve their organization. The pancreas is a complex cellular organ with a particular spatial organization. Signals from the mesenchyme, neurons, and endothelial cells instruct epithelial cell differentiation during pancreatic development. To understand the cellular diversity and spatial organization of the developing pancreatic niche, we mapped the spatial relationships between single cells over time. We found that four transcriptionally unique subtypes of mesenchyme in the developing pancreas spatially coordinate throughout development, with each subtype at fixed locations in space and time in relation to other cells, including beta cells, vasculature, and epithelial cells. Our work provides insight into the mechanisms of pancreatic development by showing that cells are organized in a space and time manner.
Single-cell transcriptomic atlas of the human testis across the reproductive lifespan
Testicular aging is associated with declining reproductive health, but the molecular mechanisms are unclear. Here we generate a dataset of 214,369 single-cell transcriptomes from testicular cells of 35 individuals aged 21–69, offering a resource for studying testicular aging and physiology. Machine learning analysis reveals a stronger aging response in somatic cells compared to germ cells. Two waves of aging-related changes are identified: the first in peritubular cells of donors in their 30s, marked by increased basement membrane thickness, indicating a priming state for aging. In their 50s, testicular cells exhibit functional changes, including altered steroid metabolism in Leydig cells and immune responses in macrophages. Further analyses reveal the impact of body mass index on spermatogenic capacity as age progresses, particularly after age 45. Altogether, our findings illuminate molecular alterations during testis aging and their relationship with body mass index, providing a foundation for future research and offering potential diagnostic markers and therapeutic targets.
The interplay between the martensitic transformation rate and the rate of plastic relaxation during martensitic transformation in low-carbon steel, a phase-field study
Introduction Low alloyed steels are among the most used materials for engineering applications due to their unique combination of properties, such as high strength and…
TFE3 and HIF1α regulates the expression of SHMT2 isoforms via alternative promoter utilization in ovarian cancer cells
Ovarian cancer ranks first lethally among gynecological malignancies. Platinum-based chemotherapy constitutes the first-line therapeutic regime. However, primary or acquired resistance seriously affects the survival rate of patients with ovarian cancer. Serine hydroxy methyltransferase (SHMT) catalyzes conversion of serine to glycine and is responsible for production of S-adenosylmethionine (SAM) for methylation. There are cytosolic SHMT1 and mitochondrial SHMT2 in human. Alternative promoter usage is a proteome-expanding mechanism that allows multiple pre-mRNAs to be transcribed from a single gene. The current study demonstrated that cisplatin-sensitive and cisplatin-resistant ovarian cancer cells expressed discrete SHMT2 isoforms, which was ascribed to the selective utilization of SHMT2 alternative promoters. SHMT2 isoforms exerted somewhat paradoxical roles in ovarian cancer cells, with tumor-suppressive role of isoform 1, and tumor-promotive role of isoform 3. In addition, the current study demonstrated that SHMT2 alternative promoter usage mediated by HIF1α and TFE3 might represent adaptive response of ovarian cancer cells to metabolic stress. Collectively, regulation of SHMT2 isoform expression via alternative promoter usage by transcription factors HIF1α and TFE3 provides a novel basis and potential drug targets for the clinical treatment of platin-resistant ovarian cancer.
Mechanism of expression regulation of head-to-head overlapping protein-coding genes INO80E and HIRIP3
Although the existence of overlapping protein-coding genes in eukaryotic genomes is known for decades, their role in regulating expression remains far from fully understood. Here, the mechanism regulating the expression of head-to-head overlapping genes, a pair of INO80E and HIRIP3 genes is presented. Based on a series of experiments, we show that the expression of these genes is strongly dependent on sense/antisense interactions. The overlapping transcripts form an RNA:RNA duplex that has a stabilizing effect on the mRNAs involved, and this stabilization may be mediated by the ELAVL1 protein. We also show that the transcription factor RARG is important for the transcription of both genes studied. In addition, we demonstrate that the overlapping isoform of INO80E forms an R-loop that may positively regulate HIRIP3 isoforms. We propose that both structures, dsRNA and R-loops, help to keep the DNA loop open to allow the transcription of the remaining variants of both genes. However, experiments suggest that RNA:RNA duplex formation plays a major role, while R-loops play only a complementary one. The absence of this dsRNA structure leads to the loss of a stable DNA opening and consequently to transcriptional interference.
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