Biology subjects

Krause, H. M.

Publications and source records attributed to Krause, H. M..

3 recordsLinked to original sources

bioRxiv2024

HR3/RORα-mediated cholesterol sensing regulates TOR signaling

Cells and organisms adjust their growth based on the availability of cholesterol, which is essential for cellular functions. However, the mechanisms by which cells sense cholesterol levels and translate these into growth signals are not fully understood. We report that cholesterol rapidly activates the master growth-regulatory TOR pathway in Drosophila tissues. We identify the nuclear receptor HR3, an ortholog of mammalian ROR, as an essential factor in cholesterol-induced TOR activation. We demonstrate that HR3 binds cholesterol and promotes TOR pathway activation through a non-genomic mechanism acting upstream of the Rag GTPases. Similarly, we find that ROR is necessary for cholesterol-mediated TOR activation in human cells, suggesting that HR3/ROR represents a conserved mechanism for cholesterol sensing that couples cholesterol availability to TOR-pathway activity. These findings advance our understanding of how cholesterol influences cell growth, with implications for cholesterol-related diseases and cancer. HighlightsO_LICholesterol leads to dynamic TOR pathway activation, driving systemic growth C_LIO_LIHR3 in Drosophila binds cholesterol and couples its availability to TOR activation C_LIO_LIHR3 acts upstream of Rag GTPases to activate TOR in response to lysosomal cholesterol C_LIO_LIMammalian HR3 ortholog ROR is required for cholesterol-induced TOR activation C_LI

cell biology↗

bioRxiv2022

Emergent dynamics of adult stem cell lineages from single nucleus and single cell RNA-Seq of Drosophila testes

Proper differentiation of sperm from germline stem cells, essential for production of the next generation, requires dramatic changes in gene expression that drive remodeling of almost all cellular components, from chromatin to organelles to cell shape itself. Here we provide a single nucleus and single cell RNA-seq resource covering all of spermatogenesis in Drosophila starting from in-depth analysis of adult testis single nucleus RNA-seq (snRNA-seq) data from the Fly Cell Atlas (FCA) study (Li et al., 2022). With over 44,000 nuclei and 6,000 cells analyzed, the data provide identification of rare cell types, mapping of intermediate steps in differentiation, and the potential to identify new factors impacting fertility or controlling differentiation of germline and supporting somatic cells. We justify assignment of key germline and somatic cell types using combinations of known markers, in situ hybridization, and analysis of extant protein traps. Comparison of single cell and single nucleus datasets proved particularly revealing of dynamic developmental transitions in germline differentiation. To complement the web-based portals for data analysis hosted by the FCA, we provide datasets compatible with commonly used software such as Seurat and Monocle. The foundation provided here will enable communities studying spermatogenesis to interrogate the datasets to identify candidate genes to test for function in vivo.

developmental biology↗

bioRxiv2021

Single-cell RNA-sequencing reveals pre-meiotic X-chromosome dosage compensation in Drosophila testis

Dosage compensation (DC) is a mechanism by which X chromosome transcription is equalized in the somatic cells of both males and females. In male fruit flies, expression levels of the X-chromosome are increased two-fold to compensate for their single X chromosome. In testis, dosage compensation is thought to cease during meiosis, however, the timing and degree of the resulting transcriptional suppression is difficult to separate from global meiotic downregulation of each chromosome. To address this, we analyzed testis single-cell RNA-sequencing (scRNA-seq) data from two Drosophila melanogaster strains. We found evidence that the X chromosome is equally transcriptionally active as autosomes in somatic and pre-meiotic cells, and less transcriptionally active than autosomes in meiotic and post-meiotic cells. In cells experiencing dosage compensation, close proximity to MSL (male-specific lethal) chromatin entry sites (CES) correlates with increased X chromosome transcription. We found low or undetectable level of germline expression of most msl genes, mle, roX1 and roX2 via sequencing or RNA-FISH, and no evidence of germline nuclear roX1/2 localization. Our results suggest that, although DC occurs in somatic and premeiotic germ cells in Drosophila testis, there might be non-canonical factors involved in the dosage compensation. The single-cell expression patterns and enrichment statistics of detected genes can be explored interactively in our database: https://zhao.labapps.rockefeller.edu/gene-expr/.

genetics↗