Biology subjects

DiNardo, S.

Publications and source records attributed to DiNardo, S..

7 recordsLinked to original sources

bioRxiv2025

Tbx1 ortholog org-1 is required to establish testis stem cell niche identity in Drosophila

Stem cells require signals from a cellular microenvironment known as the niche that regulates identity, location, and division of stem cells. Niche cell identity must be properly specified during development to form a tissue capable of functioning in the adult. Here, we show that the Tbx1 ortholog org1 is expressed in Drosophila testis niche cells in response to Slit and FGF signals. org1 is expressed during niche development and is required to specify niche cell identity. org1 mutants specified fewer niche cells, and those cells showed disruption of niche-specific markers, including loss of the niche adhesion protein Fas3 and reduced hedgehog expression. We found that org1 expression in somatic gonadal precursors is capable of inducing formation of additional niche cells. Disrupted niche identity in org1 mutants resulted in niche assembly and functionality defects. We find the conserved transcription factor islet is expressed in response to org1 and show that islet functions downstream to mediate niche identity and assembly. This work identifies a novel role for org1 in niche establishment. Summary StatementSpecification of niche identity is crucial to establish a functional stem cell microenvironment. Using a translatable model, we show that niche expression of org1 influences islet to specify niche identity.

developmental biology↗

bioRxiv2024

The Drosophila hematopoietic niche assembles through collective cell migration controlled by neighbor tissues and Slit-Robo signaling

Niches are often found in specific positions in tissues relative to the stem cells they support. Consistency of niche position suggests that placement is important for niche function. However, the complexity of most niches has precluded a thorough understanding of how their proper placement is established. To address this, we investigated the formation of a genetically tractable niche, the Drosophila Posterior Signaling Center (PSC), the assembly of which had not been previously explored. This niche controls hematopoietic progenitors of the lymph gland (LG). PSC cells were previously shown to be specified laterally in the embryo, but ultimately reside dorsally, at the LG posterior. Here, using live-imaging, we show that PSC cells migrate as a tight collective and associate with multiple tissues during their trajectory to the LG posterior. We find that Slit emanating from two extrinsic sources, visceral mesoderm and cardioblasts, is required for the PSC to remain a collective, and for its attachment to cardioblasts during migration. Without proper Slit-Robo signaling, PSC cells disperse, form aberrant contacts, and ultimately fail to reach their stereotypical position near progenitors. Our work characterizes a novel example of niche formation and identifies an extrinsic signaling relay that controls precise niche positioning. Impact StatementA new example of niche formation is provided which reveals the mode of niche cell migration, implicates extrinsic sources that deliver positional information, and uncovers the signaling pathway required for the precise, stereotypical positioning of the niche.

developmental biology↗

bioRxiv2024

Niche cytoskeletal architecture is required for proper stem cell signaling and oriented division in the Drosophila testis

Stem cells are critical to repair and regenerate tissues, and often reside in a niche that controls their behavior. The Drosophila testis niche has been a paradigm for niche-stem cell interactions and is used here to address the cell biological features that maintain niche structure and function during its steady-state operation. We report enrichment of the Myosin II (MyoII) and a key regulator of acto-myosin contractility (AMC), Rho Kinase (ROK), within the niche cell cortex at the interface with germline stem cells (GSCs). Compromising MyoII and ROK disrupts niche architecture, suggesting that AMC in niche cells is important to maintain the reproducible structure of this niche. Furthermore, defects in niche architecture cause changes in stem cell function. Our data suggest that the niche signals less robustly to adjacent germ cells, yet the disrupted structure permits increased numbers of cells to respond to the signal. Finally, compromising Myo II in niche cells leads to an increase in mis-oriented centrosomes in GSCs as well as defects in the centrosome orientation checkpoint. Ultimately, this work identifies a critical role for AMC-dependent maintenance of niche structure to ensure a proper complement of stem cells with correct execution of stem cell divisions. Summary statementActomyosin contractility regulated niche architecture is critical for proper signaling and oriented division of germline stem cells.

developmental biology↗

bioRxiv2023

An actomyosin network organizes niche morphology and responds to feedback from recruited stem cells

SummaryStem cells often rely on signals from a niche, which in many tissues adopts a precise morphology. What remains elusive is how niches are formed, and how morphology impacts function. To address this, we leverage the Drosophila gonadal niche, which affords genetic tractability and live-imaging. We have previously shown mechanisms dictating niche cell migration to their appropriate position within the gonad, and the resultant consequences on niche function. Here, we show that once positioned, niche cells robustly polarize filamentous actin (F-actin) and Non-muscle Myosin II (MyoII) towards neighboring germ cells. Actomyosin tension along the niche periphery generates a highly reproducible smoothened contour. Without contractility, niches are misshapen and exhibit defects in their ability to regulate germline stem cell behavior. We additionally show that germ cells aid in polarizing MyoII within niche cells, and that extrinsic input is required for niche morphogenesis and function. Our work reveals a feedback mechanism where stem cells shape the niche that guides their behavior.

developmental 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

Visceral mesoderm signaling regulates assembly position and function of the Drosophila testis niche

Tissue homeostasis often requires a properly placed niche to support stem cells. Morphogenetic processes that position a niche are just being described. For the Drosophila testis we recently showed that pro niche cells, specified at disparate positions during early gonadogenesis, must assemble into one collective at the anterior of the gonad. We now find that Slit and FGF signals emanating from adjacent visceral mesoderm regulate assembly. In response to signaling, niche cells express islet, which we find is also required for niche assembly. Without signaling, niche cells specified furthest from the anterior are unable to migrate, remaining dispersed. Function of such niches is severely disrupted, with niche cells evading cell cycle quiescence, compromised in their ability to signal the incipient stem cell pool, and failing to orient stem cell divisions properly. Our work identifies both extrinsic signaling and intrinsic responses required for proper assembly and placement of the testis niche.

developmental biology↗

bioRxiv2021

Fly Cell Atlas: a single-cell transcriptomic atlas of the adult fruit fly

The ability to obtain single cell transcriptomes for stable cell types and dynamic cell states is ushering in a new era for biology. We created the Tabula Drosophilae, a single cell atlas of the adult fruit fly which includes 580k cells from 15 individually dissected sexed tissues as well as the entire head and body. Over 100 researchers from the fly community contributed annotations to >250 distinct cell types across all tissues. We provide an in-depth analysis of cell type-related gene signatures and transcription factor markers, as well as sexual dimorphism, across the whole animal. Analysis of common cell types that are shared between tissues, such as blood and muscle cells, allowed the discovery of rare cell types and tissue-specific subtypes. This atlas provides a valuable resource for the entire Drosophila community and serves as a comprehensive reference to study genetic perturbations and disease models at single cell resolution.

genomics↗