Biology subjects

Mahadevaraju, S.

Publications and source records attributed to Mahadevaraju, S..

4 recordsLinked to original sources

bioRxiv2024

Diverse somatic Transformer and sex chromosome karyotype pathways regulate gene expression in Drosophila gonad development

The somatic sex determination gene transformer (tra) is required for the highly sexually dimorphic development of most somatic cells, including those of the gonads. In addition, somatic tra is required for the germline development even though it is not required for sex determination within germ cells. Germ cell autonomous gene expression is also necessary for their sex determination. To understand the interplay between these signals, we compared the phenotype and gene expression of larval wild-type gonads and the sex-transformed tra gonads. XX larval ovaries transformed into testes were dramatically smaller than wild-type, with significant reductions in germ cell number, likely due to altered geometry of the stem cell niche. Additionally, there was a defect in progression into spermatocyte stages. XY larval testes transformed into ovaries had excessive germ cells, possibly due to the earlier onset of cell division. We suggest that germ cells are neither fully female nor male following somatic sex transformation, with certain pathways characteristic of each sex expressed in tra mutants. We found multiple patterns of somatic and germline gene expression control exclusively due to tra, exclusively due to sex chromosome karyotype, but usually due to a combination of these factors showing tra and sex chromosome karyotype pathways regulate gene expression during Drosophila gonad development.

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↗

bioRxiv2020

Dynamic Sex Chromosome Expression in Drosophila Male Germ Cells

Sex chromosome gene content and expression is unusual. In many organisms the X and Y chromosomes are inactivated in spermatocytes, possibly as a defense mechanism against insertions into unpaired chromatin. In addition to current sex chromosomes, Drosophila has a small gene-poor X-chromosome relic (4th) that re-acquired autosomal status. Using single cell RNA-Seq, we demonstrate that the single X and pair of 4th chromosomes are specifically inactivated in primary spermatocytes. In contrast, genes on the single Y chromosome become maximally active in primary spermatocytes. Reduced X steady-state transcript levels are due to failed activation of RNA-Polymerase-II by phosphorylation of Serine 2 and 5. One Sentence SummarySex chromosome expression during spermatogenesis at the single cell level

developmental biology↗

bioRxiv2019

Evidence that Runt Acts as a Counter-Repressor of Groucho during Drosophila melanogaster Primary Sex Determination

Runx proteins are bifunctional transcription factors that both repress and activate transcription in animal cells. Typically Runx proteins work in concert with other transcriptional regulators, including co-activators and co-repressors to mediate their biological effects. In Drosophila melanogaster the archetypal Runx protein, Runt, functions in numerous processes including segmentation, neurogenesis and sex determination. During primary sex determination Runt acts as one of four X-linked signal element (XSE) proteins that direct female-specific activation of the establishmen promoter (Pe) of the master regulatory gene Sex-lethal (Sxl). Successful activation of SxlPe requires that the XSE proteins overcome the repressive effects of maternally deposited Groucho (Gro), a potent co-repressor of the Gro/TLE family. Runx proteins, including Runt, contain a C-terminal peptide, VWRPY, known to bind to Gro/TLE proteins to mediate transcriptional repression. We show that Runts VWRPY co-repressor-interaction domain is needed for Runt to activate SxlPe. Deletion of the Gro-interaction domain eliminates Runt-ability to activate SxlPe, whereas replacement with a higher affinity, VWRPW, sequence promotes Runt-mediated transcription. This suggest that Runt activates SxlPe by antagonizing Gro function, a conclusion consist with earlier findings that Runt is needed for Sxl expression only in embryonic regions with high Gro activity. Surprisingly we found that Runt is not required for the initial activation activation of SxlPe. Instead, Runt is needed to keep SxlPe active during the subsequent period of high-level Sxl transcription suggesting that Runt helps amplfy the difference between female and male XSE signals by counterrepressing Gro in female, but not in male, embryos.

developmental biology↗