Drosophila type II neuroblast lineages keep Prospero levels low to generate large clones that contribute to the adult brain central complex

Tissue homeostasis depends on the ability of stem cells to properly regulate self-renewal versus differentiation. Drosophila neural stem cells (neuroblasts) are a model system to study self-renewal and differentiation. Recent work has identified two types of larval neuroblasts that have different self-renewal/differentiation properties. Type I neuroblasts bud off a series of small basal daughter cells (ganglion mother cells) that each generate two neurons. Type II neuroblasts bud off small basal daughter cells called intermediate progenitors (INPs), with each INP generating 6 to 12 neurons. Type I neuroblasts and INPs have nuclear Asense and cytoplasmic Prospero, whereas type II neuroblasts lack both these transcription factors. Here we test whether Prospero distinguishes type I/II neuroblast identity or proliferation profile, using several newly characterized Gal4 lines. We misexpress prospero using the 19H09-Gal4 line (expressed in type II neuroblasts but no adjacent type I neuroblasts) or 9D11-Gal4 line (expressed in INPs but not type II neuroblasts). We find that differential prospero expression does not distinguish type I and type II neuroblast identities, but Prospero regulates proliferation in both type I and type II neuroblast lineages. In addition, we use 9D11 lineage tracing to show that type II lineages generate both small-field and large-field neurons within the adult central complex, a brain region required for locomotion, flight, and visual pattern memory

Regulation of spindle orientation and neural stem cell fate in the Drosophila optic lobe.

BACKGROUND: The choice of a stem cell to divide symmetrically or asymmetrically has profound consequences for development and disease. Unregulated symmetric division promotes tumor formation, whereas inappropriate asymmetric division affects organ morphogenesis. Despite its importance, little is known about how spindle positioning is regulated. In some tissues cell fate appears to dictate the type of cell division, whereas in other tissues it is thought that stochastic variation in spindle position dictates subsequent sibling cell fate. RESULTS: Here we investigate the relationship between neural progenitor identity and spindle positioning in the Drosophila optic lobe. We use molecular markers and live imaging to show that there are two populations of progenitors in the optic lobe: symmetrically dividing neuroepithelial cells and asymmetrically dividing neuroblasts. We use genetically marked single cell clones to show that neuroepithelial cells give rise to neuroblasts. To determine if a change in spindle orientation can trigger a neuroepithelial to neuroblast transition, we force neuroepithelial cells to divide along their apical/basal axis by misexpressing Inscuteable. We find that this does not induce neuroblasts, nor does it promote premature neuronal differentiation. CONCLUSION: We show that symmetrically dividing neuroepithelial cells give rise to asymmetrically dividing neuroblasts in the optic lobe, and that regulation of spindle orientation and division symmetry is a consequence of cell type specification, rather than a mechanism for generating cell type diversity.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Regulation of spindle orientation and neural stem cell fate in the Drosophila optic lobe

BACKGROUND: The choice of a stem cell to divide symmetrically or asymmetrically has profound consequences for development and disease. Unregulated symmetric division promotes tumor formation, whereas inappropriate asymmetric division affects organ morphogenesis. Despite its importance, little is known about how spindle positioning is regulated. In some tissues cell fate appears to dictate the type of cell division, whereas in other tissues it is thought that stochastic variation in spindle position dictates subsequent sibling cell fate. RESULTS: Here we investigate the relationship between neural progenitor identity and spindle positioning in the Drosophila optic lobe. We use molecular markers and live imaging to show that there are two populations of progenitors in the optic lobe: symmetrically dividing neuroepithelial cells and asymmetrically dividing neuroblasts. We use genetically marked single cell clones to show that neuroepithelial cells give rise to neuroblasts. To determine if a change in spindle orientation can trigger a neuroepithelial to neuroblast transition, we force neuroepithelial cells to divide along their apical/basal axis by misexpressing Inscuteable. We find that this does not induce neuroblasts, nor does it promote premature neuronal differentiation. CONCLUSION: We show that symmetrically dividing neuroepithelial cells give rise to asymmetrically dividing neuroblasts in the optic lobe, and that regulation of spindle orientation and division symmetry is a consequence of cell type specification, rather than a mechanism for generating cell type diversity

Genome-wide genetic marker discovery and genotyping using next-generation sequencing,”

Abstract | The advent of next-generation sequencing (NGS) has revolutionized genomic and transcriptomic approaches to biology. These new sequencing tools are also valuable for the discovery, validation and assessment of genetic markers in populations. Here we review and discuss best practices for several NGS methods for genome-wide genetic marker development and genotyping that use restriction enzyme digestion of target genomes to reduce the complexity of the target. These new methods -which include reduced-representation sequencing using reduced-representation libraries (RRLs) or complexity reduction of polymorphic sequences (CRoPS), restriction-site-associated DNA sequencing (RAD-seq) and low coverage genotyping -are applicable to both model organisms with high-quality reference genome sequences and, excitingly, to non-model species with no existing genomic data

Data from: Restriction site-associated DNA sequencing generates high-quality single nucleotide polymorphisms for assessing hybridization between bighead and silver carp in the United States and China

Bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix) are invasive species and listed as US federally injurious species under the Lacy Act. They have established populations in much of the Mississippi River Basin (MRB; Mississippi, Illinois, and Missouri rivers) and are capable of producing fertile hybrids and complex introgression. Characterizing the composition of this admixture requires a large set of high-quality, evolutionarily conserved, diagnostic genetic markers to aid in the identification and management of these species in the midst of morphological ambiguity. Restriction site-associated DNA (RAD) sequencing of 45 barcoded bighead and silver carp from the United States and China produced reads that were aligned to the silver carp transcriptome yielded 261 candidate single nucleotide polymorphisms (SNPs) with fixed allelic differences between the two species. We selected the highest quality 112 SNP loci for validation using 194 putative pure-species and F1 hybrids from the MRB and putative bighead carp and silver carp pure species from China (Amur, Pearl and Yangtze rivers). Fifty SNPs were omitted due to design/amplification failure or lack of diagnostic utility. A total of 57 species-diagnostic SNPs conserved between carp species in US and Chinese rivers were identified; 32 were annotated to functional gene loci. Twenty-seven of the 181 (15%) putative pure species were identified as hybrid backcrosses after validation, including three backcrosses from the Amur River, where hybridization has not been documented previously. The 57 SNPs identified through RAD sequencing provide a diagnostic tool to detect population admixture and to identify hybrid and pure-species Asian carps in the United States and China

SNP genotype file for validation

Data was generated on the MassARRAY 4 analyzer system (Sequenom, Inc., San Diego, CA) and tissue was collected in the field from the authors and other personnel listed in the acknowledgements. The SNP ID's and primer sequences are added in the supplementary information of the manuscript for reference. The top rows indicate species specific genotypes for Hypophthalmichthys nobilis (BH) and H. molitrix (SV). The remaining rows and columns give the location, field ID, genetic ID, and genotypes of individual fishes at 57 SNP loci