The BAF chromatin remodeling complex licenses planarian stem cells access to ectodermal and mesodermal cell fates.

Background: The flatworm planarian, Schmidtea mediterranea, has a large population of adult stem cells (ASCs) that replace any cell type during tissue turnover or regeneration. How planarian ASCs (called neoblasts) manage self-renewal with the ability to produce daughter cells of different cell lineages (multipotency) is not well understood. Chromatin remodeling complexes ultimately control access to DNA regions of chromosomes and together with specific transcription factors determine whether a gene is transcribed in a given cell type.

An RNA/DNA-Based Flow Cytometry Approach for Isolating Slow-Cycling Stem Cells.

Flow cytometry methods for sorting specific populations of cells based on fluorescence or physical properties have been a widely used technique for decades. Flow cytometry has been particularly vital to the study of planarians, which remain refractory to transgenic transformation, as it has provided a work-around solution for studying stem cell biology and lineage relationships in the context of regeneration. Many flow cytometry applications have been published in planarians, beginning with broad Hoechst-based strategies for isolating cycling stem cells and progressing to more function-based approaches involving vital dyes and surface antibodies.

Identification of TOR-responsive slow-cycling neoblasts in planarians.

Epimorphic regeneration commonly relies on the activation of reserved stem cells to drive new cell production. The planarian Schmidtea mediterranea is among the best regenerators in nature, thanks to its large population of adult stem cells, called neoblasts. While neoblasts have long been known to drive regeneration, whether a subset of neoblasts is reserved for this purpose is unknown.

An optimized QF-binary expression system for use in zebrafish.

The zebrafish model organism has been of exceptional utility for the study of vertebrate development and disease through the application of tissue-specific labelling and overexpression of genes carrying patient-derived mutations. However, there remains a need for a binary expression system that is both non-toxic and not silenced over animal generations by DNA methylation. The Q binary expression system derived from the fungus Neurospora crassa is ideal, because the consensus binding site for the QF transcription factor lacks CpG dinucleotides, precluding silencing by CpG-meditated methylation.

SoxB1 Activity Regulates Sensory Neuron Regeneration, Maintenance, and Function in Planarians.

SoxB1 genes play fundamental roles in neurodevelopmental processes and maintaining stem cell multipotency, but little is known about their function in regeneration. We addressed this question by analyzing the activity of the SoxB1 homolog soxB1-2 in the planarian Schmidtea mediterranea. Expression and functional analysis revealed that soxB1-2 marks ectodermal-lineage progenitors, and its activity is required for differentiation of subsets of ciliated epidermal and neuronal cells.

Comparative transcriptomic analyses and single-cell RNA sequencing of the freshwater planarian Schmidtea mediterranea identify major cell types and pathway conservation.

Background: In the Lophotrochozoa/Spiralia superphylum, few organisms have as high a capacity for rapid testing of gene function and single-cell transcriptomics as the freshwater planaria. The species Schmidtea mediterranea in particular has become a powerful model to use in studying adult stem cell biology and mechanisms of regeneration. Despite this, systematic attempts to define gene complements and their annotations are lacking, restricting comparative analyses that detail the conservation of biochemical pathways and identify lineage-specific innovations.

Myths vs. FACS: what do we know about planarian stem cell lineages?

Historically, planarian neoblasts were thought to be a homogeneous population of pluripotent stem cells; however, recent population and single-cell level analyses have refuted this idea. Evidence for lineage commitment at the neoblast level has been provided via a number of independent studies using a variety of methods. In situ hybridization experiments first demonstrated the co-expression of lineage-specific markers in neoblasts (marked by piwi-1 expression) isolated by FACS.

The planarian TCF/LEF factor Smed-tcf1 is required for the regeneration of dorsal-lateral neuronal subtypes.

The adult brain of the planarian Schmidtea mediterranea (a freshwater flatworm) is a dynamic structure with constant cell turnover as well as the ability to completely regenerate de novo. Despite this, function and pattern is achieved in a reproducible manner from individual to individual in terms of the correct spatial and temporal production of specific neuronal subtypes. Although several signaling molecules have been found to be key to scaling and cell turnover, the mechanisms by which specific neural subtypes are specified remain largely unknown.

FOX and ETS family transcription factors regulate the pigment cell lineage in planarians.

Many pigment cells acquire unique structural properties and gene expression profiles during animal development. The underlying differentiation pathways have been well characterized in cells formed during embryogenesis, such as the neural crest-derived melanocyte. However, much less is known about the developmental origins of pigment cells produced in adult organisms during tissue homeostasis and repair.

Neuronal sources of modulate neurogenesis in the adult planarian brain.

The asexual freshwater planarian is a constitutive adult, whose central nervous system (CNS) is in a state of constant homeostatic neurogenesis. However, very little is known about the extrinsic signals that act on planarian stem cells to modulate rates of neurogenesis. We have identified two planarian homeobox transcription factors, and , which are required for the maintenance of cholinergic, GABAergic, and octopaminergic neurons in the planarian CNS.

In silico lineage tracing through single cell transcriptomics identifies a neural stem cell population in planarians.

Background: The planarian Schmidtea mediterranea is a master regenerator with a large adult stem cell compartment. The lack of transgenic labeling techniques in this animal has hindered the study of lineage progression and has made understanding the mechanisms of tissue regeneration a challenge. However, recent advances in single-cell transcriptomics and analysis methods allow for the discovery of novel cell lineages as differentiation progresses from stem cell to terminally differentiated cell.