Although normally dormant, hair follicle stem cells (HFSCs) quickly become activated to divide during a new hair cycle. The quiescence of HFSCs is known to be regulated by a number of intrinsic and ...extrinsic mechanisms. Here we provide several lines of evidence to demonstrate that HFSCs utilize glycolytic metabolism and produce significantly more lactate than other cells in the epidermis. Furthermore, lactate generation appears to be critical for the activation of HFSCs as deletion of lactate dehydrogenase (Ldha) prevented their activation. Conversely, genetically promoting lactate production in HFSCs through mitochondrial pyruvate carrier 1 (Mpc1) deletion accelerated their activation and the hair cycle. Finally, we identify small molecules that increase lactate production by stimulating Myc levels or inhibiting Mpc1 carrier activity and can topically induce the hair cycle. These data suggest that HFSCs maintain a metabolic state that allows them to remain dormant and yet quickly respond to appropriate proliferative stimuli.
The
Drosophila melanogaster
hematopoietic organ, called lymph gland, proliferates and differentiates throughout the larval period. The lymph gland of the late larva is comprised of a large primary ...lobe and several smaller secondary lobes. Differentiation into two types of hemocytes, plasmatocytes and crystal cells, is confined to the outer layer (cortical zone) of the primary lobe; the center of the primary lobe (medullary zone), as well as the secondary lobes, contain only proliferating prohemocytes. A small cluster of cells located at the posterior tip of the primary lobe serves as a signaling center (PSC) that inhibits precocious differentiation of the medullary zone. The larval lymph gland is stabilized by layers of extracellular matrix (basement membranes) that surround individual hemocytes, groups of hemocytes, as well as the lymph gland as a whole. In this paper, we investigated the events shaping the lymph gland in the early pupa. The lymph gland dissociates and hemocytes disperse during the first 12 h after puparium formation (APF), leaving behind empty husks of basement membrane. Prior to lymph gland dissociation, cells of the medullary zone differentiate, expressing the early differentiation marker Peroxidasin (Pxn), as well as, in part, the late differentiation marker P1. Cells of the PSC spread throughout the pupal lymph gland prior to their dispersal. Cells of the secondary lobes undergo a rapid phase of proliferation that lasts until 8 h APF, followed by expression of Pxn and dispersal. These hemocytes do not express P1, indicating that they disperse prior to full maturation.
Replication-independent histone variants can replace the canonical replication-dependent histones. Vertebrates have multiple H2A variant histones, including H2AZ and H2AX that are present in most ...eukaryotes. H2AZ regulates transcriptional activation as well as the maintenance of gene silencing, while H2AX is important in DNA damage repair. The fruit fly
has only one histone H2A variant (H2AV), which is a chimera of H2AZ and H2AX. In this study we found that lack of H2AV led to the formation of black melanotic masses in
third instar larvae. The formation of these masses was found in conjunction with a loss of the majority of the primary lymph gland lobes. Interestingly, the cells of the posterior signaling center were preserved in these mutants. Reduction of H2AV levels by RNAi knockdown caused a milder phenotype that preserved the lymph gland structure but that included precocious differentiation of the prohemocytes located within the medullary zone and the secondary lobes of the lymph gland. Mutant rescue experiments suggest that the H2AZ-like rather than the H2AX-like function of H2AV is primarily required for normal hematopoiesis.
Establishing or ruling out a molecular diagnosis of Prader–Willi or Angelman syndrome (PWS/AS) presents unique challenges due to the variety of different genetic alterations that can lead to these ...conditions. Point mutations, copy number changes, uniparental isodisomy (i-UPD) 15 of two subclasses (segmental or total isodisomy), uniparental heterodisomy (h-UPD), and defects in the chromosome 15 imprinting center can all cause PWS/AS. Here, we outline a combined approach using whole-exome sequencing (WES) and DNA methylation data with methylation-sensitive multiplex ligation-dependent probe amplification (MLPA) to establish both the disease diagnosis and the mechanism of disease with high sensitivity using current standard of care technology and improved efficiency compared to serial methods. The authors encourage the use of this approach in the clinical setting to confirm and establish the diagnosis and genetic defect which may account for the secondary genetic conditions that may be seen in those with isodisomy 15, impacting surveillance and counseling with more accurate recurrence risks. Other similarly affected individuals due to other gene disorders or cytogenetic anomalies such as Rett syndrome or microdeletions would also be identified with this streamlined approach.
Hemocytes (blood cells) are motile cells that move throughout the extracellular space and that exist in all clades of the animal kingdom. Hemocytes play an important role in shaping the extracellular ...environment and in the immune response. Developmentally, hemocytes are closely related to the epithelial cells lining the vascular system (endothelia) and the body cavity (mesothelia). In vertebrates and insects, common progenitors, called hemangioblasts, give rise to the endothelia and blood cells. In the adult animal, many differentiated hemocytes seem to retain the ability to proliferate; however, in most cases investigated closely, the bulk of hemocyte proliferation takes place in specialized hematopoietic organs. Hematopoietic organs provide an environment where undifferentiated blood stem cells are able to self-renew, and at the same time generate offspring that differentiate into different blood cell types. Hematopoiesis in vertebrates, taking place in the bone marrow, has been subject to intensive research by immunologists and stem cell biologists. Much less is known about blood cell formation in invertebrate animals. In this review, we will survey structural and functional properties of invertebrate hematopoietic organs, with a main focus on insects and other arthropod taxa. We will then discuss similarities, at the molecular and structural level, that are apparent when comparing the development of blood cells in hematopoietic organs of vertebrates and arthropods. Our comparative review is intended to elucidate aspects of the biology of blood stem cells that are more easily missed when focusing on one or a few model species.
The heparin sulfate proteoglycan Terribly Reduced Optic Lobes (Trol) is the Drosophila melanogaster homolog of the vertebrate protein Perlecan. Trol is expressed as part of the extracellular matrix ...(ECM) found in the hematopoietic organ, called the lymph gland. In the normal lymph gland, the ECM forms thin basement membranes around individual or small groups of blood progenitors. The pattern of basement membranes, reported by Trol expression, is spatio-temporally correlated to hematopoiesis. The central, medullary zone which contain undifferentiated hematopoietic progenitors has many, closely spaced membranes. Fewer basement membranes are present in the outer, cortical zone, where differentiation of blood cells takes place. Loss of trol causes a dramatic change of the ECM into a three-dimensional, spongy mass that fills wide spaces scattered throughout the lymph gland. At the same time proliferation is reduced, leading to a significantly smaller lymph gland. Interestingly, differentiation of blood progenitors in trol mutants is precocious, resulting in the break-down of the usual zonation of the lymph gland. which normally consists of an immature center (medullary zone) where cells remain undifferentiated, and an outer cortical zone, where differentiation sets in. We present evidence that the effect of Trol on blood cell differentiation is mediated by Hedgehog (Hh) signaling, which is known to be required to maintain an immature medullary zone. Overexpression of hh in the background of a trol mutation is able to rescue the premature differentiation phenotype. Our data provide novel insight into the role of the ECM component Perlecan during Drosophila hematopoiesis.
•Study of the extracellular matrix protein Trol in the Drosophila lymph gland.•Trol mutants show abnormal extracellular matrix assembly in the lymph gland.•Trol mutant lymph glands are decreased in size and show a loss of proper zonation.•Hemocyte progenitors in trol mutant lymph glands show premature differentiation.•Trol is necessary for proper Hedgehog signaling in the lymph gland.
Blood progenitors arise from a pool of pluripotential cells (“hemangioblasts”) within the Drosophila embryonic mesoderm. The fact that the cardiogenic mesoderm consists of only a small number of ...highly stereotypically patterned cells that can be queried individually regarding their gene expression in normal and mutant embryos is one of the significant advantages that Drosophila offers to dissect the mechanism specifying the fate of these cells. We show in this paper that the expression of the Notch ligand Delta (Dl) reveals segmentally reiterated mesodermal clusters (“cardiogenic clusters”) that constitute the cardiogenic mesoderm. These clusters give rise to cardioblasts, blood progenitors and nephrocytes. Cardioblasts emerging from the cardiogenic clusters accumulate high levels of Dl, which is required to prevent more cells from adopting the cardioblast fate. In embryos lacking Dl function, all cells of the cardiogenic clusters become cardioblasts, and blood progenitors are lacking. Concomitant activation of the Mitogen Activated Protein Kinase (MAPK) pathway by Epidermal Growth Factor Receptor (EGFR) and Fibroblast Growth Factor Receptor (FGFR) is required for the specification and maintenance of the cardiogenic mesoderm; in addition, the spatially restricted localization of some of the FGFR ligands may be instrumental in controlling the spatial restriction of the Dl ligand to presumptive cardioblasts.
► Analysis of the origin and morphogenesis of the cardiogenic mesoderm in Drosophila. ► Delta required for specification of blood cell fate in hemangioblast progenitors. ► Dl expressed in early cardiogenic clusters but becomes restricted to cardioblasts. ► MAPK activity required for maintenance of Dl and cardiogenic mesoderm survival.
There have been no specific guidelines regarding which genes should be tested in the clinical setting for Parkinson's disease (PD) or parkinsonism. We evaluated the types of clinical genetic testing ...offered for PD as the first step of our gene curation.
The National Institutes of Health (NIH) Genetic Testing Registry (GTR) was queried on 12/7/2020 to identify current commercial PD genetic test offerings by clinical laboratories, internationally.
We identified 502 unique clinical genetic tests for PD, from 28 Clinical Laboratory Improvement Amendments (CLIA)-approved clinical laboratories. These included 11 diagnostic PD panels. The panels were notable for their differences in size, ranging from 5 to 62 genes. Five genes for variant query were included in all panels (SNCA, PRKN, PINK-1, PARK7 (DJ1), and LRRK2). Notably, the addition of the VPS35 and GBA genes was variable. Panel size differences stemmed from inclusion of genes linked to atypical parkinsonism and dystonia disorders, and genes in which the link to PD causation is controversial.
There is an urgent need for expert opinion regarding which genes should be included in a commercial laboratory multi-gene panel for PD.
The heparin sulfate proteoglycan Trol (
T
erribly
R
educed
O
ptic
L
obes) is the
D. melanogaster
homolog of the vertebrate protein Perlecan. Trol is expressed as part of the extracellular matrix ...(ECM) found in the hematopoietic organ, called the lymph gland. In the normal lymph gland, the ECM forms thin basement membranes around individual or small groups of blood progenitors. The pattern of basement membranes, reported by Trol expression, is spatio-temporally correlated to hematopoiesis. The central, medullary zone which contain undifferentiated hematopoietic progenitors has many, closely spaced membranes. Fewer basement membranes are present in the outer, cortical zone, where differentiation of blood cells takes place. Loss of
trol
causes a dramatic change of the ECM into a three-dimensional, spongy mass that fills wide spaces scattered throughout the lymph gland. At the same time proliferation is reduced, leading to a significantly smaller lymph gland. Interestingly, differentiation of blood progenitors in
trol
mutants is precocious, resulting in the break-down of the usual zonation of the lymph gland which normally consists of an immature center (medullary zone) where cells remain undifferentiated, and an outer cortical zone, where differentiation sets in. We present evidence that the effect of Trol on blood cell differentiation is mediated by Hedgehog (Hh) signaling, which is known to be required to maintain an immature medullary zone. Overexpression of
hh
in the background of a
trol
mutation is able to rescue the premature differentiation phenotype. Our data provide novel insight into the role of the ECM component Perlecan during
Drosophila
hematopoiesis.
This work surveys various questions regarding the heart and blood system of D. melanogaster. These questions range from topics seen in the early embryo to ones present during larval and finally pupal ...stages. In the first portion of this study, we examine signaling pathways that are an integral part in the process of cell fate determination in Drosophila embryos. Notch signaling is the switch in the determination of heart vs. blood cell fate. We determine the factors that act upstream of Notch and control its activity. We see that expression of the Notch ligand Delta is restricted to the cardioblast (heart) cells of the Drosophila embryo. Loss of this signal leads to abnormal cell fate decisions, thereby implicating it as the ligand responsible for Notch activity in the cardiogenic mesoderm. Pathways acting upstream of Delta, and modulating its expression, include the Epidermal Growth Factor (EGF) and Fibroblast Growth Factor (FGF) pathways. Modulation of the MAPK pathway, the cascade turned on by both EGF and FGF signaling, results in changes in heart and blood cell number. MAPK is thought to act together with the proneural gene lethal of scute (l'sc) in order to modulate Delta levels. In the second portion of this study we examine the extracellular matrix (ECM) protein Terribly Reduced Optic Lobes (Trol). We study expression of Trol from embryonic stages to late larval stages in the lymph gland. We find that Trol becomes preferentially expressed in a chamber like pattern in the medullary zone of third instar larvae. We study Trol mutants and find abnormal accumulation of ECM in the lymph glands of these mutants. We also see a decrease in cell division and precocious differentiation of hemocytes within the lymph gland. Trol is known to modulate a number of signaling proteins. One such protein, that is also known to maintain cells in an undifferentiated state within the lymph gland, is Hedgehog (Hh). We believe that the precocious differentiation of hemocytes may be due to a loss in proper Hh signaling, as both a transcription factor (Cubitus interruptus) and a gene (patched) that are activated by Hh signaling, show decreased expression in Trol mutant lymph glands. The third portion of our study examines the dissociation of the lymph gland during pupation. We find that the lymph gland dissociates between 10 and 12 hours following pupation. We also utilize a number of differentiation markers to look at the state of hemocyte differentiation during lymph gland dissociation. An early differentiation marker, peroxidasin, shows that a majority of the lymph gland is in a differentiated state. A later differentiation marker, specific to plasmatocytes, shows that only cells in the outer reaches of the lymph gland are differentiated. Meanwhile, crystal cells are lost altogether from the lymph gland by 6 hours following pupation. Cells of the Posterior Signaling Center (PSC), the control hub of the lymph gland, appear to migrate through and out of the lymph gland as the pupae mature. Studies looking at secondary lymph gland lobes show cell division during pupation. Such division is not seen in the primary lobes.
PDF
