Royan, M;Siddique, K;Nourizadeh-lillabadi, R;Weltzien, F;Henkel, C;FONTAINE, R;
| DOI: 10.2139/ssrn.4142092
In fish, prolactin-producing cells (lactotropes) are located in the anterior part of the pituitary and play an essential role in osmoregulation. However, small satellite lactotrope populations have been described in other parts of the pituitary in several species. The functional and developmental backgrounds of these extra populations are not known. We recently described two distinct prolactin-expressing cell types in Japanese medaka, a salinity tolerant fish, using single cell transcriptomics. In this study, we thus characterize the two transcriptomically distinct lactotrope cell types and explore the hypothesis that they represent the spatially distinct cell populations found in other species. Single cell RNA sequencing shows that one of the two lactotrope cell types exhibits an expression profile similar to that of stem cell populations. Using in situ hybridization, we show that the medaka pituitary often develops additional small satellite lactotrope cell groups, like in other teleost species. These satellite clusters arise early during development and grow in cell number throughout life regardless of the animal’s sex. Surprisingly, there seems to be no correspondence between the stem cell-like lactotropes and these newly emerging lactotrope populations. Instead, our data support a scenario in which the stem cell-like lactotropes are an intrinsic stage in the development of every spatially distinct lactotrope cluster. In addition, lactotrope activity in the medaka pituitary decreases when environmental salinity increases in the two spatially distinct lactotrope clusters, supporting their role in osmoregulation. However, this decrease appears weaker in the satellite lactotrope cell groups, suggesting that these lactotropes are differentially regulated.
Faltings, L;Sarowar, T;Virga, J;Singh, N;Kwa, B;Zhao, H;
| DOI: 10.1093/neuonc/noac079.046
Choroid plexus (CP) tumors are rare primary brain neoplasms found most commonly in children and are thought to arise from CP epithelial cells. Sox2 is a transcription factor that not only plays a role in development in the ventricular zone, CP, and roof plate, but also contributes to cancer stemness, tumorigenesis, and drug resistance. Gene expression studies demonstrate aberrant Sox2 expression in human CP tumors, suggesting a role in tumor development. A subset of CP tumors exhibit abnormal NOTCH pathway activity. Using animal models, we previously show that sustained NOTCH activity leads to CP tumors. Immunofluorescence, RT-qPCR, and RNA scope assays have revealed increased Sox2 levels in NOTCH-driven CP tumors compared to wild type CP in mice. To investigate the role of Sox2 in CP tumors, we eliminated Sox2 expression in NOTCH-driven CP tumors. Loss of Sox2 almost completely blocked NOTCH-driven CP tumor growth in these mice, supporting a role for Sox2 in these tumors. Ciliation regulation is one proposed functional pathway for tumorigenesis in CP tumors. Using immunofluorescence assays for cilia (ARL13b) and aquaporin transport protein 1 (AQP1) in combination with super resolution microscopy, we observe a stark contrast between wild type CP epithelial cells which are multiciliated and homogeneously express AQP1, indicative of normal epithelial differentiation, compared to NOTCH-driven CP tumors consisting of mono-ciliated cells with loss of AQP1 expression. In Sox2-deficient NOTCH-driven CP tumors, we observe tumor cells remain mono-ciliated and AQP1-negative, indicating that Sox2 loss does not affect the ciliation machinery. Together this warrants further study into the mechanisms of Sox2 functions in CP tumors. By unraveling the role of Sox2 in CP tumors, we may better understand their origin and biology to ultimately design improved treatment options.
Zhang, S;Zeng, J;Zhou, Y;Gao, R;Rice, S;Guo, X;Liu, Y;Feng, P;Zhao, Z;
PMID: 35164537 | DOI: 10.1177/17590914211053505
Neurotrophic herpes simplex virus type 1 (HSV-1) establishes lifelong latent infection in humans. Accumulating studies indicate that HSV-1, a risk factor of neurodegenerative diseases, exacerbates the sporadic Alzheimer's disease (AD). The analysis of viral genetic materials via genomic sequencing and quantitative PCR (qPCR) is the current approach used for the detection of HSV-1; however, this approach is limited because of its difficulty in detecting both latent and lytic phases of the HSV-1 life cycle in infected hosts. RNAscope, a novel in situ RNA hybridization assay, enables visualized detection of multiple RNA targets on tissue sections. Here, we developed a fluorescent multiplex RNAscope assay in combination with immunofluorescence to detect neuronal HSV-1 transcripts in various types of mouse brain samples and human brain tissues. Specifically, the RNA probes were designed to separately recognize two transcripts in the same brain section: (1) the HSV-1 latency-associated transcript (LAT) and (2) the lytic-associated transcript, the tegument protein gene of the unique long region 37 (UL37). As a result, both LAT and UL37 signals were detectable in neurons in the hippocampus and trigeminal ganglia (TG). The quantifications of HSV-1 transcripts in the TG and CNS neurons are correlated with the viral loads during lytic and latent infection. Collectively, the development of combinational detection of neuronal HSV-1 transcripts in mouse brains can serve as a valuable tool to visualize HSV-1 infection phases in various types of samples from AD patients and facilitate our understanding of the infectious origin of neurodegeneration and dementia.
Grams, TR;Edwards, TG;Bloom, DC;
PMID: 36722973 | DOI: 10.1128/jvi.01935-22
Herpes simplex virus 1 (HSV-1) establishes latency in neurons and expresses long noncoding RNAs termed the latency-associated transcripts (LATs). Two previous studies using HSV-1 recombinants containing deletions in the LAT promoter revealed opposing effects of the promoter deletion regarding the heterochromatinization of latent viral genomes in mice ganglia. Confounding variables in these studies include viral strains utilized (17syn+ versus KOS), anatomical infection site (footpad versus eye) and infectious virus dose (500 versus 1 × 105 PFU), and to date the basis for the differences between the two studies remains unresolved. We recently reported that 17syn+ and KOS display distinct differences in heterochromatin levels during latency in human neurons. This raised the possibility that the discrepancy seen between the two previous studies could be explained by strain-specific differences within the LAT region. Here, we examine two recombinants containing orthologous 202 bp LAT promoter deletions, 17ΔPst and KOSΔPst, in a human neuronal model of latency and reactivation (LUHMES). We found that LUHMES neurons recapitulate previous observations in mice where deletion of the LAT promoter results in an increase in H3K27me3 deposition on the viral genome compared to the parental strain 17syn+ but a decrease compared to the parental strain KOS. We also found distinct strain-specific differences in the production of viral transcripts and proteins during latency. These results indicate that the function and/or regulation of the LATs differs between HSV-1 strains and may shed light on some discrepancies found in the literature when examining the function of the LATs. IMPORTANCE Herpes simplex virus 1 (HSV-1) establishes a lifelong infection in neuronal cells. Periodically, the virus reactivates from this latent state and causes recurrent disease. Mechanisms that control entry into and maintenance of latency are not well understood, though epigenetic posttranslational modification of histones associated with the viral genome are known to play an important role. During latency, the latency-associated transcript (LAT) is known to impact epigenetic marks, but the ultimate effect has been a point of controversy. Here, we utilize a human neuronal cell line model of HSV latency and reactivation (LUHMES) to characterize latency for two HSV-1 wild-type strains and their respective LAT promoter deletion viruses. We find that the LAT acts in a strain-specific manner to influence levels of chromatin marks, viral transcription, and viral protein production. This work highlights the need to account for strain-specific differences when characterizing the LAT's function and the dynamics of reactivation.
Voronova A, Yuzwa SA, Wang BS, Zahr S, Syal C, Wang J, Kaplan DR, Miller FD.
PMID: 28472653 | DOI: 10.1016/j.neuron.2017.04.018
During development, newborn interneurons migrate throughout the embryonic brain. Here, we provide evidence that these interneurons act in a paracrine fashion to regulate developmental oligodendrocyte formation. Specifically, we show that medial ganglionic eminence (MGE) interneurons secrete factors that promote genesis of oligodendrocytes from glially biased cortical precursors in culture. Moreover, when MGE interneurons are genetically ablated in vivo prior to their migration, this causes a deficit in cortical oligodendrogenesis. Modeling of the interneuron-precursor paracrine interaction using transcriptome data identifies the cytokine fractalkine as responsible for the pro-oligodendrocyte effect in culture. This paracrine interaction is important in vivo, since knockdown of the fractalkine receptor CX3CR1 in embryonic cortical precursors, or constitutive knockout of CX3CR1, causes decreased numbers of oligodendrocyte progenitor cells (OPCs) and oligodendrocytes in the postnatal cortex. Thus, in addition to their role in regulating neuronal excitability, interneurons act in a paracrine fashion to promote the developmental genesis of oligodendrocytes.
Interleukin-6 is an activator of pituitary stem cells upon local damage, a competence quenched in the aging gland
Proceedings of the National Academy of Sciences of the United States of America
Vennekens, A;Laporte, E;Hermans, F;Cox, B;Modave, E;Janiszewski, A;Nys, C;Kobayashi, H;Malengier-Devlies, B;Chappell, J;Matthys, P;Garcia, MI;Pasque, V;Lambrechts, D;Vankelecom, H;
PMID: 34161279 | DOI: 10.1073/pnas.2100052118
Stem cells in the adult pituitary are quiescent yet show acute activation upon tissue injury. The molecular mechanisms underlying this reaction are completely unknown. We applied single-cell transcriptomics to start unraveling the acute pituitary stem cell activation process as occurring upon targeted endocrine cell-ablation damage. This stem cell reaction was contrasted with the aging (middle-aged) pituitary, known to have lost damage-repair capacity. Stem cells in the aging pituitary show regressed proliferative activation upon injury and diminished in vitro organoid formation. Single-cell RNA sequencing uncovered interleukin-6 (IL-6) as being up-regulated upon damage, however only in young but not aging pituitary. Administering IL-6 to young mice promptly triggered pituitary stem cell proliferation, while blocking IL-6 or associated signaling pathways inhibited such reaction to damage. By contrast, IL-6 did not generate a pituitary stem cell activation response in aging mice, coinciding with elevated basal IL-6 levels and raised inflammatory state in the aging gland (inflammaging). Intriguingly, in vitro stem cell activation by IL-6 was discerned in organoid culture not only from young but also from aging pituitary, indicating that the aging gland's stem cells retain intrinsic activatability in vivo, likely impeded by the prevailing inflammatory tissue milieu. Importantly, IL-6 supplementation strongly enhanced the growth capability of pituitary stem cell organoids, thereby expanding their potential as an experimental model. Our study identifies IL-6 as a pituitary stem cell activator upon local damage, a competence quenched at aging, concomitant with raised IL-6/inflammatory levels in the older gland. These insights may open the way to interfering with pituitary aging.
Nuclear isoform of FGF13 regulates post-natal neurogenesis in the hippocampus through an epigenomic mechanism
Yang, QQ;Zhai, YQ;Wang, HF;Cai, YC;Ma, XY;Yin, YQ;Li, YD;Zhou, GM;Zhang, X;Hu, G;Zhou, JW;
PMID: 34010636 | DOI: 10.1016/j.celrep.2021.109127
The hippocampus is one of two niches in the mammalian brain with persistent neurogenesis into adulthood. The neurogenic capacity of hippocampal neural stem cells (NSCs) declines with age, but the molecular mechanisms of this process remain unknown. In this study, we find that fibroblast growth factor 13 (FGF13) is essential for the post-natal neurogenesis in mouse hippocampus, and FGF13 deficiency impairs learning and memory. In particular, we find that FGF13A, the nuclear isoform of FGF13, is involved in the maintenance of NSCs and the suppression of neuronal differentiation during post-natal hippocampal development. Furthermore, we find that FGF13A interacts with ARID1B, a unit of Brahma-associated factor chromatin remodeling complex, and suppresses the expression of neuron differentiation-associated genes through chromatin modification. Our results suggest that FGF13A is an important regulator for maintaining the self-renewal and neurogenic capacity of NSCs in post-natal hippocampus, revealing an epigenomic regulatory function of FGFs in neurogenesis.
Atkinson PJ, Dong Y, Gu S, Liu W, Najarro EH, Udagawa T, Cheng AG.
PMID: 29553487 | DOI: 10.1172/JCI97248
During development, Sox2 is indispensable for cell division and differentiation, yet its roles in regenerating tissues are less clear. Here, we used combinations of transgenic mouse models to reveal that Sox2 haploinsufficiency (Sox2haplo) increases rather than impairs cochlear regeneration in vivo. Sox2haplo cochleae had delayed terminal mitosis and ectopic sensory cells, yet normal auditory function. Sox2haplo amplified and expanded domains of damage-induced Atoh1+ transitional cell formation in neonatal cochlea. Wnt activation via β-catenin stabilization (β-cateninGOF) alone failed to induce proliferation or transitional cell formation. By contrast, β-cateninGOF caused proliferation when either Sox2haplo or damage was present, and transitional cell formation when both were present in neonatal, but not mature, cochlea. Mechanistically, Sox2haplo or damaged neonatal cochleae showed lower levels of Sox2 and Hes5, but not of Wnt target genes. Together, our study unveils an interplay between Sox2 and damage in directing tissue regeneration and Wnt responsiveness and thus provides a foundation for potential combinatorial therapies aimed at stimulating mammalian cochlear regeneration to reverse hearing loss in humans.
Storer MA, Gallagher D, Fatt MP, Simonetta JV, Kaplan DR, Miller FD.
PMID: - | DOI: 10.1016/j.stemcr.2018.03.008
Circulating systemic factors can regulate adult neural stem cell (NSC) biology, but the identity of these circulating cues is still being defined. Here, we have focused on the cytokine interleukin-6 (IL-6), since increased circulating levels of IL-6 are associated with neural pathologies such as autism and bipolar disorder. We show that IL-6 promotes proliferation of post-natal murine forebrain NSCs and that, when the IL-6 receptor is inducibly knocked out in post-natal or adult neural precursors, this causes a long-term decrease in forebrain NSCs. Moreover, a transient circulating surge of IL-6 in perinatal or adult mice causes an acute increase in neural precursor proliferation followed by long-term depletion of adult NSC pools. Thus, IL-6 signaling is both necessary and sufficient for adult NSC self-renewal, and acute perturbations in circulating IL-6, as observed in many pathological situations, have long-lasting effects on the size of adult NSC pools.
Sanz-Navarro M, Delgado I, Torres M, Mustonen T, Michon F and Rice DP
PMID: 30914971 | DOI: 10.3389/fphys.2019.00249
MEIS1 is a key developmental regulator of several organs and participates in stem cell maintenance in different niches. However, despite the murine continuously growing incisor being a well described model for the study of adult stem cells, Meis1 has not been investigated in a dental context. Here, we uncover that Meis1 expression in the tooth is confined to the epithelial compartment. Its expression arises during morphogenesis and becomes restricted to the mouse incisor epithelial stem cell niche, the labial cervical loop. Meis1 is specifically expressed by Sox2(+) stem cells, which give rise to all dental epithelial cell lineages. Also, we have found that Meis1 in the incisor is coexpressed with potential binding partner Pbx1 during both embryonic and adult stages. Interestingly, Meis2 is present in different areas of the forming tooth and it is not expressed by dental epithelial stem cells, suggesting different roles for these two largely homologous genes. Additionally, we have established the expression patterns of Meis1 and Meis2 during tongue, hair, salivary gland and palate formation. Finally, analysis of Meis1-null allele mice indicated that, similarly, to SOX2, MEIS1 is not essential for tooth initiation, but might have a role during adult incisor renewal.
Guyer, RA;Stavely, R;Robertson, K;Bhave, S;Mueller, JL;Picard, NM;Hotta, R;Kaltschmidt, JA;Goldstein, AM;
PMID: 36857184 | DOI: 10.1016/j.celrep.2023.112194
The enteric nervous system (ENS) consists of glial cells (EGCs) and neurons derived from neural crest precursors. EGCs retain capacity for large-scale neurogenesis in culture, and in vivo lineage tracing has identified neurons derived from glial cells in response to inflammation. We thus hypothesize that EGCs possess a chromatin structure poised for neurogenesis. We use single-cell multiome sequencing to simultaneously assess transcription and chromatin accessibility in EGCs undergoing spontaneous neurogenesis in culture, as well as small intestine myenteric plexus EGCs. Cultured EGCs maintain open chromatin at genomic loci accessible in neurons, and neurogenesis from EGCs involves dynamic chromatin rearrangements with a net decrease in accessible chromatin. A subset of in vivo EGCs, highly enriched within the myenteric ganglia and that persist into adulthood, have a gene expression program and chromatin state consistent with neurogenic potential. These results clarify the mechanisms underlying EGC potential for neuronal fate transition.
Fractalkine signaling regulates oligodendroglial cell genesis from SVZ precursor cells
Watson, AES;de Almeida, MMA;Dittmann, NL;Li, Y;Torabi, P;Footz, T;Vetere, G;Galleguillos, D;Sipione, S;Cardona, AE;Voronova, A;
PMID: 34270934 | DOI: 10.1016/j.stemcr.2021.06.010
Neural and oligodendrocyte precursor cells (NPCs and OPCs) in the subventricular zone (SVZ) of the brain contribute to oligodendrogenesis throughout life, in part due to direct regulation by chemokines. The role of the chemokine fractalkine is well established in microglia; however, the effect of fractalkine on SVZ precursor cells is unknown. We show that murine SVZ NPCs and OPCs express the fractalkine receptor (CX3CR1) and bind fractalkine. Exogenous fractalkine directly enhances OPC and oligodendrocyte genesis from SVZ NPCs in vitro. Infusion of fractalkine into the lateral ventricle of adult NPC lineage-tracing mice leads to increased newborn OPC and oligodendrocyte formation in vivo. We also show that OPCs secrete fractalkine and that inhibition of endogenous fractalkine signaling reduces oligodendrocyte formation in vitro. Finally, we show that fractalkine signaling regulates oligodendrogenesis in cerebellar slices ex vivo. In summary, we demonstrate a novel role for fractalkine signaling in regulating oligodendrocyte genesis from postnatal CNS precursor cells.
