scholarly journals Developmental fidelity imposed by the RGL-1 “Balanced Switch” mediating opposing signals

2018 ◽  
Author(s):  
Hanna Shin ◽  
Christian Braendle ◽  
Kimberly B. Monahan ◽  
Rebecca E.W. Kaplan ◽  
Tanya P. Zand ◽  
...  
Keyword(s):  
Cell Fates ◽  
Developmental Defects ◽  
C Elegans ◽  
Canonical Map ◽  
Environmental Perturbations ◽  
Map Kinase Cascade ◽  
Vulval Precursor Cells ◽  
Genetic Epistasis ◽  
Kinase Cascade ◽  
Dsl Ligands

AbstractThe six C. elegans vulval precursor cells (VPCs) are induced to form the 30-30-20-Γ-20-3° pattern of cell fates with high fidelity. In response to EGF signal, the LET-60/Ras-LIN-45/Raf-MEK-2/MEK-MPK-1/ERK canonical MAP kinase cascade is necessary to induce 1° fate and synthesis of DSL ligands. In turn, LIN-12/Notch signal is necessary to induce neighboring cells to become 2°. We previously showed that, in response to lower dose of EGF signal, the modulatory LET-60/Ras-RGL-1/RalGEF-RAL-1/Ral signal promotes 2° fate in support of LIN-12. In this study we identify two key differences between RGL-1 and RAL-1 functions. First, deletion of RGL-1 confers no overt developmental defects, while previous studies showed RAL-1 to be essential for viability and fertility. From this observation we hypothesize that the developmentally essential functions of RAL-1 are independent of upstream activation. Second, RGL-1 plays opposing and genetically separable roles in VPC fate patterning. RGL-1 promotes 2° fate via canonical GEF-dependent activation of RAL-1 and 1° fate via a non-canonical GEF-independent activity. Our genetic epistasis experiments are consistent with RGL-1 functioning in the modulatory 1°-promoting AGE-1/PI3-Kinase-PDK-1-AKT-1 cascade. Additionally, animals without RGL-1 experience 15-fold higher rates of VPC patterning errors compared to the wild type. Yet VPC patterning in RGL-1 deletion mutants is not more sensitive to environmental perturbations. We propose that RGL-1 functions as a “Balanced Switch” that orchestrates opposing 1°- and 2°-promoting modulatory cascades to decrease inappropriate fate decisions. We speculate that such switches are broadly conserved but mostly masked by paralog redundancy or essential genes.

scholarly journals Ral Signals through a MAP4 Kinase-p38 MAP Kinase Cascade in C. elegans Cell Fate Patterning

Cell Reports ◽  
2018 ◽  
Vol 24 (10) ◽  
pp. 2669-2681.e5 ◽  
Author(s):  
Hanna Shin ◽  
Rebecca E.W. Kaplan ◽  
Tam Duong ◽  
Razan Fakieh ◽  
David J. Reiner
Keyword(s):  
Map Kinase ◽  
Cell Fate ◽  
P38 Map Kinase ◽  
C Elegans ◽  
Map Kinase Cascade ◽  
Kinase Cascade

scholarly journals ANALYSIS OF CHD-7 DEFECTIVE DAUER NEMATODES IMPLICATES COLLAGEN MISREGULATION IN CHARGE SYNDROME FEATURES

2021 ◽  
Author(s):  
Diego Martín Jofré ◽  
Dane Kristian Hoffman ◽  
Ailen S. Cervino ◽  
McKenzie Grundy ◽  
Sijung Yun ◽  
...  
Keyword(s):  
Charge Syndrome ◽  
Mrna Levels ◽  
Craniofacial Malformations ◽  
Developmental Defects ◽  
The Public ◽  
Over Expression ◽  
C Elegans ◽  
Genetic Epistasis ◽  
Collagen Genes ◽  
Craniofacial Defects

ABSTRACTCHARGE syndrome is a complex developmental disorder caused by mutations in the chromodomain helicase DNA-binding protein7 (CHD7) and characterized by retarded growth and malformations in the heart and nervous system. However, despite the public health relevance of this disorder, relevant targets of CHD7 that relate to disease pathology are still poorly understood. Here we report thatchd-7, the nematode ortholog of CHD7, is required for dauer morphogenesis, lifespan determination, and stress response. Genetic epistasis placedchd-7in the TGF-β pathway. Consistent with our discoveries, we foundchd-7to be allelic toscd-3, a previously identified dauer suppressor from the TGF-β pathway. Interestingly, DAF-12 transcriptionally upregulatedchd-7, which is necessary to repressdaf-9for execution of the dauer program. Transcriptomic analysis comparingchd-7–defective and normal dauers showed enrichment of collagen genes, consistent with a conserved role for the TGF-β pathway in expression of the extracellular matrix. To validate a conserved function forchd-7in vertebrates, we usedXenopus laevisembryos, an established model to study craniofacial development. Morpholino mediated knockdown of Chd7 led to embryonic lethality, a reduction incol2a1mRNA levels and craniofacial defects in tadpoles. Both lethality and malformations were partially rescued in Chd7-depleted embryos by over-expression ofcol2a1. We suggest that pathogenic features of CHARGE syndrome caused by Chd7 mutations, such as craniofacial malformations, result from the reduction of collagen levels. These studies establishC. elegansas an amenable animal model to study the etiology of the developmental defects associated with pathogenic Chd7.

The Hox gene lin-39 is required during C. elegans vulval induction to select the outcome of Ras signaling

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 181-190 ◽  
Author(s):  
J.N. Maloof ◽  
C. Kenyon
Keyword(s):  
Body Region ◽  
Ras Signaling ◽  
Cell Fates ◽  
Vulval Development ◽  
Ras Pathway ◽  
Hox Gene ◽  
C Elegans ◽  
Cell Divisions ◽  
Ras Activation ◽  
Vulval Precursor Cells

The Ras signaling pathway specifies a variety of cell fates in many organisms. However, little is known about the genes that function downstream of the conserved signaling cassette, or what imparts the specificity necessary to cause Ras activation to trigger different responses in different tissues. In C. elegans, activation of the Ras pathway induces cells in the central body region to generate the vulva. Vulval induction takes place in the domain of the Hox gene lin-39. We have found that lin-39 is absolutely required for Ras signaling to induce vulval development. During vulval induction, the Ras pathway, together with basal lin-39 activity, up-regulates lin-39 expression in vulval precursor cells. We find that if lin-39 function is absent at this time, no vulval cell divisions occur. Furthermore, if lin-39 is replaced with the posterior Hox gene mab-5, then posterior structures are induced instead of a vulva. Our findings suggest that in addition to permitting vulval cell divisions to occur, lin-39 is also required to specify the outcome of Ras signaling by selectively activating vulva-specific genes.

scholarly journals The Signaling Network Controlling C. elegans Vulval Cell Fate Patterning

2018 ◽  
Vol 6 (4) ◽  
pp. 30 ◽  
Author(s):  
Hanna Shin ◽  
David Reiner
Keyword(s):  
Cell Fate ◽  
Signaling Network ◽  
Signaling Cascades ◽  
Cell Fates ◽  
C Elegans ◽  
Differentiated Cells ◽  
Vulval Precursor Cells ◽  
Cell Patterns ◽  
History Of ◽  
Anchor Cell

EGF, emitted by the Anchor Cell, patterns six equipotent C. elegans vulval precursor cells to assume a precise array of three cell fates with high fidelity. A group of core and modulatory signaling cascades forms a signaling network that demonstrates plasticity during the transition from naïve to terminally differentiated cells. In this review, we summarize the history of classical developmental manipulations and molecular genetics experiments that led to our understanding of the signals governing this process, and discuss principles of signal transduction and developmental biology that have emerged from these studies.

scholarly journals Cell fate patterning during C. elegans vulval development

Development ◽  
1993 ◽  
Vol 119 (Supplement) ◽  
pp. 9-18 ◽  
Author(s):  
Russell J. Hill ◽  
Paul W. Sternberg
Keyword(s):  
Cell Fate ◽  
Short Range ◽  
Precursor Cells ◽  
Cell Fates ◽  
Vulval Development ◽  
C Elegans ◽  
Vulval Precursor Cells ◽  
Combined Action ◽  
Anchor Cell ◽  
Inductive Signal

Precursor cells of the vulva of the C. elegans hermaphrodite choose between two vulval cell fates (1° and 2°) and a non-vulval epidermal fate (3°) in response to three intercellular signals. An inductive signal produced by the anchor cell induces the vulval precursors to assume the 1° and 2° vulval fates. This inductive signal is an EGF-like growth factor encoded by the gene lin-3. An inhibitory signal mediated by lin-15, and which may originate from the surrounding epidermis, prevents the vulval precursors from assuming vulval fates in the absence of the inductive signal. A short range lateral signal, which acts through the gene lin-12, regulates the pattern of 1° and 2° fates assumed by the induced vulval precursors. The combined action of the three signals precisely directs the six vulval precursors to adopt a 3° 3° 2° 1° 2 ° 3° pattern of fates. The amount of inductive signal produced by the anchor cell appears to determine the number or vulval precursors that assume vulval fates. The three induced vulval precursors most proximal to the anchor cell are proposed to adopt the 2° 1° 2° pattern of fates in response to a gradient of the inductive signal and also in response to lateral signalling that inhibits adjacent vulval precursor cells from both assuming the 1° fate.

scholarly journals Insulated Switches: Dual-Function Protein RalGEFRGL-1 Promotes Developmental Fidelity

2020 ◽  
Vol 21 (20) ◽  
pp. 7610 ◽  
Author(s):  
Tam Duong ◽  
Neal R. Rasmussen ◽  
David J. Reiner
Keyword(s):  
Birth Defects ◽  
Dual Function ◽  
Wild Type ◽  
Cell Fates ◽  
Vulval Development ◽  
C Elegans ◽  
Vulval Precursor Cells ◽  
Anchor Cell ◽  
The Impact ◽  
Wild Type Control

The C. elegans vulva is an excellent model for the study of developmental biology and cell–cell signaling. The developmental induction of vulval precursor cells (VPCs) to assume the 3°-3°-2°-1°-2°-3° patterning of cell fates occurs with 99.8% accuracy. During C. elegans vulval development, an EGF signal from the anchor cell initiates the activation of RasLET-60 > RafLIN-45 > MEKMEK-2 > ERKMPK-1 signaling cascade to induce the 1° cell. The presumptive 1° cell signals its two neighboring cells via NotchLIN-12 to develop 2° cells. In addition, RasLET-60 switches effectors to RalGEFRGL-1 > RalRAL-1 to promote 2° fate. Shin et al. (2019) showed that RalGEFRGL-1 is a dual-function protein in VPCs fate patterning. RalGEFRGL-1 functions as a scaffold for PDKPDK-1 > AktAKT-1/2 modulatory signaling to promote 1° fate in addition to propagating the RasLET-60 modulatory signal through RalRAL-1 to promote 2° fate. The deletion of RalGEFRGL-1 increases the frequency of VPC patterning errors 15-fold compared to the wild-type control. We speculate that RalGEFRGL-1 represents an “insulated switch”, whereby the promotion of one signaling activity curtails the promotion of the opposing activity. This property might increase the impact of the switch on fidelity more than two separately encoded proteins could. Understanding how developmental fidelity is controlled will help us to better understand the origins of cancer and birth defects, which occur in part due to the misspecification of cell fates.

scholarly journals Ral signals through a MAP4 Kinase-p38 MAP kinase cascade in C. elegans cell fate patterning

2018 ◽  
Author(s):  
Hanna Shin ◽  
Rebecca E.W. Kaplan ◽  
Tam Duong ◽  
Razan Fakieh ◽  
David J. Reiner
Keyword(s):  
Map Kinase ◽  
Cell Fate ◽  
P38 Map Kinase ◽  
High Dose ◽  
C Elegans ◽  
Oncogenic Ras ◽  
Map Kinase Cascade ◽  
Kinase Cascade ◽  
Vulval Precursor Cell

SummaryC. elegans vulval precursor cell (VPC) fates are patterned by an EGF gradient. High dose EGF induces 1° VPC fate, while lower dose EGF contributes to 2° fate in support of LIN-12/Notch. We previously showed that the EGF 2°-promoting signal is mediated by LET-60/Ras switching effectors, from the canonical Raf-MEK-ERK MAP kinase cascade that promotes 1° fate to the non-canonical RalGEF-Ral that promotes 2° fate. Of oncogenic Ras effectors, RalGEF-Ral is by far the least well-understood. We use genetic analysis to identify an effector cascade downstream of C. elegans RAL-1/Ral, starting with an established Ral binding partner, Exo84 of the exocyst complex. Additionally, RAL-1 signals through GCK-2, a CNH domain-containing MAP4 kinase, and PMK-1/p38 MAP kinase cascade to promote 2° fate. Our study delineates a Ral-dependent developmental signaling cascade in vivo, thus providing the mechanism by which lower EGF dose is transduced.

Cell fates and fusion in theC. elegansvulval primordium are regulated by the EGL-18 and ELT-6 GATA factors — apparent direct targets of the LIN-39 Hox protein

Development ◽  
2002 ◽  
Vol 129 (22) ◽  
pp. 5171-5180 ◽  
Author(s):  
Kyunghee Koh ◽  
Sara M. Peyrot ◽  
Cricket G. Wood ◽  
Javier A. Wagmaister ◽  
Morris F. Maduro ◽  
...  
Keyword(s):  
Cell Fusion ◽  
Body Region ◽  
Embryonic Cells ◽  
Cell Fates ◽  
Hox Gene ◽  
C Elegans ◽  
Gata Factors ◽  
Vulval Precursor Cells ◽  
Hox Protein ◽  
Larval Lethality

Development of the vulva in C. elegans is mediated by the combinatorial action of several convergent regulatory inputs, three of which,the Ras, Wnt and Rb-related pathways, act by regulating expression of thelin-39 Hox gene. LIN-39 specifies cell fates and regulates cell fusion in the mid-body region, leading to formation of the vulva. In the lateral seam epidermis, differentiation and cell fusion have been shown to be regulated by two GATA-type transcription factors, ELT-5 and -6. We report that ELT-5 is encoded by the egl-18 gene, which was previously shown to promote formation of a functional vulva. Furthermore, we find that EGL-18(ELT-5), and its paralogue ELT-6, are redundantly required to regulate cell fates and fusion in the vulval primordium and are essential to form a vulva. Elimination of egl-18 and elt-6 activity results in arrest by the first larval stage; however, in animals rescued for this larval lethality by expression of ELT-6 in non-vulval cells, the post-embryonic cells(P3.p-P8.p) that normally become vulval precursor cells often fuse with the surrounding epidermal syncytium or undergo fewer than normal cell divisions,reminiscent of lin-39 mutants. Moreover, egl-18/elt-6reporter gene expression in the developing vulva is attenuated inlin-39(rf) mutants, and overexpression of egl-18 can partially rescue the vulval defects caused by reduced lin-39activity. LIN-39/CEH-20 heterodimers bind two consensus HOX/PBC sites in a vulval enhancer region of egl-18/elt-6, one of which is essential for vulval expression of egl-18/elt-6 reporter constructs. These findings demonstrate that the EGL-18 and ELT-6 GATA factors are essential, genetically redundant regulators of cell fates and fusion in the developing vulva and are apparent direct transcriptional targets of the LIN-39 Hox protein.

scholarly journals Nets-within-nets for modeling emergent patterns in ontogenetic processes

2021 ◽  
Author(s):  
Roberta Bardini ◽  
Alfredo Benso ◽  
Gianfranco Politano ◽  
Stefano Di Carlo
Keyword(s):  
Phenotypic Diversity ◽  
C Elegans ◽  
Environmental Perturbations ◽  
Proposed Model ◽  
Hierarchical Relations ◽  
Vulval Precursor Cells ◽  
Modeling Strategy ◽  
Almost All ◽  
Dynamic Interplay

ABSTRACTOntogenesis is the development of an organism from its earliest stage to maturity, including homeostasis maintenance throughout adulthood despite environmental perturbations. Almost all cells of a multicellular organism share the same genomic information. Nevertheless, phenotypic diversity and complex supra-cellular architectures emerge at every level, starting from tissues and organs. This is possible thanks to a robust and dynamic interplay of regulative mechanisms.To study ontogenesis, it is necessary to consider different levels of regulation, both genetic and epigenetic. Each cell undergoes a specific path across a landscape of possible regulative states affecting both its structure and its functions during development. This paper proposes using the Nets-Within-Nets formalism, which combines Petri Nets’ simplicity with the capability to represent and simulate the interplay between different layers of regulation connected by non-trivial and context-dependent hierarchical relations.In particular, this work introduces a modeling strategy based on Nets-Within-Nets that can model several critical processes involved in ontogenesis. Moreover, it presents a case study focusing on the first phase of Vulval Precursor Cells specification in C. Elegans. The case study shows that the proposed model can simulate the emergent morphogenetic pattern corresponding to the observed developmental outcome of that phase, in both the physiological case and different mutations. The model presented in the results section is available online at https://github.com/sysbio-polito/NWN_CElegans_VPC_model/

Sign in / Sign up

Export Citation Format

Share Document