Biology subjects

Elaswad, M. T.

Publications and source records attributed to Elaswad, M. T..

5 recordsLinked to original sources

bioRxiv2026

Kainate receptors coordinate primitive hematopoiesis and hemogenic niche organization to promote hematopoietic stem cell development

The adult hematopoietic system is established during embryogenesis through the generation of hematopoietic stem and progenitor cells (HSPCs) within specialized transient niches, yet the signaling mechanisms that coordinate this process remain poorly understood. Here, we identify a developmental role for kainate receptors (KARs), glutamate-gated ion channels classically associated with excitatory neurotransmission, in coordinating primitive hematopoiesis and hemogenic niche formation in zebrafish. Loss of the KAR subunits encoded by grik1b or grik5 depletes primitive blood cells and disrupts hemogenic niche organization. These defects are accompanied by endothelial oxidative stress and impaired Notch signaling, which together reduce HSPC emergence and limit the clonal diversity of the adult hematopoietic stem cell pool. Shifting primitive hematopoietic output away from erythropoiesis and toward myelopoiesis restored macrophage niche colonization, endothelial Notch activity, and HSPC formation in KAR-deficient embryos. Moreover, hemogenic cell-specific Notch reactivation rescued HSPC production, demonstrating that KAR-dependent primitive hematopoiesis regulates this process through endothelial Notch signaling. Lastly, conserved KAR expression in endothelial and hematopoietic populations across zebrafish, mouse, and human suggests that these receptors may regulate blood development across multiple cellular components. Together, these findings reveal that glutamate receptor signaling extends beyond its well-established functions in neuronal transmission to coordinate the developmental processes that establish the blood system.

developmental biology↗

bioRxiv2025

Targeted RNAi screen reveals novel regulators of RNA-binding protein phase transitions in Caenorhabditis elegans oocytes

The ability of oocytes to maintain their quality is essential for successful reproduction. One critical aspect of oocyte quality and successful embryogenesis after fertilization is the proper regulation of the stores of maternal mRNA by RNA-binding proteins. Many RNA-binding proteins undergo regulated phase transitions during oogenesis, and alterations of the protein phase can disrupt its ability to regulate mRNA stability and translation. In C. elegans, genetic screens have identified regulators of RNA-binding protein condensation in arrested oocytes of females and in embryos, but less attention has focused on phase transitions in maturing oocytes of young adult hermaphrodites. Interestingly, of the relatively few regulators of RNA-binding protein phase transitions identified to date in maturing oocytes, several genes overlap with those required for clearance of protein aggregates in maturing oocytes. To determine the extent to which the temporally linked processes of clearance of damaged proteins and maintenance of RNP complexes are coordinated at a molecular level, we conducted a targeted RNAi screen of genes required for removal of protein aggregates in maturing oocytes. We identified six novel regulators of phase transitions of the KH-domain protein MEX-3 and obtained strong evidence that the regulatory network of protein aggregate clearance overlaps with, but is distinct from, the regulation of MEX-3 phase transitions in the oocyte.

genetics↗

bioRxiv2024

The CCT chaperonin and actin modulate the ER and RNA-binding protein condensation during oogenesis to maintain translational repression of maternal mRNA and oocyte quality

The regulation of maternal mRNAs is essential for proper oogenesis, the production of viable gametes, and to avoid birth defects and infertility. Many oogenic RNA-binding proteins have been identified with roles in mRNA metabolism, some of which localize to dynamic ribonucleoprotein granules and others that appear dispersed. Here, we use a combination of in vitro condensation assays and the in vivo C. elegans oogenesis model to determine the intrinsic properties of the conserved KH-domain MEX-3 protein and to identify novel regulators of MEX-3 and the Lsm protein, CAR-1. We demonstrate that MEX-3 undergoes liquid-liquid phase separation and appears to have intrinsic gel-like properties in vitro. We also identify novel roles for the CCT chaperonin and actin in preventing ectopic RNA-binding protein condensates in maturing oocytes that appear to be independent of MEX-3 folding. CCT and actin also oppose the expansion of ER sheets that may promote ectopic condensation of RNA-binding proteins that are associated with de-repression of maternal mRNA. This regulatory network is essential to preserve oocyte quality, prevent infertility, and may have implications for understanding the role of hMex3 phase transitions in cancer. Significance statementO_LIThe molecular mechanisms that regulate phase transitions of oogenic RNA-binding proteins are critical to elucidate but are not fully understood. C_LIO_LIWe identify novel regulators of RNA-binding protein phase transitions in maturing oocytes that are required to maintain translational repression of maternal mRNAs and oocyte quality. C_LIO_LIThis study is the first to elucidate a regulatory network involving the CCT chaperonin, actin, and the ER for phase transitions of RNA-binding proteins during oogenesis. Our findings for the conserved MEX-3 protein may also be applicable to better understanding the role of hMex3 phase transitions in cancer. C_LI

developmental biology↗

bioRxiv2022

Large RNP granules in C. elegans oocytes have distinct phases of RNA binding proteins

The germ line provides an excellent in vivo system to study the regulation and function of RNP granules. Germ granules are conserved germ line-specific RNP granules that are positioned in the C. elegans adult gonad to function in RNA maintenance, regulation, and surveillance. In C. elegans, when oogenesis undergoes an extended meiotic arrest, germ granule proteins and other RNA binding proteins assemble into much larger RNP granules whose hypothesized function is to regulate RNA metabolism and maintain oocyte quality. To gain insight into the function of oocyte RNP granules, in this report we characterize distinct phases for four protein components of RNP granules in arrested oocytes. We find the RNA binding protein PGL-1 is dynamic and has liquid-like properties, while the intrinsically disordered protein MEG-3 has gel-like properties, similar to the properties of the two proteins in small germ granules of embryos. We find that MEX-3 exhibits several gel-like properties but is more dynamic than MEG-3, while CGH-1 is dynamic but does not consistently exhibit liquid-like characteristics and may be an intermediate phase within RNP granules. These distinct phases of RNA binding proteins correspond to, and may underlie, differential responses to stress. Interestingly, in oocyte RNP granules MEG-3 is not required for the condensation of PGL-1 or other RNA binding proteins, which differs from the role of MEG-3 in small, embryonic germ granules. Lastly, we show the PUF-5 translational repressor appears to promote MEX-3 and MEG-3 condensation into large RNP granules; however, this role may be associated with regulation of oogenesis.

cell biology↗

bioRxiv2021

Distinct phases within large RNP granules of C. elegans oocytes are associated with differential stress responses of RNA binding proteins

One emerging paradigm of cellular organization of RNA and RNA binding proteins is the formation of membraneless organelles (MLOs). Examples of MLOs include several types of ribonucleoprotein granules that form via phase separation. A variety of intracellular pH changes and post-translational modifications, as well as extracellular stresses can stimulate the condensation of proteins into granules. For example, the assembly of stress granules induced by oxidative stress, osmotic stress, and heat stress has been well-characterized in a variety of somatic cell types. In the germ line, similar stress-induced condensation of proteins occurs; however, less is known about the role of phase separation during gamete production. Researchers who study phase transitions often make use of fluorescent reporters to study the dynamics of RNA binding proteins during live-cell imaging. In this report, we demonstrate that certain conditions of live-imaging C. elegans can cause an inadvertent stress and trigger phase transitions of RNA binding proteins. We show that imaging stress stimulates decondensation of multiple germ granule proteins, and condensation of several P-body proteins. Proteins within larger RNP granules in meiotically-arrested oocytes do not appear to be as sensitive to imaging stress as proteins in diakinesis oocytes of young hermaphrodites, with the exception of the germ granule protein PGL-1. Our results have important methodological implications for all researchers using live-cell imaging techniques. The data also suggest that the RNA binding proteins within large RNP granules of arrested oocytes may have distinct phases which we characterize in our companion paper.

cell biology↗