Biology subjects

Poole, R. J.

Publications and source records attributed to Poole, R. J..

6 recordsLinked to original sources

bioRxiv2026

Genetically interacting mutations and mechanical stress affect the stochasticity of developmental eye defects in yap1 mutants

Congenital abnormalities of eye formation show remarkably variable penetrance with phenotypes even varying between left and right eyes. Here we explore this phenomenon through analysis of the mechanistic basis of low penetrance retinal coloboma in zebrafish yap1nl13/nl13 mutants and identification of factors that modify the probability of this phenotype. We find that the low penetrance stochastically occurring coloboma in yap1nl13/nl13 mutants is due to rupture in the ventral retina at the point of apposition of the lips of the closing choroid fissure and that provision of wild-type Yap in the retinal pigment epithelium suppressed this phenotype. Decreasing actomyosin contractility increased the penetrance of coloboma whereas increasing myosin phosphorylation rescued the phenotype suggesting that altered mechanical properties of the RPE sensitize the eye to stochastic failure of choroid fissure closure. Genetic interaction screening revealed enhanced and synthetic eye phenotypes in yap1nl13/nl13mutants upon abrogation of function of genes encoding extracellular matrix and other genes implicated in eye formation. Our data reveal that the variable penetrance of congenital eye abnormalities can be due to genetic and environmental factors impacting the stochastic variability inherent in the developmental processes underlying eye morphogenesis.

developmental biology↗

bioRxiv2023

Importin 13-dependent Axon Diameter Growth Regulates Conduction Speeds along Myelinated CNS Axons

Central nervous system neurons have axons that vary over 100-fold in diameter. This diversity contributes to the regulation of myelination and conduction velocity along axons, which is critical for proper nervous system function. Despite this importance, technical challenges have limited our understanding of mechanisms controlling axon diameter growth, preventing systematic dissection of how manipulating diameter affects conduction along individual axons. Here, we establish zebrafish as system to investigate the regulation of axon diameter and axonal conduction in vivo. We identify a role for importin 13b specifically in axon diameter growth, that is independent of axonal length and overall cell size. Impairment of diameter growth along individual myelinated axons reduced conduction velocity in proportion to the diameter, but had no effect on the precision of action potential propagation or ability to fire at high frequencies. This work highlights an axon diameter-specific mechanism of growth that regulates conduction speeds along myelinated axons.

neuroscience↗

bioRxiv2020

The GINS complex is required for the survival of rapidly proliferating retinal and tectal progenitor cells during zebrafish development

Efficient and accurate DNA replication is particularly critical in stem and progenitor cells for successful proliferation and survival. The replisome, an amalgam of protein complexes, is responsible for binding potential origins of replication, unwinding the double helix, and then synthesizing complimentary strands of DNA. According to current models, the initial steps of DNA unwinding and opening are facilitated by the CMG complex, which is composed of a GINS heterotetramer that connects Cdc45 with the mini-chromosome maintenance (Mcm) helicase. In this work, we provide evidence that in the absence of GINS function DNA replication is cell autonomously impaired, and we also show that gins1 and gins2 mutants exhibit elevated levels of apoptosis restricted to actively proliferating regions of the central nervous system (CNS). Intriguingly, our results also suggest that the rapid cell cycles during early embryonic development in zebrafish may not require the function of the GINS complex as neither Gins1 nor Gins2 seem to be present during these stages.

genetics↗

bioRxiv2019

Disruption to NKCC1 impairs the response of myelinating Schwann cells to neuronal activity and leads to severe peripheral nerve pathology

Myelinating Schwann cells of the peripheral nervous system (PNS) express numerous ion channels and transporters, and have the capacity to respond to neuronal activity. However, it remains unknown how the response of Schwann cells to neuronal activity affects peripheral nerve formation, health or function in vivo. Through a genetic screen in zebrafish, we identified a mutant, ue58, with severe disruption to the morphology of myelin along peripheral nerves and associated nerve oedema. Molecular analyses indicated that this phenotype was caused by the loss of function of a previously uncharacterized gene, slc12a2b, which encodes a zebrafish paralog of the solute carrier NKCC1. NKCC1 is a co-transporter of Na+, K+, and Cl- ions and water, typically from the extracellular space into cells. Upon impairing slc12a2b function, constitutively, or specifically in neurons or myelinating Schwann cells, we observed disruption to myelin and nerve oedema. Strikingly, we found that treatment of slc12a2b mutants with TTX completely prevented the emergence of these pathologies. Furthermore, TTX treatment rescued pathology in animals with cell-type specific loss of slc12a2b from myelinating Schwann cells. Together our data indicate that NKCC1 regulates ion homeostasis following neuronal activity and that this is required to maintain myelinated axon and peripheral nerve integrity.

neuroscience↗

bioRxiv2018

Abrogation of Stem Loop Binding Protein (Slbp) function leads to a failure of cells to transition from proliferation to differentiation, retinal coloboma and midline axon guidance deficits.

Through forward genetic screening for mutations affecting visual system development, we identified prominent coloboma and cell-autonomous retinal neuron differentiation, lamination and retinal axon projection defects in eisspalte (ele) mutant zebrafish. Additional axonal deficits were present, most notably at midline axon commissures. Genetic mapping and cloning of the ele mutation showed that the affected gene is slbp, which encodes a conserved RNA stem-loop binding protein involved in replication dependent histone mRNA metabolism. Cells throughout the central nervous system remained in the cell cycle in ele mutant embryos at stages when, and locations where, post-mitotic cells have differentiated in wild-type siblings. Indeed, RNAseq analysis showed down-regulation of many genes associated with neuronal differentiation. This was coincident with changes in the levels and spatial localisation of expression of various genes implicated, for instance, in axon guidance, that likely underlie specific ele phenotypes. These results suggest that many of the cell and tissue specific phenotypes in ele mutant embryos are secondary to altered expression of modules of developmental regulatory genes that characterise, or promote transitions in, cell state and require the correct function of Slbp-dependent histone and chromatin regulatory genes.\n\nAuthor SummaryCongenital deficits of eye formation are common in humans and to help understand the genetic basic of such conditions, we are studying zebrafish with comparable eye defects. We identified defects in both the shaping of the eye and in its connections to the brain in eisspalte mutant fish. Further analyses revealed additional deficits in the brain, most notably a severe reduction in neurons and their connections. We find that this is due to an inability of the cells that generate neurons to transition from proliferation to neuronal differentiation. By using a sequencing approach to compare mutant embryos to their normal siblings, we identified the affected gene as slbp, which encodes a protein that binds the mRNAs of other genes important for cell proliferation. This sequencing approach revealed the full extent of changes in gene expression in the mutant, helping us to better understand why the nervous system defects occur. Our study suggests that in the absence of Slbp function, cells lose the ability to transition from the proliferative to the differentiated state and this leads to additional defects in the eyes and brain.

genetics↗

bioRxiv2018

A direct glia-to-neuron natural transdifferentiation ensures nimble sensory-motor coordination of male mating behaviour

The coordinated execution of innate, stereotyped sexual behaviours, such as courtship and mating, requires sexually dimorphic sensory-motor circuits that are genetically specified during development (reviewed in [1-3]). Studies in the nematode Caenorhabditis elegans, in which the development and function of neural circuits can be interrogated with single cell resolution, have revealed two general developmental mechanisms underlying sexual dimorphism in the nervous system. The first involves the acquisition of sexually dimorphic features in sex-shared neurons during sexual maturation, which include changes in terminal gene expression, such as odorant receptors, neurotransmitters and synaptic regulators [4-10]. The second mechanism involves the generation of sex-specific neurons [11-13]. This requires sex-specific cell death [14]or neurogenesis events resulting from extensive sex differences in the cell division patterns and neurodevelopmental programmes of post-embryonic cell lineages (reviewed in [3]). Here we identify a third, novel way to generate sexual dimorphism in the nervous system. We find that during sexual maturation (L4 stage), a class of sex-shared glial cells acquires sexually dimorphic function by undergoing a direct glia-to-neuron transdifferentiation that results in the production of male-specific neurons. This plasticity is regulated cell-intrinsically by the sex-determination pathway. These previously unnoticed neurons, which we term PHDs, are putative proprioceptors that regulate male locomotion during specific steps of mating. One of these steps is a novel readjustment movement performed when intromission becomes difficult to achieve. Our results reveal sex-specific direct transdifferentiation as a novel mechanism for generating sex-specific neurons and also show the importance of proprioceptive feedback during the complex steps of mating for successful reproduction.

neuroscience↗