Biology subjects

Okenve-Ramos, P.

Publications and source records attributed to Okenve-Ramos, P..

4 recordsLinked to original sources

bioRxiv2026

Centrosome maintains the integrity of and repairs mature olfactory cilia in adult Drosophila

Mechanisms of cilium assembly are well studied; however, how mature metazoan cilia maintain their structures and functions in vivo remains unknown. It is also unclear whether the centrosome-derived basal body (BB) directly contributes to ciliary homeostasis. We combined biochemistry, genetics, high-resolution subcellular imaging, and electrophysiology to investigate long-lived ciliated olfactory sensory neurons (OSNs) and their olfactory behaviour in adult Drosophila. Several centrosome assembly proteins are absent, but another subset persists through dynamic protein exchange at the BBs of mature olfactory cilia. At this ciliary base, pericentriolar material (PCM) components, e.g., {gamma}-Tubulin23C, centrosomin, and pericentrin-like protein form an interconnected network required for ciliary maintenance. Adult- and OSN-specific depletions of these proteins, particularly in combination, disrupt accumulation of the heterotrimeric kinesin-2 at the ciliary base and, subsequently, in the shaft, causing loss of ciliary tubulin, EB1, and odorant receptor co-receptor. These dysregulations cause profound loss of ciliary shaft and impair olfactory function/behaviour. The centrosomal kinases PLK1/POLO and Aurora A also work with this PCM network and are required for mature ciliary homeostasis. Remarkably, these defects in ciliary structure, function, and adult olfactory behaviour are reversible, suggesting that this centrosome-derived BB is a dynamic homeostatic epicentre that regulates trafficking and ciliary structural and compositional integrity in vivo. These findings uncover an active, centrosome-dependent, cell-autonomous mechanism for maintaining and repairing mature metazoan cilia in fully grown organs in adulthood and also provide a possible explanation for how deregulation of conserved ciliary base components could lead to progressive, late-onset cilia-related disorders.

cell biology↗

bioRxiv2023

Microtubule decay is a driver of neuronal ageing and a promising target for intervention

Natural ageing is accompanied by a decline in motor, sensory and cognitive functions, all impacting life quality. Ageing is the predominant risk factor for many neurodegenerative diseases, including Parkinsons and Alzheimers disease. We need therefore to gain a better understanding of the cellular and physiological processes underlying age-related neuronal decay. However, gaining this understanding is a slow process due to the long time required to age mammalian or vertebrate model animals. Here we introduce a new cellular model within the Drosophila brain where neurons show typical ageing hallmarks known from the primate brain, including axonal swellings, cytoskeletal decay, a reduction in axonal calibre and morphological changes arising at synaptic terminals. In the fly brain, these changes occur within just a few weeks, ideal to study the underlying mechanisms. We observe that decay of the neuronal microtubule cytoskeleton clearly precedes other ageing hallmarks. We show that the microtubule-binding factors Tau, EB1 and Shot, are necessary for microtubule maintenance in axons and synapses. Their functional loss during ageing triggers microtubule bundle decay followed by the decline in axons and synapses. Genetic manipulations that improve microtubule networks, slow down other neuronal ageing hallmarks and confer aged specimens with the ability to outperform age-matched controls. Our work suggests therefore that microtubule networks are a key lesion site in ageing neurons and offer promising opportunities to improve neuronal decay in advanced age.

neuroscience↗

bioRxiv2020

IFT88 transports Gucy2d, a guanylyl cyclase, to maintain sensory cilia function in Drosophila

Cilia are involved in a plethora of motility and sensory-related functions. Ciliary defects cause several ciliopathies, some of which with late-onset, suggesting cilia are actively maintained. While much is known about cilia assembly, little is understood about the mechanisms of their maintenance. Given that intraflagellar transport (IFT) is essential for cilium assembly, we investigated the role of one of its main players, IFT88, in ciliary maintenance. We show that DmIFT88, the Drosophila melanogaster orthologue of IFT88, continues to move along fully formed sensory cilia, and that its acute knockdown in the ciliated neurons of the adult affects sensory behaviour. We further identify DmGucy2d, the Drosophila guanylyl cyclase 2d, as a DmIFT88 cargo, whose loss also leads to defects in sensory behaviour maintenance. DmIFT88 binds to the intracellular part of DmGucy2d, which is evolutionarily conserved and mutated in several degenerative retina diseases, taking the cyclase into the cilia. Our results offer a novel mechanism for the maintenance of sensory cilia function and its potential role in human diseases.

cell biology↗

bioRxiv2018

Efa6 regulates axon growth, branching and maintenance by eliminating off-track microtubules at the cortex

Cortical collapse factors affect microtubule (MT) dynamics at the plasma membrane. They play important roles in neurons, as suggested by inhibition of axon growth and regeneration through the Arf activator Efa6 in C. elegans, and by neurodevelopmental disorders linked to the mammalian kinesin Kif21A. How cortical collapse factors influence axon growth is little understood. Here we studied them, focussing on the function of Drosophila Efa6 in experimentally and genetically amenable fly neurons. First, we show that Drosophila Efa6 can inhibit MTs directly without interacting molecules via an N-terminal 18 amino acid motif (MT elimination domain/MTED) that binds tubulin and inhibits microtubule growth in vitro and cells. If N-terminal MTED-containing fragments are in the cytoplasm they abolish entire microtubule networks of mouse fibroblasts and whole axons of fly neurons. Full-length Efa6 is membrane-attached, hence primarily blocks MTs in the periphery of fibroblasts, and explorative MTs that have left axonal bundles in neurons. Accordingly, loss of Efa6 causes an increase of explorative MTs: in growth cones, they enhance axon growth, in axon shafts, explorative MTs cause excessive branching, as well as atrophy through perturbations of MT bundles. Efa6 over-expression causes the opposite phenotypes. Taken together, our work conceptually links molecular and sub-cellular functions of cortical collapse factors to axon growth regulation and reveals new roles in axon branching and in the prevention of axonal atrophy. Furthermore, the MTED delivers a promising tool that can be used to inhibit MTs in a compartmentalised fashion when fusing it to specifically localising protein domains.\n\nSummary statementThe cortical collapse factor Efa6 inhibits microtubule polymerising outside axonal bundles. Thereby it limits axon growth and branching, but preserves microtubule bundle organisation crucial for axon maintenance.

cell biology↗