Microtubule Acetylation Is Required for Mechanosensation in Drosophila

At the cellular level, α-tubulin acetylation alters the structure of microtubules to render them mechanically resistant to compressive forces. How this biochemical property of microtubule acetylation relates to mechanosensation remains unknown, although prior studies have shown that microtubule acetylation influences touch perception. Here, we identify the major Drosophila α-tubulin acetylase (dTAT) and show that it plays key roles in several forms of mechanosensation. dTAT is highly expressed in the larval peripheral nervous system (PNS), but it is largely dispensable for neuronal morphogenesis. Mutation of the acetylase gene or the K40 acetylation site in α-tubulin impairs mechanical sensitivity in sensory neurons and behavioral responses to gentle touch, harsh touch, gravity, and vibration stimuli, but not noxious thermal stimulus. Finally, we show that dTAT is required for mechanically induced activation of NOMPC, a microtubule-associated transient receptor potential channel, and functions to maintain integrity of the microtubule cytoskeleton in response to mechanical stimulation. Yan et al. identify the major microtubule acetylase in Drosophila and show that the enzyme and microtubule acetylation broadly control mechanosensation, but not other sensory modalities. Acetylation is required for mechanosensation by the TRP channel NOMPC, and possibly other channels, by virtue of its effects on microtubule mechanical stability and/or dynamics

Conserved Tao Kinase Activity Regulates Dendritic Arborization, Cytoskeletal Dynamics, and Sensory Function in Drosophila.

Dendritic arborization is highly regulated and requires tight control of dendritic growth, branching, cytoskeletal dynamics, and ion channel expression to ensure proper function. Abnormal dendritic development can result in altered network connectivity, which has been linked to neurodevelopmental disorders, including autism spectrum disorders (ASDs). How neuronal growth control programs tune dendritic arborization to ensure function is still not fully understood. Using Drosophila dendritic arborization (da) neurons as a model, we identified the conserved Ste20-like kinase Tao as a negative regulator of dendritic arborization. We show that Tao kinase activity regulates cytoskeletal dynamics and sensory channel localization required for proper sensory function in both male and female flies. We further provide evidence for functional conservation of Tao kinase, showing that its ASD-linked human ortholog, Tao kinase 2 (Taok2), could replace Drosophila Tao and rescue dendritic branching, dynamic microtubule alterations, and behavioral defects. However, several ASD-linked Taok2 variants displayed impaired rescue activity, suggesting that Tao/Taok2 mutations can disrupt sensory neuron development and function. Consistently, we show that Tao kinase activity is required in developing and as well as adult stages for maintaining normal dendritic arborization and sensory function to regulate escape and social behavior. Our data suggest an important role for Tao kinase signaling in cytoskeletal organization to maintain proper dendritic arborization and sensory function, providing a strong link between developmental sensory aberrations and behavioral abnormalities relevant for Taok2-dependent ASDs.SIGNIFICANCE STATEMENT Autism spectrum disorders (ASDs) are linked to abnormal dendritic arbors. However, the mechanisms of how dendritic arbors develop to promote functional and proper behavior are unclear. We identified Drosophila Tao kinase, the ortholog of the ASD risk gene Taok2, as a regulator of dendritic arborization in sensory neurons. We show that Tao kinase regulates cytoskeletal dynamics, controls sensory ion channel localization, and is required to maintain somatosensory function in vivo Interestingly, ASD-linked human Taok2 mutations rendered it nonfunctional, whereas its WT form could restore neuronal morphology and function in Drosophila lacking endogenous Tao. Our findings provide evidence for a conserved role of Tao kinase in dendritic development and function of sensory neurons, suggesting that aberrant sensory function might be a common feature of ASDs

Worldwide large-scale fluctuations of sardine and anchovy populations

Decade-scale regimes of sardine #Sardinops sagax and anchovy #Engraulis spp. have been observed in the productive coastal waters of the North-Western, North-Eastern and South-Eastern Pacific and the South-Eastern Atlantic. In each of these systems, the two genera fluctuate out of phase with each other. The subdominant genus may initiate a recovery while the other species is still abundant, so population growth is not necessarily a response to a vacant niche. Rather, it appears to be triggered by formation of one or a few powerful year-classes. At high population levels, quality of sardine and their eggs decreased in Japan, leading to decreased production and survival of eggs, poor year-classes and stock collapse. Excessive fishing of strong year-classes early in the recovery stage may prevent a species from assuming dominance, so influencing the natural succession of species. This may greatly alter the structure and functioning of an ecosystem. For example, a mesopelagic forage fish may replace an epipelagic one, with severe repercussions for predators that can only feed in the upper ocean, e.g. some seabirds. Biological factors also may influence the succession of forage fish. For example, off California, peaks in abundance of predatory species such as bonita #Sarda, and chub mackerel #Scomber separate those of the planktivorous sardine and anchovy. In the Pacific Ocean, sardine distribution has changed greatly. Compared with its range when scarce, a population at a high level of biomass can extend 1 000-1 800 miles farther along the coast and 400-2 200 miles farther out to sea. In different periods of high biomass, sardine did not always have the same distribution. In the 1930s and 1940s, near simultaneous fluctuations of sardine in the North-Western and North-Eastern Pacific were in phase. In the 1980s and 1990s, sardine in the North-Western and South-Eastern Pacific were fluctuating in phase... (D'après résumé d'auteur