Op-ed in popular media outlets about recent T. ni research
Dr. Kolosov wrote an op-ed describing his research spanning 2018-2020 - start here to understand why we study caterpillar "kidney" and follow links in Latest Publications to peer-reviewed publications to read detailed studies on the subject.
Transcriptomic survey of animal epithelia for novel mechanisms of rapid regulation of epithelial ion transport
Epithelia are tissues of multicellular organisms that specialize in directional transport of ions and water in and out of the animal. Faced with rapid changes in environmental and systemic variables, animals rely on epithelia to mount a rapid response in a timely manner aimed at maintaining homeostasis. Recent work in my research group has identified several novel molecular mechanisms used by epithelia of the insect ‘kidney’ to rapidly adjust their ion transport. These novel molecular mechanisms include the use of voltage-gated, ligand-gated and mechanosensitive ion channels, as well as the gap junctional coupling between epithelial cells. Despite the fact that these molecular components appear to be very important for the function of insect epithelia, there is no consensus on whether these ion channels are expressed in the epithelia of other animals. Projects use transcriptomics (RNAseq) to (i) identify the above-described ion channels expressed in animal epithelia, and (ii) determine which environmental (e.g., salinity) and systemic (e.g., hormone treatment) factors rely on these ion channels to adjust epithelial function. A mix of lab-generated and publicly available transcriptomic data will be used to carry out these projects.
Voltage-gated, ligand-gated and mechanosensitive ion channels regulate ion transport in (non-excitable non-contractile) epithelia of animals
Epithelia are built for unidirectional ion transport. Many epithelia, including Malpighian tubule epithelia of caterpillars are not able to contract and are not innervated. Recent work from our lab demonstrated that Malpighian tubules of caterpillars express voltage-gated, ligand-gated and mechanosensitive ion channels. Subsequent work has shown that this previously unaccounted for molecular machinery is used to regulate ion transport in the Malpighian tubules of caterpillars. Why do Malpighian tubules need to do this? Caterpillars are voracious eaters and many species grow ~1,000-fold within 4-5 weeks. This puts pressure on their kidney to constantly excrete metabolic wastes. Caterpillars have adapted for this by embedding their Malpighian tubules into the rectal complex, which enables them to use ions and water from the diet instead of their haemolymph (blood) to power excretion in their kidney. However, caterpillars eat gargantuan amounts of food, but there are periods when they're not teaching (e.g., moulting). Under these circumstances, they cannot use the dietary ions and water to power their kidney. Instead, they switch to using ions and water from the blood. All evidence to date suggest that voltage-gated, ligand-gated and mechanosensitive ion channels play a role in this ability of the caterpillar Malpighian tubules to switch between using haemolymph ions and dietary ions. Why do they need voltage-gated, ligand-gated and mechanosensitive ion channels to do this? Because this switchover takes place within minutes! This enables the caterpillar to keep its excretory function unperturbed in the face of changing dietary ion availability. Subsequent studies of divergent terrestrial and aquatic animals uncovered expression of many voltage-gated, ligand-gated and mechanosensitive ion channels in their epithelia underscoring the importance of this understudied molecular machinery in the regulation of epithelial function.
Gap junctions in ion-transporting epithelia of animals
This series of studies is focussed on establishing the role of gap junctions in vectorial ion transport in vertebrate and invertebrate epithelia. Click on the link below to read an article describing our recent discovery of how gap junctions enable ion transport in the Malpighian tubules of insects.
Ion transport mechanisms in the Malpighian tubules of the larval lepidopterans (caterpillars)
Several studies aimed at determining the molecular machinery of ion transport in the Malpighian tubules of T. ni. We are aiming our studies at understanding how the paradoxical reabsorption of cations is enabled through the secondary cells of T. ni. Additionally, of special interests is the segmented nature of the Malpighian tubule of larval lepidopterans and its ability to change between ion secretion and reabsorption depending on the hydro mineral status of the animal.