International Union of Pharmacology. XLIII. Compendium of Voltage-Gated Ion Channels: Transient Receptor Potential Channels

MCOLN1/TRPML1 in the lysosome: a promising target for autophagy modulation in diverse diseases

MCOLN1/TRPML1 is a nonselective cationic channel specifically localized to the late endosome and lysosome. With its property of mediating the release of several divalent cations such as Ca2+, Zn2+ and Fe2+ from the lysosome to the cytosol, MCOLN1 plays a pivotal role in regulating a variety of cellular events including endocytosis, exocytosis, lysosomal biogenesis, lysosome reformation, and especially in Macroautophagy/autophagy. Autophagy is a highly conserved catabolic process that maintains cytoplasmic integrity by removing superfluous proteins and damaged organelles. Acting as the terminal compartments, lysosomes are crucial for the completion of the autophagy process. This review delves into the emerging role of MCOLN1 in controlling the autophagic process by regulating lysosomal ionic homeostasis, thereby governing the fundamental functions of lysosomes. Furthermore, this review summarizes the physiological relevance as well as molecular mechanisms through which MCOLN1 orchestrates autophagy, consequently influencing mitochondria turnover, cell apoptosis and migration. In addition, we have illustrated the implications of MCOLN1-regulated autophagy in the pathological process of cancer and myocardial ischemia-reperfusion (I/R) injury. In summary, given the involvement of MCOLN1-mediated autophagy in the pathogenesis of cancer and myocardial I/R injury, targeting MCOLN1 May provide clues for developing new therapeutic strategies for the treatment of these diseases. Exploring the regulation of MCOLN1-mediated autophagy in diverse diseases contexts will surely broaden our understanding of this pathway and offer its potential as a promising drug target.Abbreviation: CCCP:carbonyl cyanide3-chlorophenylhydrazone; CQ:chloroquine; HCQ: hydroxychloroquine;I/R: ischemia-reperfusion; MAP1LC3/LC3:microtubule associated protein 1 light chain 3; MCOLN1/TRPML1:mucolipin TRP cation channel 1; MLIV: mucolipidosis type IV; MTORC1:MTOR complex 1; ROS: reactive oxygenspecies; SQSTM1/p62: sequestosome 1.

Calcium and Neural Stem Cell Proliferation

Intracellular calcium plays a pivotal role in central nervous system (CNS) development by regulating various processes such as cell proliferation, migration, differentiation, and maturation. However, understanding the involvement of calcium (Ca2+) in these processes during CNS development is challenging due to the dynamic nature of this cation and the evolving cell populations during development. While Ca2+ transient patterns have been observed in specific cell processes and molecules responsible for Ca2+ homeostasis have been identified in excitable and non-excitable cells, further research into Ca2+ dynamics and the underlying mechanisms in neural stem cells (NSCs) is required. This review focuses on molecules involved in Ca2+ entrance expressed in NSCs in vivo and in vitro, which are crucial for Ca2+ dynamics and signaling. It also discusses how these molecules might play a key role in balancing cell proliferation for self-renewal or promoting differentiation. These processes are finely regulated in a time-dependent manner throughout brain development, influenced by extrinsic and intrinsic factors that directly or indirectly modulate Ca2+ dynamics. Furthermore, this review addresses the potential implications of understanding Ca2+ dynamics in NSCs for treating neurological disorders. Despite significant progress in this field, unraveling the elements contributing to Ca2+ intracellular dynamics in cell proliferation remains a challenging puzzle that requires further investigation.

TRPM channels in health and disease

Different cell channels and transporters tightly regulate cytoplasmic levels and the intraorganelle distribution of cations. Perturbations in these processes lead to human diseases that are frequently associated with kidney impairment. The family of melastatin-related transient receptor potential (TRPM) channels, which has eight members in mammals (TRPM1-TRPM8), includes ion channels that are highly permeable to divalent cations, such as Ca2+, Mg2+ and Zn2+ (TRPM1, TRPM3, TRPM6 and TRPM7), non-selective cation channels (TRPM2 and TRPM8) and monovalent cation-selective channels (TRPM4 and TRPM5). Three family members contain an enzymatic protein moiety: TRPM6 and TRPM7 are fused to α-kinase domains, whereas TRPM2 is linked to an ADP-ribose-binding NUDT9 homology domain. TRPM channels also function as crucial cellular sensors involved in many physiological processes, including mineral homeostasis, blood pressure, cardiac rhythm and immunity, as well as photoreception, taste reception and thermoreception. TRPM channels are abundantly expressed in the kidney. Mutations in TRPM genes cause several inherited human diseases, and preclinical studies in animal models of human disease have highlighted TRPM channels as promising new therapeutic targets. Here, we provide an overview of this rapidly evolving research area and delineate the emerging role of TRPM channels in kidney pathophysiology.

Functional Analysis of TRPA1, TRPM3, and TRPV1 Channels in Human Dermal Arteries and Their Role in Vascular Modulation

Transient receptor potential (TRP) channels are pivotal in modulating vascular functions. In fact, topical application of cinnamaldehyde or capsaicin (TRPA1 and TRPV1 channel agonists, respectively) induces "local" changes in blood flow by releasing vasodilator neuropeptides. We investigated TRP channels' contributions and the pharmacological mechanisms driving vasodilation in human isolated dermal arteries. Ex vivo studies assessed the vascular function of artery segments and analyzed the effects of different compounds. Concentration-response curves to cinnamaldehyde, pregnenolone sulfate (PregS, TRPM3 agonist), and capsaicin were constructed to evaluate the effect of the antagonists HC030031 (TRPA1); isosakuranetin (TRPM3); and capsazepine (TRPV1). Additionally, the antagonists/inhibitors olcegepant (CGRP receptor); L-NAME (nitric oxide synthase); indomethacin (cyclooxygenase); TRAM-34 plus apamin (K+ channels); and MK-801 (NMDA receptors, only for PregS) were used. Moreover, CGRP release was assessed in the organ bath fluid post-agonist-exposure. In dermal arteries, cinnamaldehyde- and capsaicin-induced relaxation remained unchanged after the aforementioned antagonists, while PregS-induced relaxation was significantly inhibited by isosakuranetin, L-NAME and MK-801. Furthermore, there was a significant increase in CGRP levels post-agonist-exposure. In our experimental model, TRPA1 and TRPV1 channels seem not to be involved in cinnamaldehyde- or capsaicin-induced relaxation, respectively, whereas TRPM3 channels contribute to PregS-induced relaxation, possibly via CGRP-independent mechanisms.

The Role of TRPM7 in Oncogenesis

This review summarizes the current understanding of the role of transient receptor potential melastatin-subfamily member 7 (TRPM7) channels in the pathophysiology of neoplastic diseases. The TRPM family represents the largest and most diverse group in the TRP superfamily. Its subtypes are expressed in virtually all human organs playing a central role in (patho)physiological events. The TRPM7 protein (along with TRPM2 and TRPM6) is unique in that it has kinase activity in addition to the channel function. Numerous studies demonstrate the role of TRPM7 chanzyme in tumorigenesis and in other tumor hallmarks such as proliferation, migration, invasion and metastasis. Here we provide an up-to-date overview about the possible role of TRMP7 in a broad range of malignancies such as tumors of the nervous system, head and neck cancers, malignant neoplasms of the upper gastrointestinal tract, colorectal carcinoma, lung cancer, neoplasms of the urinary system, breast cancer, malignant tumors of the female reproductive organs, prostate cancer and other neoplastic pathologies. Experimental data show that the increased expression and/or function of TRPM7 are observed in most malignant tumor types. Thus, TRPM7 chanzyme may be a promising target in tumor therapy.

TRPA1: A promising target for pulmonary fibrosis?

Pulmonary fibrosis is a disease characterized by progressive scar formation and the ultimate manifestation of numerous lung diseases. It is known as "cancer that is not cancer" and has attracted widespread attention. However, its formation process is very complex, and the mechanism of occurrence has not been fully elucidated. Current research has found that TRPA1 may be a promising target in the pathogenesis of pulmonary fibrosis. The TRPA1 channel was first successfully isolated in human lung fibroblasts, and it was found to have a relatively concentrated distribution in the lungs and respiratory tract. It is also involved in various acute and chronic inflammatory processes of lung diseases and may even play a core role in the progression and/or prevention of pulmonary fibrosis. Natural ligands targeting TRPA1 could offer a promising alternative treatment for pulmonary diseases. Therefore, this review delves into the current understanding of pulmonary fibrogenesis, analyzes TRPA1 biological properties and regulation of lung disease with a focus on pulmonary fibrosis, summarizes the TRPA1 molecular structure and its biological function, and summarizes TRPA1 natural ligand sources, anti-pulmonary fibrosis activity and potential mechanisms. The aim is to decipher the exact role of TRPA1 channels in the pathophysiology of pulmonary fibrosis and to consider their potential in the development of new therapeutic strategies.

Temperature modulates PVN pre-sympathetic neurones via transient receptor potential ion channels

The paraventricular nucleus (PVN) of the hypothalamus plays a vital role in maintaining homeostasis and modulates cardiovascular function via autonomic pre-sympathetic neurones. We have previously shown that coupling between transient receptor potential cation channel subfamily V Member 4 (Trpv4) and small-conductance calcium-activated potassium channels (SK) in the PVN facilitate osmosensing, but since TRP channels are also thermosensitive, in this report we investigated the temperature sensitivity of these neurones. Methods: TRP channel mRNA was quantified from mouse PVN with RT-PCR and thermosensitivity of Trpv4-like PVN neuronal ion channels characterised with cell-attached patch-clamp electrophysiology. Following recovery of temperature-sensitive single-channel kinetic schema, we constructed a predictive stochastic mathematical model of these neurones and validated this with electrophysiological recordings of action current frequency. Results: 7 thermosensitive TRP channel genes were found in PVN punches. Trpv4 was the most abundant of these and was identified at the single channel level on PVN neurones. We investigated the thermosensitivity of these Trpv4-like channels; open probability (Po) markedly decreased when temperature was decreased, mediated by a decrease in mean open dwell times. Our neuronal model predicted that PVN spontaneous action current frequency (ACf) would increase as temperature is decreased and in our electrophysiological experiments, we found that ACf from PVN neurones was significantly higher at lower temperatures. The broad-spectrum channel blocker gadolinium (100 µM), was used to block the warm-activated, Ca2+-permeable Trpv4 channels. In the presence of gadolinium (100 µM), the temperature effect was largely retained. Using econazole (10 µM), a blocker of Trpm2, we found there were significant increases in overall ACf and the temperature effect was inhibited. Conclusion: Trpv4, the abundantly transcribed thermosensitive TRP channel gene in the PVN appears to contribute to intrinsic thermosensitive properties of PVN neurones. At physiological temperatures (37°C), we observed relatively low ACf primarily due to the activity of Trpm2 channels, whereas at room temperature, where most of the previous characterisation of PVN neuronal activity has been performed, ACf is much higher, and appears to be predominately due to reduced Trpv4 activity. This work gives insight into the fundamental mechanisms by which the body decodes temperature signals and maintains homeostasis.

Resiniferatoxin: Nature's Precision Medicine to Silence TRPV1-Positive Afferents

Resiniferatoxin (RTX) is an ultrapotent capsaicin analog with a unique spectrum of pharmacological actions. The therapeutic window of RTX is broad, allowing for the full desensitization of pain perception and neurogenic inflammation without causing unacceptable side effects. Intravesical RTX was shown to restore continence in a subset of patients with idiopathic and neurogenic detrusor overactivity. RTX can also ablate sensory neurons as a "molecular scalpel" to achieve permanent analgesia. This targeted (intrathecal or epidural) RTX therapy holds great promise in cancer pain management. Intra-articular RTX is undergoing clinical trials to treat moderate-to-severe knee pain in patients with osteoarthritis. Similar targeted approaches may be useful in the management of post-operative pain or pain associated with severe burn injuries. The current state of this field is reviewed, from preclinical studies through veterinary medicine to clinical trials.

Functional nanoparticle-enabled non-genetic neuromodulation

Stimulating ion channels targeting in neuromodulation by external signals with the help of functionalized nanoparticles, which integrates the pioneering achievements in the fields of neurosciences and nanomaterials, has involved into a novel interdisciplinary field. The emerging technique developed in this field enable simple, remote, non-invasive, and spatiotemporally precise nerve regulations and disease therapeutics, beyond traditional treatment methods. In this paper, we define this emerging field as nano-neuromodulation and summarize the most recent developments of non-genetic nano-neuromodulation (non-genetic NNM) over the past decade based on the innovative design concepts of neuromodulation nanoparticle systems. These nanosystems, which feature diverse compositions, structures and synthesis approaches, could absorb certain exogenous stimuli like light, sound, electric or magnetic signals, and subsequently mediate mutual transformations between above signals, or chemical reactions, to regulate stimuli-sensitive ion channels and ion migrations which play vital roles in the nervous system. We will also discuss the obstacles and challenges in the future development of non-genetic NNM, and propose its future developments, to add the further progress of this promising field.

Functional nanoparticle-enabled non-genetic neuromodulation

Stimulating ion channels targeting in neuromodulation by external signals with the help of functionalized nanoparticles, which integrates the pioneering achievements in the fields of neurosciences and nanomaterials, has involved into a novel interdisciplinary field. The emerging technique developed in this field enable simple, remote, non-invasive, and spatiotemporally precise nerve regulations and disease therapeutics, beyond traditional treatment methods. In this paper, we define this emerging field as nano-neuromodulation and summarize the most recent developments of non-genetic nano-neuromodulation (non-genetic NNM) over the past decade based on the innovative design concepts of neuromodulation nanoparticle systems. These nanosystems, which feature diverse compositions, structures and synthesis approaches, could absorb certain exogenous stimuli like light, sound, electric or magnetic signals, and subsequently mediate mutual transformations between above signals, or chemical reactions, to regulate stimuli-sensitive ion channels and ion migrations which play vital roles in the nervous system. We will also discuss the obstacles and challenges in the future development of non-genetic NNM, and propose its future developments, to add the further progress of this promising field.

Graphical Abstract

TRP (transient receptor potential) ion channel family: structures, biological functions and therapeutic interventions for diseases

Transient receptor potential (TRP) channels are sensors for a variety of cellular and environmental signals. Mammals express a total of 28 different TRP channel proteins, which can be divided into seven subfamilies based on amino acid sequence homology: TRPA (Ankyrin), TRPC (Canonical), TRPM (Melastatin), TRPML (Mucolipin), TRPN (NO-mechano-potential, NOMP), TRPP (Polycystin), TRPV (Vanilloid). They are a class of ion channels found in numerous tissues and cell types and are permeable to a wide range of cations such as Ca²⁺, Mg²⁺, Na⁺, K⁺, and others. TRP channels are responsible for various sensory responses including heat, cold, pain, stress, vision and taste and can be activated by a number of stimuli. Their predominantly location on the cell surface, their interaction with numerous physiological signaling pathways, and the unique crystal structure of TRP channels make TRPs attractive drug targets and implicate them in the treatment of a wide range of diseases. Here, we review the history of TRP channel discovery, summarize the structures and functions of the TRP ion channel family, and highlight the current understanding of the role of TRP channels in the pathogenesis of human disease. Most importantly, we describe TRP channel-related drug discovery, therapeutic interventions for diseases and the limitations of targeting TRP channels in potential clinical applications.

"ThermoTRP" Channel Expression in Cancers: Implications for Diagnosis and Prognosis (Practical Approach by a Pathologist)

Temperature-sensitive transient receptor potential (TRP) channels (so-called "thermoTRPs") are multifunctional signaling molecules with important roles in cell growth and differentiation. Several "thermoTRP" channels show altered expression in cancers, though it is unclear if this is a cause or consequence of the disease. Regardless of the underlying pathology, this altered expression may potentially be used for cancer diagnosis and prognostication. "ThermoTRP" expression may distinguish between benign and malignant lesions. For example, TRPV1 is expressed in benign gastric mucosa, but is absent in gastric adenocarcinoma. TRPV1 is also expressed both in normal urothelia and non-invasive papillary urothelial carcinoma, but no TRPV1 expression has been seen in invasive urothelial carcinoma. "ThermoTRP" expression can also be used to predict clinical outcomes. For instance, in prostate cancer, TRPM8 expression predicts aggressive behavior with early metastatic disease. Furthermore, TRPV1 expression can dissect a subset of pulmonary adenocarcinoma patients with bad prognosis and resistance to a number of commonly used chemotherapeutic agents. This review will explore the current state of this rapidly evolving field with special emphasis on immunostains that can already be added to the armoire of diagnostic pathologists.

Thermal stress involved in TRPV2 promotes tumorigenesis through the pathways of HSP70/27 and PI3K/Akt/mTOR in esophageal squamous cell carcinoma

BACKGROUND

The transient receptor potential vanilloid receptor 2 (TRPV2) has been found to participate in the pathogenesis of various types of cancers, however, its role(s) in the tumorigenesis of ESCC remain poorly understood.

METHODS

Western blotting and immunohistochemistry were performed to determine the expression profiles of TRPV2 in the ESCC patient tissues. A series of in vitro and in vivo experiments were conducted to reveal the role of TRPV2 in the tumorigenesis of ESCC.

RESULTS

Our study first uncovered that the activation of TRPV2 by recurrent acute thermal stress (54 °C) or O1821 (20 μM) promoted cancerous behaviours in ESCC cells. The pro-angiogenic capacity of the ESCC cells was found to be enhanced profoundly and both tumour formation and metastasis that originated from the cells were substantially promoted in nude mouse models upon the activation of TRPV2. These effects were inhibited significantly by tranilast (120 μM) and abolished by TRPV2 knockout. Conversely, overexpression of TRPV2 could switch the cells to tumorigenesis upon activation of TRPV2. Mechanistically, the driving role of TRPV2 in the progression of ESCC is mainly regulated by the HSP70/27 and PI3K/Akt/mTOR signalling pathways.

CONCLUSIONS

We revealed that TRPV2-PI3K/Akt/mTOR is a novel and promising target for the prevention and treatment of ESCC.

Transient Receptor Potential (TRP) and Thermoregulation in Animals: Structural Biology and Neurophysiological Aspects

This review presents and analyzes recent scientific findings on the structure, physiology, and neurotransmission mechanisms of transient receptor potential (TRP) and their function in the thermoregulation of mammals. The aim is to better understand the functionality of these receptors and their role in maintaining the temperature of animals, or those susceptible to thermal stress. The majority of peripheral receptors are TRP cation channels formed from transmembrane proteins that function as transductors through changes in the membrane potential. TRP are classified into seven families and two groups. The data gathered for this review include controversial aspects because we do not fully know the mechanisms that operate the opening and closing of the TRP gates. Deductions, however, suggest the intervention of mechanisms related to G protein-coupled receptors, dephosphorylation, and ligands. Several questions emerge from the review as well. For example, the future uses of these data for controlling thermoregulatory disorders and the invitation to researchers to conduct more extensive studies to broaden our understanding of these mechanisms and achieve substantial advances in controlling fever, hyperthermia, and hypothermia.

Endothelial TRPV4 channels in lung edema and injury

The alveolo-capillary barrier is relatively impermeable, and facilitates gas exchange via the large alveolar surface in the lung. Disruption of alveolo-capillary barrier leads to accumulation of edema fluid in lung injury. Studies in animal models of various forms of lung injury provide evidence that TRPV4 channels play a critical role in disruption of the alveolo-capillary barrier and pathogenesis of lung injury. TRPV4 channels from capillary endothelial cells, alveolar epithelial cells, and immune cells have been implicated in the pathogenesis of lung injury. Recent studies in endothelium-specific TRPV4 knockout mice point to a central role for endothelial TRPV4 channels in lung injury. In this chapter, we review the findings on the pathological roles of endothelial TRPV4 channels in different forms of lung injury and future directions for further investigation.

S100A4 plays a key role in TRPV3 ion channel expression and its electrophysiological function

Transient receptor potential vanilloid 3 (TRPV3), a non-selective cation ion channel, is regulated by small molecules such as Ca²⁺ and calmodulin (CaM). Together with S100A4 (S100 calcium-binding protein family), is critical in cell proliferation and progression. Although TRPV3 has been proved to play a role in Ca²⁺ regulation and participate in Ca²⁺-related cellular processes, its molecular mechanism remains unclear. In this study, we found that TRPV3 and S100A4 were co-expressed in the same region of the cell, and surprisingly, the protein expression level of TRPV3 significantly increased with the overexpression of S100A4. Moreover, co-immunoprecipitation results showed that these two proteins could bind with each other. Functionally, we found that when S100A4 was simultaneously expressed in cells, more Ca²⁺ would be transferred into the cells through the TRPV3 ion channel. Consistent with Ca²⁺ regulation results, electrophysiological recordings demonstrated that S100A4 improved the function of TRPV3 in ions' flux, suggesting that the S100A4 could bind with TRPV3 and simultaneously promoted its expression, thus affecting its functions on related ions' flux. Our findings identified the link between S100A4 and TRPV3 and provided a novel molecular mechanism for TRPV3 regulation.

Gene expression profiles of transient receptor potential (TRP) channels in the peripheral blood mononuclear cells of psoriasis patients

Psoriasis is a chronic autoimmune disease in which peripheral blood mononuclear cells (PBMCs) are involved in the pathological process. Transient receptor potential (TRP) channels expressed in immune cells have been shown to be associated with inflammatory diseases. We aimed to evaluate mRNA expression levels of TRP channels in PBMCs of patients with psoriasis. 30 patients with plaque psoriasis and 30 healthy age- and gender-matched control subjects were included in this study. mRNA expression levels of TRP channels in psoriasis patients were determined by Real-time polymerase chain reaction. A decreased TRPM4, TRPM7, TRPV3, TRPV4, and TRPC6 genes expression levels were found in the patient group compared to controls, respectively (p = 0.045, p = 0.000, p = 0.000, p = 0.045, p = 0.009), whereas, an increased expression level was found in TRPM2 and TRPV1 genes in the patient group compared to controls (p = 0.001 and p = 0.028). This is the first study showing the TRP channel mRNA expressions in PBMCs of psoriasis patients. Different expression patterns of TRP channels may have a role in pathogenesis of psoriasis.

TRPV1 is crucial for thermal homeostasis in the mouse by heat loss behaviors under warm ambient temperature

Thermal homeostasis in mammalians is a self-regulating process by which biological systems maintain an internal thermal stability, even under different temperature conditions; however, the molecular mechanisms involved under warm ambient temperature remain unclear. Here, we aimed to clarify functional significance of transient receptor potential vanilloid receptor 1 (TRPV1) under warm ambient temperature. TRPV1 KO mice exhibited transient hyperthermia when exposed to 30.0 and 32.5 °C, whereas wild-type (WT) mice did not. TRPV1 KO mice exhibited prolonged and prominent hyperthermia upon exposure to 35.0 °C, whereas WT mice showed transient hyperthermia. Hyperthermia also occurs in WT mice that received intracerebroventricular injection of TRPV1 antagonist AMG9810 upon exposure to 35.0 °C. Heat loss behaviors, sleeping and body licking, were deficient in TRPV1 KO mice exposed to warm temperatures. Therefore, the present results indicate that central TRPV1 is crucial for maintaining a constant body temperature via the initiation of heat loss behaviors under warm ambient temperature.

Transient receptor potential cation channel subfamily V and breast cancer

Transient receptor potential cation channel subfamily V (TRPV) channels play important roles in a variety of cellular processes. One example includes the sensory role of TRPV1 that is sensitive to elevated temperatures and acidic environments and is activated by the hot pepper component capsaicin. Another example is the importance of the highly Ca²⁺ selective channels TRPV5 and TRPV6 in Ca²⁺ absorption/reabsorption in the intestine and kidney. However, in some cases such as TRPV4 and TRPV6, breast cancer cells appear to overexpress TRPV channels. Moreover, TRPV mediated Ca²⁺ influx may contribute to enhanced breast cancer cell proliferation and other processes important in tumor progression such as angiogenesis. It appears that the overexpression of some TRPV channels in breast cancer and/or their involvement in breast cancer cell processes, processes important in the tumor microenvironment or pain may make some TRPV channels potential targets for breast cancer therapy. In this review, we provide an overview of TRPV expression in breast cancer subtypes, the roles of TRPV channels in various aspects of breast cancer progression and consider implications for future therapeutic approaches.

Endothelial TRPV4 channels and vasodilator reactivity

Transient receptor potential vanilloid 4 (TRPV4) ion channels on the endothelial cell membrane are widely regarded as a crucial Ca²⁺ influx pathway that promotes endothelium-dependent vasodilation. The downstream vasodilatory targets of endothelial TRPV4 channels vary among different vascular beds, potentially contributing to endothelial cell heterogeneity. Although numerous studies have examined the role of endothelial TRPV4 channels using specific pharmacological tools over the past decade, their physiological significance remains unclear, mainly due to a lack of endothelium-specific knockouts. Moreover, the loss of endothelium-dependent vasodilation is a significant contributor to vascular dysfunction in cardiovascular disease. The activity of endothelial TRPV4 channels is impaired in cardiovascular disease; therefore, strategies targeting the mechanisms that reduce endothelial TRPV4 channel activity may restore vascular function and provide therapeutic benefit. In this chapter, we discuss endothelial TRPV4 channel-dependent signaling mechanisms, the heterogeneity in endogenous activators and targets of endothelial TRPV4 channels, and the role of endothelial TRPV4 channels in the pathogenesis of cardiovascular diseases. We also discuss potentially interesting future research directions that may provide novel insights into the physiological and pathological roles of endothelial TRPV4 channels.

What's Bred in the Bone: Calcium Channels in Lymphocytes

Calcium (Ca²⁺) is an important second messenger in lymphocytes and is essential in regulating various intracellular pathways that control critical cell functions. Ca²⁺ channels are located in the plasma membrane and intracellular membranes, facilitating Ca²⁺ entry into the cytoplasm. Upon Ag receptor stimulation, Ca²⁺ can enter the lymphocyte via the Ca²⁺ release-activated Ca²⁺ channel found in the plasma membrane. The increase of cytosolic Ca²⁺ modulates signaling pathways, resulting in the transcription of target genes implicated in differentiation, activation, proliferation, survival, and apoptosis of lymphocytes. Along with Ca²⁺ release-activated Ca²⁺ channels, several other channels have been found in the membranes of T and B lymphocytes contributing to key cellular events. Among them are the transient receptor potential channels, the P2X receptors, voltage-dependent Ca²⁺ channels, and the inositol 1,4,5-trisphosphate receptor as well as the N-methyl-d-aspartate receptors. In this article, we review the contributions of these channels to mediating Ca²⁺ currents that drive specific lymphocyte functions.

Trpc5 deficiency causes hypoprolactinemia and altered function of oscillatory dopamine neurons in the arcuate nucleus

Dopamine neurons of the hypothalamic arcuate nucleus (ARC) tonically inhibit the release of the protein hormone prolactin from lactotropic cells in the anterior pituitary gland and thus play a central role in prolactin homeostasis of the body. Prolactin, in turn, orchestrates numerous important biological functions such as maternal behavior, reproduction, and sexual arousal. Here, we identify the canonical transient receptor potential channel Trpc5 as an essential requirement for normal function of dopamine ARC neurons and prolactin homeostasis. By analyzing female mice carrying targeted mutations in the Trpc5 gene including a conditional Trpc5 deletion, we show that Trpc5 is required for maintaining highly stereotyped infraslow membrane potential oscillations of dopamine ARC neurons. Trpc5 is also required for eliciting prolactin-evoked tonic plateau potentials in these neurons that are part of a regulatory feedback circuit. Trpc5 mutant females show severe prolactin deficiency or hypoprolactinemia that is associated with irregular reproductive cyclicity, gonadotropin imbalance, and impaired reproductive capabilities. These results reveal a previously unknown role for the cation channel Trpc5 in prolactin homeostasis of female mice and provide strategies to explore the genetic basis of reproductive disorders and other malfunctions associated with defective prolactin regulation in humans.

Transient Receptor Potential Channels and Endothelial Cell Calcium Signaling

The vascular endothelium is a broadly distributed and highly specialized organ. The endothelium has a number of functions including the control of blood vessels diameter through the production and release of potent vasoactive substances or direct electrical communication with underlying smooth muscle cells, regulates the permeability of the vascular barrier, stimulates the formation of new blood vessels, and influences inflammatory and thrombotic processes. Endothelial cells that make up the endothelium express a variety of cell-surface receptors and ion channels on the plasma membrane that are capable of detecting circulating hormones, neurotransmitters, oxygen tension, and shear stress across the vascular wall. Changes in these stimuli activate signaling cascades that initiate an appropriate physiological response. Increases in the global intracellular Ca²⁺ concentration and localized Ca²⁺ signals that occur within specialized subcellular microdomains are fundamentally important components of many signaling pathways in the endothelium. The transient receptor potential (TRP) channels are a superfamily of cation-permeable ion channels that act as a primary means of increasing cytosolic Ca²⁺ in endothelial cells. Consequently, TRP channels are vitally important for the major functions of the endothelium. In this review, we provide an in-depth discussion of Ca²⁺ -permeable TRP channels in the endothelium and their role in vascular regulation. © 2019 American Physiological Society. Compr Physiol 9:1249-1277, 2019.

Emerging Diversity in Lipid-Protein Interactions

Membrane lipids interact with proteins in a variety of ways, ranging from providing a stable membrane environment for proteins to being embedded in to detailed roles in complicated and well-regulated protein functions. Experimental and computational advances are converging in a rapidly expanding research area of lipid-protein interactions. Experimentally, the database of high-resolution membrane protein structures is growing, as are capabilities to identify the complex lipid composition of different membranes, to probe the challenging time and length scales of lipid-protein interactions, and to link lipid-protein interactions to protein function in a variety of proteins. Computationally, more accurate membrane models and more powerful computers now enable a detailed look at lipid-protein interactions and increasing overlap with experimental observations for validation and joint interpretation of simulation and experiment. Here we review papers that use computational approaches to study detailed lipid-protein interactions, together with brief experimental and physiological contexts, aiming at comprehensive coverage of simulation papers in the last five years. Overall, a complex picture of lipid-protein interactions emerges, through a range of mechanisms including modulation of the physical properties of the lipid environment, detailed chemical interactions between lipids and proteins, and key functional roles of very specific lipids binding to well-defined binding sites on proteins. Computationally, despite important limitations, molecular dynamics simulations with current computer power and theoretical models are now in an excellent position to answer detailed questions about lipid-protein interactions.

Recurrent activations of transient receptor potential vanilloid-1 and vanilloid-4 promote cellular proliferation and migration in esophageal squamous cell carcinoma cells

Some members of the transient receptor potential vanilloid (TRPV) subfamily of cation channels are thermosensitive. Earlier studies have revealed the distribution and functions of these thermo‐TRPVs (TRPV1–4) in various organs, but their expression and function in the human esophagus are not fully understood. Here, we probed for the expression of the thermo‐TRPVs in one nontumor human esophageal squamous cell line and two esophageal squamous cell carcinoma (ESCC) cell lines. TRPV1, TRPV2, and TRPV4 proteins were found to be upregulated in ESCC cells, while TRPV3 was not detectable in any of these cell lines. Subsequently, channel function was evaluated via monitoring of Ca²⁺ transients by Ca²⁺ imaging and nonselective cation channel currents were recorded by whole‐cell patch clamp. We found that TRPV4 was activated by heat at 28 °C–35 °C, whereas TRPV1 and TRPV2 were activated by higher, noxious temperatures (44 °C and 53 °C, respectively). Furthermore, TRPV1 was activated by capsaicin (EC₅₀ = 20.32 μm), and this effect was antagonized by AMG9810; TRPV2 was activated by a newly developed cannabinoid compound, O1821, and inhibited by tranilast. In addition, TRPV4 was activated by hypotonic solutions (220 m Osm), and this effect was abolished by ruthenium red. The effects of TRPV1 and TRPV4 on ESCC were also explored. Our data, for the first time, showed that the overactivation of TRPV1 and TRPV4 promoted the proliferation and/or migration of ESCC cells. In summary, TRPV1, TRPV2, and TRPV4 were functionally expressed in human esophageal squamous cells, and thermo‐TRPVs might play an important role in the development of ESCC.

TRPA1: a molecular view

The transient receptor potential ankyrin 1 (TRPA1) ion channel is expressed in pain-sensing neurons and other tissues and has become a major target in the development of novel pharmaceuticals. A remarkable feature of the channel is its long list of activators, many of which we are exposed to in daily life. Many of these agonists induce pain and inflammation, making TRPA1 a major target for anti-inflammatory and analgesic therapies. Studies in human patients and in experimental animals have confirmed an important role for TRPA1 in a number of pain conditions. Over the recent years, much progress has been made in elucidating the molecular structure of TRPA1 and in discovering binding sites and modulatory sites of the channel. Because the list of published mutations and important molecular sites is steadily growing and because it has become difficult to see the forest for the trees, this review aims at summarizing the current knowledge about TRPA1, with a special focus on the molecular structure and the known binding or gating sites of the channel.

Potential therapeutic value of transient receptor potential channels in male urogenital system

Transient receptor potential (TRP) channels comprise a family of cation channels implicated in a variety of cellular processes including light, mechanical or chemical stimuli, temperature, pH, or osmolarity. TRP channel proteins are a diverse family of proteins that are expressed in many tissues. We debated our recent knowledge about the expression, function, and regulation of TRP channels in the different parts of the male urogenital system in health and disease. Emerging evidence suggests that dysfunction of TRP channels significantly contributes to the pathophysiology of urogenital diseases. So far, there are many efforts underway to determine if these channels can be used as drug targets to reverse declines in male urogenital function. Furthermore, developing safe and efficacious TRP channel modulators is warranted for male urogenital disorders in a clinical setting.

TRPM2 in the Brain: Role in Health and Disease

Transient receptor potential (TRP) proteins have been implicated in several cell functions as non-selective cation channels, with about 30 different mammalian TRP channels having been recognized. Among them, TRP-melastatin 2 (TRPM2) is particularly involved in the response to oxidative stress and inflammation, while its activity depends on the presence of intracellular calcium (Ca²⁺). TRPM2 is involved in several physiological and pathological processes in the brain through the modulation of multiple signaling pathways. The aim of the present review is to provide a brief summary of the current insights of TRPM2 role in health and disease to focalize our attention on future potential neuroprotective strategies.

TRPV4 regulates migration and tube formation of human retinal capillary endothelial cells

Background

Ca²⁺ entry plays an important role in modulating endothelial cell migration and tube formation. Transient receptor potential cation channel subfamily V member 4 (TRPV4) is a Ca²⁺-permeable channel that is widely expressed in endothelial cells. It has been reported that TRPV4 is expressed in HRCECs and regulates Ca²⁺ entry. However, the function of TRPV4 in human retinal capillary endothelial cells (HRCECs) remains unknown.

Methods

In this study we used western blot and immunostaining assay to verify TRPV4 expression in HRCECs. And then we pretreated HRCECs with HC067047 and transfected with specific shRNA of TRPV4. The functional presence of TrpV4 was determined by using fluorescence, migration and tube formation assay in TrpV4 knockdown cells or control cells.

Results

Using western blot and immunostaining, we confirmed TRPV4 expression in HRCECs. Moreover, inhibition of TRPV4 using the specific inhibitor HC067047 and the knockdown of TRPV4 with shRNA significantly suppressed tube formation and migration by HRCECs.

Conclusions

TRPV4 is essential for HRCEC migration and tube formation, and maybe a potential therapeutic target for retinal vascular diseases.

Electronic supplementary material

The online version of this article (10.1186/s12886-018-0697-2) contains supplementary material, which is available to authorized users.

PhoDAGs Enable Optical Control of Diacylglycerol-Sensitive Transient Receptor Potential Channels

Diacylglycerol-sensitive transient receptor potential (TRP) channels play crucial roles in a wide variety of biological processes and systems, but their activation mechanism is not well understood. We describe an optical toolkit by which activation and deactivation of these ion channels can be controlled with unprecedented speed and precision through light stimuli. We show that the photoswitchable diacylglycerols PhoDAG-1 and PhoDAG-3 enable rapid photoactivation of two DAG-sensitive TRP channels, Trpc2 and TRPC6, upon stimulation with UV-A light, whereas exposure to blue light terminates channel activation. PhoDAG photoconversion can be applied in heterologous expression systems, in native cells, and even in mammalian tissue slices. Combined laser scanning-controlled photoswitching and Ca²⁺ imaging enables both large-scale mapping of TRP channel-mediated neuronal activation and localized mapping in small cellular compartments. Light-switchable PhoDAGs provide an important advance to explore the pathophysiological relevance of DAG-sensitive TRP channels in the maintenance of body homeostasis.

Actions and Regulation of Ionotropic Cannabinoid Receptors

Almost three decades have passed since the identification of the two specific metabotropic receptors mediating cannabinoid pharmacology. Thereafter, many cannabinoid effects, both at central and peripheral levels, have been well documented and characterized. However, numerous evidences demonstrated that these pharmacological actions could not be attributable solely to the activation of CB1 and CB2 receptors since several important cannabimimetic actions have been found in biological systems lacking CB1 or CB2 gene such as in specific cell lines or transgenic mice. It is now well accepted that, beyond their receptor-mediated effects, these molecules can act also via CB1/CB2-receptor-independent mechanism. Cannabinoids have been demonstrated to modulate several voltage-gated channels (including Ca²⁺, Na⁺, and various type of K⁺ channels), ligand-gated ion channels (i.e., GABA, glycine), and ion-transporting membranes proteins such as transient potential receptor class (TRP) channels. The first direct, cannabinoid receptor-independent interaction was reported on the function of serotonin 5-HT₃ receptor-ion channel complex. Similar effects were reported also on the other above mentioned ion channels. In the early ninety, studies searching for endogenous modulators of L-type Ca²⁺ channels identified anandamide as ligand for L-type Ca²⁺ channel. Later investigations indicated that other types of Ca²⁺ currents are also affected by endocannabinoids, and, in the late ninety, it was discovered that endocannabinoids activate the vanilloid receptor subtype 1 (TRPV1), and nowadays, it is known that (endo)cannabinoids gate at least five distinct TRP channels. This chapter focuses on cannabinoid regulation of ion channels and lays special emphasis on their action at transient receptor channels.

The TRPM2 channel is a hypothalamic heat sensor that limits fever and can drive hypothermia

Body temperature homeostasis is critical for survival and requires precise regulation by the nervous system. The hypothalamus serves as the principal thermostat that detects and regulates internal temperature. We demonstrate that the ion channel TRPM2 [of the transient receptor potential (TRP) channel family] is a temperature sensor in a subpopulation of hypothalamic neurons. TRPM2 limits the fever response and may detect increased temperatures to prevent overheating. Furthermore, chemogenetic activation and inhibition of hypothalamic TRPM2-expressing neurons in vivo decreased and increased body temperature, respectively. Such manipulation may allow analysis of the beneficial effects of altered body temperature on diverse disease states. Identification of a functional role for TRP channels in monitoring internal body temperature should promote further analysis of molecular mechanisms governing thermoregulation and foster the genetic dissection of hypothalamic circuits involved with temperature homeostasis.

Transient Receptor Potential Channels in Microglia: Roles in Physiology and Disease

Microglia modulate the nervous system cellular environment and induce neuroprotective and neurotoxic effects. Various molecules are involved in these processes, including families of ion channels expressed in microglial cells, such as transient receptor potential (TRP) channels. TRP channels comprise a family of non-selective cation channels that can be activated by mechanical, thermal, and chemical stimuli, and which contribute to the regulation of intracellular calcium concentrations. TRP channels have been shown to be involved in cellular processes such as osmotic regulation, cytokine production, proliferation, activation, cell death, and oxidative stress responses. Given the significance of these processes in microglial activity, studies of TRP channels in microglia have focused on determining their roles in both neuroprotective and neurotoxic processes. TRP channel activity has been proposed to play an important function in neurodegenerative diseases, ischemia, inflammatory responses, and neuropathic pain. Modulation of TRP channel activity may thus be considered as a potential therapeutic strategy for the treatment of various diseases associated with alterations of the central nervous system (CNS). In this review, we describe the expression of different subfamilies of TRP channels in microglia, focusing on their physiological and pathophysiological roles, and consider their potential use as therapeutic targets in CNS diseases.

TRP functions in the broncho-pulmonary system

The current understanding of the role of transient receptor potential (TRP) channels in the airways and lung was initially based on the localization of a series of such channels in a subset of sensory nerve fibers of the respiratory tract. Soon after, TRP channel expression and function have been identified in respiratory nonneuronal cells. In these two locations, TRPs regulate physiological processes aimed at integrating different stimuli to maintain homeostasis and to react to harmful agents and tissue injury by building up inflammatory responses and repair processes. There is no doubt that TRPs localized in the sensory network contribute to airway neurogenic inflammation, and emerging evidence underlines the role of nonneuronal TRPs in orchestrating inflammation and repair in the respiratory tract. However, recent basic and clinical studies have offered clues regarding the contribution of neuronal and nonneuronal TRPs in the mechanism of asthma, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, cough, and other respiratory diseases.

"TRP inflammation" relationship in cardiovascular system

Despite considerable advances in the research and treatment, the precise relationship between inflammation and cardiovascular (CV) disease remains incompletely understood. Therefore, understanding the immunoinflammatory processes underlying the initiation, progression, and exacerbation of many cardiovascular diseases is of prime importance. The innate immune system has an ancient origin and is well conserved across species. Its activation occurs in response to pathogens or tissue injury. Recent studies suggest that altered ionic balance, and production of noxious gaseous mediators link to immune and inflammatory responses with altered ion channel expression and function. Among plausible candidates for this are transient receptor potential (TRP) channels that function as polymodal sensors and scaffolding proteins involved in many physiological and pathological processes. In this review, we will first focus on the relevance of TRP channel to both exogenous and endogenous factors related to innate immune response and transcription factors related to sustained inflammatory status. The emerging role of inflammasome to regulate innate immunity and its possible connection to TRP channels will also be discussed. Secondly, we will discuss about the linkage of TRP channels to inflammatory CV diseases, from a viewpoint of inflammation in a general sense which is not restricted to the innate immunity. These knowledge may serve to provide new insights into the pathogenesis of various inflammatory CV diseases and their novel therapeutic strategies.

Transient receptor potential channels in the vasculature

The mammalian genome encodes 28 distinct members of the transient receptor potential (TRP) superfamily of cation channels, which exhibit varying degrees of selectivity for different ionic species. Multiple TRP channels are present in all cells and are involved in diverse aspects of cellular function, including sensory perception and signal transduction. Notably, TRP channels are involved in regulating vascular function and pathophysiology, the focus of this review. TRP channels in vascular smooth muscle cells participate in regulating contractility and proliferation, whereas endothelial TRP channel activity is an important contributor to endothelium-dependent vasodilation, vascular wall permeability, and angiogenesis. TRP channels are also present in perivascular sensory neurons and astrocytic endfeet proximal to cerebral arterioles, where they participate in the regulation of vascular tone. Almost all of these functions are mediated by changes in global intracellular Ca(2+) levels or subcellular Ca(2+) signaling events. In addition to directly mediating Ca(2+) entry, TRP channels influence intracellular Ca(2+) dynamics through membrane depolarization associated with the influx of cations or through receptor- or store-operated mechanisms. Dysregulation of TRP channels is associated with vascular-related pathologies, including hypertension, neointimal injury, ischemia-reperfusion injury, pulmonary edema, and neurogenic inflammation. In this review, we briefly consider general aspects of TRP channel biology and provide an in-depth discussion of the functions of TRP channels in vascular smooth muscle cells, endothelial cells, and perivascular cells under normal and pathophysiological conditions.

Tweeters, Woofers and Horns: The Complex Orchestration of Calcium Currents in T Lymphocytes

Elevation of intracellular calcium ion (Ca²⁺) levels is a vital event that regulates T lymphocyte homeostasis, activation, proliferation, differentiation, and apoptosis. The mechanisms that regulate intracellular Ca²⁺ signaling in lymphocytes involve tightly controlled concinnity of multiple ion channels, membrane receptors, and signaling molecules. T cell receptor (TCR) engagement results in depletion of endoplasmic reticulum (ER) Ca²⁺ stores and subsequent sustained influx of extracellular Ca²⁺ through Ca²⁺ release-activated Ca²⁺ (CRAC) channels in the plasma membrane. This process termed store-operated Ca²⁺ entry (SOCE) involves the ER Ca²⁺ sensing molecule, STIM1, and a pore-forming plasma membrane protein, ORAI1. However, several other important Ca²⁺ channels that are instrumental in T cell function also exist. In this review, we discuss the role of additional Ca²⁺ channel families expressed on the plasma membrane of T cells that likely contribute to Ca²⁺ influx following TCR engagement, which include the TRP channels, the NMDA receptors, the P2X receptors, and the IP₃ receptors, with a focus on the voltage-dependent Ca²⁺ (Ca_V) channels.

Neurotransmitter receptor localization: from autoradiography to imaging mass spectrometry

Autoradiography is used to determine the anatomical distribution of biological molecules in human tissue and experimental animal models. This method is based on the analysis of the specific binding of radiolabeled compounds to locate neurotransmitter receptors or transporters in fresh frozen tissue slices. The anatomical resolution obtained by quantification of the radioligands has allowed the density of receptor proteins to be mapped over the last 40 years. The data yielded by autoradiography identify the receptors at their specific microscopic localization in the tissues and also in their native microenvironment, the intact cell membrane. Furthermore, in functional autoradiography, the effects of small molecules on the activity of G protein-coupled receptors are evaluated. More recently, autoradiography has been combined with membrane microarrays to improve the high-throughput screening of compounds. These technical advances have made autoradiography an essential analytical method for the progress of drug discovery. We include the future prospects and some preliminary results for imaging mass spectrometry (IMS) as a useful new method in pharmacodynamic and pharmacokinetic studies, complementing autoradiographic studies. IMS results could also be presented as density maps of molecules, proteins, and metabolites in tissue sections that can be identified, localized, and quantified, with the advantage of avoiding any labeling of marker molecules. The limitations and future developments of these techniques are discussed here.

Characterization of a Trpc6 Transgenic Mouse Associated with Early Onset FSGS

Rationale:

Mutations in Transient Receptor Potential Channel 6 (TRPC6) gene are associated with autosomal dominant focal and segmental glomerulosclerosis (FSGS). The majority of the identified mutations affect the ion channel function. Since calcium channels are promising candidate drug targets, there is an an urgent need for a mouse model to assess new therapeutic drugs and to help delineate the pathogenic process leading to FSGS. We have previously reported the generation of three independent transgenic mouse lines carrying different Trpc6 mutations that display a glomerular disease comparable to the phenotype presented by individuals with FSGS. However, the utility of these models for drug testing is dampened by the late-onset of the presentation and the mild phenotypic manifestations.

Methodology:

In order to obtain a time-effective mouse model for Trpc6-associated FSGS we generated a new transgenic mutant Trpc6 mouse model emulating the amino acid change carried by the first pediatric patient of FSGS associated with a TRPC6 mutation: M132T.

Results:

Mice carrying the orthologous Trpc6 M131T transgene showed early onset proteinuria and early signs of FSGS. When exploring molecular consequences of the overexpression of this mutated form of Trpc6 in podocytes, differences in expression levels of Axin2 and β-catenin were found in glomeruli from transgenic Trpc6 M131T mice. These data supports the proposed molecular mechanisms related to the activation of calcineurin-NFAT/Wnt signaling, as outcome of the increased calcium influx caused by the mutated form of Trpc6.

Conclusion:

Given that the Trpc6 M131T mouse develops an early onset of FSGS-like phenotypes it represents a promising model for studying the pathogenesis of FSGS caused by TRpC6, facilitating the assessment of new drugs as treatments and allowing further studies to understand underlying molecular pathways involved in the development of the TRPC6 mediated disease.

Comparative transcriptome analysis of two oysters, Crassostrea gigas and Crassostrea hongkongensis provides insights into adaptation to hypo-osmotic conditions

Environmental salinity creates a key barrier to limit the distribution of most aquatic organisms. Adaptation to osmotic fluctuation is believed to be a factor facilitating species diversification. Adaptive evolution often involves beneficial mutations at more than one locus. Bivalves hold great interest, with numerous species living in waters, as osmoconformers, who maintain the osmotic pressure balance mostly by free amino acids. In this study, 107,076,589 reads from two groups of Crassostrea hongkongensis were produced and the assembled into 130,629 contigs. Transcripts putatively involved in stress-response, innate immunity and cell processes were identified according to Gene ontology and KEGG pathway analyses. Comparing with the transcriptome of C. gigas to characterize the diversity of transcripts between species with osmotic divergence, we identified 182,806 high-quality single nucleotide polymorphisms (SNPs) for C. hongkongensis, and 196,779 SNPs for C. gigas. Comparison of 11,602 pairs of putative orthologs allowed for identification of 14 protein-coding genes that experienced strong positive selection (Ka/Ks>1). In addition, 45 genes that may show signs of moderate positive selection (1 ≥ Ka/Ks>0.5) were also identified. Based on Ks ratios and divergence time between the two species published previously, we estimated a neutral transcriptome-wide substitution mutation rate of 1.39 × 10(-9) per site per year. Several genes were differentially expressed across the control and treated groups of each species. This is the first time to sequence the transcriptome of C. hongkongensis and provide the most comprehensive transcriptomic resource available for it. The increasing amount of transcriptome data on Crassostrea provides an excellent resource for phylogenetic analysis. A large number of SNPs identified in this work are expected to provide valuable resources for future marker and genotyping assay development. The analysis of natural selection provides an innovative view on the adaptation within species and sets the basis for future genetic and evolutionary studies.