CDK13 RNA Over-Editing Mediated by ADAR1 Associates with Poor Prognosis of Hepatocellular Carcinoma Patients

Background/Aims: Aberrant RNA editing, mediated by adenosine deaminases acting on RNA (ADAR), serves as a post-transcriptional event participating in tumorigenesis and prognosis. However, the RNA editing profiles during HCC progression and their clinical correlations remain unclear. Methods: Multiple tissue samples were collected from an advanced HCC patient. RNA-seq was performed to obtain the RNA editing profiles for each sample. Two RNA editing sites from CDK13 were further validated in 60 HCC patients; and their potential regulatory mechanisms were investigated. Results: In-depth analysis of the RNA-seq data revealed a significant number of editing sites (632-816) in coding regions for each tissue sample, showing branched evolution during tumorigenesis and metastasis. Two editing sites (Q103R and K96R) in CDK13 showed significant over-editing in tumor, and these phenomenon were validated in 60 HCC patients. Furthermore, the clinicopathological analysis revealed that these CDK13 over-editing sites were positively associated with TNM, PVTT and poor prognosis. In addition, the editing level of these sites were significantly correlated with the expression of ADAR1. Loss of function assays further proved that these CDK13 over-editing sites were mediated by ADAR1 in HCC cells. Conclusions: CDK13 RNA over-editing sites mediated by ADAR1 may serve as novel cancer driver events in HCC progression

Cyclic Nucleotide-gated Channels on the Flagellum Control Ca2+ Entry into Sperm

Cyclic nucleotide-gated (CNG) channels are key elements of cGMP- and cAMP-signaling pathways in vertebrate photoreceptor cells and in olfactory sensory neurons, respectively. These channels form heterooligomeric complexes composed of at least two distinct subunits (α and β). The α subunit of cone photoreceptors is also present in mammalian sperm. Here we identify one short and several long less abundant transcripts of β subunits in testis. The α and β subunits are expressed in a characteristic temporal and spatial pattern in sperm and precursor cells. In mature sperm, the α subunit is observed along the entire flagellum, whereas the short β subunit is restricted to the principal piece of the flagellum. These findings suggest that different forms of CNG channels coexist in the flagellum. Confocal microscopy in conjunction with the Ca2+ indicator Fluo-3 shows that the CNG channels serve as a Ca2+ entry pathway that responds more sensitively to cGMP than to cAMP. Assuming that CNG channel subtypes differ in their Ca2+ permeability, dissimilar localization of α and β subunits may give rise to a pattern of Ca2+ microdomains along the flagellum, thereby providing the structural basis for control of flagellar bending waves

Calcium-activated chloride current amplifies the response to urine in mouse vomeronasal sensory neurons

The vomeronasal organ (VNO) is an odor detection system that mediates many pheromone-sensitive behaviors. Vomeronasal sensory neurons (VSNs), located in the VNO, are the initial site of interaction with odors/pheromones. However, how an individual VSN transduces chemical signals into electrical signals is still unresolved. Here, we show that a Ca2+-activated Cl− current contributes ∼80% of the response to urine in mouse VSNs. Using perforated patch clamp recordings with gramicidin, which leaves intracellular chloride undisrupted, we found that the urine-induced inward current (Vhold = −80 mV) was decreased in the presence of chloride channel blockers. This was confirmed using whole cell recordings and altering extracellular chloride to shift the reversal potential. Further, the urine-induced currents were eliminated when both extracellular Ca2+ and Na+ were removed. Using inside-out patches from dendritic tips, we recorded Ca2+-activated Cl− channel activity. Several candidates for this Ca2+-activated Cl− channel were detected in VNO by reverse transcription–polymerase chain reaction. In addition, a chloride cotransporter, Na+-K+-2Cl− isoform 1, was detected and found to mediate much of the chloride accumulation in VSNs. Collectively, our data demonstrate that chloride acts as a major amplifier for signal transduction in mouse VSNs. This amplification would increase the responsiveness to pheromones or odorants