Phylogenetic and developmental analyses indicate complex functions of calcium‐activated potassium channels in zebrafish embryonic development

Abstract

Background: Calcium-activated potassium channels (KCa) are a specific type of potassium channel activated by intracellular calcium concentration changes. This group of potassium channels plays fundamental roles ranging from regulating neuronal excitability to immune cell activation. Many human diseases such as schizophrenia, hypertension, epilepsy, and cancers have been linked to mutations in this group of potassium channels. Although the KCa channels have been extensively studied electrophysiologically and pharmacologically, their spatiotemporal gene expression during embryogenesis remains mostly unknown.Results: Using zebrafish as a model, we identified and renamed 14 KCa genes.We further performed phylogenetic and syntenic analyses on vertebrate KCa genes. Our data revealed that the number of KCa genes in zebrafish was increased, most likely due to teleost-specific whole-genome duplication. Moreover, we examined zebrafish KCa gene expression during early embryogenesis. The duplicated ohnologous genes show distinct and overlapped gene expression. Furthermore, we found that zebrafish KCa genes are expressed in various tissues and organs (somites, fins, olfactory regions, eye, kidney, and so on) and neuronal tissues, suggesting that they may play important roles during zebrafish embryogenesis. Conclusions: Our phylogenetic and developmental analyses shed light on the potential functions of the KCa genes during embryogenesis related to congenital diseases and human channelopathies.calcium-activated potassium ion channels, in situ hybridization, KCa channels, KCNMA, KCNMB, KCNN, KCNT, phylogeny, whole genome duplication (WGD), zebrafish | INTRODUCTIONPotassium ion channels play critical roles in regulating fundamental physiological processes, from membrane potential maintainance, neuronal action potential firing, to hormone secretion, cellular volume control, cell migration, cell cycle, cell death, and cancers. 1,2 There are 78 potassium channel coding genes in the human

Zebrafish Embryos Display Characteristic Bioelectric Signals during Early Development

“…However, the underlying ion channels and connexins that generate these signals are unknown. Our recent gene expression analysis of calcium-gated potassium channels (KCa) and inwardly rectifying potassium channels (Kir) revealed that many ( kcnn1b , kcnn3 , kcnma1a , kcnma1b , kcnmb2b , kcnmb3 , kcnj4 , kcnj2a , kcnj2b , kcnj11 , kcnj5 , kcnj21 ) have a somite-specific expression at similar developmental stages [ 37 , 38 ]. Their presence in the developing somites may indicate that these channel activities underlie the tissue-level bioelectricity.…”

Evolution of inwardly rectifying potassium channels and their gene expression in zebrafish embryos

“…Phylogenetic and syntenic analyses were performed as we described previously 49,57‐60 . Briefly, multiple protein sequences were aligned using MUSCLE program 61 .…”

“…[46][47][48] Thus, the temporal and transient kir genes' expression could be a cellular bioelectric signal for developmental patternings, such as seen in the ectopic somite gene expression of kcnj13 in our long-fin mutant Dhi2059. It is reasonable to speculate that the somite expression of kcnj2a, kcnj11, kcnj5, and other K+ channels (eg, KCa) 49 could be part of a general endogenous fin patterning regulation system for zebrafish fins. In addition, we found multiple genes were expressed in the pectoral fin buds (kcnj2a, kcnj4, kcnj5, kcnj6, and kcnj11), suggesting they might also be involved in fin growth or patterning.…”

“…Phylogenetic and syntenic analyses were performed as we described previously. 49,[57][58][59][60] Briefly, multiple protein sequences were aligned using MUSCLE program. 61 To identify the best evolutionary model for phylogenetic analysis, we carried out the best model test using maximum likelihood (ML) and default parameters in MEGA6.…”

“…Whole-mount in situ hybridizations were performed according to our established method with some modifications. 49,59,60 Briefly, zebrafish embryos were collected, maintained, and staged according to the zebrafish development staging guide. 56 Chorions were using pronase (Sigma) treatment before fixation for 1 to 3 dpf fish embryos.…”