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Regular heartbeat rhythm at the heartbeat initiation stage is essential for normal cardiogenesis at low temperature.

ABSTRACT: BACKGROUND: The development of blood flow in the heart is crucial for heart function and embryonic survival. Recent studies have revealed the importance of the extracellular matrix and the mechanical stress applied to the valve cushion that controls blood flow to the formation of the cardiac valve during embryogenesis. However, the events that trigger such valve formation and mechanical stress, and their temperature dependence have not been explained completely. Medaka (Oryzias latipes) inhabits a wide range of East Asia and adapts to a wide range of climates. We used medaka embryos from different genomic backgrounds and analyzed heartbeat characteristics including back-and-forth blood flow and bradyarrhythmia in embryos incubated at low temperature. We also used high-speed imaging analysis to examine the heartbeat of these animals after transient exposure to low temperature. RESULTS: Embryos of the Hd-rR medaka strain exhibited back-and-forth blood flow in the heart (blood regurgitation) after incubation at 15 °C. This regurgitation was induced by exposure to low temperature around the heartbeat initiation period and was related to abnormalities in the maintenance or pattern of contraction of the atrium or the atrioventricular canal. The Odate strain from the northern Japanese group exhibited normal blood flow after incubation at 15 °C. High-speed time-lapse analysis of the heartbeat revealed that bradyarrhythmia occurred only in Hd-rR embryos incubated at 15 °C. The coefficient of contraction, defined as the quotient of the length of the atrium at systole divided by its length at diastole, was not affected in either strain. The average heart rate after removing the effect of arrhythmia did not differ significantly between the two strains, suggesting that the mechanical stress of individual myocardial contractions and the total mechanical stress could be equivalent, regardless of the presence of arrhythmia or the heart rate. Test-cross experiments suggested that this circulation phenotype was caused by a single major genomic locus. CONCLUSIONS: These results suggest that cardiogenesis at low temperature requires a constant heartbeat. Abnormal contraction rhythms at the stage of heartbeat initiation may cause regurgitation at later stages. From the evolutionary viewpoint, strains that exhibit normal cardiogenesis during development at low temperature inhabit northern environments.

SUBMITTER: Watanabe-Asaka T

PROVIDER: S-EPMC3936829 | biostudies-other | 2014

REPOSITORIES: biostudies-other

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Regular heartbeat rhythm at the heartbeat initiation stage is essential for normal cardiogenesis at low temperature.

Watanabe-Asaka Tomomi T Sekiya Yoshio Y Wada Hironori H Yasuda Takako T Okubo Ikuya I Oda Shoji S Mitani Hiroshi H

BMC developmental biology 20140225

<h4>Background</h4>The development of blood flow in the heart is crucial for heart function and embryonic survival. Recent studies have revealed the importance of the extracellular matrix and the mechanical stress applied to the valve cushion that controls blood flow to the formation of the cardiac valve during embryogenesis. However, the events that trigger such valve formation and mechanical stress, and their temperature dependence have not been explained completely. Medaka (Oryzias latipes) i ...[more]

PMID: 24564206

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Project description:Purpose: We aimed to provide a basis for the adaptive mechanism and a rich resource for the discovery and identification of novel genes involved in the cold stress response in Solenopsis japonica. Retinal transcriptome profiling (RNA-seq) to microarray and quantitative reverse transcription polymerase chain reaction (qRT–PCR) methods and to evaluate protocols for optimal high-throughput data analysis Methods: Solenopsis japonica was reared at lab condition, and incubated at 2 different temperature for 24h (9, and 25℃) under dark conditions. RNA was extracted using Trizol reagent and Illumina sequencing was performed at Macrogen. Illumina short reads were quality-filtered and Illumina-based de novo transcriptome assembly was performed. Differential Gene Expression Analysis was studied for different tempearture conditions. Results: Totally 89,657 unigenes was obtained which overall 43,375 were annotated with gene descriptions, gene ontology terms, and metabolic pathways. 86 GO functional sub-groups and 25 EggNOG terms resulted. DEGs with FC≥2 and FC≤-2, P-value<0.05 were screened and were compared at two different temperatures. We found 138 DEG down regulated and 271 DEG up regulated when the S. japonica incubated at 9 ℃ and compared with 25℃ treated group. Comparing transcriptome profiles for differential gene expression resulted various DE proteins and genes, including cytochrome P450, NADH dehydrogenase subunit 1, cuticle protein and HSP which have previously been reported to be involved in cold and high temperature resistance. GO analysis revealed that antioxidant activity up-regulated under high temperature stress. Conclusions: we compared the transcriptomes of S. japonica under normal room temperature and low-temperature using RNA-Seq technology based on the high-throughput sequencing. Comparative transcriptome analysis identified many genes and a large number of changes were discovered in metabolic pathway through the GO and KEGG enrichment analysis. Our data will facilitate further molecular investigations and genomic research. Many low-temperature significantly up-regulated genes were first identified in this study. These newly found genes may be important and necessary to S. japonica overwintering and its behavior for adaptation in new environment.

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Regular heartbeat rhythm at the heartbeat initiation stage is essential for normal cardiogenesis at low temperature.

Publications

Regular heartbeat rhythm at the heartbeat initiation stage is essential for normal cardiogenesis at low temperature.

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