Details for: CL0002129

Cell ID: CL0002129

Cell Name: regular atrial cardiac myocyte

Description: Regular atrial cardiac myocytes, also known as atrial myocytes, are specialized muscle cells found in the atria – the upper chambers of the heart. They contract and relax during the heart's cycle, modulating the pumping of blood through the atria and into the ventricles. Additionally, endowed with inherent rhythmic electrical activity, atrial myocytes contribute significantly to the initiation and propagation of the heart’s electrical impulses. A distinguishing feature that separates atrial myocytes from other cardiac myocytes is their ability to synthesize and secrete atrial natriuretic peptide (ANP) in response to atrial stretch or dilatation. ANP acts as a potent vasodilator and diuretic, helping to maintain blood pressure and volume homeostasis. The phenomena of atrial stretch or distension, which triggers ANP release, is often in response to excess blood volume entering the heart, providing a mechanism at the cellular level which actively regulates systemic cardiovascular balance. Like all cardiac myocytes, atrial myocytes are embedded in a dense network of connective tissue that provides structural support. These cells are characterized by a single, centrally located nucleus, and overall, have a rod-like appearance with branching ends that connect with adjacent cells to form a continuous, synchronized ensemble. Their cytoplasm is abundant with mitochondria, reflecting the high energy demand associated with constant contraction and relaxation. At the ultrastructural level, atrial myocytes display striations due to the regular arrangement of actin and myosin proteins, which facilitate the contraction process essential for the heart's pump function. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.)

Synonyms: atrial myocyte, regular atrial cardiac muscle fiber, regular cardiac muscle cell of atrium, atrial cardiac muscle cell

Selected Context(s): Overall

Gene Significance Landscape

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Cell Significance Index (CSI) is uniquely calculated to reveal cell-specific gene markers. More info here

Significant Genes List

Genes with the highest and lowest Percentile Rank Scores (PRS) for regular atrial cardiac myocyte within the selected context(s).

Gene ID: A unique numerical identifier for this specific gene.
Symbol: Shortened abbreviation or name that represents this gene.
Ensembl Gene ID: A unique identifier assigned by Ensembl for genomic data mapping.
CSI Score: A combined effect size and statistical significance measure for regular atrial cardiac myocyte. Higher scores indicate a stronger, more significant difference in expression.
(Previously described as "Fold Change", but now represents Cliff's Delta × –log10(p).)

Gene ID: A unique numerical identifier for this specific gene.
Symbol: Shortened abbreviation or name that represents this gene.
Ensembl Gene ID: A unique identifier assigned by Ensembl for genomic data mapping.
CSI Score: A combined effect size and statistical significance measure for regular atrial cardiac myocyte. Higher scores indicate a stronger, more significant difference in expression.
Average CSI: csi sum / gene count
Cell network configuration

This network visualizes key genes for regular atrial cardiac myocyte. It primarily includes:
1. Top genes highly significant for this cell (Num. Top Cell Genes - based on the 'Min. CSI' setting).
2. Any additional specific 'Context Genes' you add below.
The final network is a combined view. Choose an Interaction Source (pathways or protein interactions) and optionally compare CSI scores with a Baseline Cell Type.

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Target Cell for CSI:  regular atrial cardiac myocyte (CL0002129)

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Edges (Interactions):
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## Summary The [regular atrial cardiac myocyte](/details-cell/CL0002129) is a specialized muscle cell of the heart's atria, responsible for both contraction to pump blood into the ventricles and for contributing to the heart's electrical rhythm. The gene significance profile underscores this dual identity. **Overall**, the high expression specificity ([csi_z](/glossary/csi_z)) of genes related to the contractile apparatus, such as [MYOZ2](/details-gene/51778), and electrophysiology, such as the muscarinic receptor [CHRM2](/details-gene/1129) and the pacemaker channel [HCN1](/details-gene/348980), confirms its core functions. Notably, the most specific marker is the long non-coding RNA [NEAT1](/details-gene/283131), suggesting that post-transcriptional gene regulation is a critical and defining feature for maintaining the unique phenotype of this cell type. ## Key Characteristics and Function Analysis of top marker genes, ranked by expression specificity (`csi_z`), reveals distinct functional clusters that define the [regular atrial cardiac myocyte](/details-cell/CL0002129). * **Electrophysiology and Autonomic Regulation:** The cell's role in cardiac rhythm and response to nervous system input is highlighted by several highly specific markers. [CHRM2](/details-gene/1129) (Cholinergic Receptor Muscarinic 2) is a key receptor for the parasympathetic nervous system, mediating the slowing of heart rate. Its high specificity is complemented by that of [RGS6](/details-gene/9628), a regulator of G-protein signaling that likely fine-tunes this response. Furthermore, the high specificity of [HCN1](/details-gene/348980), a hyperpolarization-activated "pacemaker" channel, is consistent with the atrial myocyte's contribution to initiating and propagating the heart's electrical impulses ([Link](https://doi.org/10.1016/s0092-8674(00)81434-8)). * **Contractile Machinery and Calcium Signaling:** The cell's primary mechanical function is underscored by the specific expression of [MYOZ2](/details-gene/51778) (myozenin 2), a sarcomeric protein that tethers calcineurin to the Z-line, thereby linking calcium signaling directly to the contractile apparatus ([Link](https://doi.org/10.1073/pnas.260501097)). The specificity of [MYLK3](/details-gene/91807) (myosin light chain kinase 3), a calcium/calmodulin-dependent kinase, further emphasizes the tight regulation of muscle contraction. * **Transcriptional and Post-Transcriptional Control:** A striking feature of this cell is the high specificity of genes involved in gene regulation. The top marker, [NEAT1](/details-gene/283131), is a long non-coding RNA that functions as a scaffold for nuclear paraspeckles, involved in gene silencing and mRNA regulation. The transcription corepressor [MLIP](/details-gene/90523) and the RNA-binding splicing factor [RBFOX1](/details-gene/54715) also rank highly. This suggests that a complex, multi-layered regulatory network is essential for establishing and maintaining the unique atrial myocyte transcriptome, distinguishing it from other cardiac cell types. * **Anti-Markers:** The analysis of genes with the lowest specificity provides valuable negative context. The strong negative `csi_z` scores for numerous core mitochondrial genes (e.g., [COX1](/details-gene/4512), [COX2](/details-gene/4513), [COX3](/details-gene/4514), [ATP6](/details-gene/4508), [ND4](/details-gene/4538)) are particularly informative. While atrial myocytes have high energy demands and abundant mitochondria, the expression of these essential mitochondrial components is not a unique or specific feature compared to other cell types in the body. Similarly, the lack of specificity for genes like [B2M](/details-gene/567) confirms its non-immune lineage, and the negative scores for housekeeping genes like histones ([H3-3B](/details-gene/3021)) and ferritin ([FTL](/details-gene/2512)) are consistent with their ubiquitous expression. ## Clinical Significance and Contextual Roles The gene signature of the [regular atrial cardiac myocyte](/details-cell/CL0002129) provides insights into its potential role in cardiovascular disease, particularly arrhythmias and cardiomyopathies. The specific expression of ion channels and receptors central to electrophysiology, such as [HCN1](/details-gene/348980) and [CHRM2](/details-gene/1129), positions this cell type as a critical player in atrial fibrillation and other supraventricular arrhythmias. Dysregulation of these genes could alter atrial conductivity and rhythmicity. The co-expression of the signaling modulator [RGS6](/details-gene/9628) suggests that disruption in the fine-tuning of autonomic responses could also be a pathogenic mechanism. Genes related to the sarcomere and cellular structure are linked to cardiomyopathies. For instance, [MYOZ2](/details-gene/51778) was identified in a search for candidate genes related to arrhythmogenic right ventricular dysplasia (ARVD), a condition involving structural and electrical abnormalities of the heart muscle ([Link](https://doi.org/10.1006/geno.2000.6399)). The high specificity of [SOD1](/details-gene/6647), a key enzyme in managing oxidative stress, suggests these cells possess a specialized defense mechanism against the high metabolic load. Failures in this system could contribute to cellular damage seen in heart failure. Finally, the prominent role of regulatory factors like [NEAT1](/details-gene/283131) and [RBFOX1](/details-gene/54715) implies that disruptions in the transcriptional or splicing programs could be upstream drivers of atrial myocyte dysfunction in disease. ## Potential Mechanisms and Research Directions The data suggest several hypotheses regarding the unique biology of the [regular atrial cardiac myocyte](/details-cell/CL0002129). 1. **Hypothesis: The atrial myocyte phenotype is actively maintained by a specialized network of non-coding and RNA-binding proteins that orchestrate a unique splicing and gene expression landscape.** * **Surprising Findings:** It is noteworthy that a long non-coding RNA, [NEAT1](/details-gene/283131), and a transcription corepressor, [MLIP](/details-gene/90523), are the most specific gene markers for this cell type, outranking canonical muscle-specific structural proteins. This suggests that the identity of this terminally differentiated cell is less defined by the mere presence of muscle proteins and more by the precise regulatory systems that control their expression. * **Testable Questions:** Does targeted degradation of [NEAT1](/details-gene/283131) transcripts in cultured human iPSC-derived atrial myocytes lead to a detectable shift in their electrophysiological properties or an altered expression profile of key contractile genes like [MYOZ2](/details-gene/51778)? 2. **Hypothesis: The high specificity of both the [CHRM2](/details-gene/1129) receptor and its signaling attenuator, [RGS6](/details-gene/9628), reflects a tightly-regulated "excitability rheostat" essential for maintaining atrial rhythm and preventing excessive parasympathetic stimulation.** * **Surprising Findings:** The high specificity of a negative regulator of GPCR signaling, [RGS6](/details-gene/9628), is as pronounced as that of the receptor it helps regulate. This implies that the ability to rapidly terminate a signal is a defining and specialized feature of the [regular atrial cardiac myocyte](/details-cell/CL0002129), likely crucial for preventing bradyarrhythmias and ensuring rhythmic stability in the face of fluctuating autonomic input. * **Testable Questions:** In an animal model, does atrial-specific knockout of [RGS6](/details-gene/9628) result in an exaggerated heart rate and atrioventricular conduction response to vagal nerve stimulation compared to wild-type controls?