Left‐asymmetric expression of Galanin in the linear heart tube of the mouse embryo is independent of the nodal co‐receptor gene cryptic

Abstract

Only very few left/right asymmetrically expressed genes are known in the mammalian embryo. In a screen for novel factors we identified the gene encoding the neuropeptide Galanin in mouse. At embryonic day (E) 8.5 asymmetric mRNA transcription was found in the left half of the linear heart tube. During heart looping and morphogenesis expression became restricted to the atrio-ventricular (AV) canal, followed by specific staining of the AV-node and AV-rings in the four-chambered heart. Expression was inverted in inv/inv and randomized in homozygous iv mutant embryos. Left-sided heart-specific transcription of mouse Gal thus should be controlled by the left-right pathway. The asymmetric pattern was retained in cryptic mutant embryos, in which the Nodal signaling cascade is disrupted. Surprisingly, Pitx2c was found to be expressed in 50% of cryptic mutant hearts as well, suggesting that some aspects of asymmetric gene expression in the heart are independent of cryptic. Developmental Dynamics 237:3557-3564, 2008.

Physiology, Signaling, and Pharmacology of Galanin Peptides and Receptors: Three Decades of Emerging Diversity

“…Furthermore, it was recently suggested that galanin promotes glucose uptake into cardiac muscle of diabetic rats by increasing glucose transporter 4 expression in cardiomyocytes (Fang et al, 2013b). In addition to a role in the central and peripheral regulation of cardiovascular function, galanin is also involved in heart development (Schweickert et al, 2008;Jones et al, 2009). Interestingly, galanin expression decreases during cardiomyocyte differentiation (Beqqali et al, 2006).…”

The evolution and conservation of left-right patterning mechanisms

“…For example, the neuropeptide galanin was shown to be asymmetrically expressed, in a flow-dependent manner, on the left side of the mouse heart anlage. As galanin asymmetry was not detected in Xenopus embryonic heart, this species-specific difference might relate to the much higher complexity of the mammalian fourchambered heart (Schweickert et al, 2008). Galanin might have been co-opted to the Nodal cascade through evolution of Pitx2 binding sites in its promoter, an option that has yet to be tackled experimentally.…”

Twist1 Transcriptional Targets in the Developing Atrio-Ventricular Canal of the Mouse

“…The gene expression differences between the AVC and OFT could also reflect differences in timing of cushion formation, the cells populating these regions, or the cardiogenic lineage giving rise to them. For example, the most differentially expressed gene in the OFT was Isl1 , a marker of the secondary heart field that contributes cells to the OFT and right ventricle [57], while the most highly AVC-specific gene was Galanin , a neuropeptide known to be expressed in the AVC before becoming restricted to AV-node and AV-rings [58].…”