High impact information on Mesp1

• We isolated a novel bHLH protein gene Mesp2 (for mesoderm posterior 2) that cross-hybridizes with Mesp1 expressed in the early mouse mesoderm [1].
• This indicates that Mesp1 has a significant role in the epithelialization of somitic mesoderm [2].
• Differential contributions of Mesp1 and Mesp2 to the epithelialization and rostro-caudal patterning of somites [2].
• Here, we show that Cs-Mesp, the sole ortholog of vertebrate Mesp genes in the ascidian Ciona savignyi, is specifically and transiently expressed in the embryonic heart progenitor cells (B7.5 cells) [3].
• Disruption of the Mesp1 gene leads to aberrant heart morphogenesis, resulting in cardia bifida [4].

Biological context of Mesp1

• The Mesp1 gene encodes the basic HLH protein MesP1 which is expressed in the mesodermal cell lineage during early gastrulation [4].
• In order to study the defects in Mesp1-expressing cells during gastrulation and in the specification of mesodermal cell lineages, we introduced a (beta)-galactosidase gene (lacZ) under the control of the Mesp1 promoter by homologous recombination [4].
• Moreover, we have found that somitogenesis in the early stages is more susceptible to changes in the Mesp gene dosage, indicating that a threshold level of Mesp activity must be required for the progression of normal somitogenesis [5].

Anatomical context of Mesp1

• In contrast, Mesp1-expressing cells in the homozygous deficient embryos stayed in the primitive streak for a longer period of time before departure [4].
• The expression of FLK-1, an early marker of endothelial cell precursors including heart precursors, also accumulated abnormally in the posterior region in Mesp1-deficient embryos [4].
• Previous fate mapping analysis, using Cre recombinase driven by the Mesp1 locus, revealed that Mesp1 is expressed in almost all of the precursors of the cardiovascular system, including the endothelium, endocardium, myocardium, and epicardium [6].

Other interactions of Mesp1

• Mesp1-nonexpressing cells contribute to the ventricular cardiac conduction system [6].

References