The amphibian second heart field: Xenopus islet-1 is required for cardiovascular development.
Islet-1 is a LIM-homeodomain transcription factor that has been defined to label cardiac progenitor cells of the second heart field. Here we provide the first analysis of the expression pattern of Xenopus islet-1 (Xisl-1) in the context of cardiovascular development. During early stages of heart development Xisl-1 is co-expressed with Nkx2.5 in the cardiac crescent in Xenopus supporting the notion of an initially single heart field. At subsequent stages of cardiogenesis the expression domains of Xisl-1 and Nkx2.5 become more distinct with Xisl-1 being detected more anterior to Nkx2.5, however both factors continue to be co-expressed in the dorsal mesocardium and pericardial roof of the linear heart tube. The presence of a cardiac Xisl-1 progenitor pool in an amphibian whose heart lacks an anatomically separated right ventricle is intriguing. Functional analyses show that Xisl-1 is required for normal heart development. Inhibition of Xisl-1 results in defects in heart morphogenesis and in the downregulation of early cardiac markers implicating a role for Xisl-1 in cardiac specification. Additionally, Xisl-1 loss-of-function affects the expression of several vascular markers demonstrating the involvement of Xisl-1 in vasculogenesis.
Brade
Thomas
T
Institute for Biochemistry and Molecular Biology, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany.
Gessert
Susanne
S
Kühl
Michael
M
Pandur
Petra
P
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001808:Blood Vessels / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000033:anatomy & histology / Q000196:embryology / Q000254:growth & development; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D017403:In Situ Hybridization; D060850:LIM-Homeodomain Proteins; D009024:Morphogenesis; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000033:anatomy & histology / Q000196:embryology / Q000502:physiology
D015415:Biomarkers; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; C092720:NKX2-5 protein, Xenopus; D016376:Oligonucleotides, Antisense; D014157:Transcription Factors; D029867:Xenopus Proteins; C063843:insulin gene enhancer binding protein Isl-1