title: Islet 1 is expressed in distinct cardiovascular lineages, including pacemaker and coronary vascular cells.
abstract: Islet1 (Isl1) is a LIM homedomain protein that plays a pivotal role in cardiac progenitors of the second heart field. Here, lineage studies with an inducible isl1-cre demonstrated that most Isl1 progenitors have migrated into the heart by E9. Although Isl1 expression is downregulated in most cardiac progenitors as they differentiate, analysis of an isl1-nlacZ mouse and coimmunostaining for Isl1 and lineage markers demonstrated that Isl1 is expressed in distinct subdomains of the heart, and in diverse cardiovascular lineages. Isl1 expression was observed in myocardial lineages of the distal outflow tract, atrial septum, and in sinoatrial and atrioventricular node. The myocardialized septum of the outflow tract was found to derive from Isl1 expressing cells. Isl1 expressing cells also contribute to endothelial and vascular smooth muscle lineages including smooth muscle of the coronary vessels. Our data indicate that Isl1 is a specific marker for a subset of pacemaker cells at developmental stages examined, and suggest genetic heterogeneity within the central conduction system and coronary smooth muscle. Our studies suggest a role for Isl1 in these distinct domains of expression within the heart.
authors.affiliation: Skaggs School of Pharmacy, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
authors.forename: Yunfu
authors.initials: Y
authors.lastname: Sun
authors.forename: Xingqun
authors.initials: X
authors.lastname: Liang
authors.forename: Nader
authors.initials: N
authors.lastname: Najafi
authors.forename: Margaret
authors.initials: M
authors.lastname: Cass
authors.forename: Lizhu
authors.initials: L
authors.lastname: Lin
authors.forename: Cheng-Leng
authors.initials: CL
authors.lastname: Cai
authors.forename: Ju
authors.initials: J
authors.lastname: Chen
authors.forename: Sylvia M
authors.initials: SM
authors.lastname: Evans
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D019070:Cell Lineage / Q000502:physiology; D003331:Coronary Vessels / Q000166:cytology / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins; D006321:Heart / Q000196:embryology*; D018398:Homeodomain Proteins / Q000378:metabolism*; D060850:LIM-Homeodomain Proteins; D051379:Mice; D008856:Microscopy, Fluorescence; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D014157:Transcription Factors
chemical_list: D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D014157:Transcription Factors; C485184:enhanced green fluorescent protein; C063843:insulin gene enhancer binding protein Isl-1; D049452:Green Fluorescent Proteins