Genetically distinct cardial cells within the Drosophila heart.
Although often viewed as a simple pulsating tube, the Drosophila dorsal vessel is intricate in terms of its structure, cell types, and patterns of gene expression. Two nonidentical groups of cardial cells are observed in segments of the heart based on the differential expression of transcriptional regulators. These include sets of four cell pairs that express the homeodomain protein Tinman (Tin), alternating with groups of two cell pairs that express the orphan steroid hormone receptor Seven Up (Svp). Here we show that these myocardial cell populations are distinct in terms of their formation and gene expression profiles. The Svp-expressing cells are generated by asymmetric cell divisions of precursor cells based on decreases or increases in their numbers in numb or sanpodo mutant embryos. In contrast, the numbers of Tin-expressing cardial cells are unchanged in these genetic backgrounds, suggesting they arise from symmetric cell divisions. One function for Svp in the two pairs of cardial cells is to repress the expression of the tin gene and at least one of its targets, the beta3 tubulin gene. Further differences in the cells are substantiated by the identification of separable enhancers for D-mef2 gene transcription in the distinct cardioblast sets. Taken together, these results demonstrate a greater cellular and genetic complexity of the Drosophila heart than previously appreciated.
Gajewski
K
K
Department of Biochemistry and Molecular Biology, Graduate Program in Genes & Development, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
Choi
C Y
CY
Kim
Y
Y
Schulz
R A
RA
D000818:Animals; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics* / Q000502:physiology*; D004742:Enhancer Elements, Genetic / Q000502:physiology; D005786:Gene Expression Regulation; D017344:Genes, Insect / Q000502:physiology*; D006321:Heart / Q000033:anatomy & histology / Q000502:physiology; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics; D019476:Insect Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D011987:Receptors, Steroid / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; D064326:MEF2 Transcription Factors; C499409:Mef2 protein, Drosophila; D018006:Myogenic Regulatory Factors; D011987:Receptors, Steroid; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C094295:svp protein, Drosophila; C102933:tin protein, Drosophila