Microarray analysis of normal and abnormal chick myocardial development

The goal of this study was to determine developmental differences in gene expression between left and right ventricle, and to assess the differential effect of altered hemodynamic loading on left and right ventricle. Chick ventricles from different developmental stages were isolated for assessment of normal developmental profiles. Conotruncal banding or partial ligation of the left atrial appendage was performed in ovo at embryonic day 4 and ventricles were isolated at embryonic day 5 (banding) or 8 (ligation) for assessment of altered loading effects. Normal heart and ventricle tissues were collected from chicks at embryonic day 4, 5, 6, 8, or 10 (Hamurger-Hamilton stages 29, 34, and 36). Conotruncal banding (CTB) or left atrial ligation (LCL) was performed for experimental groups in ovo at embryonic day 4 and tissues isolated at embryonic day 5 (CTB) or day 8 (LAL). For each sample type, tissues were carefully dissected, collected and stored in RNAlater, and then pooled for RNA isolation. Each sample contained 6 to 12 separate biological specimens. A single pooled RNA sample was generated for each normal and experimental condition. Following preparation of labeled samples for hybridization, samples were split and hybridized in duplicate to separate microarrays (i.e., technical replicates).