Figure 8.

Altering HCN4 expression leads to improper distribution of the homeodomain transcription factor Pitx2. (A) In situ hybridization of representative embryos displaying normal and examples of the most commonly observed Pitx2 expression defects. Uninjected embryos have asymmetric, left-sided expression (i lateral view; iv ventral view). Overexpression and injection of the dominant-negative construct resulted in a variety of molecular phenotypes including expansion or reduction of the endogenous field (ii, iii) and bilateral Pitx2 expression (v). Anterior at top of images. (B) All manipulations caused significantly higher percentages of abnormal Pitx2 expression compared with uninjected embryos (χ² = 64.71, df = 4, *p < 0.05). There was no statistical difference between overexpression and dominant-negative phenotypes. n = 54–86 embryos per condition across 3 biological replicates. OE = HCN4-OE, DN = HCN4-DN(AAA). Scale bars = 200 μm.