Fig. 6

hoxb5b Morphants Display an Increased Number of Atrial Cardiomyocytes

(A) MOs targeting the donor site of the single intron in either hoxb5a or hoxb5b efficiently abrogate splicing of the respective transcript without affecting the other transcript. Larger bands in lanes 2 and 4 represent the retained introns of hoxb5a and hoxb5b, respectively.

(B–E, G, and H) hoxb5a morphants have no evident morphological defects, and hoxb5b morphants exhibit enlarged hearts, pericardial edema, and overtly normal pectoral fins. Lateral views, anterior to the left, 48 hpf, with higher magnification of pectoral fin outlined in (E), (G), and (H). (F) Genomic intron-exon structure is completely conserved and nucleotide sequences are highly conserved in the locations that we targeted with anti-hoxb5b and anti-hoxb5a MOs. Uppercase letters designate first exon sequence, and lowercase letters are intronic sequence. Underline indicates the respective MO target sequences. Asterisks indicate sequence differences.

(I–R) hoxb5b morphants display an increased number of atrial cardiomyocytes and a normal number of ventricular cardiomyocytes. Views and graphs are as presented in Figure 1. Error bars represent SD.