C-terminal Ig domains maintain Z-disc cohesion perpendicular to the myofibril.

<p>(<b>A</b>, <b>B</b>) TEM of two <i>cher</i> C-terminal mutants. (<b>A</b>) <i>cher</i>^{<i>Q1415sd</i>} mutant sarcomere shows actin accumulation at the H-zone and a smaller Z-disc (purple box, enlarged in <b>A’</b>). (<b>A’</b>) Z-disc material (red arrowhead) and actin filaments (blue arrowhead) are observed detaching from the myofibril. (<b>B</b>) <i>cher</i>^{<i>Q1042x</i>} mutant sarcomere displays mild defects, with Z-disc material pulled into the H-zone (enlarged in <b>B’</b>). (<b>C</b>) Quantification of the number of widened Z-discs in different <i>cher</i> mutants. Only mutants affecting the actin-binding CherD isoform display a widened Z-disc in the IFM. Statistical significance assessed by one-way ANOVA with post hoc Tukey: n.s. = not significant, **** = P ≤ 0.0001. (<b>D</b>) Schematic representation of the laser tachometer used to measure wing beat frequency. (<b>E</b>) All <i>cher</i> homozygous mutants have very short flying times, compared to the wild type control OregonR. The average of 10 flies with standard deviation is shown.