Fig. 6.

Rescue of 4-d-old heterozygous Mhc^K1728del/+ fly muscle function and morphology with overexpression of abba/thin. (A) Adult jump ability at 4 d of age: jump ability of Mhc^K1728del/+ and Mhc^K1728del/Mhc¹⁰ flies is significantly reduced, compared with controls. Overexpression of Abba in flies with Mhc^K1728del in trans to Mhc¹⁰ (Mhc^K1728del/Mhc¹⁰;UAS-Abba/Mef2-Gal4), did not cause any significant rescue of jump ability. Jump ability of heterozygous Mhc^K1728del/+ flies was restored upon overexpression of Abba (Mhc^K1728del/+;UAS-Abba/Mef2-Gal4) to levels comparable with controls (P < 0.0001). Flies heterozygous for both Mhc^K1728del and the loss-of-function allele abba^MJO0348 (Mhc^K1728del/abba^MJO0348) did not show significant alteration in jump ability compared with flies heterozygous only for Mhc^K1728del (Mhc^K1728del/+). ns, P > 0.05; **P < 0.001. (B and C) IFMs of 4-d-old adult flies were labeled for Mhc and Kettin/Titin (B) or Mhc and Obscurin (C). Control flies, flies with overexpression of Abba (UAS-Abba/Mef2-Gal4), and flies heterozygous for the loss of function Abba allele (abba^MJO0348) show parallel periodic sarcomeric striations in the IFMs. Less-defined sarcomeric structures are observed in the IFM of heterozygous Mhc^K1728del/+ flies. Structured periodic sarcomeric striations are restored in heterozygous Mhc^K1728del animals that overexpress Abba (Mhc^K1728del/+;UAS-Abba/Mef2-Gal4). Overexpression of Abba in flies that carry Mhc^K1728del in trans to Mhc¹⁰ (Mhc^K1728del/Mhc¹⁰;UAS-Abba/Mef2-Gal4) does not improve sarcomeric organization, but results in an apparent reduction in aberrant myosin accumulation seen in flies with Mhc^K1728del in trans to Mhc¹⁰ (Mhc^K1728del/Mhc¹⁰). Flies heterozygous for Mhc^K1728del and abba^MJO0348 (Mhc^K1728del/abba^MJO0348) show IFMs with fragmentation of sarcomeres and amorphous myosin, Z-disks and M-bands observed. (Scale bars, 5 µm.)