Fig. 4: Progressive protein aggregation and Z-disc myofibrillar disruption in skeletal muscle of Ldb3Ala165Val/+ mice.
Representative immunofluorescence staining on perfused tibialis anterior muscle consecutive longitudinal sections of 4-month-old (a–e) and 8-month-old (f–j) Ldb3Ala165Val/+ mice and their Ldb3+/+ littermates. a Muscle sections of 4-month-old Ldb3+/+ mice (n = 4) show normal Z-disc staining for LDB3, filamin C, myotilin, BAG3, and HSPA8 proteins. b, c Muscle sections of 4-month-old Ldb3Ala165Val/+ mice (n = 6) show same muscle fiber co-stained with LDB3 and filamin C antibodies (b), and LDB3 and myotilin antibodies (c). d, e Muscle sections of 4-month-old Ldb3Ala165Val/+ mice (n = 6) show same muscle fiber co-stained with filamin C and HSPA8 antibodies (d), and BAG3 and HSPA8 antibodies (e). Filamin C, HSPA8, and BAG3 aggregates are seen at the Z-disc spanning multiple sarcomeres in same fiber. In contrast, the LDB3 and myotilin antibodies show normal Z-disc staining in the fiber with filamin C aggregates. f Muscle sections of 8-month-old Ldb3+/+ mice (n = 5) show normal Z-disc staining for LDB3, filamin C, myotilin, BAG3, and HSPA8 proteins. Top and bottom panel each shows same muscle fiber co-stained with LDB3 and filamin C antibodies (g), and LDB3 and myotilin antibodies (h) in muscle sections of 8-month-old Ldb3Ala165Val/+ mice (n = 7). Muscle sections of 8-month-old Ldb3Ala165Val/+ mice (n = 7) show same muscle fiber co-stained with LDB3 and BAG3 antibodies (i), and LDB3 and HSPA8 antibodies (j). LDB3 aggregates colocalize with filamin C, myotilin, BAG3, and HSPA8 at the Z-discs in muscle fibers. The protein aggregates are seen in muscle fibers with normal periodicity of the Z-discs and with disorganized Z-disc periodicity indicating Z-disc myofibrillar disruption. A part of adjacent muscle fiber with normal staining pattern is shown at bottom in each image for comparison. Scale bar = 10 μm and applies to all images.
