Figure 1.

Axonal degeneration from the distal end and neuronal cell death in the ventral ganglion are apparent at third instar in DfhIR larvae. A, Anti-frataxin immunoblots were performed with extracts of whole larvae, at second, early third and late third instar (2, E3 and L3, respectively) quantified, and normalized for GFP content using anti-GFP. DfhIR crossed into the mito-GFP background resulted in a 30–40% reduction in whole-larval frataxin expression relative to wild type at the same stage. Bodian- and H&E-stained paraffin sections of larvae were used to quantitate changes during development: B shows wild-type and DfhIR segmental nerve cross sections at L3 in the distal axon; D shows wild-type and DfhIR ventral ganglia at L3. C, Quantitive morphometry showed that in wild-type larvae, the cross sectional area of the segmental nerve did not change during development, or along the proximodistal axis at any point during development. In DfhIR larvae, the cross sectional area was significantly decreased in the distal region of the nerve (at segments A6 and A8) at L3. E, F, Morphometry of cell bodies in the ventral ganglion showed that in DfhIR larvae, both the area of the cortical region of the ganglion (E) and the number of cell bodies (F) were significantly decreased at L3 in DfhIR relative to wild type. All error bars represent the SD, and significant differences between DfhIR and wild-type values for specific stages or regions are indicated (*p < 0.05, n = 40 for all experiments).