The spectrin-actin lattice displays larger and more variable pore sizes, and actin filament lengths are more variable in the absence of Tmod1. (A-B) Electron micrographs of platinum replicas of unspread RBC membrane skeletons from Tmod1^+/+Tg+ mice or Tmod1^−/−Tg+ mice. Asterisks indicate pores in the lattice that appear larger in the absence of Tmod1. Bars, (A) 400 nm; (B) 200 nm. (C) Histogram of pore sizes shows 10-fold more size variability and a 2-fold increase in average sizes in the absence of Tmod1; n = 5 skeletons per genotype, with 200 adjacent pores per micrograph. Average pore sizes: 6310 nm² (± 2820 nm²) for wild-type and 13 352 nm² (± 12 355 nm²) for Tmod1-null RBCs (P < .001). (D) Electron micrographs of negatively stained junctional complexes in expanded membrane skeletons from wild-type (top) and Tmod1-null mice (middle and bottom). Red brackets indicate actin filaments. Bars, 50 nm. Actin filament lengths are uniform in wild-type junctional complexes but appear shorter or longer in Tmod1-null junctional complexes. (E) Measurements of actin filament lengths in junctional complexes of membrane skeletons from wild-type or Tmod1-null mice. Each dot represents 1 measurement. Average filament lengths: 36.90 nm (± 2.85 nm; n = 17) for wild-type and 36.74 nm (± 11.70 nm; n = 14) for Tmod1-null. Range of filament lengths: 32.80 to 42.64 nm for wild-type and 19.18 to 56.42 nm for Tmod1-null. Differences in average filament lengths between genotypes are not significant, but differences in the range of filament lengths are significant based on an F test for variance (P < .001).