Figure 4. TMEM184b loss causes morphological defects at motor and sensory terminals. A, B, NMJs at the EHL muscle in heterozygous (A) or mutant (B) 8–10-week-old mice. All nerves are green (YFP); acetylcholine receptors in muscle are red (labeled with BTX). Arrows point to synaptic swellings at mutant synapses; yellow asterisk indicates a morphologically normal synapse. C, D, TMEM184b mutant NMJs showing individual nerves (YFP, green) and acetylcholine receptors (BTX, red) in 6.5-month-old mice. Dashed lines in D indicate locations of presynaptic swellings where little receptor apposition is found. E, F, Intraepidermal nerve fibers of wild-type and mutant animals, stained with PGP9.5 (red) and DAPI (blue). Dashed line shows the border between dermis (left) and epidermis (right). Mutants show abnormal swellings within epidermal fibers (arrows). G, Quantification of synaptic swellings in control (filled boxes) and mutant (open boxes) animals over time. p = 2.5 × 10−4 at 18 d; 1.6 × 10−4 at 8–10 weeks; 2.1 × 10−5 at 6.5 months. N = 3–4 animals per genotype (**p < 0.01). H, Quantification of the percentage of presynaptic terminal area opposed by acetylcholine receptors (BTX). Black bars, Wild type; gray bars, mutant. Graph shows the percentage of analyzed synapses (n = 40–60 synapses per mouse, 3 mice per genotype) that have the indicated levels of apposition. P values calculated using one-way ANOVA (p = 0.025, 0.16, and 0.0033 for lowest, middle, and highest levels of apposition, respectively). Scale bars: (in A) A, B, 20 μm; (in C) C, D, 10 μm; (in E) E, F, 20 μm.