LTP is impaired in <i>Lrp4</i>^{<i>ECD/ECD</i>} but not in <i>Lrp4</i>^{<i>ΔICD/ΔICD</i>} mice.

<p><b>A</b>: <i>Upper Panel</i>, Sample traces before and 40 min after theta-burst stimulation (TBS); <i>Lower Panel</i>, Results of experiments from <i>Lrp4</i>^{<i>ECD/ECD</i>} mice compared to their <i>Lrp4</i>^{<i>WT-KI/WT-KI</i>} controls. TBS induced on average a 37.63 ± 7.88% increase in <i>Lrp4</i>^{<i>WT-KI/WT-KI</i>} control slices (open squares, n = 16, N = 5), but only 14.83 ± 3.39% LTP in slices from the <i>Lrp4</i>^{<i>ECD/ECD</i>} mice (black triangles, n = 10, N = 3). <b>B</b>: Unpaired t-test was used to compare each sample for LTP calculated 40–60 min after theta-burst. Values are the means of the normalized fEPSP slopes. * denotes significance, p = 0.0387. <b>C:</b><i>Upper Panel</i>, Sample traces before and 40 min after TBS. <i>Lower Panel</i>, Results of experiments from <i>Lrp4</i>^{<i>ΔICD/ΔICD</i>} mice compared to their <i>Lrp4</i>^{<i>WT-KI/WT-KI</i>} controls. <i>Lrp4</i>^{<i>WT-KI/WT-KI</i>} slices were recorded on consecutive days and used as internal controls and pooled together. TBS induced a 37.63 ± 7.88% LTP in <i>Lrp4</i>^{<i>WT-KI/WT-KI</i>} control slices (open squares, n = 16, N = 5), and 32.42 ± 6.27% LTP in slices from the <i>Lrp4</i>^{<i>ΔICD/ΔICD</i>} mice (gray filled rhombus, n = 11, N = 5). <b>D</b>: There was no significant difference in LTP between <i>Lrp4</i>^{<i>WT-KI/WT-KI</i>}<i>and Lrp4</i>^{<i>ΔICD/ΔICD</i>} mice (p = 0.63). <b>E.</b> Input-output curves calculated as a function of fiber volley amplitude to the slopes of fEPSP’s. Average peak amplitudes for <i>Lrp4</i>^{<i>WT-KI/WT-KI</i>}, <i>Lrp4</i>^{<i>ECD/ECD</i>} and <i>Lrp4</i>^{<i>ΔICD/ΔICD</i>} slices used in the experiments were 1.68 ± 0.15 mV, 1.27 ± 0.25 mV, and 1.50 ± 0.20 mV), respectively, and were not significantly different from each other. (One-way ANOVA, F = 1.124, p = 0.33.) <b>F:</b> Theta-burst analysis or <b>G:</b> paired pulse ratios (n = 8, N = 3 for each) did not reveal any significant differences between <i>Lrp4</i>^{<i>WT-KI/WT-KI</i>} and <i>Lrp4</i>^{<i>ECD/ECD</i>} (two-way ANOVA, F(3,56) = 0.46, p = 0.71). N = number of animals.</p

Limb and bone structure of different <i>Lrp4</i> KI mutants.

<p><b>A</b>: Illustration of the different Lrp4 protein products of all KI mutants. Panels are aligned to paw images in B and C to indicate genotypes. <b>B</b>: Ventral view of fore and hind limbs of <i>Lrp4</i> KI mutants. Homozygous mutant mice for each allelic variant (<i>KI/KI</i>) and compound mutant mice that carry one allelic variant and one KO allele (<i>KO/KI</i>) are shown. Note that there are strong defects in the limb pattering of <i>Lrp4</i>^{<i>ECD/ECD</i>}, intermediate defects in <i>Lrp4</i>^{<i>ΔICD/ΔIC</i>}, and only mild defects in <i>Lrp4</i>^{<i>LDLR-ICD/LDLR-ICD</i>} (red arrows). <b>C</b>: Ventral view of alizarin red (stains bones) and alcian blue (stains cartilage) of different <i>Lrp4</i> KI mutants. A WT-KI allele (2^nd panel in A and B) was generated to control for the lack of introns in the ICD-cassette in the other KI mutants. Black arrowheads: ectopic bone or bony fusion; red arrowheads: soft-tissue fusion. (modified from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116701#pone.0116701.ref022" target="_blank">22</a>]).</p

Normal brain development in <i>Lrp4</i>^{<i>ECD/ECD</i>} and <i>Lrp4</i>^<i>-/-</i> mice.

<p><b>A-D</b>: Sagittal slices of the <i>Lrp4</i>^{<i>ECD/ECD</i>} (A,C) and wild type (<i>Lrp4</i>^<i>+/+</i> B,D) mouse cerebellum labeled with NeuN (green), Brn1 (red) and DAPI (blue). Brn1 and NeuN are commonly used markers to label neurons. ML = molecular layer, PL = Purkinje cell layer, and GCL = granule cell layer are clearly distinguishable and not different in the cerebellum of <i>Lrp4</i>^{<i>ECD/ECD</i>} and <i>Lrp4</i>^<i>+/+</i> adult mice (>2 months). <b>E-H</b>: Coronal sections of <i>Lrp4</i>^{<i>ECD/ECD</i>} (E,F) and <i>Lrp4</i>^<i>+/+</i> (G,H) brains showing hippocampus (E,G) and somatosensory cortex (F,H). Slices are labeled for NeuN and DAPI to visualize normal cortical lamination (layers I-VI). I-N: Coronal sections of E18.5 <i>Lrp4</i>^<i>-/-</i> brains compared to their wild type litter mates. Brn1 (I,J) and GFAP (K,L) immunoreactivity in the cortex and hippocampus and Tbr1 plus NeuN double labeling in the cortex are illustrated. Scale bars = 200 μm (A-H), 400 μm (I-L), 100 μm (M,N).</p