Figure 2. Comparison of gene expression profiles in synaptic and extrasynaptic regions of wild-type and meltrin β^−/− diaphragms at E18.5.

(A) Schematic diagram of synapse-rich (synaptic) (B, marked by a square) and synapse-free (extrasynaptic) (C, marked by a square) regions in the diaphragm. The primary phrenic nerve trunks and AChR clusters are indicated by green lines and red dots, respectively. (B and C) Wild-type and meltrin β^−/− diaphragms at E18.5 were stained with Alexa-594–conjugated BTX (red) and DAPI (blue), and their synaptic (B) and extrasynaptic (C) regions were dissected for a microarray analysis. Bar: 100 µm. (D) All the genes expressed in the synaptic or extrasynaptic regions from wild-type and meltrin β^−/− mice were classified into 3 groups that were analyzed with GCOS software. Green: genes expressed more highly in synaptic regions than in extrasynaptic regions of wild-type muscle, Red: genes expressed in synaptic regions more highly in wild-type than in meltrin β ^−/− muscle, Blue: genes expressed in extrasynaptic region more highly or expressed similarly in synaptic and extrasynaptic regions in meltrin β^−/− muscles. (E) The preferential expression of the AChR α subunit and ephrin-A5 genes in synaptic regions is aberrant in meltrin β^−/− diaphragm muscles at E18.5. Transcripts of several genes in synaptic (S) and extrasynaptic (E) regions were analyzed by RT-PCR. Compared with transcripts of the G3PDH gene as a control, those of AChR α subunit, MuSK, and ephrin-A5 were expressed differentially in synaptic and extrasynaptic regions in wild-type diaphragms, but the AChR α subunit and ephrin-A5 genes were expressed similarly in synaptic and extrasynaptic regions in meltrin β ^−/− diaphragms.