Fig. 3.

Agrin Z exon skipping results in drastically decreased levels of Z⁺ agrin mRNA and protein in SMA MNs. (A) RT-PCR reactions confirmed agrin Z exon skipping in P1 SMA MNs. Similar results have been obtained from at least another P1 SMA mouse littermate. Spliced isoforms are shown as boxes labeled with the corresponding exon number. Black dots on top of the boxes indicate primer binding sites. The red arrows indicate splicing abnormalities observed in SMA mice. (B) Immunofluorescence staining was performed to detect Z⁺ agrin in lumbar MNs of P1 SMA mice. Dramatic loss of Z⁺ agrin was detected in P1 SMA MNs. Similar results have been obtained from at least three P1 SMA mice. Immunostaining of p75^NTR was used to identify MNs in the anterior horn region of the lumbar spinal cord. (Scale bar, 25 μm.) (C) Immunofluorescence staining was performed to detect Z⁺ agrin in lumbar MNs of P3 SMA mice. Z⁺ agrin was completely undetectable in P3 SMA MNs. (Scale bar, 25 µm.) Similar results have been obtained from at least three P3 SMA mice.