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. 2012 Jun 20;32(25):8703–8715. doi: 10.1523/JNEUROSCI.0204-12.2012

Figure 2.

Figure 2.

SMN is expressed in a tissue-specific manner in conditional SMA mice. A, Schematic demonstrating the exonic structures of the possible transcript products of the SmnRes hybrid allele. In the absence of Cre recombinase, truncated hybrid transcript (SMN 68) is made containing upstream mouse Smn (exons 1–6), human SMN2 exon 8, and no exon 7 sequence. In the presence of Cre recombinase, a full-length hybrid transcript (SMN 678) containing mouse Smn exons 1–7 and human SMN2 exon 8 sequence may be made. The positions of qRT-PCR primers used are indicated with arrows indicating forward and reverse primers and asterisks indicating the positions of the probes. SMN6m8h primers detect both truncated and full-length hybrid transcripts, the SMN67m8h primers only detect full-length transcripts, and the SMN12m primers were used as an endogenous control. B, SMN6m8h primers detect hybrid transcripts in both spinal cord and muscle of P10 Cre+ Het, Cre− SMA, and Cre+ SMA mice, but not in WT mice. C, SMN67m8-h primers detect SMN 678 transcripts in spinal cord only in ChATCre+ and to a lesser extent, in Myf5Cre+ Het and SMA mice. SMN 678 transcripts are expressed in muscle only in MyoDiCre+ and Myf5Cre+ Het and SMA mice (n = 3–8 per genotype). D, SMN protein levels were determined in spinal cord (top row) and muscle (bottom row) tissues of P10 WT, Cre− SMA, and Cre+ SMA mice from each conditional SMA line. Both full-length (FL) and truncated (Δ7) SMN protein isoforms are visible and are compared with the endogenous controls, actin or GAPDH. E, Densitometry analysis of FL SMN protein expression shows reduced FL SMN expression in Cre− SMA mice compared with WT mice in all three lines in both spinal cord and muscle. FL-SMN expression is significantly increased in the muscles of MyoDiCre+ and Myf5Cre+ SMA mice compared with Cre− SMA mice. *p < 0.01. F, SMN6m8h primers detect hybrid transcripts in the DRGs of all lines of Cre+ SMA mice, but (G) SMN67m8 h primers detect SMN 678 transcripts only in DRGs of Myf5Cre+ SMA mice, not ChATCre+ or MyoDiCre+ SMA mice (n = 2–3 per genotype). H, SMN6m8-h primers and I, SMN67m8h primers detect hybrid transcripts that are expressed in the appropriate tissue-specific patterns at early developmental time points. (All tissues isolated from mice at P2 except 2 of 3 Myf5Cre+ SMA mice, which were isolated at P5). n = 2–4 per genotype.