An ENU-Induced Mutation of Nrg1 Causes Dilated Pupils and a Reduction in Muscarinic Receptors in the Sphincter Pupillae
Figure 3
Nrg1 gene structure and mutation identification.
(A) Mouse Nrg1 gene structure. Exons are represented as vertical bars and are numbered as per Steinthorsdottir et al. [2004], Paul et al. [2006] and Chen et al. [2008]. In the absence of an agreed or definitive exon numbering system for NRG1, exons are labeled as described by Steinthorsdottir et al. [2004] with the number denoting their length in nucleotides. The 5′ exons, which define the “types” of NRG1, are in black with the corresponding Roman numeral above (including three additional 5′ exons found in humans that encode type IV, V, and VI). In mice, exon E171 may encode isoforms with a “3” stalk (see Figure 4 and 5). (B) Sequence analysis of the Nrg1 gene product obtained using PCR of genomic DNA discovered a G to A transition mutation in Dp1/Dp1 homozygous mice compared to wild-type B6 mice. (C) The mutation located in the 5′ splice donor site that flanks exon E59 encoding the EGFβ domain. (D) Electrophoresis results using primers specific for CRD-Nrg1 and Ig-Nrg1 from homozygous Dp1 and wild-type B6 mice, respectively. M, molecular weight markers. GAPDH, glyceraldehyde-3-phosphate dehydrogenase. (E) Quantitative analysis of Nrg1 mRNA levels in band b by densitometry. Ratio: ratio of volume (intensity) of respective Nrg1 and GAPDH mRNA RT-PCR product. **p<0.01 vs. respective Dp1/Dp1 group (n = 4).