Figure 1.
Necdin expression is absent in DRGs of mutant mice lacking the paternal necdin gene. A, The restriction map of mouse Ndn locus. A 7 kb Ndn sequence containing coding (black) and 3′,5′ noncoding (hatched) regions was subcloned into the targeting vector. The 1.5 kb expression unit containing the pgk promoter with Neor gene (Pgk1/neor), polyadenylation signal [Poly(A) signal], was inserted to disrupt the Ndn coding sequence. The vector was introduced to TT2 cells for homologous recombination as described in Materials and Methods. B, Absence of necdin expression in the brain and spinal cord of mice deficient in the paternal necdin gene. Frozen sections of the hypothalamus and spinal cord from E13.5 wild-type (Ndn+m/+p) and necdin-deficient (Ndn+m/-p) littermates were immunostained for necdin. HT, Hypothalamus; SC, spinal cord; DBB, diagonal band of Broca; ML, mantle layer. Scale bars: HT, 50 μm; SC, 100 μm. C, Expression patterns of TrkA and p75NTR in necdin-deficient DRGs. Frozen sections of cervical DRGs from E12.5 wild-type (Ndn+m/+p) and necdin-deficient (Ndn+m/-p) littermates were immunostained for necdin, TrkA, and p75NTR. Scale bar, 50 μm. D, E, Western blot analysis of necdin, TrkA, p75NTR, and phosphorylated MAPK. Equal amounts of DRG lysates from E12.5 embryos were analyzed by Western blotting. Each lane represents pooled DRGs from a single embryo. Molecular sizes in kilodaltons are shown to the right. E, Signal intensities of TrkA, p75NTR, and pMAPK shown in D were normalized to those of tubulin (TB) and MAPK (mean ± SEM; n = 5 for each protein). *p < 0.05. NS, Not significant (p > 0.05).