NDEL1 is another
DISC1 interacting protein that regulates neuronal development in vivo (Duan et al., 2007, Sasaki et al., 2005 and Shu et al., 2004). Consistent with our previous findings (Duan et al., 2007), expression of a specific shRNA against mouse ndel1 (shRNA-N1) led to developmental defects of newborn dentate granule cells, mostly in the appearance of ectopic dendrites and aberrant positioning ( Figure 4). Thus, FEZ1 and NDEL1 appear to mediate DISC1 signaling in a complementary set of neuronal developmental processes. To determine whether FEZ1 and NDEL1 also functionally interact to regulate development of Vandetanib newborn neurons, we performed double knockdown experiments in vivo. The effect of coexpressing shRNA-F1 and shRNA-N1 on dendritic growth and soma size of newborn neurons was very similar to those expressing
shRNA-F1 alone ( Figures 4A–4C), whereas the effect on ectopic dendrites and neuronal positioning was similar to those expressing shRNA-N1 alone ( Figures 4D and 4E). Thus, concomitant suppression of NDEL1 and FEZ1 only leads to Adriamycin manufacturer additive effects of individual knockdown, instead of a synergistic action. These results further support the notion that FEZ1 and NDEL1 differentially regulate distinct aspects of new neuron development in the adult brain. KIAA1212/Girdin is also a DISC1 binding partner that regulates development of newborn dentate granule cells in the hippocampus (Enomoto et al., 2009 and Kim et al., 2009). We next examined whether KIAA1212 interacts with FEZ1 or NDEL1 in regulating neuronal development. Consistent with previous findings, DISC1 was co-IPed with each of also the three proteins, NDEL1, FEZ1, or KIAA1212, when each pair was coexpressed in the heterologous system (Figure S4A).
Furthermore, these four proteins could be co-IPed together with DISC1 when all were coexpressed (Figure S4A). Also consistent with the previous finding (Kim et al., 2009), overexpression of KIAA1212 led to increased total dendritic length, number of primary dendrites, and soma size in newborn neurons in the adult dentate gyrus (Figures S4B–S4D). Compared with KIAA1212 overexpression or FEZ1 knockdown alone, comanipulation exacerbated phenotypes of increased dendritic length and soma size, but not the number of primary dendrites and positioning of newborn neurons (Figures S4B–S4E). On the other hand, simultaneous KIAA1212 overexpression and NDEL1 knockdown exhibited phenotypes very similar to those of NDEL1 knockdown alone (Figures S4B–S4E). Taken together, these results support a model that DISC1 interacts with FEZ1 and KIAA1212 mainly to regulate dendritic growth and soma size of newborn neurons during adult neurogenesis, whereas DISC1 interacts with NDEL1 mainly to regulate positioning of newborn neurons (Table 1).