Characterization of aberrant neuronal phenotype in the developing striatum of Nolz-1 knockout mice

• Main Authors: Janice Hsien-Jou Hao, 郝先柔
• Other Authors: Fu-Chin Liu
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/24274124921945811691

碩士 === 國立陽明大學 === 神經科學研究所 === 101 === Abstract Nolz1 is a zinc finger transcription factor whose expression is enriched in the developing striatum and is initially expressed in the subventricular zone (SVZ) of the lateral ganglionic eminence (LGE). Previous studies have shown that Nolz-1 is expressed by early differentiating neurons (Tuj1) and striatal differentiated neurons (DARPP-32), suggested that Nolz-1 may be involved in controlling striatal development. However, the function of Nolz-1 remains unknown. In addition, Nolz-1 null mutant mice exhibit two striatal malformations, including the enlargement of striatal SVZ, and the expansion of ventral striatum. We hypothesized that Nolz-1 might regulate genes expression in the striatum and further cause striatal morphology changes in the developing striatum. In the present study, we first examined genes that are expressed in the LGE, including Dlx1, Dlx2, Dlx5 and Six3. Notably, we found an increase of Dlx1, Dlx2, Dlx5 and Six3 mRNA expression in the mantle zone (MZ) of striatum. In order to clarify the changes of interneurons and striatal progenitors, we further assayed the expression of interneuron by Lhx6 and Er81, and neuronal progenitor by Mash-1 and Pax6. The result shows no obvious difference of Lhx6, Mash-1 and Pax6 expression between Nolz-1 null mutant and wild type (WT). However, the Er81-positive cell clusters increase in the mutant ventral striatum. On the other hand, analysis of neuronal morphology in Nolz-1 mutant striatum by Golgi’s stain shows that, the total lengths of neurite has no difference between knockout (KO) and WT. However, the numbers of neurons with long multiple neurites with branches were significantly reduced, whereas the numbers of neuron with short multiple neurites with branches and long single neurite were normal. Our findings imply that Nolz-1 might affect neuronal differentiation without altering the population of interneurons and neuronal progenitors. We further analyzed the migration defect by verifying migration-related genes including Netrin-1, DCC, Robo1, Robo2, Slit1, and Slit2 in Nolz-1 null mutant. Quantification results reveal that, the mRNA expression of DCC in SVZ, Robo2 in MZ, Slit1 and Slit2 in VZ were dramatically decreased in Nolz-1 null mutant striatum. This result indicates that, the down-regulation of chemorepulsive ligand and receptors expressions in Nolz-1 knockout striatum might be the reason of the striatal malformation. In addition, two Nolz-1 conditional knockout mice were analyzed in this study, which were the neuronal NestinCre; Nolz-1 f/f mice and the temporal NestinCre-ER; Nolz-1 f/f; CAG-CAT-EGFP mice. The neuronal NestinCre exhibit a complete knockout of Nolz-1 expression, which demonstrates that all Nolz-1 expressing cells belonging to the Nestin cell lineage. Furthermore, we used the temporal Nolz-1 KO mice to knockout early-born cells at E11.5 and E12.5. The results showed 46% of cells in the dorsal striatum, and 38 % of cells in the ventral striatum were knockout of Nolz-1, but no obvious difference of early born cell accumulation in the KO ventral striatum was found. Because of the low knockout efficiency in NestinCre-ER; Nolz-1 f/f; CAG-CAT-EGFP mutant striatum, this set of experiment was inconclusive with respect to the accumulation of E12.5-labeled BrdU cells in the ventral striatum, Before this study, Nolz-1 affect striatal architecture has not been well known. Our findings raise a possibility that Nolz-1 control the striatum architecture by regulating migration-related mechanisms. Furthermore, the possibility that the ectopic early-born cell distribution pattern in the ventral striatum of Nolz-1 null mutants may be caused by non-cell autonomous mechanisms. Therefore, the role of Nolz-1 in striatal development is complicate and it needs further studies in the future to be clarified.