Biomedical subjects

Minoree Kohwi

Publications and source records attributed to Minoree Kohwi.

3 recordsLinked to original sources

PubMed2005

Pax6 is required for making specific subpopulations of granule and periglomerular neurons in the olfactory bulb.

The subventricular zone (SVZ) produces different subclasses of olfactory bulb (OB) interneurons throughout life. Little is known about the molecular mechanisms controlling the production of different types of interneurons. Here we show that most proliferating adult SVZ progenitors express the transcription factor Pax6, but only a small subpopulation of migrating neuroblasts and new OB interneurons derived from these progenitors retains Pax6 expression. To elucidate the cell-autonomous role of Pax6 in OB neurogenesis, we transplanted green fluorescent protein-expressing embryonic forebrain progenitors of the dorsal lateral ganglionic eminence from Pax6 mutant Small Eye (Pax6(Sey/Sey)) mice into the SVZ of adult wild-type mice. Pax6(Sey/Sey) progenitors produce neuroblasts capable of migrating into the OB but fail to generate dopaminergic periglomerular and superficial granule cells. Interestingly, superficial granule neurons also express mRNA for tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. Our data show that SVZ neuroblasts are heterogeneous and that Pax6 is required in a cell-autonomous manner for the production of cells in the dopaminergic lineage.

Animals↗

PubMed2003

N- and C-terminal domains of beta-catenin, respectively, are required to initiate and shape axon arbors of retinal ganglion cells in vivo.

We used deletion mutants to study beta-catenin function in axon arborization of retinal ganglion cells (RGCs) in live Xenopus laevis tadpoles. A deletion mutant betacatDeltaARM consists of the N- and C-terminal domains of wild-type beta-catenin that contain, respectively, alpha-catenin and postsynaptic density-95 (PSD-95)/discs large (Dlg)/zona occludens-1 (ZO-1) (PDZ) binding sites but lacks the central armadillo repeat region that binds cadherins and other proteins. Expression of DeltaARM in RGCs of live tadpoles perturbed axon arborization in two distinct ways: some RGC axons did not form arbors, whereas the remaining RGC axons formed arbors with abnormally long and tangled branches. Expression of the N- and C-terminal domains of beta-catenin separately in RGCs resulted in segregation of these two phenotypes. The axons of RGCs overexpressing the N-terminal domain of beta-catenin developed no or very few branches, whereas axons of RGCs overexpressing the C-terminal domain of beta-catenin formed arbors with long, tangled branches. Additional analysis revealed that the axons of RGCs that did not form arbors after overexpression of DeltaARM or the N-terminal domain of beta-catenin were frequently mistargeted within the tectum. These results suggest that interactions of the N-terminal domain of beta-catenin with alpha-catenin and of the C-terminal domain with PDZ domain-containing proteins are required, respectively, to initiate and shape axon arbors of RGCs in vivo.

Animals↗

PubMed2002

Postsynaptic targeting of alternative postsynaptic density-95 isoforms by distinct mechanisms.

Members of the postsynaptic density-95 (PSD95)/synapse-associated protein-90 (SAP90) family of scaffolding proteins contain a common set of modular protein interaction motifs including PDZ (postsynaptic density-95/Discs large/zona occludens-1), Src homology 3, and guanylate kinase domains, which regulate signaling and plasticity at excitatory synapses. We report that N-terminal alternative splicing of PSD95 generates an isoform, PSD95beta that contains an additional "L27" motif, which is also present in SAP97. Using yeast two hybrid and coimmunoprecipitation assays, we demonstrate that this N-terminal L27 domain of PSD-95beta, binds to an L27 domain in the membrane-associated guanylate kinase calcium/calmodulin-dependent serine kinase, and to Hrs, an endosomal ATPase that regulates vesicular trafficking. By transfecting heterologous cells and hippocampal neurons, we find that interactions with the L27 domain regulate synaptic clustering of PSD95beta. Disrupting Hrs-regulated early endosomal sorting in hippocampal neurons selectively blocks synaptic clustering of PSD95beta but does not interfere with trafficking of the palmitoylated isoform, PSD95alpha. These studies identify molecular and functional heterogeneity in synaptic PSD95 complexes and reveal critical roles for L27 domain interactions and Hrs regulated vesicular trafficking in postsynaptic protein clustering.

Adaptor Proteins, Signal Transducing↗