野田 泰子

Glucose metabolism is regulated by insulin, which is produced from β-cells in the pancreas. Because insulin is secreted into vessels in response to blood glucose, vascular structures of the pancreas, especially the relationship between vessels and β-cells, are important for physiological and pathological glucose metabolism. Here, we developed a system to visualize vessels surrounding mature β-cells expressing transcription factor MafA in a three-dimensional manner. Optical clearing of the pancreas prevented light scattering of fluorescence driven by the bacterial artificial chromosome (BAC)-mafA promoter in β-cells. Reconstruction of confocal images demonstrated mature β-cells and the glomerular-like structures of β-cell vasculatures labeled with DyLight 488-conjugated lectin in normal mice as well as in low-dose streptozotocin-injected diabetes model mice with reduced β-cell mass. This technological innovation of organ imaging can be used to investigate morphological changes in vascular structures during transplantation, regeneration and diabetes development.

Pathological complete response (pCR) is considered to be a useful prognostic marker for neoadjuvant chemotherapy to improve the survival rate of patients with operable breast cancer. In the present study, we identified differentially expressed microRNAs (miRNAs) between pCR and non-pCR groups of patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer who received neoadjuvant chemotherapy with trastuzumab. Expression profiles were examined by miRNA microarrays using total RNA extracted from formalin-fixed, paraffin-embedded tissues from pretreatment biopsy specimens. Significant differences were observed in miRNAs associated with pCR between the luminal B-like (HER2-positive) and HER2posi-tive (nonluminal) subtypes, which were further classified according to their estrogen receptor (ER) status. Prediction models constructed with differentially expressed miRNAs performed well. In conclusion, the combination of miRNA profiles and ER status may improve the accuracy of pCR prediction in patients with HER2-positive breast cancer and enable the development of personalized treatment regimens.

Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor critical for synaptic plasticity, neuronal development and neurite extension. BDNF mRNA is transported to dendrites and axons, where it is expressed locally. We previously reported that dendritic targeting elements in the BDNF 3' UTR are necessary for dendritic transport and interact with cytoplasmic polyadenylation element binding

We surveyed medical and dental schools to promote the exchange of information about university efforts to increase the number of research-oriented doctors. Periods in which students rotate through laboratories to conduct research were reported by more than two thirds of universities. Many comments asserted that these efforts are effective. However, a small number of respondents reported low student motivation and insufficient time for laboratory experience. MD-PhD courses, in which students take a leave of absence in the middle of undergraduate training and follow a PhD curriculum, have been employed by more than 10 universities. However, relatively few students have chosen such programs. Modified MD-PhD courses have recently been introduced by several universities. In these courses, by taking part of the graduate school curriculum in advance, undergraduate students can shorten the time they spend in graduate school. Students who take such courses are increasing. There were many opinions that extra positions and financial support for research-oriented doctors are effective and should be enhanced. There were also many opinions that emphasize the importance of identifying research-oriented students, improving laboratory working environments, attending academic meetings and inter-university consortia to maintain students' motivation, and promoting collaboration with departments of clinical medicine.

AMPA receptor (AMPA-R) complexes consist of channel-forming subunits, GluA1-4, and auxiliary proteins, including TARPs, CNIHs, synDIG1, and CKAMP44, which can modulate AMPA-R function in specific ways. The combinatorial effects of four GluA subunits binding to various auxiliary subunits amplify the functional diversity of AMPA-Rs. The significance and magnitude of molecular diversity, however, remain elusive. To gain insight into the molecular complexity of AMPA and kainate receptors, we compared the proteins that copurify with each receptor type in the rat brain. This interactome study identified the majority of known interacting proteins and, more importantly, provides candidates for additional studies. We validate the claudin homolog GSG1L as a newly identified binding protein and unique modulator of AMPA-R gating, as determined by detailed molecular, cellular, electrophysiological, and biochemical experiments. GSG1L extends the functional variety of AMPA-R complexes, and further investigation of other candidates may reveal additional complexity of ionotropic glutamate receptor function.

The cytoskeletal components of endothelial cells in the renal artery were examined by analysis of en face preparations under confocal laser scanning microscopy. Renal arterial endothelial cells were shown to be elongated along the direction of blood flow, while stress fibers ran perpendicular to the flow in the basal portion. Focal adhesions were observed along the stress fibers in dot-like configurations. On the other hand, stress fibers in the apical portion of cells ran along the direction of flow. The localizations of stress fibers and focal adhesions in endothelial cells in the renal artery differed from those of unperturbed aortic and venous endothelial cells. Tyrosine-phosphorylated proteins were mainly detected at the sites of cell-to-cell apposition, but not in focal adhesions. Pulsatile pressure and fluid shear stress applied over endothelial cells in the renal artery induce stress fiber organization and localization of focal adhesions. These observations suggest that the morphological alignment of endothelial cells along the direction of blood flow and the organization of cytoskeletal components are independently regulated. Copyright 2012 Kazuo Katoh and Yasuko Noda.

The working group for the future planning of the Japanese Association of Anatomists (JAA) has been working to address the issues that were consulted from the president of JAA since October 2009. After making the interim report in March 2010, a public hearing for general members of the JAA was held and a final report was submitted to the President in January 2011. The report contains the analysis of the current situation, the directions in which we should proceed, and recommendations of concrete actions that JAA should take for each issue. The issues discussed were as follows: 1. Future prospects of anatomy and morphological sciences. How can we maintain the specialties of morphological and anatomical sciences in the rapidly advancing field of life sciences and develop collaborations with other fields? 2. Improvement of the JAA academic meetings. How can we increase JAA members and young participants in the academic meetings of the JAA? 3. Fostering the next generation of young researchers. How can we increase young researchers graduated from the schools of Medicine or Dentistry? 4. Future prospects of education of gross anatomy. Prospects of education in gross anatomy and the body donation registration system in relation with some new cadaver-related movements.

Stress fibres and associated focal adhesions in cells constitute a contractile apparatus that regulates cell motility and contraction. Rho-kinase, an effector molecule of small GTPases, regulates non-muscle cell motility and contractility. Rho-kinase mediates the contraction of stress fibres in a Ca(2+)-independent manner, and is responsible for slower and more finely tuned contraction of stress fibres than that regulated by myosin light chain kinase activity in living cells. The specific inhibition of the Rho-kinase activity causes cells to not only lose their stress fibres and focal adhesions, but also to appear to lose their cytoplasmic tension. Activated Rho-kinase is also involved in the organization of newly formed stress fibres and focal adhesions in living cells.

Intracellular transport is fundamental for cellular function, survival and morphogenesis. Kinesin superfamily proteins (also known as KIFs) are important molecular motors that directionally transport various cargos, including membranous organelles, protein complexes and mRNAs. The mechanisms by which different kinesins recognize and bind to specific cargos, as well as how kinesins unload cargo and determine the direction of transport, have now been identified. Furthermore, recent molecular genetic experiments have uncovered important and unexpected roles for kinesins in the regulation of such physiological processes as higher brain function, tumour suppression and developmental patterning. These findings open exciting new areas of kinesin research.

Various molecular cell biology and molecular genetic approaches have indicated significant roles for kinesin superfamily proteins (KIFs) in intracellular transport and have shown that they are critical for cellular morphogenesis, functioning, and survival. KIFs not only transport various membrane organelles, protein complexes, and mRNAs for the maintenance of basic cellular activity, but also play significant roles for various mechanisms fundamental for life, such as brain wiring, higher brain functions such as memory and learning and activity-dependent neuronal survival during brain development, and for the determination of important developmental processes such as left-right asymmetry formation and suppression of tumorigenesis. Accumulating data have revealed a molecular mechanism of cargo recognition involving scaffolding or adaptor protein complexes. Intramolecular folding and phosphorylation also regulate the binding activity of motor proteins. New techniques using molecular biophysics, cryoelectron microscopy, and X-ray crystallography have detected structural changes in motor proteins, synchronized with ATP hydrolysis cycles, leading to the development of independent models of monomer and dimer motors for processive movement along microtubules.

Through interactions with microtubules, the kinesin superfamily of proteins (KIFs) could have multiple roles in neuronal function and development. During neuronal development, postmitotic neurons develop primary axons extending toward targets, while other collateral branches remain short. Although the process of collateral branching is important for correct wiring of the brain, the mechanisms involved are not well understood. In this study, we analyzed kif2a(-/-) mice, whose brains showed multiple phenotypes, including aberrant axonal branching due to overextension of collateral branches. In kif2a(-/-) growth cones, microtubule-depolymerizing activity decreased. Moreover, many individual microtubules showed abnormal behavior at the kif2a(-/-) cell edge. Based on these results, we propose that KIF2A regulates microtubule dynamics at the growth cone edge by depolymerizing microtubules and that it plays an important role in the suppression of collateral branch extension.

KIFC3, a microtubule (MT) minus end-directed kinesin superfamily protein, is expressed abundantly and is associated with the Golgi apparatus in adrenocortical cells. We report here that disruption of the kifC3 gene induced fragmentation of the Golgi apparatus when cholesterol was depleted. Analysis of the reassembly process of the Golgi apparatus revealed bidirectional movement of the Golgi fragments in both wild-type and kifC3(-/-) cells. However, we observed a markedly reduced inwardly directed motility of the Golgi fragments in cholesterol-depleted kifC3(-/-) cells compared with either cholesterol-depleted wild-type cells or cholesterol-replenished kifC3(-/-) cells. These results suggest that (a) under the cholesterol-depleted condition, reduced inwardly directed motility of the Golgi apparatus results in the observed Golgi scattering phenotype in kifC3(-/-) cells, and (b) cholesterol is necessary for the Golgi fragments to attain sufficient inwardly directed motility by MT minus end-directed motors other than KIFC3, such as dynein, in kifC3(-/-) cells. Furthermore, we showed that Golgi scattering was much more drastic in kifC3(-/-) cells than in wild-type cells to the exogenous dynamitin expression even in the presence of cholesterol. These results collectively demonstrate that KIFC3 plays a complementary role in Golgi positioning and integration with cytoplasmic dynein.

KIF1C is a new member of the kinesin superfamily of proteins (KIFs), which act as microtubule-based molecular motors involved in intracellular transport. We cloned full-length mouse kif1C cDNA. which turned out to have a high homology to a mitochondrial motor KIF1Balpha and to be expressed ubiquitously. To investigate the in vivo significance of KIF1C, we generated kif1C(-/-) mice by, knocking in the beta-galactosidase gene into the motor domain of kif1C gene. On staining of LacZ, we detected its expression in the heart, liver. hippocampus, and cerebellum. Unexpectedly, kif1C(-/-) mice were viable and showed no obvious abnormalities. Because immunocytochemistry showed partial colocalization of KIF1C with the Golgi marker protein, we compared the organelle distribution in primary lung fibroblasts from kif1C(+/+) and kif1C(-/-) mice. We found that there was no significant difference in the distribution of the Golgi apparatus or in the transport from the Golgi apparatus to the endoplasmic reticulum (ER) facilitated by brefeldin A between the two cells. This retrograde membrane transport was further confirmed to be normal by time-lapse analysis. Consequently, KIF1C is dispensable for the motor-dependent retrograde transport from the Golgi apparatus to the ER.

Lysosomes concentrate juxtanuclearly in the region around the microtubule-organizing center by interaction with microtubules. Different experimental and physiological conditions can induce these organelles to move to the cell periphery by a mechanism implying a plus-end-directed microtubule-motor protein (a kinesin-like motor). The responsible kinesin-superfamily protein, however, is unknown. We have identified a new mouse isoform of the kinesin superfamily, KIF2β, an alternatively spliced isoform of the known, neuronal kinesin, KIF2. Developmental expression pattern and cell-type analysis in vivo and in vitro reveal that KIF2β is abundant at early developmental stages of the hippocampus but is then downregulated in differentiated neuronal cells, and it is mainly or uniquely expressed in non-neuronal cells while KIF2 remains exclusively neuronal. Electron microscopy of mouse fibroblasts and immunofluorescence of KIF2β-transiently-transfected fibroblasts show KIF2 and KIF2β primarily associated with lysosomes, and this association can be disrupted by detergent treatment. In KIF2β-overexpressing cells, lysosomes (labeled with anti-lysosome-associated membrane protein-1) become abnormally large and peripherally located at some distance from their usual perinuclear positions. Overexpression of KIF2 or KIF2β does not change the size or distribution of early, late and recycling endosomes nor does overexpression of different kinesin superfamily proteins result in changes in lysosome size or positioning. These results implicate KIF2β as a motor responsible for the peripheral translocation of lysosomes.

We have cloned two novel C-terminal motor domain-type kinesin superfamily motor proteins (KIFCs) from mouse brain by utilizing a KIFC-specific consensus sequence. The first protein was the murine homologue of CHO2 antigen, a member of the kar3-type mitotic motor subfamily, and we designated this protein KIFC1. The other protein, KIFC2 (792 amino acids), is novel, with no significant similarity to known kinesin superfamily proteins (KIFs). KIFC2 was specifically expressed in adult neurons, and was immunofluorescently localized to punctate structures in cell bodies and dendrites, but was not detected in axons. Electron microscopic analysis of the immunoisolated KIFC2-bound organelles revealed that KIFC2 associates with multivesicular body (mvb)-like organelles, suggesting that KIFC2 functions as the motor for the transport of mvb-like organelles in dendrites.

Kinesin superfamily proteins (KIFs) are probable motors in vesicular and non-vesicular transport along microtubular tracks. Since a variety of KIFs have been recently identified in the motile flagella of Chlamydomonas, we sought to ascertain whether KIFs are also associated with the connecting cilia of vertebrate rod photoreceptors. As the only structural link between the rod inner segment and the photosensitive rod outer segment, the connecting cilium is thought to be the channel through which all material passes into and out of the outer segment from the rod cell body. We have performed immunological tests on isolated sunfish rod inner-outer segments (RIS-ROS) using two antibodies that recognize the conserved motor domain of numerous KIFs (anti-LAGSE, a peptide antibody, and anti-Klp1 head, generated against the N terminus of Chlamydomonas Klp1) as well as an antibody specific to a neuronal KIF, KIF3A. On immunoblots of RIS-ROS, LAGSE antibody detected a prominent band at ~ 117 kDa, which is likely to be kinesin heavy chain, and Klp1 head antibody detected a single band at ~ 170 kDa KIF3A antibody detected a polypeptide at ~ 85 kDa which co-migrated with mammalian KIF3A and displayed ATP-dependent release from rod cytoskeletons. Immunofluorescence localizations with anti-LAGSE and anti-Klp1 head antibodies detected epitopes in the axoneme and ellipsoid, and immunoelectron microscopy with the LAGSE antibody showed that the connecting cilium region was particularly antigenic. Immunofluorescence with anti-KIF3A showed prominent labelling of the connecting cilium and the area surrounding its basal body the outer segment axoneme and parts of the inner segment coincident with microtubules were also labelled. We propose that these putative kinesin superfamily proteins may be involved in the translocation of material between the rod inner and outer segments.

Kinesin is known as a representative cytoskeletal motor protein that is engaged in cell division and axonal transport. In addition to the mutant assay, recent advances using the PCR cloning technique have elucidated the existence of many kinds of kinesin-related proteins in yeast, Drosophila, and mice. We previously cloned five different members of kinesin superfamily proteins (KIFs) in mouse brain (Aizawa, H., Y. Sekine, R. Takemura, Z. Zhang, M. Nangaku, and N. Hirokawa. 1992. J. Cell Biol. 119:1287-1296) and demonstrated that one of them, KIF3A, is an anterograde motor (Kondo, S., R. Sato-Yashitake, Y. Noda, H. Aizawa, T. Nakata, Y. Matsuura, and N. Hirokawa. J. Cell. Biol. 1994. 125:1095-1107). We have now characterized another axonal transport motor, KIF2. Different from other KIFs, KIF2 is a central type motor, since its motor domain is located in the center of the molecule. Recombinant KIF2 exists as a dimer with a bigger head and plus-end directionally moves microtubules at a velocity of 0.47 ± 0.11 μm/s, which is two thirds that of kinesin's. Immunocytological examination showed that native KIF2 is abundant in developing axons and that it accumulates in the proximal region of the ligated nerves after a 20-h ligation. Soluble KIF2 exists without a light chain, and KIF2's associated-vesicles, immunoprecipitated by anti-KIF2 antibody, are different from those carried by existing motors such as kinesin and KIF3A. They are also distinct from synaptic vesicles, although KIF2 is accumulated in so-called synaptic vesicle fractions and embryonal growth cone particles. Our results strongly suggest that KIF2 functions as a new anterograde motor, being specialized for a particular group of membranous organelles involved in fast axonal transport.

To further elucidate the mechanism of organelle transport, we cloned a novel member of the mouse kinesin superfamily, KIF1B. This N-terminal-type motor protein is expressed ubiquitously in various kinds of tissues. In situ hybridization revealed that KIF1B is expressed abundantly in differentiated nerve cells. Interestingly, KIF1B works as a monomer, having a microtubule plus end-directed motility. Our rotary shadowing electron microscopy revealed mostly single globular structures. Immunocytochemically, KIF1B was colocalized with mitochondria in vivo. Furthermore, a subcellular fractionation study showed that KIF1B was concentrated in the mitochondrial fraction, and purified KIF1B could transport mitochondria along microtubules in vitro. These data strongly suggested that KIF1B works as a monomeric motor for anterograde transport of mitochondria. © 1994.

To understand the mechanisms of transport for organelles in the axon, we isolated and sequenced the cDNA encoding KIF4 from murine brain, and characterized the molecule biochemically and immunocytochemically. Complete amino acid sequence analysis of KIF4 and ultrastructural studies of KIF4 molecules expressed in Sf9 cells revealed that the protein contains 1,231 amino acid residues (M(r) 139,550) and that the molecule (116-nm rod with globular heads and tail) consists of three domains: an NH2-terminal globular motor domain, a central α-helical stalk domain and a COOH-terminal tail domain. KIF4 protein has the property of nucleotide-dependent binding to microtubules, microtubule-activated ATPase activity, and microtubule plus- end-directed motility. Northern blot analysis and in situ hybridization demonstrated that KIF4 is strongly expressed in juvenile tissues including differentiated young neurons, while its expression is decreased considerably in adult mice except in spleen. Immunocytochemical studies revealed that KIF4 colocalized with membranous organelles both in growth cones of differentiated neurons and in the cytoplasm of cultured fibroblasts. During mitotic phase of cell cycle, KIF4 appears to colocalize with membranous organelles in the mitotic spindle. Hence we conclude that KIF4 is a novel microtubule- associated anterograde motor protein for membranous organelles, the expression of which is regulated developmentally.

Neurons are highly polarized cells composed of dendrites, cell bodies, and long axons. Because of the lack of protein synthesis machinery in axons, materials required in axons and synapses have to be transported down the axons after synthesis in the cell body. Fast anterograde transport conveys different kinds of membranous organelles such as mitochondria and precursors of synaptic vesicles and axonal membranes, while organelles such as endosomes and autophagic prelysosomal organelles are conveyed retrogradely. Although kinesin and dynein have been identified as good candidates for microtubule-based anterograde and retrograde transporters, respectively, the existence of other motors for performing these complex axonal transports seems quite likely. Here we characterized a new member of the kinesin superfamily KIF3A (50-nm rod with globular head and tail), and found that it is localized in neurons, associated with membrane organelle fractions, and accumulates with anterogradely moving membrane organelles after ligation of peripheral nerves. Furthermore, native KIF3A (a complex of 80/85 KIF3A heavy chain and a 95-kD polypeptide) revealed microtubule gliding activity and baculovirus-expressed KIF3A heavy chain demonstrated microtubule plus end-directed (anterograde) motility in vitro. These findings strongly suggest that KIF3A is a new motor protein for the anterograde fast axonal transport.

Insulin drives the formation of a complex between tyrosine-phosphorylated IRS-1 and SH2-containing proteins. The SH2-containing protein Grb2 also possesses adjacent SH3 domains, which bind the Ras guanine nucleotide exchange factor Sos. In this report, we examined the involvement of another SH3 binding protein, dynamin, in insulin signal transduction. SH3 domains of Grb2 as GST fusion proteins bound dynamin from lysates of CHO cells expressing wild-type insulin receptor (IR) (CHO-IR cells) in a cell-free system (in vitro). Immunoprecipitation studies using specific antibodies against Grb2 revealed that Grb2 was co-immunoprecipitated with dynamin from unstimulated CHO-IR cells. After insulin treatment of CHO-IR cells, anti-dynamin antibodies co-immunoprecipitated the IR β-subunit and IRS-1, as tyrosinephosphorylated proteins and PI 3-kinase activity. However, purified rat brain dynamin did not bind directly to either the IR, IRS-1 or the p85 subunit of PI 3-kinase in vitro. Together, these results suggest that in CHO-IR cells, insulin stimulates the binding of dynamin to tyrosine-phosphorylated IRS-1 via Grb2 and that IRS-1 also associates with PI 3-kinase in response to insulin. This complex formation was reconstituted in vitro using recombinant baculovirusexpressed IRS-1, GST-Grb2 fusion proteins and dynamin peptides containing proline-rich sequences. Furthermore, dynamin GTPase activity was found to be stimulated when an IRS-1-derived phosphopeptide, containing the Grb2 binding site, was added to the dynamin-Grb2 complex in vitro. These findings provide evidence that dynamin is complexed with Grb2 in CHO-IR cells and, after insulin stimulation, the IRS-1 molecule is able to bind this Grb2-dynamin complex and may regulate dynamin GTPase activity in the complex in intact cells (in vivo).

Tissue distribution and intracellular localization of dynamin by immunoblotting and immunocytochemistry is investigated in this study. Dynamin was widely expressed in all the neurons we examined, and was especially abundant in the central nervous system after maturation, although its expression presented regional heterogeneity. Dynamin was present most abundantly in cerebellar Purkinje cells and hippocampal pyramidal cells, and to a lesser extent in motor neurons and peripheral nerves. However, dynamin was nearly absent in cells such as anterior pituitary cells and adrenal medullary cells which secrete mainly dense-cored vesicles. Dynamin was localized not only in cell bodies, axons, and synapses but also in dendrites. Subcellular fractionation indicated that dynamin existed in the membrane fraction as well as in the soluble fraction. In ligated peripheral nerves, dynamin colocalized with tubulovesicular membranous organelles transported mainly anterogradely. By transfection of dynamin cDNA into mouse fibroblast L-cells, we showed it colocalized with some membranous organelles but not with microtubules. Our results show that dynamin is associated with membranous organelles in vivo, although a certain amount of dynamin also exists in the soluble fraction and is distributed diffusely throughout mature neurons. The data suggest that dynamin's fundamental role involves membrane trafficking in neurons in the central nervous system rather than in sliding microtubules as a motor protein.

We purified a large amount of dynamin with high enzymatical activity from rat brain tissue by a new procedure. Dynamin 0.48 mg was obtained from 20 g of rat brain. The purity of dynamin was almost 98%. Dynamin plays a role of GTPase rather than ATPase. In the absence of microtubules, Michaelis constant (K(m)) and maximum velocity (V(max)) for dynamin GTPase were 370 μM and 0.25 min-1, respectively, and in their presence, both were significantly accelerated up to 25 μM and 5.5 min-1. On the other hand, the ATPase activity was very low in the absence of microtubules, and even in their presence, K(m) and V(max) for dynamin ATPase were 0.2 mM and 0.91 min-1. Despite slow GTPase turnover rate in the absence of microtubules, binding of GTP and its nonhydrolizing analogues was very fast, indicating that GTP binding step is not rate limiting. Dynamin did not cause a one-directional consistent microtubule sliding movement just like kinesin or dynein in the presence of 2 mM ATP or 2 mM GTP. We observed the molecular structure of dynamin with low-angle rotary shadowing technique and revealed that the dynamin molecule is globular in shape. Gel filtration assay revealed that these globules were the oligomers of 100-kDa dynamin polypeptide. Dynamin bound to microtubules with a 1:1 ~ 1.2 molar ratio in the absence of GTP. Quick-freeze deep-etch electron microscopy of the dynamin-microtubule complex showed that dynamin decorates the surface of microtubules helically, like a screw bolt, very orderly and tightly with 11.4 ± 0.9 (SD)nm period. Contrary to the previous report, microtubules make bundles by the attachment of the dynamin helixes around each adjacent microtubule, and no cross-bridge formation was observed.

We have cloned a cDNA for dynamin, a 100 kd microtubule-associated motor protein whose 5′ region contains a GTP-binding motif homologous to that of the Mx proteins, from a rat brain library and analyzed its expression. Dynamin mRNA is 3.6 kb and is preferentially expressed in the brain after postnatal day 7, parallel to the developmental increase of the protein. In situ hybridization revealed high levels of dynamin transcripts in neural cells in the cerebellar cortex, hippocampus (particularly in the CA3 area), and cerebral cortex. The transcripts appeared in cerebellar granular cells only after they had ceased dividing and had migrated to the inner granular layer. We show that dynamin is expressed predominantly in neural cells after elongation of their processes, suggesting a role especially in mature neurons. © 1991.