Overexpression of neurogenin1 induces neurite outgrowth in F11 neuroblastoma cells

Neurogenin1 (Ngn1) is a basic helix-loop-helix (bHLH) transcription factor expressed in neuronal precursors in the developing nervous system. The function of Ngn1 in neurogenesis has been shown in various aspects. In this study, we investigated the neurogenic potential of Ngn1 using neuroblastoma cell line, F11, which could be induced to differentiate into neurons in the presence of cAMP. To investigate the expression of Ngn1, expression vectors for the full-length and the C- terminal deletion mutant of Ngn1 were constructed and their transactivation potential was verified using reporter gene containing the E-box sequence. Overexpression of the full-length Ngn1 induced neurite outgrowth in F11 cells in the absence of cAMP. A C-terminal deletion mutant, Ngn1(1-197), inhibited neurite outgrowth induced by cAMP in F11 cells. These results indicate that the Ngn1 plays an important role in differentiation of neuroblastoma cells and the C terminus of Ngn1 is essential for the efficient differentiation.

Inhibition of Neurite Outgrowth by Stably Expressed Go alpha in F11 Cells / 대한해부학회지

Heterotrimeric G proteins mediate signals generated by neurotransmitters and hormones. Among G proteins, Go is found in a large quantity in brain and growth cone membranes of neurons. In spite of its abundance in neurons, the role of Go is not fully understood. In the previous study, we showed that transient expression of the alpha subunit of Go (alpha o) modulated neurite outgrowth in F11 cells. It is possible that transient transfection may cause transient accumulation of the protein, which itself may alter differentiation process in non-specific manner. In this study, we determined that modulation of neurite outgrowth by alpha o was specific by evaluating the effect of alpha o in stably transformed F11 cells. F11 cells stably expressing the wild type alpha o (alphao(wt)) and a constitutively active form of alpha o (alpha oQ205L) were established. In normal F11 cells and alpha o-stable cell lines, the neurite length was measured in the presence of dibutyryl cAMP. In normal F11 cells, the average length of neurites was 57.9+/-7.0 microgram. In alpha o(wt)- and alpha o(Q205L)-expressing cells, the average length were 34.4+/-5.1 microgram 30.5+/-3.6 microgram, respectively. Thus, stable expression of alpha o(wt) and alpha o(Q205L) caused a decrease in neurite outgrowth by 40.6%, 47.3% respectively. This result indicates that modulation of neurite by alpha o was specific to the function of alpha o but not due to accumulation of exogenous proteins.

Neuronal Differentiatin of P19 Cells / 대한해부학회지

P19, murine embryonal carcinoma (EC) cells can be induced to differentiate into neurons in the presence of retinoic acid (RA). To investigate neuronal differentiation of P19 cells in details, P19 aggregates were obtained in the presence or absence of RA, ascorbic acid (AA) and 2-mercaptoethanol (2-ME) in bacteriological Petri dishes. When the aggregates were transferred into the serum depleted medium, P19 cells exhibited dramatic morphological changes. Cells contained long and thin processes as detected in differentiated neurons. Western blot analysis showed that treatment of RA and AA induced expression of neuron-specific markers such as NCAM, NSE and Tuj1. Expression of GFAP was not detected, suggesting that P19 cells differentiate into neurons under our experimental condition. Immunocytochemical studies also revealed that treatment of RA and AA increased expression of NCAM and Tuj1. On the contrary, 2-ME was ineffective in the neuronal differentiation of P19 cells, which is consistent the results from the western blot analysis. These results suggest that differentiated P19 cells have similar characteristics to those of typically differentiated neurons. This study also suggests that P19 cells may provide useful tools to study neuronal differentiation in vitro.

A Computer Program for Understanding Brain Morphology and Magnetic Resonance Image / 한국의학교육

Understanding of brain morphology and magnetic resonance image(MRI) is essential for accurate diagnosis and treatment of the brain diseases. As education tools, the cadaver dissection, plastic models, and neuroanatomy books have been used for understanding brain morphology; and the MRI films and radiology books have been used for understanding brain MRI. Recently, due to the popularization of powerful personal computers, computer programs compensating the conventional education tools have been used. But these computer programs have a disadvantage that it is not possible to visualize the details of brain morphology or to compare the corresponding sectioned specimens and MRI. Therefore, we attempted to make a computer program which could visualize not only the details of brain morphology but also the corresponding sectioned specimens and MRI by using the brains removed from Korean cadavers. Three brains were removed from Korean cadavers. With a brain, 122 MRI and 122 serially-sectioned specimens with an 1.4mm interval were acquired and inputted into the computer. Ten brain structures were segmented, and 83 fine structures were designated on the images. With two brains, 27 dissected specimens were acquired and inputted into the computer. One-hundred two fine structures were designated on the images. Based on these images, a computer program for understanding brain morphology and MRI was made. The computer program, which was made in this study, visualized the corresponding sectioned specimens, MRI, and segmented images after sectioning a brain horizontally or at any angles. In addition, the computer program visualized the images of dissected brain. This computer program is helpful to understand brain morphology and MRI. This computer program is expected to be used through CD-title or Internet as an educational tool for medical students and doctors.