Lee Eun Jung, Lee Hyun Gyu, Park Sung Hye, Choi Eun Young, Park Seong Hoe
Department of Pathology, College of Medicine, Seoul National University, Seoul, Korea.
Exp Mol Med. 2003 Oct 31;35(5):438-47. doi: 10.1038/emm.2003.57.
CD99 is a 32-kDa cell surface molecule present on thymocytes, peripheral T cells, many other hematopoietic stem cells and somatic cells were implicated in cell-cell adhesion and cell-activation phenomena. Two major subtypes have been identified so far, designated CD99 type I and type II. We have investigated the correlation between the degree of neural differentiation and the expression of CD99 subtypes in three differentially differentiated cell lines such as CADO-ES1, RD-ES, and SH-N-SY5Y, in order of differentiation. In addition, we induced differentiation of the RD-ES cell line by N6,2'-dibutyryl-cAMP (db-cAMP). Six days after treatment with db-cAMP, RD-ES cell line has changed its morphology from uniform round cells to cells with neurites, and initially CD99 type II-overexpressed RD-ES cells showed significant down-regulation of CD99 type II, whereas CD99 type I expression remained constant. When RD- ES cells were transfected with the cDNA encoding for CD99 type I-green fluorescence protein (GFP) and type II-GFP, CD99 type II transfected RD-ES cell line remained unchanged with morphology of undifferentiated form. Our data suggest that CD99 type II acts as a negative regulator in the neural differentiation of precursor cells that might occur during nerve system development.
CD99是一种32 kDa的细胞表面分子，存在于胸腺细胞、外周T细胞、许多其他造血干细胞和体细胞中，与细胞间黏附和细胞激活现象有关。迄今为止已鉴定出两种主要亚型，分别命名为CD99 I型和II型。我们按照分化程度研究了三种差异分化的细胞系CADO-ES1、RD-ES和SH-N-SY5Y中神经分化程度与CD99亚型表达之间的相关性。此外，我们用N6,2'-二丁酰环磷腺苷（db-cAMP）诱导RD-ES细胞系分化。用db-cAMP处理六天后，RD-ES细胞系的形态从均匀的圆形细胞变为具有神经突的细胞，最初II型CD99过表达的RD-ES细胞显示II型CD99显著下调，而I型CD99表达保持不变。当用编码I型CD99-绿色荧光蛋白（GFP）和II型GFP的cDNA转染RD-ES细胞时，转染II型CD99的RD-ES细胞系形态保持未分化形式不变。我们的数据表明，II型CD99在神经系统发育过程中可能发生的前体细胞神经分化中起负调节作用。
