CLONING AND CHARACTERIZATION OF MYOSIN-RELATED CDNAS FROM XENOPUS LAEVIS

II类非肌肉肌球蛋白参与参与多种 生物过程，如胞质分裂、细胞化、细胞形状 变化和原肠形成。两条截然不同的非肌肉肌球蛋白重链 所有脊椎动物的基因都已被报道：非肌肉肌球蛋白重 链-A(NMHC-A)和-B(NMHC-B)。我们正在致力于隔离 非洲爪哇的NMHC-A同源物和正在进行的比较 NMHC-A的发育和空间表达模式分析 和之前分离的NMHC-B来解决NMHC在 脊椎动物的发育。一个7.5 kb的NMHC-A mRNA在母体中存在 未受精卵和整个胚胎发育过程以及所有成体 组织检查。NMHC-A的额外8.3 kb合子转录本 在阶段15第一次可检测到，在阶段25-30之间达到峰值 到第47阶段就大大减少了。整装原位杂交 尾芽期胚胎显示NMHC-A mRNA主要表达 而NMHC-B mRNA在体节中表达， 大脑、眼睛和颧弓。有趣的是， NMHC-B在发育中的体节逐渐局限于中心 随着分化的进行，每个体节形成一种表达模式 尾芽阶段的垂直线。DAPI核染色 NMHC-B染色的胚胎切片显示NMHC-B mRNA是 与核和/或核周区共存。戴着动物帽 实验，激活素A治疗上调NMHC-B以及 肌肉肌动蛋白mRNAs和下调NMHC-A mRNA，与NMHC-A一致- B蛋白在躯体肌肉中的表达和NMHC-A在 表皮。因此，NMHC-A和NMHC-B的mRNAs表达存在差异 非洲爪蛙发育过程中NMHC-B基因的核定位 提示该基因在体细胞发生过程中具有独特的功能。

Class II nonmuscle myosins are implicated in participating in diverse biological processes such as cytokinesis, cellularization, cell shape changes and gastrulation. Two distinct nonmuscle myosin heavy chain genes have been reported in all vertebrates: nonmuscle myosin heavy chain-A (NMHC-A) and -B (NMHC-B). We are working on the isolation of the Xenopus homolog of NMHC-A and are carrying out a comparative analysis of the developmental and spatial expression patterns of NMHC-A and the previously isolated NMHC-B to address the role of NMHCs in vertebrate development. A 7.5 kb NMHC-A mRNA is present maternally in unfertilized eggs and throughout embryogenesis as well as in all adult tissues examined. An additional 8.3 kb zygotic transcript for NMHC-A is first detectable at stage 15, peaks between stages 25-30 and is greatly diminished by stage 47. Whole mount in situ hybridization with tailbud stage embryos shows that NMHC-A mRNA is predominantly expressed in the epidermis, whereas NMHC-B mRNA is expressed in the somites, brain, eyes and branchial arches. Interestingly, the expression of NMHC-B in developing somites is gradually restricted to the center of each somite as differentiation proceeds, forming an expression pattern of vertical lines at the tailbud stage. DAPI nuclear staining of sections from NMHC-B stained embryos demonstrated that NMHC-B mRNA is colocalized with the nuclei and/or perinuclear area. In animal cap experiments, treatment with activin A up-regulates NMHC-B as well as muscle actin mRNAs and down-regulates NMHC-A mRNA, consistent with NMHC- B expression in the somitic muscle and NMHC-A expression in the epidermis. Thus, NMHC-A and NMHC-B mRNAs are differentially expressed in Xenopus development and the nuclear localization of NMHC-B mRNA suggests a unique function of this gene during somitogenesis.