Obata S, Sago H, Mori N, Davidson M, St John T, Suzuki S T
Doheny Eye Institute, Los Angeles, CA 90033, USA.
Cell Adhes Commun. 1998;6(4):323-33. doi: 10.3109/15419069809010791.
To study the diversity of protocadherins, a rat brain cDNA library was screened using a cDNA for the cytoplasmic domain of human protocadherin Pcdh2 as a probe. The resultant clones contained three different types. One type corresponds to rat Pcdh2; the other two types are distinct from Pcdh2 but contain the same sequence in their cytoplasmic domains and part of the 3' flanking sequence. To clarify the structure of the proteins defined by the new clones, a putative entire coding sequence corresponding to one of the clones was determined. The overall structure is essentially the same as Pcdh2, indicating that the proteins defined by this clone, and probably by other clones, belong to the protocadherin family. Two PCR experiments and an RNase protection assay showed the existence of the corresponding mRNAs in rat brain preparations. Human and mouse cDNA clones with the same sequence properties were also isolated. Taken together, these results indicate that the clones are not cloning artifacts and that corresponding mRNAs are actually expressed in brains of various species. The results of in situ hybridization showed that the mRNAs corresponding to these clones were expressed in different regions in brain. Since protocadherins encoded by these mRNAs are likely to have different specificity in their interaction and share a common activity at their cytoplasmic domains, these protocadherins may provide a molecular basis, in part, to support the complex cell cell interaction in brain.
为了研究原钙黏蛋白的多样性，使用人原钙黏蛋白Pcdh2胞质结构域的cDNA作为探针筛选大鼠脑cDNA文库。所得克隆包含三种不同类型。一种类型对应大鼠Pcdh2；另外两种类型与Pcdh2不同，但在其胞质结构域和部分3'侧翼序列中含有相同序列。为了阐明由新克隆定义的蛋白质的结构，确定了对应于其中一个克隆的推定完整编码序列。整体结构与Pcdh2基本相同，表明由该克隆以及可能由其他克隆定义的蛋白质属于原钙黏蛋白家族。两项PCR实验和一项核糖核酸酶保护试验表明，大鼠脑提取物中存在相应的mRNA。还分离出具有相同序列特性的人和小鼠cDNA克隆。综上所述，这些结果表明这些克隆不是克隆假象，并且相应的mRNA确实在各种物种的脑中表达。原位杂交结果表明，与这些克隆相对应的mRNA在脑中的不同区域表达。由于由这些mRNA编码的原钙黏蛋白在其相互作用中可能具有不同的特异性，并且在其胞质结构域具有共同的活性，因此这些原钙黏蛋白可能部分地为支持脑中复杂的细胞间相互作用提供分子基础。
