Mechanism of formation of differentiation pattern in the cellular slime mold

在细胞黏菌的发育过程中，细胞聚集形成组织，其中两种类型的细胞(前柄和前孢子)分化并占据组织的前部和后部。为了阐明这些生物的模式形成机制，我们进行了以下研究。对我们先前分离的前孢子特异的Dp87基因的表达研究表明，在前孢子细胞分化过程中，该基因在其他前孢子基因中表达最早。利用由Dp87启动子和β-半乳糖苷酶基因组成的嵌合基因检测组织中的基因表达，结果表明，前孢子细胞首先在早期的聚集流中随机出现。然而，随着发育的进行，它们被分类到组织的底部。这些都证实了我们的主张，即分化的细胞与它们在组织中的位置无关，它们被分类形成分化的模式。我们允许大肠杆菌产生大量的Dp87基因产物，针对这些产物产生一种特异性抗体，并用于检测其发育变化。该基因产物首先以81kD蛋白的形式出现在聚集细胞的内质网中，然后被修饰为83kD蛋白，并聚集在鼻涕虫细胞的孢子前小泡的纤维质中。在孢子形成过程中，蛋白质被排出，形成孢子间基质。通过同源重组，获得了一株缺失Dp87基因的突变株。该突变体在结构和功能上均表现正常。我们研究了Dp87基因5‘-上游区域的转录调控，发现有四个区域对前孢子特异转录进行正控制，一个对非前孢子转录进行负控制，另一个对细胞类型无关的转录进行正控制，表明它们参与了对该基因转录的细胞类型和发育阶段的特异调控。

In the development of the cellular slime molds, cells aggregate to form a tissue, in which two types of cells (prestalk and prespore) differentiate and occupy the anterior and the postirior parts of the tissue. To elucidate the mechanism of pattern formation in these organisms, we made following studies.1. Studies on expression of prespore-specific Dp87 gene, previously isolated by us, revealed that upon differentiation of prespore cells, the gene was expressed earliest among the other prespore genes. Examination of the gene expression in the tissue using a chimeric gene consiting of Dp87 promoter and beta-galactosidase gene showed that prespore cells first appeared randomly in early aggregation streams. As development proceeded, however, they were sorted out to the bottom part of the tissue. These substantiate our claim that cells which have differentiated independent of their positions in the tissue are sorted out to form a pattern of differentiation.2. We allowed E.coli to produce a large amount of Dp87 gene product, against which a specific antibody was produced and used for examining its developmental changes. The gene product first appeared as 81kD protein in ER of aggregating cells and was then modified to become 83kD protein which accumulated in fibrous material of prespore vesicles of slug cells. Upon spore formation, the protein was exocytosed and constituted the interspore matrix.3. We obtained a mutant strain which lacks in Dp87 gene, by using homologous recombination. The mutant appeared normal both structurally and functionally.4. We examined the 5'-upstream region of Dp87 gene for its transcriptional regulation and found four regions for positive control of prespore-specific transcription, one for negative control of non-prespore transcription, and another for positive control of cell type-independent transcription, indicating that they are involved in cell-type- and developmental stage-specific regulation of the gene transcription.