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（前柄细胞和前孢子细胞）分化并占据组织的前部和后部。为了阐明这些生物模式形成的机制，我们进行了以下研究。我们之前分离的pre - spore特异性Dp87基因的表达研究表明，在pre - spore细胞分化时，该基因在其他pre - spore基因中表达最早。用Dp87启动子基因和β -半乳糖苷酶基因嵌合基因检测该基因在组织中的表达，发现孢子前细胞在早期聚集流中首先随机出现。然而，随着发育的进行，它们被分类到组织的底部。这些结果证实了我们的观点，即那些独立于它们在组织中的位置而分化的细胞被分类出来形成一种分化模式。我们允许大肠杆菌产生大量Dp87基因产物，并针对其产生特异性抗体，用于检测其发育变化。该基因产物首先在聚集细胞内质网中以81kD蛋白的形式出现，然后被修饰为83kD蛋白，在鼻涕虫细胞孢子前囊泡的纤维物质中积累。在孢子形成时，蛋白质被胞吐并构成孢子间基质。通过同源重组获得了一株缺乏Dp87基因的突变株。突变体在结构和功能上都表现正常。我们检测了Dp87基因的5'上游区域的转录调控，发现4个区域对pre - spore特异性转录有阳性控制，一个区域对非pre - spore转录有阴性控制，另一个区域对细胞类型无关的转录有阳性控制，表明它们参与了基因转录的细胞类型和发育阶段特异性调控。

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.