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.对我们以前分离的前孢子特异基因Dp 87的表达研究表明，在前孢子细胞分化时，该基因在其他前孢子基因中表达最早。用Dp 87启动子和β-半乳糖苷酶基因嵌合基因检测组织中基因表达，发现前孢子细胞首先随机出现在早期聚集流中。然而，随着发育的进行，它们被分选到组织的底部。这些证实了我们的主张，即已经分化的细胞与它们在组织中的位置无关，它们被分选出来形成一种分化模式。我们让大肠杆菌产生大量的Dp 87基因产物，针对其产生特异性抗体并用于检查其发育变化。该基因产物首先以81 kD的蛋白质形式出现在聚集细胞的内质网中，然后经修饰形成83 kD的蛋白质，积累在蛞蝓细胞的前孢子囊泡的纤维状物质中。孢子形成后，蛋白质被胞外化，构成孢子间基质.利用同源重组技术获得了一株缺失Dp 87基因的突变株。该突变体在结构和功能上均正常.我们研究了Dp 87基因5 '上游区域的转录调控，发现4个前孢子特异性转录的正调控区域，1个非前孢子特异性转录的负调控区域，以及1个非细胞类型依赖性转录的正调控区域，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.