Mechanisms of growth and patterning of the mollusc shell

软体动物是最成功的动物群体之一，部分原因是它们坚固耐用的外壳。 在一个单独的软体动物群体中，蜗牛，有各种各样不同的外壳形状，但都是同一种几何形状的变化，螺旋形。 由于这种潜在的简单性，蜗牛壳是理解新生物结构如何形成的重要模型，但产生壳的细胞和发育机制尚不清楚。 这些研究人员检查了分泌贝壳的组织中的细胞分裂模式，发现了两个不同的生长区。 值得注意的是，每个区域都显示了细胞分裂模式，可以解释驱动外壳形状的生长。 研究人员还发现了令人惊讶的细胞形状和基因活性的精细模式，这些模式导致了外壳的形成。研究人员将测试这些基因形成外壳的能力，并在另一个具有不同外壳卷曲的物种中检查这些模式。 由于蜗牛壳是生命多样性的一个常见例子，这项工作将提供一个很好的例子，说明基因和细胞的微小差异可以创造新的不同形状。 该项目还将加强对研究生和本科生的培训，并将创建两个关于贝壳形状的课堂模块，用于向当地一个高度贫困地区的初中和高中学生进行宣传。该项目包括三个目标，调查细胞分裂和基因表达的能力，以形成螺旋盘绕的伊利亚纳萨蜗牛分泌的贝壳。 首先，研究人员将定义细胞分裂的模式，这些模式有助于壳的形状，然后功能性地测试可能驱动这些模式的几种信号通路。 然后将在另一种蜗牛中测试细胞分裂，以确定细胞分裂模式是否保守，以及具有相反卷曲手性的菌株是否具有与壳卷曲方向相关的不对称分裂模式。 第二个目标是通过对胚胎的转录组进行测序，发现新的生长、模式化和矿化的候选调节因子，其中胚胎的壳发育被细胞消融特异性阻断。 将通过原位杂交检查差异调节的转录物，以验证其在套膜边缘的表达。 初步数据表明，这一目标将揭示地幔边缘复杂的空间模式，并恢复可能调节生长和模式的新基因。 最后，特定的基因敲除技术将测试推定的调节因子和矿化基因的功能。 初步结果表明，它们可以扰乱壳生产和壳形态。 该项目将提供基本的见解，产生软体动物壳的机制，并提供一个细胞水平的系统，用于评估与形态学的数学建模相关的假设。预计该项目还将把生物矿化的知识与发育生物学结合起来。

Molluscs are among the most successful animal groups, due in part to their strong and durable shells. Within a single group of molluscs, the snails, there is an enormous variety of different shell shapes, but all are variations on the same geometry, the helical spiral. Because of this underlying simplicity, snail shells are an important model for understanding how new biological structures are formed, but the cellular and developmental mechanisms that generate the shell are unknown. These researchers examined the patterns of cell division in the tissue that secretes the shell, and discovered two distinct growth zones. Remarkably, each zone displays cell division patterns that can explain the growth that drives shell shape. The researchers also found surprising fine-scale patterns in cell shape and gene activity that cause shell formation. The researchers will test the ability of these genes to form shells, and examine these patterns in another species with different shell coiling. Since snail shells are a familiar example of the great diversity of life, this work will provide an excellent example of the ways that small differences in genes and cells can create new and different shapes. The project will also enhance training of graduate and undergraduate students, and will create two classroom modules about shell shape to be used for outreach to middle school and high school students in a local high-poverty district.This project contains three aims to investigate the ability of cell division and gene expression to pattern the helically coiled secreted shells of the snail Ilyanassa. First, the researchers will define patterns of cell division that putatively contribute to shell shape, then functionally test several signaling pathways that may drive these patterns. Cell division will then be tested in another snail, Lymnaea stagnalis, to determine if the cell division patterns are conserved, and if strains with opposite coiling chirality have asymmetric division patterns correlated with the direction of shell coiling. The second aim will discover new candidate regulators of growth, patterning, and mineralization, via sequencing transcriptomes of embryos where shell development has been specifically blocked by cell ablation. Differentially regulated transcripts will be examined by in situ hybridization to validate their expression in the mantle edge. Preliminary data suggests that this aim will reveal intricate spatial patterning of the mantle edge, and recover new genes that might be regulating growth and patterning. Finally, specific gene-knockdown techniques will test the function of putative regulatory factors and mineralization genes. Preliminary results indicate that they can perturb both shell production and shell morphology. This project will provide fundamental insights into the mechanisms that generate the molluscan shell, and provide a cellular-level system for evaluating hypotheses related to mathematical modeling of morphology. The project is also expected to integrate knowledge of biomineralization with developmental biology.