Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071, China.
Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266000, China.
Dev Genes Evol. 2020 Jan;230(1):39-45. doi: 10.1007/s00427-020-00646-9. Epub 2020 Jan 20.
The molluscan larval shell formation is a complicated process. There is evidence that the mantle of the primary larva (trochophore) contains functionally different cell populations with distinct gene expression profiles. However, it remains unclear how these cells are specified. In the present study, we identified three cell populations from the shell gland in earlier stages (gastrula) from the bivalve mollusc Crassostrea gigas. These cell populations were determined by analyzing the co-expression relationships among six potential shell formation (pSF) genes using two-color hybridization. The three cell populations, which we designated as SGCPs (shell gland cell populations), formed a concentric-circle pattern from outside to inside of the shell gland. SGCP I was located in the outer edge of the shell gland and the cells expressed pax2/5/8, gata2/3, and bmp2/4. SGCP II was located more internally and the cells expressed two engrailed genes. The last population, SGCP III, was located in the central region of the shell gland and the cells expressed lox4. Determination of the gene expression profiles of SGCPs would help trace their origins and fates and elucidate how these cell populations are specified. Moreover, potential roles of the SGCPs, e.g., development of sensory cells and shell biogenesis, are suggested. Our results reveal the internal organization of the embryonic shell gland at the molecular level and add to the knowledge of larval shell formation.
软体动物幼虫壳的形成是一个复杂的过程。有证据表明，初级幼虫（担轮幼虫）的套膜含有功能不同的细胞群体，具有不同的基因表达谱。然而，这些细胞是如何被特化的仍不清楚。在本研究中，我们从双壳贝类贻贝（Crassostrea gigas）的早期（原肠胚期）壳腺中鉴定出了三个细胞群体。这些细胞群体是通过分析六个潜在的壳形成（pSF）基因之间的共表达关系，使用双色杂交来确定的。这三个细胞群体，我们称之为 SGCPs（壳腺细胞群体），从壳腺的外部到内部形成一个同心圆形的模式。SGCP I 位于壳腺的外边缘，细胞表达 pax2/5/8、gata2/3 和 bmp2/4。SGCP II 位于更内部，细胞表达两个 engrailed 基因。最后一个群体，SGCP III，位于壳腺的中心区域，细胞表达 lox4。确定 SGCPs 的基因表达谱将有助于追踪它们的起源和命运，并阐明这些细胞群体是如何被特化的。此外，还提出了 SGCPs 的潜在作用，例如感觉细胞的发育和壳的生物发生。我们的研究结果揭示了胚胎壳腺在分子水平上的内部组织，增加了对幼虫壳形成的认识。
