Boyle M, Bonini N, DiNardo S
The Rockefeller University, NYC, NY 10021-6399, USA.
Development. 1997 Mar;124(5):971-82. doi: 10.1242/dev.124.5.971.
The gonad forms from cells of two lineages: the germline and soma. The somatic gonadal cells generate the various cell types within the testis or ovary that support gametogenesis. These cells derive from embryonic mesoderm, but how they are specified is unknown. Here, we describe a novel regulator of Drosophila gonadogenesis, clift, mutations in which abolish gonad formation. clift is expressed within somatic gonadal precursors as these cells first form, demonstrating that 9-12 cells are selected as somatic gonadal precursors within each of three posterior parasegments at early stages in gonadogenesis. Despite this early expression, somatic gonadal precursors are specified in the absence of clift function. However, they fail to maintain their fate and, as a consequence, germ cells do not coalesce into a gonad. In addition, using clift as a marker, we show that the anteroposterior and dorsoventral position of the somatic gonadal precursor cells within a parasegment are established by the secreted growth factor Wg, coupled with a gene regulatory hierarchy within the mesoderm. While loss of wg abolishes gonadal precursors, ectopic expression expands the population such that most cells within lateral mesoderm adopt gonadal precursor fates. Initial dorsoventral positioning of somatic gonadal precursors relies on a regulatory cascade that establishes dorsal fates within the mesoderm and is subsequently refined through negative regulation by bagpipe, a gene that specifies nearby visceral mesoderm. Thus, these studies identify essential regulators of gonadal precursor specification and differentiation and reveal novel aspects of the general mechanism whereby distinct fates are allocated within the mesoderm.
生殖系和体细胞。体细胞性腺细胞产生睾丸或卵巢内支持配子发生的各种细胞类型。这些细胞源自胚胎中胚层，但它们如何被特化尚不清楚。在这里，我们描述了一种果蝇性腺发生的新型调节因子clift，其突变会导致性腺形成缺失。clift在体细胞性腺前体细胞刚形成时就在其中表达，这表明在性腺发生的早期阶段，三个后副节中的每一个都有9 - 12个细胞被选为体细胞性腺前体细胞。尽管有这种早期表达，但体细胞性腺前体细胞在没有clift功能的情况下仍能被特化。然而，它们无法维持其命运，结果生殖细胞不能聚集成性腺。此外，利用clift作为标记，我们表明副节内体细胞性腺前体细胞的前后和背腹位置是由分泌的生长因子Wg以及中胚层内的基因调控层级所确定的。虽然wg的缺失会消除性腺前体细胞，但异位表达会扩大细胞群体，使得外侧中胚层内的大多数细胞都采用性腺前体细胞命运。体细胞性腺前体细胞的初始背腹定位依赖于一个调节级联反应，该反应在中胚层内建立背侧命运，随后通过指定附近内脏中胚层的基因bagpipe的负调控进行细化。因此，这些研究确定了性腺前体细胞特化和分化的关键调节因子，并揭示了中胚层内分配不同命运的一般机制的新方面。
