Veltmaat Jacqueline M, Van Veelen Wendy, Thiery Jean Paul, Bellusci Saverio
UMR 144-CNRS-Institut Curie, Equipe de Morphogenèse Cellulaire et Progression Tumorale, Paris, France.
Dev Dyn. 2004 Feb;229(2):349-56. doi: 10.1002/dvdy.10441.
Mammogenesis in rabbit, rat, and human begins with the formation of an elevated ectodermal ridge in the embryo. Attempts to demonstrate a morphologically or histologically equivalent mammary line in the mouse have yielded controversial results. We show here that a mammary line exists in the mouse embryo at embryonic day (E) 11.25 as a concise line of Wnt10b expression and a broader band of Wnt6 expression in the surface ectoderm, between the subaxillary and suprainguinal region of each flank. Additional streaks of Wnt10b expression in the axillary and inguinal region join the mammary line on the flank slightly later. Expression of Wnt10b and Wnt6 becomes restricted to the placodes within 1.5 days. The ectoderm of the mammary line is organized as a pseudostratified epithelium connecting the developing mammary placodes at around E11.5, whereas all other surface ectoderm is single-layered. Thus, the mammary line expressing Wnt10b defines a distinct ectodermal region that we consider the equivalent of the ectodermal ridge in, for example, rabbit. To date, the formation of the mammary line expressing Wnt10b is the earliest discernible ectodermal event in murine embryonic mammary gland development.
兔、大鼠和人类的乳腺发生始于胚胎中一个隆起的外胚层嵴的形成。在小鼠中试图证明形态学或组织学上等效的乳腺线的尝试产生了有争议的结果。我们在此表明，在胚胎第11.25天（E11.25）的小鼠胚胎中存在一条乳腺线，表现为在每个胁腹的腋下和腹股沟上方区域之间的表面外胚层中，Wnt10b表达的一条简洁线和Wnt6表达的一条更宽带。在腋窝和腹股沟区域额外的Wnt10b表达条纹稍后与胁腹上的乳腺线相连。Wnt10b和Wnt6的表达在1.5天内局限于基板。在大约E11.5时，乳腺线的外胚层组织为连接发育中的乳腺基板的假复层上皮，而所有其他表面外胚层为单层。因此，表达Wnt10b的乳腺线定义了一个独特的外胚层区域，我们认为它等同于例如兔中的外胚层嵴。迄今为止，表达Wnt10b的乳腺线的形成是小鼠胚胎乳腺发育中最早可辨别的外胚层事件。
