FgfrL1 is a novel growth factor receptor that is primarily expressed in musculoskeletal tissues and the kidney. FgfrL1-deficient mice have a malformed diaphragm and no kidneys. Such animals die immediately after birth because they are not able to inflate their lungs. The FgfrL1 molecule is composed of three extracellular Ig domains, a transmembrane helix and a short intracellular domain. To investigate the contribution of each of these domains to the function of the novel receptor, we generated mice with deletions of the individual domains. Mice lacking the intracellular domain are viable and phenotypically normal. Mice lacking the first (N-terminal) Ig domain are also viable and normal, but have a reduced life span. Mice lacking the Ig2 or the Ig3 domain are born alive, but die within 24 h after birth. Ig2-deficient animals exhibit substantially smaller kidneys than wild-type littermates and contain a lower number of glomeruli. Ig3-deficient mice completely lack metanephric kidneys. Interestingly, both the Ig2 and the Ig3-deficient animals show only minor alterations in the diaphragm, which still enables them to inflate their lungs after birth. Our results demonstrate that the principal function of the FgfrL1 receptor is to control the growth of the metanephric kidneys by regulating nephrogenesis. It appears that this function is primarily accomplished by the Ig3 domain with some contribution of the Ig2 domain. It is conceivable that the two domains interact with an Fgf ligand and another molecule from the surface of neighboring cells to induce condensation of the metanephric mesenchyme to renal epithelia and glomeruli.

中文翻译：

---

FgfrL1受体的功能域。

FgfrL1是一种新型的生长因子受体，主要在肌肉骨骼组织和肾脏中表达。缺乏FgfrL1的小鼠的diaphragm肌畸形，没有肾脏。这些动物出生后会立即死亡，因为它们无法使肺膨胀。FgfrL1分子由三个细胞外Ig结构域，一个跨膜螺旋结构和一个短细胞内结构域组成。为了研究每个域对新型受体功能的贡献，我们生成了缺失单个域的小鼠。缺乏细胞内结构域的小鼠是有活力的，并且在表型上是正常的。缺少第一个（N端）Ig结构域的小鼠也可行且正常，但寿命缩短。缺少Ig2或Ig3结构域的小鼠活着出生，但在出生后24小时内死亡。缺乏Ig2的动物比野生同窝动物的肾脏要小得多，肾小球的数量也较少。缺乏Ig3的小鼠完全缺乏后肾肾脏。有趣的是，Ig2和Ig3缺陷型动物的the肌仅表现出细微的变化，这仍然使它们在出生后能够使肺膨胀。我们的研究结果表明FgfrL1受体的主要功能是通过调节肾发生来控制后肾的生长。似乎该功能主要由Ig3域完成，并具有Ig2域的某些贡献。可以想象这两个结构域与Fgf配体和邻近细胞表面的另一个分子相互作用，以诱导后肾间充质凝结至肾上皮和肾小球。