SPECIFICATION OF MUSCLE PATTERN IN THE AMNIOTE LIMB

在发育中的羊膜肢体中，肌肉模式规范的分子机制以及肌肉模式规范与骨骼和肌腱模式规范的关系在很大程度上是未知的。肌原性前体细胞迁移到肢体，最终分化成慢速和快速肌纤维，分布在45块解剖肌肉中。为了描述肌源性细胞何时何地被图图化，克隆相关的肌源性细胞的命运将通过用CHAPOL复制缺陷逆转录病毒文库标记肌源性前体来分析。lmx1和hox转录因子似乎对确定背-腹侧、前后和近端-远端肢体肌肉模式至关重要。这些基因在肌肉形态发生的特定阶段的作用将通过lmx1和hoxd-11逆转录病毒在发育中的鸡肢体的不同时间和空间不适当的位置的错误表达来评估。鹌鹑-鸡嵌合体和逆转录病毒基因表达的组织特异性操作将确定lmx1和hoxd-11最初在肢体芽中表皮表达，如何将其模式信息传递给肌肉，并为解剖肢体发育过程中肌肉、肌腱和骨骼形态发生之间的关系提供重要手段。[此外，正在通过鸡肢体文库筛选编码分泌蛋白的基因来寻找与肌肉模式有关的新基因]。

The molecular mechanisms underlying the specification of muscle pattern and the relationship of muscle pattern specification to skeletal and tendon pattern specification in the developing amniote limb are largely unknown. Myogenic precursor cells migrate into the limb and eventually differentiate into slow and fast myofibers arranged into 45 anatomical muscles. [To delineate when and where myogenic cells are being patterned, the fate of clonally-related myogenic cells will be analyzed by labeling myogenic precursors with CHAPOL replication defective retrovirus library.] lmx1 and hox transcription factors appear to be critical for specifying dorsal-ventral, anterior-posterior, and proximal-distal limb muscle pattern. The role of these genes in patterning particular phases of muscle morphogenesis will be assessed by retroviral misexpression of lmx1 and hoxd-11 in spatially inappropriate locations and at different times in the developing chick limb. Quail-chick chimeras and retroviral, tissue-specific manipulations of gene expression will determine how lmx1 and hoxd-11, initially expressed in the limb bud mesoderm, transmit their patterning information to muscle and provide an important means of dissecting the relationship between muscle, tendon, and skeleton morphogenesis during limb development. [In addition, novel genes involved in muscle patterning are being sought via a screen of a chick limb library for genes encoding secreted proteins].