Tomarev S I, Sundin O, Banerjee-Basu S, Duncan M K, Yang J M, Piatigorsky J
Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892-2730, USA.
Dev Dyn. 1996 Aug;206(4):354-67. doi: 10.1002/(SICI)1097-0177(199608)206:4<354::AID-AJA2>3.0.CO;2-H.
Prox 1 is the vertebrate homolog of Drosophila prospero, a gene known to be expressed in the lens-secreting cone cells of fly ommatidia. Chicken Prox 1 cDNAs were isolated from 14 day embryonic chicken lenses, and a complete open reading frame encoding an 83 kDa protein was elucidated. The homeodomains of chicken and mouse Prox 1 are identical at the amino acid level and are 65-67% similar to the homeodomains of Drosophila and C. elegans prospero. The homology between these proteins extends beyond the homeodomain. There is 56% identity between chicken Prox 1 and Drosophila prospero in the C-terminal region downstream of the homeodomain, whereas there is little similarity upstream of the homeodomain. Prox 1 is expressed most actively in the developing lens and midgut and at lower levels in the developing brain, heart, muscle, and retina. cDNA sequencing has established that there are alternatively spliced forms of the single Prox 1 gene, which probably account for the two abundant RNAs of about 2 and 8 kb and two less abundant RNAs close to 3.5 kb in length in the lens. In the lens fibers, only the shortest mRNA was present, whereas, in the epithelial cells, both short and long mRNAs were detected. By using in situ hybridization, expression of the Prox 1 gene was first detected at stage 14 in the early lens placode and slightly preceded the expression of delta 1-crystallin, the first crystallin gene expressed in the developing chicken lens. At later stages of development, Prox 1 mRNA was observed throughout the lens, but it appeared more abundant around the bow region of the equator than in the anterior epithelium or the fibers. In the retina, expression of the Prox 1 gene was detected mainly in the inner nuclear layer during later stages of histogenesis. The conserved pattern of Prox 1/prospero gene expression in vertebrates and Drosophila suggests that Prox 1, like Pax-6, may be essential for eye development in different systematic groups.
Prox 1是果蝇prospero在脊椎动物中的同源基因，已知该基因在果蝇小眼的晶状体分泌锥细胞中表达。从14日龄鸡胚晶状体中分离出鸡Prox 1 cDNA，并阐明了一个编码83 kDa蛋白质的完整开放阅读框。鸡和小鼠Prox 1的同源结构域在氨基酸水平上相同，与果蝇和秀丽隐杆线虫prospero的同源结构域相似性为65 - 67%。这些蛋白质之间的同源性延伸到同源结构域之外。鸡Prox 1与果蝇prospero在同源结构域下游的C末端区域有56%的同一性，而在同源结构域上游则几乎没有相似性。Prox 1在发育中的晶状体和中肠中表达最为活跃，在发育中的脑、心脏、肌肉和视网膜中表达水平较低。cDNA测序已确定单个Prox 1基因存在可变剪接形式，这可能是晶状体中约2 kb和8 kb的两种丰富RNA以及长度接近3.5 kb的两种较少丰富RNA的原因。在晶状体纤维中，只存在最短的mRNA，而在上皮细胞中，检测到了短mRNA和长mRNA。通过原位杂交，在发育早期的第14阶段，在晶状体原基中首次检测到Prox 1基因的表达，略早于发育中的鸡晶状体中第一个表达的晶状体蛋白基因δ1 - 晶状体蛋白的表达。在发育的后期阶段，在整个晶状体中都观察到了Prox 1 mRNA，但在赤道弓区域周围比在前上皮或纤维中显得更为丰富。在视网膜中，在组织发生的后期阶段，Prox 1基因的表达主要在内核层中检测到。Prox 1/prospero基因在脊椎动物和果蝇中保守的表达模式表明，Prox 1与Pax - 6一样，可能对不同系统类群的眼睛发育至关重要。
