den Hollander A I, Johnson K, de Kok Y J, Klebes A, Brunner H G, Knust E, Cremers F P
Department of Human Genetics, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Hum Mol Genet. 2001 Nov 15;10(24):2767-73. doi: 10.1093/hmg/10.24.2767.
Mutations in the human Crumbs homologue 1 (CRB1) gene cause severe retinal dystrophies, ranging from retinitis pigmentosa to Leber congenital amaurosis. The CRB1 gene is expressed specifically in human retina and brain and encodes a protein homologous to the Drosophila Crumbs protein. In crumbs mutant embryos apico-basal polarity of epithelial cells is lost, leading to widespread epidermal cell death. The small cytoplasmic domain of Crumbs organizes an intracellular protein scaffold that defines the assembly of a continuous zonula adherens. The crumbs mutant phenotype can be partially rescued by expression of just the membrane-bound cytoplasmic domain, and overexpression of this domain in a wild-type background results in a multilayered epidermis. A striking difference between CRB1 and Crumbs was that the latter contains a transmembrane region and a 37 amino acid cytoplasmic domain. Here we describe an alternative splice variant of human CRB1 that encodes a cytoplasmic domain 72% similar to that of Drosophila Crumbs. Two intracellular subdomains that are necessary for function in Drosophila are absolutely conserved. Rescuing and overexpression studies in Drosophila show that the cytoplasmic domains are functionally related between these distant species. This suggests that CRB1 organizes an intracellular protein scaffold in the human retina. Human homologues of proteins binding to Crumbs may be part of this complex and represent candidate genes for retinal dystrophies.
人类Crb1同源物1（CRB1）基因突变会导致严重的视网膜营养不良，范围从色素性视网膜炎到莱伯先天性黑矇。CRB1基因在人类视网膜和大脑中特异性表达，编码一种与果蝇Crb蛋白同源的蛋白质。在Crb突变胚胎中，上皮细胞的顶-基极性丧失，导致广泛的表皮细胞死亡。Crb的小细胞质结构域组织了一个细胞内蛋白质支架，该支架定义了连续黏着小带的组装。仅表达膜结合的细胞质结构域可部分挽救Crb突变体表型，在野生型背景中过表达该结构域会导致多层表皮。CRB1和Crb之间的一个显著差异是，后者包含一个跨膜区域和一个37个氨基酸的细胞质结构域。在这里，我们描述了人类CRB1的一种可变剪接变体，其编码的细胞质结构域与果蝇Crb的细胞质结构域相似度为72%。果蝇中功能所必需的两个细胞内亚结构域是完全保守的。在果蝇中的挽救和过表达研究表明，这些远缘物种的细胞质结构域在功能上是相关的。这表明CRB1在人类视网膜中组织了一个细胞内蛋白质支架。与Crb结合的蛋白质的人类同源物可能是这个复合体的一部分，并代表视网膜营养不良的候选基因。
