CLONING OF A HUMAN HOMOLOG OF THE XENOPUS-LAEVIS APX GENE FROM THE OCULAR ALBINISM TYPE-1 CRITICAL REGION
CLONING OF A HUMAN HOMOLOG OF THE XENOPUS-LAEVIS APX GENE FROM THE OCULAR ALBINISM TYPE-1 CRITICAL REGION
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DOI：
10.1093/hmg/4.3.373
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发表时间：
1995-03-01
影响因子：
3.5
通讯作者：
BALLABIO, A
中科院分区：
文献类型：
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作者：
SCHIAFFINO, MV;BASSI, MT;BALLABIO, A
1 型眼白化病 (OA1) 是一种 X 连锁隐性遗传性疾病，其特征是视力严重受损、眼球震颤、斜视、畏光和视网膜色素减退。通过对携带涉及 X 染色体远端短臂 (Xp22.3) 缺失和易位的患者的分析，我们确定了 OA1 基因必须位于其中的大约 110 kb 的区域。我们使用多种技术广泛搜索了该区域的基因，包括外显子扩增、cDNA 选择以及粘粒插入片段与 cDNA 文库的直接杂交。通过外显子扩增鉴定的推定外显子用于筛选人视网膜cDNA文库，并分离和表征了对应于大约7.5kb转录物的几个cDNA克隆。人们发现这种新发现的基因的转录本在视网膜和黑色素瘤中含量丰富，并且在大脑、胎盘、肺、肾和胰腺中也可以检测到。有趣的是，序列分析表明，这个新基因编码一个 1616 个氨基酸的蛋白质，与非洲爪蟾 (APX) 的顶端蛋白 (APX) 具有显着相似性，后者与阿米洛利敏感的钠通道活性有关。该基因被称为 APXL (APX-Like)，全长约 160 kb，包含 10 个外显子，覆盖 OA1 110 kb 关键区域的 70% 以上。截短的假基因与大鼠 eF-5 基因（一种真核翻译起始因子）具有非常高水平的同源性；被发现位于内含子 1 的中间。APXL 在两名患有包括 OA1 在内的邻近基因综合征的患者和一名患有孤立 OA1 的患者中被发现缺失。绘图、表达和患者分析数据使我们认为 APXL 基因是 OA1 基因的有力候选者。因此，使用 SSCP 分析和直接测序对 57 名无关 OA1 患者的 DNA 进行了编码区突变扫描。未发现功能上显着的突变，表明 APXL 不直接参与 OA1。需要进一步的研究来阐明这个高度保守基因的生理作用。
Ocular albinism type 1 (OA1) is an X-linked recessive disorder characterized by a major impairment of visual acuity, nystagmus, strabismus, photophobia and retinal hypopigmentation. From the analysis of patients carrying deletions and translocations involving the distal short arm of the X chromosome (Xp22.3) we have identified a region of approximately 110 kb in which the OA1 gene must lie. We have extensively searched for genes in this region using a variety of techniques which included exon amplification, cDNA selection and direct hybridization of cosmid inserts to cDNA libraries. Putative exons identified by exon amplification were used to screen a human retina cDNA library and several cDNA clones corresponding to an approximately 7.5 kb transcript were isolated and characterized. Transcripts of this newly identified gene were found to be abundant in retina and melanoma and could also be detected in brain, placenta, lung, kidney and pancreas. Interestingly, sequence analysis revealed that this new gene encodes a 1616 amino acid protein sharing significant similarities with the Apical Protein from Xenopus laevis (APX) which is implicated in amiloride-sensitive sodium channel activity. The gene, termed APXL (APX-Like), spans approximately 160 kb, contains 10 exons and covers over 70% of the 110 kb critical region for OA1. A truncated pseudogene sharing very high levels of homology with the rat elF-5 gene, a eukaryotic translation initiation factor; was found to lie in the middle of intron 1. APXL was found deleted in two patients with contiguous gene syndromes including OA1 and in one patient with isolated OA1. Mapping, expression and patient analysis data led us to consider the APXL gene a strong candidate for the OA1 gene. DNA from 57 unrelated patients with OA1 was, therefore, scanned for mutations in the coding region, using both SSCP analysis and direct sequencing. No functionally significant mutation was identified, suggesting that APXL is not directly involved in OA1. Further studies are needed to clarify the physiologic role of this highly conserved gene.