Molecular Genetics of Human Albinism

1. 以小鼠酪氨酸酶cDNA为探针，从正常人肝脏文库中分离到一个包含5'侧区和第一外显子的人酪氨酸酶基因。在转录起始位点的5'上游区域，存在一个假定的TATA盒和CAAT盒以及一些回文序列。酶促DNA扩增和直接DNA测序检测酪氨酸酶基因突变的日本患者与酪氨酸酶阴性白化病。单碱基变化可通过直接测序检测。这种碱基变化（G到A）被认为导致患者酪氨酸酶的氨基酸变化（精氨酸到谷氨酸）。突变等位基因也可以用MspI进行southern blot杂交鉴定，因为这种变化破坏了MspI位点。我们将人类基因组5'非编码侧翼序列与小鼠酪氨酸酶cDNA融合的人-鼠融合小基因hh -tyrs- j引入到白化小鼠受精卵中。我们获得了两只色素小鼠，并建立了一些转基因系。组织学分析显示，在转基因小鼠中，黑色素化仅限于毛球和眼睛的黑色素细胞。这些结果表明，该基因编码有活性的酪氨酸酶蛋白，其5'侧区含有酪氨酸酶基因表达的调控序列，小鼠和人类在酪氨酸酶基因调控方面存在共同或非常相似的机制。

1. A human tyrosinase gene containing a 5'-flanking region and the first exon was isolated from a normal human liver library using mouse tyrosinase cDNA as a probe for screening. In the 5'-upstream region of transcription start sites, there is a putative TATA box and CAAT box and some palindromic sequences.2. Enzymatic DNA amplification and direct DNA sequencing were used to detect a mutation in the tyrosinase gene of a Japanese patient with tyrosinase-negative albinism. Single-base change could be detected by direct sequencing. This base change (G to A) is thought to result in an amino acid change (Arg to Gln) in tyrosinase of the patient. The mutant allele can be also identified by Southem blot hybridization using MspI because the change destroys the MspI site.3. We introduced a human-mouse fused minigene, hg-tyrs-J, in which the human genomic 5' non-coding flanking sequence was fused to a mouse tyrosinase cDNA, into fertilized eggs of albino mice. We obtained two pigmented mice and established some transgenic lines. Histological analysis revealed that melanization was restricted to melanocytes in hair bulbs and eyes in transgenic mice. These results suggested that this minigene encodes active throsinase protein and that its 5'-flanking region contains the regulatory sequences for the expression and that there is a common or very similar mechanism between mice and humans in tyrosinase gene regulation.