Identification of a novel mutation in the amelogenesis-related genes in Japanese families affected with amelogenesis imperfecta and an approach toward gene therapy

釉质生成不全症 (AI) 是一组异质性遗传性疾病，其特征是牙釉质形成缺陷。1) 我们对一个可能具有常染色体显性遗传形式的 Al 的日本家庭进行了分子遗传学研究，发现了釉质基因中的一种新突变。在受影响的兄弟及其父亲中检测到的突变是牙釉质基因外显子 9-intion 9 边界处一系列 7G 残基内的杂合单 G 缺失。在其他未受影响的家庭成员或对照个体中未检测到牙釉质基因突变，这表明牙釉质基因的突变导致了常染色体显性遗传性发育不全形式的AI。2）我们研究了一个日本家庭，该家族表现出牙齿形成的遗传异常，其特征是牙齿有垂直凹槽（女性）和小棕色牙齿（男性），并发现位于X染色体p22.1-22.3区域的牙釉蛋白基因发生突变。突变分析揭示了牙釉蛋白基因的外显子5中的C至G点突变，这将用精氨酸替代脯氨酸^<52>。这种取代与受影响的家族成员中的牙齿异常以及在其他哺乳动物中高度保守的编码脯氨酸^ 52 的基因座共分离。这一结果表明，在这个日本家族中检测到的突变与X连锁AI有关。3)我们还测试了一种新型逆转录病毒载体GcsapM-ADA在造血细胞中转导基因的能力，发现这种方法对患者有益。4)检查了巨噬细胞迁移抑制因子（MIF）对破骨细胞形成的调节作用，我们发现MIF通过阻止多核过程来抑制成熟破骨细胞的形成。

Amelogenesis imperfecta (AI) is a heterogeneous group of genetic disorders characterized by the defects of tooth enamel formation.1) We performed molecular genetic studies for a Japanese family with a possible autosomal dominant form of Al, and found a novel mutation in the enamelin gene. The mutation detected in the affected brothers and their father was a heterozygous single-G deletion within a series of 7G residues at the exon 9-intion 9 boundary of the enamelin gene. The enamelin gene mutation was not detected in other unaffected family members or control individuals suggesting that the mutation in the enamelin gene is responsible for an autosomal dominant hypoplastic form of AI.2) We studied a Japanese family that exhibits inherited abnormality in tooth formation characterized by teeth with vertical grooves (female) and small brownish teeth (male), and found a mutation in the amelogenin gene located in the p22.1-22.3 region of the X chromosome. Mutation analysis revealed a C to G point mutation in exon 5 of the amelogenin gene, which would substitute arginine for proline^<52>. This substitution co-segregated with the tooth abnormality in the affected family members and the locus encoding proline^<52> highly conserved in other mammals. This result indicates that the mutation detected in this Japanese family is responsible for the X-linked AI.3) We also tested a novel retroviral vector GcsapM-ADA for its ability to transduce genes in hematopoietic cells and found this method to be beneficial to patients.4) The regulatory effects of the macrophage migration inhibitory factor (MIF) on osteoclast formation were examined and we found that MIF inhibits formation of mature osteoclasts by preventing the multinucleation process.