Ohnishi Tetsuo, Miura Ikuo, Ohba Hisako, Shimamoto Chie, Iwayama Yoshimi, Wakana Shigeharu, Yoshikawa Takeo
Laboratory for Molecular Psychiatry, RIKEN Brain Science Institute, Wako, Saitama, Japan.
Technology and Development Team for Mouse Phenotype Analysis, RIKEN BioResource Center, Tsukuba, Ibaraki, Japan.
Gene. 2017 Apr 5;607:16-22. doi: 10.1016/j.gene.2016.12.037. Epub 2016 Dec 30.
Genes responsible for reduced pigmentation phenotypes in rodents are associated with human developmental defects, such as Waardenburg syndrome, where patients display congenital deafness along with various abnormalities mostly related to neural crest development deficiency.
In this study, we identified a spontaneous mutant mouse line Rwa, which displays variable white spots on mouse bellies and white digits and tail, on a C57BL/6N genetic background. Curly tail and spina bifida were also observed, although at a lower penetrance. These phenotypes were dominantly inherited by offspring. We searched for the genetic mechanism of the observed phenotypes.
We harnessed a rapid mouse gene mapping system newly developed in our laboratories to identify a responsible gene.
We detected a region within chromosome 1 as a probable locus for the causal mutation. Dense mapping using interval markers narrowed the locus down to a 670-kbp region, containing four genes including Pax3, a gene known to be implicated in the types I and III Waardenburg syndrome. Extensive mutation screening of Pax3 detected an 841-bp deletion, spanning the promoter region and intron 1 of the gene. The defective allele of Pax3, named Pax3, lacked the first coding exon and co-segregated perfectly with the phenotypes, confirming its causal nature. The genetic background of Rwa mice is almost identical to that of inbred C57BL/6N.
These results highlight Pax3 mice as a beneficial tool for analyzing biological processes involving Pax3, in particular the development and migration of neural crest cells and melanocytes.
导致啮齿动物色素沉着表型降低的基因与人类发育缺陷有关，如瓦登伯革氏综合征，患者表现为先天性耳聋以及各种主要与神经嵴发育缺陷相关的异常。
在本研究中，我们鉴定了一个自发突变小鼠品系Rwa，其在C57BL/6N遗传背景下，小鼠腹部、白色趾部和尾巴上出现可变的白色斑点。还观察到卷尾和脊柱裂，尽管其外显率较低。这些表型由后代显性遗传。我们寻找所观察到的表型的遗传机制。
我们利用实验室新开发的快速小鼠基因定位系统来鉴定致病基因。
我们检测到1号染色体上的一个区域可能是因果突变的位点。使用区间标记进行密集定位将该位点缩小到一个670千碱基对的区域，该区域包含四个基因，包括已知与I型和III型瓦登伯革氏综合征有关的Pax3基因。对Pax3进行广泛的突变筛查发现了一个841碱基对的缺失，跨越该基因的启动子区域和内含子1。Pax3的缺陷等位基因，命名为Pax3，缺少第一个编码外显子，并且与表型完全共分离，证实了其因果性质。Rwa小鼠的遗传背景与近交C57BL/6N几乎相同。
这些结果突出了Pax3小鼠作为分析涉及Pax3的生物学过程，特别是神经嵴细胞和黑素细胞的发育和迁移的有益工具。
