Kondoh Shinji, Sugawara Hirobumi, Harada Naoki, Matsumoto Naomichi, Ohashi Hirofumi, Sato Masato, Kantaputra Piranit N, Ogino Toshihiko, Tomita Hiroaki, Ohta Tohru, Kishino Tatsuya, Fukushima Yoshimitsu, Niikawa Norio, Yoshiura Koh-ichiro
Department of Human Genetics, Nagasaki University School of Medicine, Sakamoto, Japan.
J Hum Genet. 2002;47(3):136-9. doi: 10.1007/s100380200015.
Mirror-image polydactyly of hands and feet (MIP) is a very rare congenital anomaly characterized by mirror-image duplication of digits. To isolate the gene responsible for MIP, we performed translocation breakpoint cloning from an MIP patient with t(2;14)(p23.3;q13). We isolated a good candidate gene for MIP that was disrupted by the translocation of the patient. We had previously con structed a 1.2-megabase bacterial artificial chromosome (BAC)/P1-derived artificial chromosome (PAC) contig covering the 14q13 breakpoint of t(2;14)(p23.3;q13). From a 500-kb segment consisting of seven BAC/PAC clones in the contig, we isolated a novel gene (the mirror-image polydactyly 1 gene, designated as MIPOL1, GenBank Accession No. AY059470), in addition to the hepatocyte nuclear factor 3 alpha gene (HNF3A, GenBank Accession No. XM 007360). MIPOL1 spans about 350kb, comprises 15 exons, and encodes 442 amino acids. Northern blot analysis revealed that MIPOL1 expression is definite but very weak in adult heart, liver, skeletal muscle, kidney, and pancreas, and in fetal kidney. In view of the genome sequence and the contig map constructed, the 14q13 breakpoint of the patient was identified as located in intron 11 of MIPOL1, indicating that the gene was disrupted by the translocation, and that the breakage resulted in MIPOL1 protein truncation. Whole-mount in situ hybridization in mouse resulted in mouse Mipol1 signals all over E10.5-E13.5 mouse embryos. Two other unrelated patients with limb anomalies similar to MIP were subjected to mutation analysis of MIPOL1, but none had any mutations. We then isolated BAC clones from the other breakpoint, 2p23.3. A search for genes and expressed sequence tags in a more than 300-kb region around the 2p23.3 breakpoint found only the neuroblastoma-amplified protein gene (NAG, GenBank Accession No. NM 015909), which is located at least 50kb centromeric to the breakpoint and is not likely to be related to MIP. MIPOL1 is a good candidate gene for the MIP type of anomaly.
手足镜像多指（趾）畸形（MIP）是一种非常罕见的先天性异常，其特征为手指（脚趾）的镜像重复。为了分离出导致MIP的基因，我们对一名患有t(2;14)(p23.3;q13)的MIP患者进行了易位断点克隆。我们分离出了一个MIP的良好候选基因，该基因因患者的易位而被破坏。我们之前构建了一个覆盖t(2;14)(p23.3;q13)的14q13断点的1.2兆碱基细菌人工染色体（BAC）/P1衍生人工染色体（PAC）重叠群。从重叠群中由七个BAC/PAC克隆组成的500千碱基片段中，除了肝细胞核因子3α基因（HNF3A，GenBank登录号XM_007360）外，我们还分离出了一个新基因（镜像多指（趾）畸形1基因，命名为MIPOL1，GenBank登录号AY059470）。MIPOL1跨度约350kb，包含15个外显子，编码442个氨基酸。Northern印迹分析显示，MIPOL1在成年心脏、肝脏、骨骼肌、肾脏和胰腺以及胎儿肾脏中的表达是确定的，但非常微弱。鉴于构建的基因组序列和重叠群图谱，该患者的14q13断点被确定位于MIPOL1的第11内含子中，这表明该基因因易位而被破坏，且断裂导致MIPOL1蛋白截短。在小鼠中进行的全胚胎原位杂交在整个E10.5 - E13.5小鼠胚胎中都产生了小鼠Mipol1信号。另外两名患有与MIP相似肢体异常的无关患者接受了MIPOL1的突变分析，但均未发现任何突变。然后我们从另一个断点2p23.3分离出BAC克隆。在2p23.3断点周围超过300千碱基的区域中搜索基因和表达序列标签，仅发现了神经母细胞瘤扩增蛋白基因（NAG，GenBank登录号NM_015909），它位于断点着丝粒侧至少50kb处，不太可能与MIP相关。MIPOL1是MIP类型异常的一个良好候选基因。
