Congenital insensitivity to pain with anhidrosis : phenotypes and mutations in TRKA(NTRK1) gane encoding the receptor tyrosine kinase for nerve growth factor

1.人类TRKA基因（NTRK1）位于染色体1q21-q22上，编码神经生长因子受体酪氨酸激酶。我们报道了TRKA基因是导致先天性无汗性疼痛不敏感（CIPA）的原因。我们在此进一步报道了来自5个国家的9个CIPA家族中检测到的8个纯合或杂合状态的新突变。突变的孟德尔遗传在七个家庭中得到了证实，这些家庭的父母双方都有样本。然而，当只有来自母亲和兄弟姐妹的样本（而不是来自更远的）可用时，非孟德尔遗传似乎对家庭来说是可能的。1号染色体父系单系二体可能是该家族TRKA基因突变降为纯合性的原因。来自美国的西班牙裔患者有两种常染色体遗传疾病，CIPA和丙酮酸激酶缺乏症，其遗传位点都映射到一个紧密相连的染色体区域。在纯合先证者的TRKA和plklr基因中分别检测到一个剪接突变和一个错义突变。因此，两种疾病的同时发生归因于两个独立的突变基因的组合，而不是一个连续的基因综合征。这一发现提示了一种导致一名患者出现两种常染色体遗传疾病的机制。我们利用体外诱变技术将假定的错义突变引入TRKA cDNA，并检测了ngf刺激的自磷酸化。细胞外区域的突变体被异常处理，并在神经元细胞中表现出自磷酸化减少。酪氨酸激酶结构域的突变体被处理为野生型TRKA，但在细胞中显著减少了自磷酸化。所有这些数据进一步支持TRKA缺陷可导致不同种族的CIPA的研究结果。这将有助于这种无痛但严重的遗传疾病的诊断和遗传咨询。

1.The human TRKA gene(NTRK1), located on chromosome 1q21-q22 encodes the receptor tyrosine kinase for nerve growth factor. We reported that TRKA is the gene responsible for congenital insensitivity to pain with anhidrosis(CIPA). We here further report eight novel mutations detected as either a homozygous or heterozygous state in nine CIPA families from five countries.2.Mendelian inheritance of the mutations was confirmed in seven families for which samples from either parent were available. However, non-mendelian inheritance seems for likely for the family when only samples from the mother and siblings, (but not from the farther) were available. A paternal uniparental disomy for chromosome 1 is likely to be the cause of reduction to homozygosity of the TRKA gene mutation in this family.3.A Hispanic patient from the USA has two autosomal genetic disorders, CIPA and pyruvate kinase deficiency, whose genetic loci are both mapped to a closely linked chromosomal region. A splice mutation and a missense mutation were detected in the TRKA and PKLR genes from the homozygous proband, respectively. Thus, concomitant occurrence of two disorders is ascribed to a combination of two separate mutant genes, not a contiguous gene syndrome. This finding suggests a mechanism responsible for two autosomal genetic disorders in one patient.4.We introduced the putative missense mutations into the TRKA cDNA, using in vitro mutagenesis, and examined NGF-stimulated autophosphorylation. Mutants in the extracellular domain were aberrantly processed and showed diminished autophosphorylation in neuronal cells. Mutants in the tyrosine kinase domain were processed as wild-type TRKA but significantly diminished autophosphorylation in cells.5.All these data further support findings that TRKA defects can cause CIPA in various ethnic groups. This will aid in diagnosis and genetic counseling of this painless but severe genetic disorders.