STUDY ON CANINE CONGENITAL DEAFNESS

遗传性综合征性感音神经性耳聋已在几只近交犬中被报道。先天性耳聋经常与色素沉着障碍有关，例如白色的毛发和蓝色的眼睛。这些发现与人类的瓦登堡综合征相似。我们将伴发色素沉着障碍的犬系统性耳聋解释为Waardenburg综合征的对应物，并分析了与Waardenburg综合征相关的基因，包括MITF、PAX3和Sox10基因。虽然在人类中有几种亚型的报道，但在狗中只描述了MITF基因的两种亚型。犬MITF基因的克隆本研究表明，除了MITF-M和MITF-H两种亚型外，MITF-A亚型在犬组织中也有表达。对MITF亚型表达的分析表明，MITF-H和MITF-A亚型在正常犬中普遍表达，而MITF-M在正常犬的肾脏、大脑、小脑、心脏和上消化系统等特定器官中有表达。虽然对犬MITF基因三种异构体的编码区进行了扩增和测序，但在先天综合征耳聋患者中未检测到突变。Pax3和Sox10基因也与先天性综合征性听力障碍有关。为了确定基因结构，从一只健康的狗样本中克隆并分析了cDNA片段。在确定每个基因的结构后，用内含子上构建的引物扩增编码氨基酸的每个外显子，并进行测序。然而，引起氨基酸变化的核苷酸在患病犬和正常健康犬之间没有发现差异。在这项研究中，虽然没有在与瓦伦堡综合征相关的三个基因中检测到突变，但这种方法将能够分析狗的先天性耳聋。

Inherited syndromic sensorineural deafness has been reported in several inbreed dogs. Congenital deafness is frequently associated with pigmentation disorders such as white coat color and blue eyes. These findings are similar to those of Waardenburg syndrome in human. We interpreted the dog sydromic deafness with pigmentation disorder as the counterpart of Waardenburg syndrome and analyzed the genes associated with Waardenburg syndrome including MITF, PAX3 and SOX10 genes in affected dogs. Although several isoforms were reported in human, only two isoforms for MITF gene have been described in dogs. Cloning of canine MITF cDNA in this study presented that, in addition to two isoforms of MITF-M and MITF-H, MITF-A isoform was expressed in dog tissues. Analysis of the expression of MITF isoforms showed that isoforms MITF-H and MITF-A expressed ubiquitous, but MITF-M expression was observed in specific organs including kidney, cerebrum, cerebellum, heart and upper digestive system in normal dog by RT-PCR methods. Although the coding regions of three isoforms for canine MITF gene was amplified and sequenced, no mutation was detected in the affected dogs with congenital syndromic deafness. PAX3 and SOX10 genes are also associated with congenital syndromic hearing disorder. For determination of gene construction, cDNA fragments were cloned and analyzed from a healthy dog sample. After the determination of each gene structure, each exon coding amino acids was amplified by primers constructed in introns and sequenced. However, No differences of nucleotide that induced the changes of amino acid was detected between the affected dogs and normal healthy dog. In this study, although the mutations were not detected in three genes associated with Waarenburg syndrome, this method will be able to analysis on congenital deafness in dogs.