NON-SYNDROMIC DEAFNESS IN POINTER DOGS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。非综合征性神经上皮性耳聋发生在一组最初因行为异常而被调查的指示犬中（Klein等人（1988））。Behav 43:307)。行为异常和毛色都与听力障碍无关（Steinberg et al (1994) J. Hered. 85:56）。耳聋是双侧遗传，遗传方式为常染色体隐性遗传。在受影响的幼犬中，明显正常的听力（通过脑干听觉诱发反应（BAER）检测）逐渐消失，BAER在大约100日龄时消失。前庭信号缺失。初步组织学检查显示雷氏膜和血管纹外观正常，Corti脏器严重受损。一只聋犬的内淋巴电位为+47 mV，这在耳蜗-囊性耳聋（斑点狗）中是不存在的。由于这些狗听力正常，然后发展为深度耳聋，它们可能为研究听力损失和预防这一过程的方法提供有价值的模型。为了进一步表征该模型，对59只来自聋哑指示犬谱系的动物进行了全基因组扫描，其中近一半受到影响。用两点分析法检测耳聋位点与犬4号染色体（CFA4）标记间的连锁，有3个标记的LOD值大于6。所鉴定的CFA4区域两侧有标记物FH3310和FH2412。一个单一的人类隐性耳聋基因位点cadherin-23 （CDH23；见遗传性听力损失主页，HHH，网址http://www.uia.ac.be/dnalab/hhh/）预计位于CFA4上。CDH23编码糖基化跨膜蛋白钙粘蛋白家族的一个成员。该蛋白由27个钙粘蛋白细胞外重复序列、一个跨膜结构域和一个细胞质结构域组成。在人类中，CDH23的突变等位基因会导致非综合征性耳聋和Usher综合征1D型，这取决于突变的类型（见HHH）。对一只患病狗的CDH23基因的69个外显子进行测序，发现该基因的开放阅读框中有一个沉默替换和一个错义替换。错义突变是一个高度保守的脯氨酸残基的脯氨酸到丝氨酸的替代，这是钙粘蛋白结构域的一个特征残基。这种替换与谱系中80多只狗的耳聋完全相关，而在25只德国短毛指示犬的DNA中没有发现。指针性耳聋与这种替换的关联，它与聋人中发现的CDH23突变的相似性，以及残基的进化保守性，提供了强有力的证据，表明丝氨酸替换构成了导致耳聋的等位基因。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Non-syndromic neuroepithelial deafness occurs in a line of pointer dogs that were originally investigated for a behavioral abnormality (Klein et al (1988) Physiol. Behav. 43:307). Both the behavioral abnormality and coat color are independent of the hearing disorder (Steinberg et al (1994) J. Hered. 85:56). Deafness is always bilateral and the mode of inheritance is as an autosomal recessive trait. In affected pups, apparently normal hearing (assayed by the Brainstem Auditory Evoked Response, or BAER) gradually disappears, and a BAER is absent by approximately 100 days of age. Vestibular signs are absent. Preliminary histologic examination revealed the normal appearance of Reissner¿s membrane and the stria vascularis while the Organ of Corti is severely damaged. The endolymphatic potential, which is absent in cochleo-saccular form of deafness (Dalmatians), was +47 mV in a single deaf dog. Because these dogs hear normally, then progress to profound deafness, they may provide a valuable model for the study of hearing loss and methods to prevent this process. To further characterize the model, a whole-genome scan was performed on fifty-nine animals from the deaf pointer pedigree, of which nearly half were affected. Linkage between the deafness locus and markers on canine chromosome 4 (CFA4) was detected by two-point analysis, with LOD scores greater than 6 for three markers. The CFA4 region identified is flanked by markers FH3310 and FH2412. A single human recessive deafness gene locus, cadherin-23 (CDH23; see the Hereditary Hearing Loss Homepage, HHH, at http://www.uia.ac.be/dnalab/hhh/), is predicted to reside on CFA4. CDH23 encodes a member of the cadherin family of glycosylated transmembrane proteins. The protein is composed of 27 cadherin extracellular repeats, a transmembrane domain, and a cytoplasmic domain. In humans, mutant alleles of CDH23 give rise to both non-syndromic deafness and Usher¿s syndrome type 1D, depending on the type of mutation (see HHH). Sequencing the 69 exons of the CDH23 gene from an affected dog revealed one silent and one missense substitution in the open reading frame of the gene. The missense mutation is a proline to serine substitution of a highly conserved proline residue that is a signature residue of the cadherin domain. This substitution correlates completely with deafness in over 80 dogs in the pedigree and was not seen in the DNA of 25 German short-haired pointer dogs. The association of pointer deafness with this substitution, its similarity to CDH23 mutations found in deaf people, and the evolutionary conservation of the residue provide strong evidence that the serine substitution constitutes a deafness-causing allele.