Functional Studies of Kallikrein 4

描述(申请人提供)：激肽释放酶4(KLK4)是一种丝氨酸蛋白酶，在牙釉质形成过程中表达。在人类中，KLK4缺陷会导致常染色体隐性、色素沉着、成釉发育不全，这是一种鲜为人知的疾病，目前还没有治愈的方法。通过基因打靶，我们培育了一种Klk4基因敲除/ss-半乳糖苷酶敲入小鼠，其釉质表现与人类相似。与野生型小鼠不同，Klk4缺失的小鼠将釉质蛋白保留在釉质层中，釉质在牙本质-牙釉质交界处或附近分层。KLK4基因敲除/SS-半乳糖苷酶敲入小鼠提供了独特的机会来更好地确定KLK4表达的时间和空间模式，并获得关于KLK4在体内牙釉质形成中的S作用的有价值的信息。此外，我们还开发了用于体外分析的高效分离基质金属蛋白酶-20和KLK4的程序。我们最重要的假设是，Klk4是釉质成熟所必需的，并且作为系统的一部分，用于去除在成釉发生的分泌阶段分泌和部分消化的釉质蛋白。提出了五个特定的目标：SA1：确定KLK4在成釉细胞分泌期、过渡期、成熟期和成牙本质细胞中的时空表达。SA2：在没有KLK4表达的情况下表征釉质的形成。SA3：研究KLK4对成釉蛋白、成釉蛋白和釉蛋白的催化活性。目的：研究成釉细胞中蛋白水解酶激活受体(PARs)的表达。SA5：鉴定其他表达KLK4的器官和组织。KLK4在成釉细胞和成牙本质细胞中的表达通过组织化学、SS-半乳糖苷酶(LacZ)表达分析和免疫组织化学在光镜和电子显微镜水平上进行检测。对Klk4缺失小鼠的釉质层进行了扫描电子显微镜、透射电子显微镜、X线片、显微CT、诺氏显微硬度测试，并在发育中的上颌门牙和下颌切牙上以规则间隔的增量测定了蛋白质和矿物质的含量。提取和鉴定Klk4缺失小鼠的残留釉质蛋白，并用Klk4消化，以了解Klk4如何降解成熟期釉质的有机部分。我们通过RT-PCR和原位杂交来确定PARs是否在发育中的牙齿中表达，并使用合成的荧光肽来确定哪些PARs可以被KLK4切割。我们希望证明Klk4在成釉过程的成熟阶段积极地切割釉质蛋白，这一功能对于釉质晶体的正常成熟是必不可少的。 公共卫生相关性：激肽释放酶4(KLK4)是一种丝氨酸蛋白酶，在牙釉质形成过程中表达。在人类中，KLK4基因的缺陷会导致遗传性釉质畸形，称为常染色体隐性遗传低成熟釉质发育不全，这种疾病鲜为人知，无法治愈。通过基因打靶，我们培育出了一只患有这种疾病的Klk4基因敲除小鼠。我们将描述Klk4基因敲除的特征，以更好地了解人类患者的病理，并希望最终发现治愈方法。

DESCRIPTION (provided by applicant): Kallikrein 4 (Klk4) is a serine protease expressed during dental enamel formation. In humans, KLK4 defects cause autosomal recessive, pigmented, hypomaturation amelogenesis imperfecta, a poorly understood condition for which there is no cure. Through gene targeting we have developed a Klk4 knock-out/ss-galactosidase knock-in mouse exhibiting enamel manifestations homologous to the human condition. Unlike wild-type mice, the Klk4 null mice retain enamel proteins in the enamel layer, and the enamel delaminates at or near the dentino-enamel junction. The Klk4 knock-out/ss-galactosidase knock- in mouse offers unique opportunities to better define the temporal and spatial patterns of Klk4 expression and to gain valuable information concerning Klk4's role in dental enamel formation in vivo. Furthermore we have developed efficient procedures for the isolation of matrix metalloproteinase-20 and Klk4 for in vitro analyses. Our overriding hypothesis is that Klk4 is required for enamel maturation and functions as a part of the system for removing enamel proteins that were secreted and partially digested during the secretory stage of amelogenesis. Five specific aims are posed: SA1: To determine the temporal and spatial expression of Klk4 in ameloblasts during the secretory, transition, and maturation stages and in the underlying odontoblasts. SA2: To characterize enamel formation in the absence of Klk4 expression. SA3: To characterize the enzymatic activity of Klk4 on amelogenin, ameloblastin and enamelin. SA4: To investigate the expression of protease activated receptors (PARs) by ameloblasts. SA5: To identify other organs and tissues that express Klk4. The expression of Klk4 in ameloblasts and odontoblasts is determined by histochemistry using the ss- galactosidase (lacZ) expression assay and by immunohistochemistry at the light and electron microscopy levels. The enamel layer of the Klk4 null mouse is characterized by SEM, TEM, radiography, microCT, Knoop microhardness testing, and by determining protein and mineral contents in regularly-spaced increments along the developing maxillary and mandibular incisors. The residual enamel protein in the Klk4 null mouse is extracted and characterized, and digested with Klk4 to learn how Klk4 degrades the organic portion of maturation stage enamel. We determine if PARs are expressed in developing teeth by RT-PCR and in situ hybridization, and determine which PARs can be cleaved by Klk4 using synthetic fluorescent peptides. We expect to prove that Klk4 aggressively cleaves enamel proteins during the maturation stage of amelogenesis and that this function is essential for the proper maturation of enamel crystals. PUBLIC HEALTH RELEVANCE: Kallikrein 4 (Klk4) is a serine protease expressed during dental enamel formation. In humans, defects in the KLK4 gene cause inherited enamel malformations known as autosomal recessive hypomaturation amelogenesis imperfecta, a poorly understood condition for which there is no cure. Through gene targeting we have developed a Klk4 knock-out mouse that has this disease. We will characterize the Klk4 knock-out to better understand the pathology in human patients and hope, eventually, to discover a cure.