Islet Dysregulation in Infants with Congenital Hyperinsulinism

描述(申请人提供)：先天性高胰岛素血症(HI)是婴儿和儿童持续低血糖的最常见原因。患有HI的儿童癫痫发作和永久性脑损伤的风险很高，他们的低血糖的治疗极其困难。最近的研究表明，HI与调节β细胞胰岛素分泌的途径中的遗传缺陷有关。虽然已经发现了6个这样的基因座，但许多HI儿童没有发现这些基因的可识别突变。这包括三分之一需要胰腺切除的弥漫性HI病例和一半对二氮卓药物治疗有反应的病例。我们的假设是，这些儿童的高胰岛素血症既涉及已知基因座的新分子缺陷，也涉及以前未识别的新遗传基因座。我们的长期目标是确定这些疾病中的基因-表型相关性，以指导诊断和治疗，并发现新形式的先天性高胰岛素血症。目的1鉴定McQuarrie于1954年报道的具有重要历史意义的显性HI家族中的新的遗传位点。初步数据已将这种形式的HI定位于染色体10q上的8.4mb区域，该区域包括高亲和力己糖激酶HK1。将通过对胰岛素分泌的临床研究来确定受影响家庭成员的胰岛功能失调的表型。将使用连锁分析和新可用的基因捕获和高通量测序方法来确定导致这种新型HI的致病突变。目标2将在我们的一大群患有二氮卓反应性高胰岛素血症的儿童中寻找新的候选基因的缺陷，这些儿童没有可识别的突变。外周血基因组DNA的突变分析将用于检测潜在的候选基因，包括在AIM 1、HADH/Schad、SLC16A1/MCT-1、TCF1/HNF1、TCF4/HNF4、SIR2L4/SIRT4等中鉴定的10q上的新基因。目标3将确定对二氮卓无效并需要胰腺切除的儿童的分子缺陷的机制。我们将寻找11P上两个相邻基因的新的分子缺陷，这两个基因与大多数这种形式的HI有关：ABCC8/SUR1和KCNJ11/Kir6.2。这将包括使用高通量测序对这些基因的全部120kb区域进行突变分析；分析胰腺组织以寻找合子后马赛克突变的遗传和组织学证据；测试启动子区、3‘UTR区和microRNA位点的突变；以及筛查表观遗传甲基化缺陷。与公共卫生相关：这项翻译研究项目代表着继续努力确定先天性高胰岛素血症(HI)的分子原因，这是婴儿和儿童最常见和最难诊断和治疗的低血糖形式。这项新的建议利用了为全基因组关联研究和高通量DNA测序开发的新技术，以确定这些儿童中新的分子缺陷和新的基因突变位置。这些数据将为正常人类胰岛素分泌的调节提供重要的洞察力，并为改善儿童HI的诊断和治疗提供指导。

DESCRIPTION (provided by applicant): Congenital hyperinsulinism (HI) is the most frequent cause of persistent hypoglycemia in infants and children. Children with HI are at high risk of seizures and permanent brain damage and treatment of their hypoglycemia is extremely difficult. Recent work has shown that HI is associated with genetic defects in the pathways regulating beta-cell insulin secretion. Although 6 such loci have been found, many children with HI have no identifiable mutation of these genes. This includes one-third of diffuse HI cases that require pancreatectomy and half of cases that are responsive to medical treatment with diazoxide. Our hypothesis is that hyperinsulinism in these groups of children involves both novel molecular defects of known loci, as well as, previously unrecognized new genetic loci. Our long-term goal is to identify genotype-phenotype correlations in these disorders to guide diagnosis and treatment and to uncover new forms of congenital hyperinsulinism. Aim 1 will identify the novel genetic locus in the historically-important dominant HI family reported by McQuarrie in 1954. Preliminary data have mapped this form of HI to an 8.4 mb region on chromosome 10q that includes the high affinity hexokinase enzyme, HK1. The phenotype of islet dysregulation in affected family members will be defined by clinical studies of insulin secretion. Linkage analysis and newly-available gene capture and high- throughput sequencing methods will be used to identify the disease-causing mutation responsible for this novel form of HI. Aim 2 will search for defects in novel candidate genes in our large group of children with diazoxide- responsive hyperinsulinism that have no identifiable mutation. Mutation analysis of peripheral blood genomic DNA will be used to examine potential candidate genes, including the novel gene on 10q that will be identified in Aim 1, HADH/SCHAD, SLC16A1/MCT-1, TCF1/HNF1, TCF4/HNF4, SIR2L4/SIRT4, and others. Aim 3 will define the mechanisms of molecular defects in children who fail to respond to diazoxide and require pancreatectomy. We will search for novel molecular defects of the two adjacent genes on 11p that are responsible for most cases of this form of HI: ABCC8/SUR1 and KCNJ11/Kir6.2. This will include mutation analysis of the entire 120 kb region of these genes using high-throughput sequencing; analyzing pancreatic tissue for genetic and histological evidence of post-zygotic, mosaic mutations; testing for mutations in promoter regions, 3'UTR regions, and microRNA sites; and screening for epigenetic methylation defects. PUBLIC HEALTH RELEVANCE: This translational research project represents a continuation of efforts to define the molecular causes of congenital hyperinsulinism (HI), the most common and most difficult form of hypoglycemia to diagnose and treat in infants and children. This new proposal takes advantage of new technologies developed for genome- wide association studies and high-throughput DNA sequencing to identify novel molecular defects and new sites of genetic mutation in these children. The data will provide important insight into regulation of insulin secretion in normal humans as well as a guide to improving the diagnosis and treatment of children with HI.