Islet Dysregulation in Infants with Congenital Hyperinsulinism

描述（由申请人提供）：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，治疗低血糖非常困难。最近的研究表明，HI与调节β细胞胰岛素分泌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，但许多患有HI的儿童没有这些基因的可识别突变。这包括三分之一需要胰腺切除术的弥漫性HI病例和一半对二氮氧化合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位点的新分子缺陷，也涉及以前未识别的新遗传位点。我们的长期目标是确定这些疾病的基因型-表型相关性，以指导诊断和治疗，并发现先天性高胰岛素血症的新形式。目的1将在McQuarrie于1954年报道的具有历史意义的显性HI家族中确定新的遗传位点。初步数据显示，这种形式的HI位于染色体10q上一个8.4 mb的区域，该区域包含高亲和力的己糖激酶HK1。受影响的家族成员中胰岛失调的表型将通过胰岛素分泌的临床研究来确定。连锁分析和新获得的基因捕获和高通量测序方法将用于确定导致这种新型HI的致病突变。Aim 2将在我们的大群患有二氮氧化合物反应性高胰岛素症的儿童中寻找新的候选基因缺陷，这些基因没有可识别的突变。外周血基因组DNA的突变分析将用于检测潜在的候选基因，包括将在Aim 1、HADH/SCHAD、SLC16A1/MCT-1、TCF1/HNF1、TCF4/HNF4、SIR2L4/SIRT4等中鉴定的10q上的新基因。目的3将定义分子缺陷的机制在儿童谁未能响应二氮氧化物和需要胰腺切除术。我们将寻找11p上两个相邻基因（ABCC8/SUR1和KCNJ11/Kir6.2）的新分子缺陷，这两个基因是导致大多数这种形式HI的原因。这将包括使用高通量测序对这些基因的整个120kb区域进行突变分析；分析胰腺组织，寻找合子后嵌合突变的遗传和组织学证据；检测启动子区域、3'UTR区域和microRNA位点的突变；以及表观遗传甲基化缺陷的筛查。公共卫生相关性：这个转化研究项目代表了确定先天性高胰岛素症（HI）的分子原因的继续努力，HI是婴儿和儿童中最常见和最难诊断和治疗的低血糖症。这项新提议利用了全基因组关联研究和高通量DNA测序的新技术来鉴定这些儿童的新分子缺陷和新的基因突变位点。这些数据将为正常人类胰岛素分泌的调节提供重要的见解，并为改善HI儿童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.