Islet Dysregulation in Infants with Congenital Hyperinsulinism

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9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。该研究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将扩展和扩展高胰岛素血症的新基因位点的研究，该基因位点在历史上重要的显性HI家族中由McQuarrie于1954年报道。临床表型分析、连锁分析和下一代测序方法已确定HK1为可能的候选基因。这将通过招募额外的家系和功能分析得到证实。Aim 2将在我们大量的没有可识别突变的二氮氧化合物反应性高胰岛素症儿童中扩展寻找新的候选基因缺陷。我们将寻求确定已知位点的合子后突变或使用有针对性的下一代测序方法鉴定新的额外位点。目的3将继续我们的努力，以确定分子缺陷的机制，儿童对二氮氧化物没有反应，需要胰腺切除术。我们将在11p上的两个相邻基因（ABCC8/SUR1和KCNJ11/Kir6.2）中寻找新的隐性或镶嵌突变，这两个基因是导致大多数这种形式的HI的原因。这将包括胰岛素释放的功能测试和手术患者培养胰岛的分子分析，以确定合子后、镶嵌突变；非编码区和microRNA位点的突变；或者表观遗传甲基化缺陷。

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 9 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. The long-term goals of the research are to identify genotype-phenotype correlations in these disorders to guide diagnosis and treatment and to uncover new forms of congenital hyperinsulinism. Aim 1 will extend and expand studies of the novel genetic locus for hyperinsulinism in the historically-important dominant HI family reported by McQuarrie in 1954. Clinical phenotyping, linkage analysis, and next-gen sequencing methods have identified HK1 as a likely candidate gene. This will be confirmed by recruitment of additional pedigrees and by functional assays. Aim 2 will extend the search for defects in novel candidate genes in our large series of children with diazoxide responsive hyperinsulinism that have no identifiable mutation. We will seek to identify either post-zygotic mutations of known loci or novel additional loci using targeted next-gen sequencing methods. Aim 3 will continue our efforts to define the mechanisms of molecular defects in children who fail to respond to diazoxide and require pancreatectomy. We will search for novel cryptic or mosaic mutations 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 functional testing of insulin release and molecular analysis of cultured islets from patients undergoing surgery to identify post-zygotic, mosaic mutations; mutations in non-coding regions, and microRNA sites; or epigenetic methylation defects. RELEVANCE (See instructions): This translational research project seeks to define the molecular causes of congenital hyperinsulinemic hypoglycemia (HI). Novel candidate genes will be sought using next-gen DNA sequencing and advanced micro-methods to study pancreatic islets from children requiring pancreatectomy. The results will improve the treatment of children with HI and provide new insight into regulation of insulin secretion in normal humans.