Innovative Therapies and Clinical Studies for Classic Galactosemia

描述（由申请方提供）：在人类中，由GALT基因突变引起的半乳糖-1-磷酸尿苷转移酶（GALT）缺乏可导致潜在致死性疾病，即典型半乳糖血症。 如果在出生后5 ~ 90天内不从受影响的婴儿的饮食中去除半乳糖，一些新生儿会死于肝功能衰竭和大肠杆菌败血症。 尽管美国所有50个州都将这种代谢紊乱纳入新生儿筛查计划，并且半乳糖限制饮食可以防止一些受影响婴儿的新生儿死亡，但许多存活的患者会出现使人衰弱的并发症，包括生长受限，卵巢早衰，言语障碍，共济失调和其他神经缺陷。 该项目的长期目标是为典型半乳糖血症患者开发更有效的治疗方法。 早些时候，研究人员定义了特定GALT突变的结构-功能基础，并建立了疾病严重程度和结果的基因型-表型关系。 使用Q188 R-GALT突变纯合的患者细胞，他们最近表明，半乳糖对这些细胞的损伤导致半乳糖-1-磷酸（Gal-1-P）的积累和细胞死亡前内质网（ER）应激的表现。 通过偶然发现，他们还发现补充特定的抗氧化剂可以保护这些细胞免受半乳糖毒性的影响。 他们假设，患者基因型决定了Gal-1-P的积累量，通过涉及ER应激和氧化应激的机制定义了细胞毒性的程度。 为了验证这一假设，研究人员提出，在具体目标1，衍生二倍体成纤维细胞株半乳糖血症患者纯合子的三个不同的突变等位基因：Q188 R，S135 L，和？5kb。 他们将表征这些细胞株并使用它们来测试新疗法的功效;在特定目标2中，发现人半乳糖激酶（GALK）的小分子抑制剂，GALK是负责Gal-1-P产生的酶，并测试它们在预防按基因型分层的GALT缺陷细胞中的ER应激的功效;在具体目标3中，描述了抗氧化剂补充保护GALT缺陷细胞免受半乳糖毒性的分子机制，按基因型分层。

DESCRIPTION (provided by applicant): In humans, deficiency of galactose-1-phosphate uridyltransferase (GALT) caused by mutations in the GALT gene leads to a potentially lethal disease, classic galactosemia. If galactose is not withdrawn from the diet of affected infants within five to nince days of life, some newborns die of hepatic failure and Escherichia coli sepsis. Although all 50 states in the U.S. include this metabolic disorder in newborn screening programs and a galactose-restricted diet prevents neonatal death in some affected infants, many surviving patients develop debilitating complications including growth restriction, premature ovarian failure, speech dyspraxia, ataxia, and other neurological deficits. The long-term goal of this project is to develop more effective therapies for patients with classic galactosemia. Earlier, the investigators defined the structure-function basis of specific GALT mutations and established genotype-phenotype relationships for disease severity and outcome. Using patient cells that are homozygous for the Q188R-GALT mutation, they recently showed that galactose insult to these cells resulted in accumulation of galactose-1-phosphate (Gal-1-P) and manifestation of endoplasmic reticulum (ER) stress prior to cell death. Through serendipity, they also discovered that supplementation of specific antioxidants protected these cells from galactose toxicity. They hypothesize that patient genotypes, which dictate the amount of Gal-1-P accumulated, define the degree of cellular toxicity via mechanisms involving ER stress and oxidative stress. To test this hypothesis, the investigators propose, in Specific Aim 1, to derive diploid fibroblast cells strains from galactosemic patients homozygous for three different mutant alleles: Q188R, S135L, and ?5kb. They will characterize these cell strains and use them to test the efficacies of novel therapies; in Specific Aim 2, to discover small molecule inhibitors for human galactokinase (GALK), the enzyme responsible for the production of Gal-1-P, and to test their efficacy in preventing ER stress in GALT-deficient cells stratified by genotypes; and in Specific Aim 3, to delineate the molecular mechanisms by which antioxidant supplementation protects GALT-deficient cells from galactose toxicity, stratified by genotype.