Innovative Therapies and Clinical Studies for Classic Galactosemia

描述(申请人提供)：在人类中，由于半乳糖-1-磷酸尿苷转移酶(GALT)基因突变导致的GALT缺乏导致一种潜在的致命疾病，典型的半乳糖血症。如果受影响的婴儿在出生后五到五天内不停止饮食中的半乳糖，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个州都在新生儿筛查计划中包括了这种代谢障碍，限制半乳糖的饮食可以防止一些受影响的婴儿死亡，但许多存活下来的患者会出现令人衰弱的并发症，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的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预后的基因-表型关系。使用Q188R-GALT突变纯合的患者细胞，他们最近发现，半乳糖对这些细胞的侮辱导致半乳糖-1-磷酸(Gal-1-P)的积聚，并在细胞死亡之前表现出内质网(ER)应激。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。他们假设，决定Gal-1-P积累量的患者基因型别通过涉及内质网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，研究人员建议，在特定目标1中，从半乳糖症患者中获得纯合三种不同突变等位基因：Q188R、S135L和？5kb的二倍体成纤维细胞株。他们将确定这些细胞株的特征，并用它们来测试新疗法的有效性；在特定目标2中，发现人类半乳糖激酶(Galk)的小分子抑制剂，这种酶负责产生Gal-1-P，并测试它们在防止按基因分层的GALT缺乏细胞中的内质网应激方面的有效性；以及在特定目标3，描绘补充抗氧化剂保护GALT缺乏细胞免受按基因分层的半乳糖毒性的分子机制。

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 If galactose is not withdrawn from the diet of affected infants within five to nince days of life, some newborns die of hepatic failure and Escherichia coli sepsis.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.