FAMILIAL GLUCOSE GALACTOSE MALABSORPTION

葡萄糖-半乳糖吸收不良（GGM）的特征是 新生儿发生几次腹泻，除非 从饮食中去除有害的糖。 它是由一个 刷状缘Na/葡萄糖协同转运蛋白（SGLT 1）缺陷。 我们 已经确定了转运蛋白，克隆并绘制了基因图谱， 在33名患者中发现了导致这种疾病的突变。 现在的目标是了解的分子和细胞生物学的 GGM。 我们计划：继续筛查新患者的突变; 确定突变如何导致吸收不良;设计新的 治疗患者的治疗方法;并解决是否携带 GGM突变使葡萄糖吸收受损。 新病人 将使用基因组DNA，外显子的PCR扩增， 单链构象多态性（SSCP）凝胶，和 测序 90%的突变发生在基因编码中 区域，并导致产生突变体和截短的 proteins. 我们的假设是，截短的蛋白质是 有缺陷的，突变蛋白质不插入血浆 膜的 我们将通过表达突变体来验证这一假设， 非洲爪蟾卵母细胞和使用电生理， 免疫学、生物化学和显微技术。 一旦 在模型中确定了糖运输受损的原因 表达系统，我们将测试这在活检样品从 患者 在那些突变导致缺陷的情况下， SGLT 1蛋白在内质网和 质膜，我们将制定策略，以增加 将SGLT 1递送至质膜。 最后，在Kinetics 在我们已经确定GGM突变的地方，我们将筛选家庭， 杂合子和正常纯合子。 糖 将使用H呼吸测试测量吸收，以确定是否 携带者表现出任何吸收不良的症状。 本研究将 使我们能够识别和治疗糖吸收不良的患者 由于SGLT 1基因突变，并将提供独特的 关于合成、贩运和功能的资料， 协同转运蛋白

Glucose-Galactose Malabsorption (GGM) is characterized by a neonatal onset of a several diarrhea that results in death unless the offending sugars are removed from the diet. It is caused by a defect in the brush border Na/glucose cotransporter (SGLT1). We have identified the transporter, cloned and mapped the gene, and found the mutations responsible for the disease in 33 patients. The goal now is to understand the molecular and cell biology of GGM. We plan to: continue screening new patients for mutations; determine how the mutations cause the malabsorption; devise new therapies to treat patients; and resolve whether or not carriers of GGM mutations have impaired glucose absorption. New patients will be screened using genomic DNA, PCR-amplification of exons, single strand conformational polymorphism (SSCP) gels, and sequencing. 90 percent of the mutations are in the gene coding region and result in the production of mutant and truncated proteins. Our hypothesis is that the truncated proteins are defective and that mutant proteins are not inserted into the plasma membrane. We will test this hypothesis by expressing mutants in Xenopus laevis oocytes an using electrophysiological, immunological, biochemical and microscopic techniques. Once the reason for impaired sugar transport is determined in the model expression system, we will test this in biopsy samples from the patients. In those cases where mutations cause a defect in trafficking SGLT1 protein between the endoplasmic reticulum and the plasma membrane, we will devise strategies to increase the delivery of SGLT1 to the plasma membrane. Finally, in kindreds where we have identified GGM mutations, we will screen family members for heterozygotes and normal homozygotes. Sugar absorption will be measured using H-breath tests to determine if carriers exhibit any symptoms of malabsorption. This study will enable us to identify and treat patients with sugar malabsorption due to mutations in the SGLT1 gene, and will provide unique information about the synthesis, trafficking and function of the cotransporter.