Cell Fate Determination of the Intestine and Chronic Diarrhea in Children

描述(由申请人提供)：先天性腹泻是一种不常见但具有破坏性的临床症状，经常导致肠道衰竭。许多婴儿早期慢性/先天性腹泻患者在营养和离子消化吸收过程中具有重要作用的转运蛋白和酶存在缺陷。目前，有很大比例的先天性腹泻儿童具有全身性吸收不良形式，其临床特征尚未得到很好的描述，其分子基础尚不清楚。最近在空白小鼠中的研究发现，两种碱性螺旋-环-螺旋(BHLH)转录因子，小鼠无性同系物1(MATH1)和神经原蛋白-3(NGN-3)影响肠道内分泌、Paneth、杯状和上皮细胞命运的决定。在这项赠款的初步结果部分，我们首次介绍了一种新的人类疾病的临床特征和分子基础，该疾病表现为严重的先天性吸收不良腹泻。2例组织学检查显示小肠和大肠内分泌细胞缺失，其他类型的肠道细胞包括盘状细胞、杯状细胞和吸收细胞形态正常。分子分析发现了两个神经原蛋白-3纯合子突变，它们改变了神经原蛋白基因家族DNA结合域中高度保守的氨基酸残基。在这项研究中，我们的中心假设是，由NGN-3(或其上游调节因子HATH1)功能丧失突变引起的肠道内分泌细胞发育异常是婴儿期慢性吸收不良腹泻的常见原因，但目前尚未被认识到。因此，为了验证我们的中心假设，我们建议：[1]评估神经原蛋白-3的功能丧失突变是否经常出现在患有慢性先天性腹泻的儿童中；[2]神经原素-3的调节因子HATH1的突变是否可以在婴儿早期出现先天腹泻的病例子集中识别出来。这项建议的长期目标是评估人类小肠细胞命运决定的异常是否与胃肠道症状和其他潜在的临床问题有关。

DESCRIPTION (provided by applicant): Congenital diarrhea is an uncommon yet devastating clinical condition that frequently leads to intestinal failure. Many patients with chronic/congenital diarrhea of early infancy have defects in a variety of transporters and enzymes that have important roles in the process of nutrient and ion digestion and absorption. Presently, a large proportion of children with congenital diarrhea have a generalized malabsorptive form that has not been well characterized clinically, and its molecular basis has yet to be elucidated. Recent studies in null mice have determined that two basic-helix-loop-helix (bHLH) transcriptional factors, mouse atonal homolog 1 (MATH1) and neurogenin-3 (ngn-3) influence enteroendocrine, Paneth, goblet and epithelial cell fate determination. In the preliminary results section of this grant, we present for the first time the clinical characteristics and molecular basis of a novel human disorder that presented with severe congenital malabsorptive diarrhea. Histological evaluation of two cases revealed an absence of small and large bowel enteroendocrine cells, while the other intestinal cell types, including Paneth, goblet and absorptive cells were of normal appearance. Molecular analysis identified two homozygous mutations in neurogenin-3 that alter highly conserved amino acid residues in the DNA binding domain of the neurogenin gene family. In this grant, our central hypothesis is that abnormalities of enteroendocrine cell development, resulting from loss-of-function mutations of ngn-3 (or its upstream regulator HATH1) are a common yet currently unappreciated cause of chronic malabsorptive diarrhea during early infancy. Therefore, to test our central hypothesis, we propose to: [1] assess whether loss-of-function mutations of neurogenin-3 is frequently seen in children that present with chronic congenital malabsorptive diarrhea; [2] whether mutations of HATH1, the regulator of neurogenin-3, can be identified in a subset of cases that present with congenital diarrhea during early infancy. The long-term objective of this proposal is to assess whether abnormalities of small bowel cell fate determination in humans are associated with gastrointestinal symptoms and other potential clinical problems.