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Abstract：
BACKGROUND: With recent advances in gene sequencing technology, more than 60 genetic mutations associated with very early onset inflammatory bowel disease (VEO-IBD) have been reported. Most of the genes are associated with immune deficiencies. The Myosin 5B (MYO5B) gene is primarily involved in cell motility and material transport which is associated with congenital intractable diarrhea and cholestasis. No studies have examined the relationship between the MYO5B gene and VEO-IBD. We report a case of a child with a mutation in the MYO5B gene who was diagnosed with VEO-IBD, then we investigated the association between the MYO5B gene and VEO-IBD.
METHODS: A 7-month-old baby girl with a chief complaint of \"blood in the stool for more than 4 months and vaginal pus and blood discharge for 3 weeks\" was diagnosed with VEO-IBD, and her symptoms improved after treatment with mesalazine. The whole-exome sequencing was performed with peripheral blood. Immunohistochemistry was performed on the terminal ileal tissue. Western blotting, quantitative polymerase chain reaction (Q-PCR) and immunofluorescence were performed with cultured organoid tissue from the terminal ileum. Whole-exome sequencing identified heterozygous missense of MYO5B variant of unknown significance (p. [I769N]; [T1546M]). Immunohistochemistry revealed a significant decrease in the expression of MYO5B protein in the terminal ileum of the child with MYO5B mutation; Q-PCR revealed a decrease in the mRNA levels of occludin and ZO-1 and both the mRNA levels and protein levels of MYO5B was downregulated in the patient. Immunofluorescence images showed that MYO5B gene mutation disrupted the apical delivery of transporters SGLT1, NHE3 and AQP7.
CONCLUSIONS: MYO5B gene mutation leading to the downregulation of MYO5B protein may promote the occurrence of VEO-IBD by decreasing mRNA and protein levels of intestinal tight junction genes and dislocating the apical transporters.
METHODS: A 7-month-old baby girl with a chief complaint of \"blood in the stool for more than 4 months and vaginal pus and blood discharge for 3 weeks\" was diagnosed with VEO-IBD, and her symptoms improved after treatment with mesalazine. The whole-exome sequencing was performed with peripheral blood. Immunohistochemistry was performed on the terminal ileal tissue. Western blotting, quantitative polymerase chain reaction (Q-PCR) and immunofluorescence were performed with cultured organoid tissue from the terminal ileum. Whole-exome sequencing identified heterozygous missense of MYO5B variant of unknown significance (p. [I769N]; [T1546M]). Immunohistochemistry revealed a significant decrease in the expression of MYO5B protein in the terminal ileum of the child with MYO5B mutation; Q-PCR revealed a decrease in the mRNA levels of occludin and ZO-1 and both the mRNA levels and protein levels of MYO5B was downregulated in the patient. Immunofluorescence images showed that MYO5B gene mutation disrupted the apical delivery of transporters SGLT1, NHE3 and AQP7.
CONCLUSIONS: MYO5B gene mutation leading to the downregulation of MYO5B protein may promote the occurrence of VEO-IBD by decreasing mRNA and protein levels of intestinal tight junction genes and dislocating the apical transporters.
摘要：
背景：随着基因测序技术的最新进展，已经报道了超过60个与极早发病的炎症性肠病(VEO-IBD)相关的基因突变.大多数基因与免疫缺陷有关。肌球蛋白5B（MYO5B）基因主要参与细胞运动和物质运输，与先天性顽固性腹泻和胆汁淤积有关。没有研究检查MYO5B基因与VEO-IBD之间的关系。我们报告了一例MYO5B基因突变的儿童，他被诊断为VEO-IBD，然后我们研究了MYO5B基因与VEO-IBD之间的关联。
方法:一名7个月大的女婴,主诉“便血4个月以上,阴道脓血排出3周”,被诊断为VEO-IBD,美沙拉嗪治疗后症状好转.用外周血进行全外显子组测序。对末端回肠组织进行免疫组织化学。西方印迹,对来自末端回肠的培养的类器官组织进行定量聚合酶链反应（Q-PCR）和免疫荧光。全外显子组测序鉴定出意义未知的MYO5B变体的杂合错义（p。[I769N]；[T1546M])。免疫组织化学显示MYO5B突变患儿回肠末端的MYO5B蛋白表达显着降低；Q-PCR显示患者中occludin和ZO-1的mRNA水平降低，MYO5B的mRNA水平和蛋白水平均下调。免疫荧光图像显示MYO5B基因突变破坏了转运蛋白SGLT1、NHE3和AQP7的顶端递送。
结论：MYO5B基因突变导致MYO5B蛋白下调，可能通过降低肠紧密连接基因的mRNA和蛋白水平，使顶端转运蛋白脱位来促进VEO-IBD的发生。
方法:一名7个月大的女婴,主诉“便血4个月以上,阴道脓血排出3周”,被诊断为VEO-IBD,美沙拉嗪治疗后症状好转.用外周血进行全外显子组测序。对末端回肠组织进行免疫组织化学。西方印迹,对来自末端回肠的培养的类器官组织进行定量聚合酶链反应（Q-PCR）和免疫荧光。全外显子组测序鉴定出意义未知的MYO5B变体的杂合错义（p。[I769N]；[T1546M])。免疫组织化学显示MYO5B突变患儿回肠末端的MYO5B蛋白表达显着降低；Q-PCR显示患者中occludin和ZO-1的mRNA水平降低，MYO5B的mRNA水平和蛋白水平均下调。免疫荧光图像显示MYO5B基因突变破坏了转运蛋白SGLT1、NHE3和AQP7的顶端递送。
结论：MYO5B基因突变导致MYO5B蛋白下调，可能通过降低肠紧密连接基因的mRNA和蛋白水平，使顶端转运蛋白脱位来促进VEO-IBD的发生。
