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.
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。