Nucleoside diphosphate-linked moiety X-type motif 15 R139C genotypes impact 6-thioguanine nucleotide cut-off levels to predict thiopurine-induced leukopenia in Crohn’s disease patients

BACKGROUND Thiopurine-induced leukopenia(TIL)is a life-threatening toxicity and occurs with a high frequency in the Asian population.Although nucleoside diphosphate-linked moiety X-type motif 15(NUDT15)variants significantly improve the predictive sensitivity of TIL,more than 50%of cases of this toxicity cannot be predicted by this mutation.The potential use of the 6-thioguanine nucleotide(6TGN)level to predict TIL has been explored,but no decisive conclusion has been reached.Can we increase the predictive sensitivity based on 6TGN by subgrouping patients according to their NUDT15 R139C genotypes?AIM To determine the 6TGN cut-off levels after dividing patients into subgroups according to their NUDT15 R139C genotypes.METHODS Patients’clinical and epidemiological characteristics were collected from medical records from July 2014 to February 2017.NUDT15 R139C,thiopurine S methyltransferase,and 6TGN concentrations were measured.RESULTS A total of 411 Crohn’s disease patients were included.TIL was observed in 72 individuals with a median 6TGN level of 323.4 pmol/8×10^8 red blood cells(RBC),which was not different from that of patients without TIL(P=0.071).Then,we compared the 6TGN levels based on NUDT15 R139C.For CC(n=342)and CT(n=65)genotypes,the median 6TGN level in patients with TIL was significantly higher than that in patients without(474.8 vs 306.0 pmol/8×10^8 RBC,P=9.4×10-^5;291.7 vs 217.6 pmol/8×10^8 RBC,P=0.039,respectively).The four TT carriers developed TIL,with a median 6TGN concentration of 135.8 pmol/8×10^8 RBC.The 6TGN cut-off levels were 411.5 and 319.2 pmol/8×108 RBC for the CC and CT groups,respectively.CONCLUSION The predictive sensitivity of TIL based on 6TGN is dramatically increased after subgrouping according to NUDT15 R139C genotypes.Applying 6TGN cut-off levels to adjust thiopurine therapies based on NUDT15 is strongly recommended.

NUDT2基因致智力障碍伴或不伴周围神经病1例并文献复习

目的总结报道1例智力障碍伴或不伴周围神经病(intellectual developmental disorder with or without peripheral neuropathy,IDDPN)患儿的临床特点和基因核苷二磷酸连接片段X型基序2(nucleoside diphosphate linked moiety X-type motif 2,NUDT2)的致病变异。方法采用回顾性分析,对2023年4月就诊于天津市儿童医院康复医学科的1例IDDPN患儿临床资料进行总结,并对现有报道NUDT2变异所致IDDPN患儿的临床表型与其基因突变谱的关系进行分析。结果本例患儿全面发育迟缓,面容特殊,四肢肌张力减退,伴有周围神经损害,全外显子测序发现患儿携带NUDT2基因的一个纯合突变c.34C>T(p.R12X)为无义突变。Sanger法验证,父母双方均为c.34C>T杂合子突变携带者。纳入国外已报道的10例IDDPN患者,发现导致发病的均为纯合突变,临床表型均有不同程度的认知障碍、运动障碍,其中3例合并周围神经损害。结论本例患儿低出生体质量/身长,婴儿期吸吮无力,肌张力减退,全面发育迟缓伴周围神经损害,基因检测提示NUDT2基因的纯合无义突变,诊断为IDDPN,为临床对该病的认识提供证据支持。

METTL3调节皮肤成纤维细胞衰老的机制

目的探讨甲基转移酶(METTL)3调节皮肤成纤维细胞衰老的机制。方法酶消化法提取小鼠原代皮肤成纤维细胞,对照(Control)组、D-半乳糖(D-gal)组、转染阴性对照siRNA(NC)组、转染METTL3 siRNA(si-METTL3)组、转染核苷二磷酸连接部分X型基元(NUDT)18 siRNA(si-NUDT18)组,D-gal(20 g/L)建立皮肤成纤维细胞衰老模型。采用衰老相关β-半乳糖苷酶(SA-β-gal)染色法检测细胞衰老,实时荧光定量聚合酶链反应(qRT-PCR)检测METTL3 mRNA表达。SA-β-gal染色法、5-乙炔基-2′-脱氧尿苷(EdU)染色法检测si-METTL3组细胞衰老与增殖。蛋白质质谱分析D-gal组与si-METTL3组中的差异蛋白,qRT-PCR验证差异基因成熟与前体的表达水平。SA-β-gal染色法、EdU染色法、JC-1线粒体膜电位检测法和共聚焦显微镜检测线粒体自噬法分别检测si-NUDT18组细胞衰老、增殖、线粒体膜电位和线粒体自噬的表达变化。结果METTL3 mRNA在衰老皮肤成纤维细胞中表达明显降低,低表达METTL3后细胞衰老水平明显增加,增殖能力明显降低(均P<0.01)。D-gal组与si-METTL3组中NUDT18 mRNA表达明显低于Control组及NC组(P<0.01),pre-NUDT18 mRNA表达无统计学差异(P>0.05)。与NC组相比,si-NUDT18组皮肤成纤维细胞衰老水平明显增加,细胞增殖能力、线粒体膜电位和线粒体自噬水平明显降低(均P<0.01)。结论METTL3下调可能通过影响NUDT18 mRNA的剪接过程促进皮肤成纤维细胞衰老,抑制增殖及线粒体功能。