三例CHARGE综合征患儿的临床表型和CHD7基因变异分析

目的对3例CHARGE综合征患者进行基因变异检测,明确其可能的遗传学病因。方法先证者及父母进行全外显子测序检测相关致病基因,对检出致病变异进行Sanger测序验证。结果3例患儿均有程度不同的眼部病变,包括小眼球、小角膜、虹膜缺损、晶状体混浊、视神经视网膜脉络膜缺损等。测序结果示例1的CHD7基因第2外显子存在c.1447delG(p.Val483Leufs*12)杂合移码变异;例2的CHD7基因第36外显子存在c.7957C>T(p.Arg2653*)杂合无义变异;例3的CHD7基因第2外显子存在c.1021_1048delAATCAGTCCGTACCAAGATACCCCAATG(p.Asn341Leufs*2)杂合移码变异,其中c.1447delG(p.Val483Leufs*12)和c.1021_1048delAATCAGTCCGTACCAAGATACCCCAATG(p.Asn341Leufs*2)变异未见报道,根据美国医学遗传学与基因组学学会遗传变异分类标准与指南,这两个均判定为致病性变异(PVS1+PM2+PM6);c.7957C>T(p.Arg2653*)变异为已报道的可能致病性变异(PVS1+PM2+PP4)。Sanger测序结果验证例1和例3的变异为新发变异(de novo),例2的变异为可疑新发变异。结论CHD7基因变异可能为3例CHARGE综合征患者的致病原因。     

七个鸟氨酸氨甲酰基转移酶缺陷症家系基因变异分析及产前诊断

目的对7个鸟氨酸氨甲酰基转移酶缺陷症(ornithine transcarbamylase deficiency,OTCD)家系进行OTC基因变异检测,明确其致病原因并为家系的遗传咨询和产前诊断提供依据。方法应用靶向高通量测序(next-generation sequencing,NGS)技术对7例经串联质谱筛查或临床诊断可疑OTCD的患儿或其母亲进行遗传代谢病相关基因panel检测,发现可疑致病变异位点后,应用PCR扩增和Sanger测序进行变异验证分析。在患儿母亲再次妊娠时抽取绒毛或羊水细胞进行相应基因变异检测,用于产前诊断。结果7个家系中共检测到7种OTC基因变异,分别为c.583G>A(p.Glyl95Arg).c.6260 T(p.Ala209Val)、c.6740 T(p.Pro225Leu)、c.482A>G(p.Asnl61Ser)、IVS1-2A>G、c.116G>T(p.Gly39Val).c.898delT(p.300Phefs*22),其中IVSl-2A>G、c・116G>T(p.Gly39Val)和c.898delT(p.300Phefs*22)为未报道过的新变异。产前诊断家系中3例胎儿基因测序均发现携带OTC基因变异半合子,性别为男性,孕妇选择终止妊娠,胎儿流产组织基因变异分析结果与产前诊断一致;另1例胎儿为OTC基因杂合变异,性别为女性,出生后新生儿筛查结果阴性,随访12个月,生长发育未见异常。结论OTC基因变异为7个OTCD家系的致病原因,致病变异的检出为家系的遗传咨询和产前诊断提供了依据。     

神经发育障碍伴或不伴自闭症特征和(或)脑结构异常患儿1例的 NOVA2基因变异分析

目的探讨1例神经发育障碍伴或不伴自闭症特征和(或)脑结构异常患儿的遗传学病因。方法选取2021年7月至郑州大学第三附属医院就诊的1例NEDASB患儿为研究对象。抽取患儿及其父母的外周血样, 采用高通量测序技术对患儿进行基因检测, 对候选变异进行Sanger测序验证以及生物信息学分析。结果基因检测结果显示患儿携带NOVA2基因c.820₈28delinsCTTCA(p.Thr274Leufs*121)杂合变异。其父母均未携带相同的变异。根据美国医学遗传学与基因组学学会相关指南, 判断其为致病变异。结论 NOVA2基因c.820₈28delinsCTTCA(p.Thr274Leufs*121)杂合变异可能是本例患儿的遗传学病因。上述发现丰富了NOVA2基因的变异谱, 为遗传咨询及产前诊断提供了依据。     

五个成骨不全家系COL1A1基因的变异分析

目的分析5个成骨不全家系的COL1A1基因致病变异位点,为家系遗传咨询及产前诊断提供依据。方法应用高通量测序方法对5个成骨不全家系的先证者进行225个骨病相关基因进行检测分析,所检岀的可疑变异经PCR扩增后进行Sanger测序,对5个家系的先证者及其家庭成员和100名正常个体进行验证,确定致病性变异后,对1个家系中的高危胎儿进行产前诊断。结果5个家系的先证者分别携带COL1A1基因c.3226G>A(p.Glyl076Ser)杂合错义变异、c.579delT(p.Glyl94Valfs*71)移码变异、c・2911_2912insAG(p.Gly971Glufs*138)插入变异、c.3037G>A(p.Glyl013Arg)杂合错义变异,以及c.642+5G>A杂合剪接变异;家系1胎儿产前诊断结果提示胎儿未携带与先证者相同的变异,与超声检查结果一致。5个家系的父母均未携带相应的变异,均为新发变异。100名正常个体均未检出上述变异。其中COL1A1基因c.3037G>A(p.Glyl013Arg),c.29U_2912insAG(p.Gly971Glufs*138)变异为未报道的新变异。结论COL1A1基因变异是5个成骨不全家系的致病病因。本研究的结果丰富了COL1A1基因的变异谱,为家系遗传咨询和产前诊断提供了依据。     

甲硫氨酸腺苷转移酶Ⅰ/Ⅲ缺乏症的新生儿筛查及基因变异研究

目的探讨甲硫氨酸腺苷转移酶Ⅰ/Ⅲ(methionine adenosyltransferaseⅠ/Ⅲ,MATⅠ/Ⅲ)缺乏症的新生儿筛查及MAT1A基因变异情况。方法应用串联质谱技术对泉州地区364545份新生儿样本进行遗传代谢病筛查,应用高通量测序技术结合Sanger测序法对MATⅠ/Ⅲ缺乏症患儿的相关致病基因进行检测,寻找可能的致病变异位点。采用MutationTaster和HSF软件对发现的新变异进行致病性分析预测。结果新生儿筛查检测出3例MATⅠ/Ⅲ缺乏症患儿,发病率为1/121515。氨基酸和酰基肉碱分析结果显示3例患儿的血甲硫氨酸浓度在筛查和随访期间均有不同程度的升高,随访期间生长发育正常。3例患儿均被检测到MAT1A基因变异,共发现3种变异类型,包括2种错义变异c.776C>T(p.Ala259Val)、c.791G>A(p.Arg264His),和1种同义变异c.360C>T(p.Cys120Cys)。MAT1A基因c.776C>T(p.Ala259Val)和c.791G>A(p.Arg264His)变异为已知的致病变异,c.360C>T(p.Cys120Cys)为尚未见报道的新变异。用MutationTaster和HSF对c.360C>T(p.Cys120Cys)进行预测分析,结果显示变异会引起剪接改变,进而影响蛋白的结构和功能。结论本研究较为系统的分析了本地区MATⅠ/Ⅲ缺乏症的新生儿筛查及MAT1A基因变异情况,阐明了本地区MATⅠ/Ⅲ缺乏症的发病率,发现1个新的MAT1A基因变异,丰富了MAT1A基因变异谱,为MATⅠ/Ⅲ缺乏症的诊断提供了依据。     

SLC12A3基因新变异致Gitelman综合征一例报道CSCD

目的对1例低钾血症的患儿进行临床和基因分析,以明确诊断和遗传学病因。方法收集1例15岁低钾血症患儿的临床资料和血样,行内分泌系统遗传病相关基因检测,确定SLC12A3基因的疑似致病变异后,对其他家系成员进行相应位点的验证。结果患儿实验室检查提示血钾低,血镁低,24小时尿钾高,肾素、血管紧张素高,患儿基因检测结果:SLC12A3基因位点c.179C>T(p.Thr60Met)和c.1379G>C(p.Gly460Ala)杂合变异,母亲及妹妹为c.179C>T(p.Thr60Met)变异基因的携带者,父亲及弟弟则为c.1379G>C(p.Gly460Ala)变异基因的携带者。结论低钾血症时应注意Gitelman综合征,基因检测有助于明确诊断。该患儿诊断为Gitelman综合征患者,c.1379G>C(p.Gly460Ala)为SLC12A3基因上新的致病等位基因。     

12例多种羧化酶缺乏症的基因突变分析

目的 旨在从基因水平证实多种羧化酶缺乏症(multiple carboxylase deficiency,MCD)的诊断,探讨我国MCD患儿的基因突变情况.方法 12例MCD患儿接受基因诊断.采用PCR及直接测序法分别对4例生物素酶(biotinidase,BT)缺乏症和8例全羧化酶合成酶(holocarboxylase synthetas,HLCS)缺乏症进行BT基因和HLCS基因突变分析,对基因新突变通过限制性片段长度多态性分析及患儿父母和50名正常对照者基因检测以证实.结果 12例患儿基因突变检出率100%.4例BT缺乏症中发现BT基因突变6种:c.98-104del7ins3,c.1369G>A(V457M),c.1157G>A(W386X),c.1284C>A(Y428X),c.1384delA,c.1493_1494insT,后4种为新突变.8例HLCS缺乏症中发现HLCS基因突变4种:c.126G>T(E42D),c.1994G>C(R665P),c.1088T>A(V363D),c.1522C>T(R508W),后两种为热点突变[75%(12/16)],c.1994G>C为新突变.结论 本研究从基因水平上证实了12例MCD的诊断.共发现了6种BT基因突变,4种HLCS基因突变,其中5种为新突变;得出2种HLCS基因的热点突变.     

结节性硬化症5个家系致病变异的鉴定

目的 对5个结节性硬化症(TSC)家系进行致病变异鉴定,为相关家系的遗传咨询和产前诊断提供依据。方法 选取2020年1月至2021年7月间在中国医学科学院基础医学研究所进行远程遗传咨询的5个无关TSC家系的8例患者为研究对象;抽取患者及其家系成员静脉外周血3～5 mL,应用常规酚/氯仿法提取基因组DNA;通过panel测序(PS)发现候选致病变异,经PCR-Sanger测序验证并联合生物信息学分析对先证者及其家系成员进行TSC1/TSC2致病变异鉴定。结果 5个TSC家系患者均存在TSC1或TSC2的变异,包括3个已报道致病变异和2个新发现的疑似致病变异。2个新变异,TSC2:c.245G>A和TSC2:c.235delG,预测可分别造成无义变异p.(Trp82^*)和移码变异p.(Val79Lysfs27^*),形成提前终止密码子,并经家系共分离和生物信息学分析判定为致病性变异。结论 本研究为相关家庭的遗传咨询和产前诊断提供了依据,进一步拓展了TSC2致病变异谱。     

Dravet综合征患者SCN1A基因变异分析

目的分析Dravet综合征(Dravet syndrome,DS)患者的临床特征和基因变异特点,明确其致病原因。方法采集患者及其父母外周血并提取基因组DNA,应用高通量测序技术进行检测,对疑似致病变异进行Sanger测序验证及生物信息学分析。结果高通量测序显示例1 SCN1A基因第12外显子存在c.2135delC(p.Thr712Lysfs*1)杂合变异,例2 SCN1A基因第10外显子存在c.1522 G>T(p.Glu508*)(杂合变异),生物信息学分析预测为致病性。Sanger测序验证结果显示患者父母未检测到相同变异,均为新发变异(de novo)。根据美国医学遗传学与基因组学学会遗传变异分类标准与指南,SCN1A基因c.2135delC和c.1522G>A变异均为致病性变异(PVS1+PS2+PM2+PP3)。结论SCN1A基因变异可能为两例Dravet综合征患者的致病原因,新变异的检出丰富了基因变异谱,为家系的遗传咨询提供了依据。     

七例Alström综合征的ALMS1基因变异分析

目的对7例Alstr?m综合征患者的ALMS1基因进行变异分析,明确其致病原因,为临床诊断提供依据。方法提取7例患儿及其父母外周血DNA,对患儿进行全外显子组基因测序,应用Sanger测序对患儿及父母进行变异位点验证及致病性分析。结果基因测序结果显示在7例患儿中检出12个ALMS1变异位点,分别是c.5418delC(p.Tyr1807Thrfs*23)、c.10549C>T(p.Gln3517*)、c.9145dupC(p.Thr3049Asnfs*12)、c.10819C>T(p.Arg3607*)、c.5701_5704delGAGA(p.Glu1901Argfs*18)、c.9154_9155delCT(p.Cys3053Serfs*9)、c.9460delG(p.Val3154*)、c.9379C>T(p.Gln3127*)、c.12115C>T(p.Gln4039*)、c.1468dupA(p.Thr490Asnfs*15)、c.10825C>T(p.Arg3609*)和c.3902C>A(p.Ser1301*);其中7个为无义变异,5个为移码变异;c.9154_9155delCT、c.9460delG、c.9379C>T和c.1468dupA是未报道过的新变异。根据美国医学遗传学与基因组学学会遗传变异分类标准与指南,c.9379C>T和c.12115C>T变异判定为可能致病性变异(PVS1+PM2)、其余10个变异均判定为致病性变异(PVS1+PM2+PP3+PP4)。结论ALMS1基因变异为这7例患儿的致病原因,基因检测可以为临床诊断提供依据,新变异的检出拓展了ALMS1变异谱。     

Low frequency of deafness-associated GJB2 variants in Kenya and Sudan and novel GJB2 variants

A large proportion of non-syndromic autosomal recessive deafness (NSARD) in many populations is caused by variants of the GJB2 gene. Here, the frequency of GJB2 variants was studied in 406 and 183 apparently unrelated children from Kenya and Sudan, respectively, with mostly severe to profound non-syndromic deafness. Nine (2.2 %) Kenyan and 12 (6.6 %) of the Sudanese children only were carriers of variants within the coding sequence of the GJB2 gene. Variants in the 5'-adjacent region were detected in further 115 individuals. A total of 10 novel variants was recognized, among them four variants in the adjacent 5'-region of the GJB2 coding exon 2 (g.3318-6T>A, g.3318-15C>T, g.3318-34C>T, g.3318-35T>G), a 6 base-pair deletion (g.3455_3460del [p.Asp46_Gln48delinsGlu]), a variant leading to a stop codon (g.3512C>A [p.Tyr65X]), synonymous variants (g.3395C>T [p.Thr26], g.3503C>T [p.Asn62], g.3627A>C [p.Arg104]), and one non-synonymous variant (g.3816C>A [p.Val167Met]). In addition, the previously described variants g.3352delG (commonly designated 30delG or 35 delG), g.3426G>A [p.Val37Ile], g.3697G>A [p.Arg127His], g.3774G>A [p.Val153Ile], and g.3795G>A [p.Gly160Ser] were identified. With the exception of g.3318-34C>T and g.3352delG, all variants occurred heterozygously. For most of the variants identified in the Kenyan and Sudanese study population, a causative association with NSARD appears to be unlikely. Compared to many other ethnic groups, deafness-associated variants of the coding region of GJB2 are rare in Sudan and Kenya, suggesting a role of other genetic, or epigenetic factors as a cause for deafness in these countries.     

Mutations in the holocarboxylase synthetase gene HLCS

Holocarboxylase synthetase (HLCS) deficiency is an autosomal recessive disorder. HLCS is an enzyme that catalyzes biotin incorporation into carboxylases and histones. Since the first report of the cDNA sequence, 30 mutations in the HLCS gene have been reported. Mutations occur throughout the entire coding region except exons 6 and 10. The types of mutations are one single amino acid deletion, five single nucleotide insertions/deletions, 22 missense mutations, and two nonsense mutations. The only intronic mutation identified thus far is c.1519+5G>A (also designated IVS10+5G>A), which causes a splice error. Several lines of evidence suggest that c.1519+5G>A is a founder mutation in Scandinavian patients. Prevalence of this mutation is about 10 times higher in the Faroe Islands than in the rest of the world. The mutations p.L237P and c.780delG are predominant only in Japanese patients. These are probably founder mutations in this population. Mutations p.R508W and p.V550M are identified in several ethic groups and accompanied with various haplotypes, suggesting that these are recurrent mutations. There is a good relationship between clinical biotin responsiveness and the residual activity of HLCS. A combination of a null mutation and a point mutation that shows less than a few percent of the normal activity results in neonatal onset. Patients who have mutant HLCS with higher residual activity develop symptom after the neonatal period and show a good clinical response to biotin therapy.     

Mutation analysis of the GJB2 (connexin 26) gene in Egypt

Fifty to eighty percent of autosomal recessive deafness is due to mutations in the GJB2 gene encoding connexin 26. Among Caucasians, the c.35delG mutation in this gene accounts for up to 30 to 70% of all cases with early childhood deafness. In this study, we present the analysis of the GJB2 gene in 159 Egyptians from 111 families with non-syndromic mild to profound hearing impairment. An additional family with Vohwinkel syndrome, a combination of hearing impairment and palmoplantar keratoderma with constriction of the digits, was also included. We used direct sequencing analysis to detect all possible coding GJB2 variants in this population. The presence of the g.1777179_2085947del mutation (hereafter called del(GJB6-D13S1830)) was also investigated as it was shown to be the second most common mutation causing non-syndromic prelingual hearing impairment in Spain. Sequencing analysis of one randomly chosen individual per family revealed that the c.35delG mutation was present in 24 out of 222 chromosomes (10.8%), making it the most frequent mutation in the GJB2 gene in Egypt. Five other mutations were already described previously [p.Thr8Met, p.Val37Ile, p.Val153Ile, c.333_334delAA, c.1-3172G>A (commonly designated as IVS1+1G>A)]. This study also revealed three other novel gene variants resulting in amino acid substitutions (p.Phe142del, p.Asp117His, p.Ala148Pro). In contrast with most populations, the del(GJB6-D13S1830) mutation upstream of the GJB2 gene was not present in this Egyptian population. A dominant mutation at a highly conserved residue, p.Gly130Val, was found in the family with Vohwinkel syndrome.     

五个Dysferlinopathy家系的DYSF基因变异分析

目的对5个Dysferlinopathy家系进行DYSF基因变异分析,明确其致病原因。方法应用高通量测序技术进行检测,确定可疑变异后应用Sanger测序进行变异位点验证,根据美国医学遗传学及基因组学学会(American College of Medical Genetics and Genomics,ACMG)遗传变异分类标准与指南对变异的致病性进行评估。结果高通量靶向测序和Sanger测序结果显示,5个Dysferlinopathy家系中共检测出10个DYSF基因变异位点(5个移码变异、3个剪切区变异、1个错义变异和1个无义变异)。其中c.1375dupA(p.Met459Asnfs*15)、c.610C>T(p.Arg204X)、c.1180+5G>A和c.1284+2T>C为已报道过的致病性变异,而c.4008_4010delCCTinsAC(p.Leu1337Argfs*8)、c.1137_1169del(p.379_390del)、c.754 A>G(p.Thr252Ala)、c.1175_1176insGCAGAGTG(p.Met394Serfs*7)、c.3114_3115insCGGC(p.Arg1040 Profs*74)和c.1053+3G>C为未报道过的新变异,根据ACMG遗传变异分类标准与指南,c.1137_1169del、c.1175_1176 insGCAGAGTG和c.3114_3115insCGGC为致病性变异(PVS1+PM2+PM3),c.4008_4010delCCTinsAC变异为可能致病性变异(PVS1+PM2),c.754A>G和c.1053+3G>C为意义不明确的变异(PM2+PM3+PP3)。结论DYSF基因变异可能为这5个Dysferlinopathy家系患者的致病原因,新变异的检出丰富了DYSF基因变异谱。     

Expanding the phenotype of biallelic loss‐of‐function variants in the NSUN2 gene: Description of four individuals with juvenile cataract,chronic nephritis,or brain anomaly as novel complications

The NSUN2 gene encodes a tRNA cytosine methyltransferase that functions in the maturation of leucyl tRNA (Leu) (CAA) precursors, which is crucial for the anticodon‐codon pairing and correct translation of mRNA. Biallelic loss of function variants in NSUN2 are known to cause moderate to severe intellectual disability. Microcephaly, postnatal growth retardation, and dysmorphic facial features are common complications in this genetic disorder, and delayed puberty is occasionally observed. Here, we report four individuals, two sets of siblings, with biallelic loss‐of‐function variants in the NSUN2 gene. The first set of siblings have compound heterozygous frameshift variants: c.546_547insCT, p.Met183Leufs*13; c.1583del, p.Pro528Hisfs*19, and the other siblings carry a homozygous frameshift variant: c.1269dup, p.Val424Cysfs*14. In addition to previously reported clinical features, the first set of siblings showed novel complications of juvenile cataract and chronic nephritis. The other siblings showed hypomyelination and simplified gyral pattern in neuroimaging. NSUN2‐related intellectual disability is a very rare condition, and less than 20 cases have been reported previously. Juvenile cataract, chronic nephritis, and brain anomaly shown in the present patients have not been previously described. Our report suggests clinical diversity of NSUN2‐related intellectual disability.     

一例β-酮硫解酶缺乏症患儿ACAT1基因变异分析

目的探讨1例经新生儿疾病筛查拟诊为β-酮硫解酶缺乏症(β-ketothiolase deficiency,BKD)患儿的致病基因变异特点,明确其致病原因。方法通过多重探针杂交富集患儿ACAT1基因的全部编码区及其侧翼区序列进行高通量测序,确定可疑变异后应用Sanger测序进行变异位点验证。采用多种在线软件对所检出的变异进行致病性分析。结果在患儿ACAT1基因检测到c.121-3C>G和c.275G>A(p.Gly92Asp)复合杂合变异。Sanger测序验证显示父亲和两个姐姐均携带c.121-3C>G杂合变异;家系其他成员均未检测到c.275G>A变异,但在该变异下游的第4内含子检出患儿携带c.334+172C>G(rs12226047)杂合多态性改变,其两个姐姐及母亲也检测到相同SNP位点,其父亲未检测到此SNP位点。表明c.275G>A与172C位于同一染色体上。经软件预测,提示c.121-3C>G和c.275G>A变异均为有害性。根据美国医学遗传学与基因组学学会遗传变异分类标准与指南,ACAT1基因c.275G>A变异为致病性变异(PS2+PM2+PM3+PP3+PP4);c.121-3C>G变异为可能致病性变异(PM2+PM3+PP3+PP4)。结论ACTAT1基因c.121-3C>G和c.275G>A变异可能是患儿的致病原因,本研究变异类型丰富了ACAT1基因的变异谱。