Prader-Willi综合征研究现状

Prader-Willi综合征(PWS)因最早(1956年)由Prader报道而得名,是一种临床诊断的遗传障碍性疾病,通常与15号染色体上的q11-13片段印迹的缺失有关[1,3],对于诊断PWS的主要临床标准包括:摄食过量和威胁生命的病态肥胖,智力缺陷,行为异常和生长激素缺乏导致的身材矮小以及性腺机能减退[4].     

新生儿Prader-Willi综合征13例临床表型分析

目的 分析Prader-Willi综合征（PWS）新生儿期的临床表现,为临床早期筛选及进一步行分子诊断提供帮助。方法 回顾性分析2009年8月至2011年8月在北京军区总医院附属八一儿童医院依据MS-PCR和MS-MLPA方法确诊为PWS患儿的诊断、分型和临床表型资料,分析中国PWS新生儿期典型特征。结果 13例PWS进入分析,男9例,女4例,确诊年龄4～28 d。足月儿10例,早产儿2例,过期产儿1例。孕母高龄9例（69.2%）,羊水污染8例（61.5%）,羊水过多3例（23.1%）,胎膜早破5例（38.5%）,异常胎位4例（30.8%）,宫内窘迫9例（69.2%）。 9例为父源性15q11.2-q13区域缺失致病,4例为母源性同源二倍体。4例母源性同源二倍体患儿均可见中枢性肌张力低下和皮肤色素减退,吸吮缓慢2例(50.0%)、哭声微弱3例(75.0%)、男性隐睾1例(25.0%)、女性小阴唇3例(75.0%);均未见特殊面容和唾液黏稠,均不需特殊喂养。9例父源性15q11.2-q13区域缺失患儿均可见中枢性肌张力低下、皮肤色素减退和哭声微弱,吸吮缓慢2例(22.2%)、需特殊喂养7例(77.8%)、特殊面容5例(55.6%)、男性隐睾7例(77.8%)、阴茎短小4例（44.4%）、女性小阴唇1例(11.1%)、唾液黏稠5例(55.6%)。结论 母源性同源二倍体患儿的特殊面容和男性生殖器发育不全的发生率低于父源性15q11.2-q13区域缺失患儿。新生儿期皮肤色素减退及中枢性肌张力低下是中国PWS新生儿普遍存在的特征,可作为进一步行PWS分子诊断的初步筛选指标。     

Prader-Willi综合征的遗传学研究进展

普拉德-威利综合征(PWS)是一种因为缺乏父源染色体15q11.2-q13区域相关基因的表达而引起的多系统受累的复杂遗传性疾病。其主要遗传机制有3种类型,即父源缺失型、母源单亲二倍体型和印记缺陷型。基于PWS的不同遗传机制可进行遗传咨询,对已生育该病患者的夫妇进行再次生育评估及产前诊断。PWS的致病原因及机制较为复杂,...     

22q11.2微缺失综合征的分子诊断及缺失范围检测

目的 分别采用多重连接探针扩增技术(MLPA)与荧光原位杂交技术(FISH)对22q1 1.2微缺失综合征外周血标本患者基因缺失/重复突变的类型及变异范围进行检测,分析在22q11.2微缺失综合征诊断中二者联合应用的诊断价值.方法 采集1例仅心脏异常患儿及其父母外周血,取200 μL外周血提取DNA后采用MLPA技术对患儿及其父母的染色体22q11.2缺失的范围进行检测,取外周血1 mL进行培养,采用DiGeorge/VCFS N25(D22S75)的FISH探针对培养后的中期淋巴细胞进行杂交.结果 患儿淋巴细胞分裂中期细胞应用FISH技术检测结果为22号染色体上的DiGeorge/VCFS N25(D22S75)区杂合性缺失;MLPA验证结果显示患儿与22q11.2微缺失综合征相关的6个探针对应的片段大小位置在3100的电泳图上荧光峰值相比健康对照明显出现减半,其父母亲均在正常范围.患儿的临床表现仅有先天性心脏病,无其他异常,与其基因缺失片段长度(2.0 Mb)极不相称.结论 联合应用FISH和MLPA检测22q11.2微缺失综合征,可以明显提高诊断的准确性.22q11.2微缺失综合征的临床表现与基因缺失片段的长度无相关性.     

甲基化特异性MLPA技术在Prader-Willi综合征诊断中的应用价值

目的：不同发病机制的Prader-Willi综合征（PWS）在临床表现、预后和遗传风险上均存在一定差异,目前临床常用的确诊方法甲基化特异性PCR（MS-PCR）不能区分发病机制,本研究采用甲基化特异性多重连接依赖的探针扩增（MS-MLPA）技术诊断PWS,探讨其在诊断以及分辨发病机制上的优势。方法：采用系统对照的方法,取经临床MS-PCR检查的30例患儿的外周血样本,其中包括通过MS-PCR确诊为PWS的病例16例,阴性对照病例14例,重新提取DNA,采用MS-MLPA试剂盒Me028进行基因检测分析。结果MS-MLPA检测结果与MS-PCR检测结果一致,且检测出16例PWS病例中4例源于母源性同源二倍体,12例源于父源性15q11-q13区域缺失。结论：MS-MLPA是能鉴别PWS发病机制的一种可靠的实验诊断方法。     

新生儿Prader-Willi综合征14例临床表型与基因型分析

目的观察Prader-Willi综合征(PWS)新生儿期的临床表现,结合基因检测结果,分析临床表型与基因型之间的关系,为临床早期筛选PWS相关患者及进一步行分子诊断提供线索。方法 2013年3月至2016年12月在广东省妇幼保健院出生或门诊就诊的新生儿3321例,根据临床表现,首先采用甲基化特异性聚合酶链式反应(MS-PCR)进行初筛,对临床表现可疑患儿或MS-PCR初筛阳性者,进一步采用多重荧光PCR-STR连锁分析、染色体微阵列分析等方法,进行确诊。对确诊的PWS患儿,进一步对临床表型和基因型进行分析,探索其中的联系。结果 14例PWS新生儿中,男8例,女6例,年龄1~28 d,其中足月儿10例,早产儿3例,过期产儿1例。14例患儿中,11例为父源性15q11.2-q13区域缺失,3例为母源性单亲二倍体(1例为同源性单亲二倍体,2例为异源性单亲二倍体)。父源性缺失型组,11例患儿均存在肌张力低下、皮肤毛发色素减退和哭声低(100%),吃奶吸吮缓慢6例(54.5%)、男性隐睾或睾丸下降不良4例(36.4%)、小阴茎4例(36.4%)、女性阴唇发育不良1例(9.1%)、唾液黏稠3例(27.3%)、特殊面容9例(81.8%)。母源性单亲二倍体组,3例患儿均存在肌张力低下(100%),皮肤毛发色素减退2例(66.7%)、吃奶吸吮缓慢2例(66.7%)、哭声微弱2例(66.7%)、女性小阴唇1例(33.3%);无特殊面容和唾液黏稠,均不需特殊喂养。结论新生儿期中枢性肌张力低下、皮肤毛发色素减退、哭声减弱是PWS新生儿普遍存在的特征,可作为进一步行PWS分子诊断的初步筛选指标。     

甲基化方法诊断3例Prader-Willi综合征

目的为临床怀疑Prader-Willi综合征（PWS）的患者建立快速准确的分子诊断方法,有利于早期治疗。方法对门诊以肥胖和智力落后就诊的6例患者,根据2001年Meral等提出的临床诊断PWS标准,将3例完全符合临床诊断标准归为高度怀疑组,另3例不完全符合临床诊断标准归为低度怀疑组。用甲基化特异性酶消化患者DNA后,同时扩增15q11．2-13位置SNRPN基因的1号外显子和内参照基因H19。结果3例高度怀疑者均确诊为PWS,均有典型PWS表现,如新生儿期严重肌张力低下,喂养困难,1岁后肌张力好转,食欲增大,肥胖,轻中度智力落后及特殊面容。另3例低度怀疑的患者有智力落后和肥胖,但无新生儿期严重肌张力低下和喂养困难者,排除了PWS诊断。结论甲基化方法结果与临床诊断吻合度高。在临床高度怀疑PWS时,建议用甲基化方法快速确诊,以使患儿能得到及时治疗。     

4例女性Prader-Willi综合征患儿的内分泌代谢特点

4例Prader-Willi综合征(PWS)患儿均为女性,确诊年龄6~12岁,均有肥胖,特殊面容,发育迟缓、智力障碍等临床表现,遗传学检测提示其中2例为15q11.2-q13区域父源性缺失,1例为15q11.2-q13区域母源性同源二倍体,1例15q11.2-q13区域未发现异常。4例患者存在不同程度的内分泌代谢紊乱:2例身材矮小,其中1例第二性征延迟,另1例合并2型糖尿病;1例表现为胰岛素抵抗,无乳腺发育;1例患儿的身高处于P_3~P_(10),性早熟。PWS患者存在多种内分泌功能紊乱,长期内分泌专科随访及管理十分重要。     

22q11.2΢ȱʧ�ۺ���7������ٴ����ͼ��������

目的 探讨22q11.2微缺失综合征患儿的不同临床表现.方法 收集2006年7月至2007年6月在英国Oxford儿童医院临床所见的7例经分子细胞遗传学分析(FISH检测)确诊为22q11.2微缺失综合征患儿的临床资料,分析其临床表现、诊断及治疗情况.结果 7例中男2例,女5例.7例均通过FISH检测确诊,1例为产前诊断,余6例的平均确诊年龄为2个月.2例(28.4%)为父母遗传致病,5例(71.6%)为基因突变致病.其中,先天性心脏病和面容异常的发生率均为100%,免疫功能异常28.6%,颚裂14.3%,低钙14.3%.根据患儿的不同临床表现进行对症治疗.结论 22q11.2微缺失综合征患儿以心脏畸形及面容异常为突出表现,结合FISH检测可早期诊断,基因突变是其主要病因,以流出道受损为主的心脏畸形及以T淋巴细胞数量减少为主的免疫功能异常是影响预后的关键因素.     

中国Phelan-McDermid综合征1例患儿的临床及分子遗传学分析

目的 对1例不明原因的生长过快、发育迟缓患儿进行临床特征及基因诊断分析.方法 描述患儿临床特点;实验室检查采用常规G显带分析染色体核型,进一步通过多重连接依赖探针扩增(MLPA)对微小缺失片段进行拷贝数变异(CNVs)检测,同时应用比较基因组杂交芯片技术(array CGH)检测全染色体微小改变,并采用荧光原位杂交技术(FISH)对新发现的缺失片段进行实验验证.结果 1.患儿,男,1.5岁,宽额,尖下巴,生长过快,全面的发育迟缓,语言发育障碍、孤独症样表现.2.常规G带染色体核型示46,XY,MLPA结果显示患儿22q13段的SHANK3基因的9～23外显子及ACR、RABL2B基因的杂合性缺失,比较基因组杂交芯片分析证实22q13段杂合性缺失,并排除其他染色体的微改变,FISH进一步证实22q13段的缺失.结论 根据临床表现,结合各项实验室检查结果可诊断患儿为Phelan-McDermid综合征;针对性的CNVs适宜采用MLPA技术,而array CGH更宜作为全染色体CNVs的筛查.     

Molecular analysis in Prader-Willi syndrome diagnosis

Prader-Willi syndrome is a rare neurogenetic disorder, which is evidence of genomic imprinting in undercentromeric region of chromosome 15. Defects of the SNRPN gene are the main cause of the syndrome. PWS is an incurable disorder. Nevertheless a diagnosis based on DNA analysis is possible. Molecular diagnostic research includes DNA methylation analysis in the 15q11-q13 region, the gene dosage analysis of the SNRPN gene and the microsatellite polymorphism analysis. The result of DNA analysis is the base of verification of the clinical diagnosis. It also enables to determine the type of molecular defect, from which a genetic risk is depended and what is the base of genetic counselling.     

Clinical features and molecular genetic analysis of a boy with Prader-Willi syndrome caused by an imprinting defect

Abstract Prader-Willi syndrome (PWS) is a neuroendocrine disorder caused by a non-functioning paternally derived gene(s) within the chromosome region 15q11-q13. Most cases result from microscopically visible deletions of paternal origin, or maternal uniparental disomy of chromosome 15. In both instances no recurrence has been reported. In rare cases, PWS is associated with lack of gene expression from the paternal allele due to an imprinting defect. We report the clinical features and the molecular genetic analysis of the first Danish child with PWS due to a defect of the putative imprinting centre (IC). When the imprinting mutation is inherited from a carrier father, the risk that future children will be affected is theoretically 50%. It is therefore important that these families are referred to a geneticist for counselling and further investigation. Prenatal diagnosis is currently only feasible when the mutation has been identified in the affected child.     

Unique maternal deletion of 15q in a patient with some symptoms of Prader-Willi syndrome

BACKGROUND: Human chromosome 15q11-q13 is a critical region for Prader-Willi syndrome (PWS) and Angelman syndrome (AS) and most of the genes are under the condition of imprinting mechanism. PWS results from the loss of expression of paternally expressed genes and AS of maternally expressed genes. In this study molecular studies about a patient with congenital anomalies and mental retardation are analyzed. METHODS: Highly polymorphic microsatellite markers were analyzed by PCR. These markers exist within 15q11-q13 and distal to 15q13. RESULTS: Only the maternal D15S986 locus within 15q11-q13 was deleted and other markers were biallelic. CONCLUSIONS: The result of maternal small region deletion in this patient is different from the typical PWS with paternal chromosome deletion and it suggests that nearby the deleted region there exists a gene (genes) which is not imprinted but needs biallelic expression.     

Genetic abnormalities in Prader-Willi syndrome and lessons from mouse models

Prader-Willi syndrome is a multigenic disorder with developmental and neurobehavioural abnormalities. There are multiple genetic causes, although all ultimately involve the loss of paternally derived gene expression of chromosome region 15q11-q13. Multiple imprinted genes expressed only from the paternal allele have been identified in the specific region of human chromosome 15q associated with Prader-Willi syndrome and in the syntenic mouse chromosome 7C region, including a novel polycistronic gene ( SNURF-SNRPN ) that encodes two independent proteins. The latter genetic locus may play a key role in Prader-Willi syndrome and the evolution of imprinting in this domain, because it is uniquely involved with mutations in the imprinting process and balanced translocations in this syndrome. Indeed, based on the co-localization of SNURF and SNRPN within the imprinting control region critical to Prader-Willi syndrome, evolutionary arguments would suggest that this genetic locus is a prime candidate for mutations producing the failure-to-thrive phenotype of neonates with this syndrome and of corresponding mouse models. Hence the SNURF-SNRPN gene may encode a paternally derived postnatal growth factor.     

Changeability of the fully methylated status of the 15q11.2 region in induced pluripotent stem cells derived from a patient with Prader‐Willi syndrome

Prader‐Will syndrome (PWS) is characterized by hyperphagia, growth hormone deficiency and central hypogonadism caused by the dysfunction of the hypothalamus. Patients with PWS present with methylation abnormalities of the PWS‐imprinting control region in chromosome 15q11.2, subject to parent‐of‐origin‐specific methylation and controlling the parent‐of‐origin‐specific expression of other paternally expressed genes flanking the region. In theory, the reversal of hypermethylation in the hypothalamic cells could be a promising strategy for the treatment of PWS patients, since cardinal symptoms of PWS patients are correlated with dysfunction of the hypothalamus. The genome‐wide methylation status dramatically changes during the reprograming of somatic cells into induced pluripotent stem cells (iPSCs) and during the in vitro culture of iPSCs. Here, we tested the methylation status of the chromosome 15q11.2 region in iPSCs from a PWS patient using pyrosequencing and a more detailed method of genome‐wide DNA methylation profiling to reveal whether iPSCs with a partially unmethylated status for the chromosome 15q11.2 region exhibit global methylation aberrations. As a result, we were able to show that a fully methylated status for chromosome 15q11.2 in a PWS patient could be reversed to a partially unmethylated status in at least some of the PWS‐iPSC lines. Genome‐wide DNA methylation profiling revealed that the partial unmethylation occurred at differentially methylated regions located in chromosome 15q11.2, but not at other differentially methylated regions associated with genome imprinting. The present data potentially opens a door to cell‐based therapy for PWS patients and, possibly, patients with other disorders associated with genomic imprinting.     

Genetic abnormalities in Prader-Willi syndrome and lessons from mouse models

Prader-Willi syndrome is a multigenic disorder with developmental and neurobehavioural abnormalities. There are multiple genetic causes, although all ultimately involve the loss of paternally derived gene expression of chromosome region 15q11-q13. Multiple imprinted genes expressed only from the paternal allele have been identified in the specific region of human chromosome 15q associated with Prader-Willi syndrome and in the syntenic mouse chromosome 7C region, including a novel polycistronic gene (SNURF-SNRPN) that encodes two independent proteins. The latter genetic locus may play a key role in Prader-Willi syndrome and the evolution of imprinting in this domain, because it is uniquely involved with mutations in the imprinting process and balanced translocations in this syndrome. Indeed, based on the co-localization of SNURF and SNRPN within the imprinting control region critical to Prader-Willi syndrome, evolutionary arguments would suggest that this genetic locus is a prime candidate for mutations producing the failure-to-thrive phenotype of neonates with this syndrome and of corresponding mouse models. Hence, the SNURF-SNRPN gene may encode a paternally derived postnatal growth factor.     

Prader–Willi syndrome in Taiwan

BACKGROUND: Prader-Willi syndrome (PWS) is a congenital disorder caused by absent expression of paternal genes in 15q11-13 affecting multiple systems. The information concerning the clinical features of this genetic disorder is incomplete in Taiwan. METHODS: A retrospective analysis was carried out of 70 PWS patients (39 male, 31 females; age range, 1 month-22 years) seen in four major medical centers in Taiwan from January 1980 through June 2005. All cases were confirmed by methylation-specific polymerase chain reaction. The molecular characteristics, birth history, clinical presentation and laboratory studies were analyzed. RESULTS: Complete genetic analysis was performed in 52 of the 70 patients with PWS. The abnormalities found included deletions in 45 (87%), maternal uniparental disomy (UPD) in five (10%), and a probable imprinting center deletion or an imprinting defect in two (4%). The average weight of the patients at birth was 2588 +/- 540 g. Bone age delay of >2 years and growth hormone (GH) deficiency were noted in 11/40 (28%) and 12/20 (60%), respectively. In the 18 in whom both bone age and GH were assessed, abnormalities of both were found in two (11%). In 2000, Taiwan instituted the Rare Diseases and Orphan Drugs Act and mandated a three-phase screening protocol for PWS. Of the 41 patients diagnosed with PWS before 2000, only four (10%) were diagnosed before the age of 3 months; in the 29 patients diagnosed after 2000, in 15 (52%) the syndrome was confirmed before 3 months of age (P < 0.001). CONCLUSIONS: The present finding is in contrast to that of most previous reports that indicated a higher incidence of UPD in PWS. It is unclear whether this discrepancy in the incidence of UPD arises from under-diagnosis or because of ethnic differences, a question worthy of further study. The three-phase screening protocol has generated notable improvement in the early diagnosis of PWS in Taiwan.     

Genotype and phenotype in patients with Prader-Willi syndrome in Taiwan

AIM: Several different genetic defects have been found to result in the characteristic phenotypic expression of Prader-Willi syndrome (PWS). METHODS: We performed a retrospective analysis of 67 cases of molecularly confirmed PWS diagnosed from January 1980 through July 2006 in five medical centres in Taiwan. Clinical manifestations were compared between patients with deletion and those with maternal uniparental disomy (UPD). RESULTS: Deletion was present in 56 (84%), UPD in 10 (15%), and a probable imprinting centre deletion or imprinting defect in 1 (1%). PWS with deletion was more likely than that with UPD to be characterized by hypogonadism (p < 0.001), small hands and feet (p < 0.001), and hypopigmentation (p < 0.002). Both maternal (p = 0.015) and paternal age (p = 0.021) were higher in the UPD group. No other clinical features differed significantly different between the two groups. CONCLUSION: In contrast to most Western populations with a higher incidence of UPD, this study of PWS in Taiwan shows a higher incidence of deletion. There may be subtle phenotypic differences between the UPD and deletion genotypes, but its not clear that these are important clinically.     

Neonatal presentation of Prader Willi sindrome. Personal records

Prader Willi Syndrome (PWS) is characterized by typical appearance, obesity, short stature, hypothalamic hypogonadism, cryptorchidism, hypotonia, behavioural abnormalities and mental retardation. It is considered as a continuous genes syndrome with different genotypes: microdeletion of the region 15q11-q13 with paternal imprinting; maternal uniparental disomy (UPD) of chromosome 15; chromosomal rearrangement. Clinical manifestations evolve with age from newborn (hypotonia, poor sucking, hypoplastic external genitalia) to childhood (delay in psychomotor development, hyperphagia, obesity, acromicria and craniofacial dysmorphisms). We present five newborns who received an early diagnosis, based on clinical presentation. The early treatment and follow-up can in fact improve the natural evolution of the syndrome in order to prevent respiratory tract diseases and obesity, and to improve growth.