Preparation of chromosomes from plant leaf meristems for karyotype analysis and in situ hybridization

A reliable method for preparing metaphase chromosomes from plant leaf tissues is described. The chromosomes are suitable for karyotype analysis and gene mapping by fluorescence in situ hybridisation (FISH). The method is based on enzymatic digestion of young leaf tissues (shoot-tips) after which the resulting protoplasts are treated hypotonically before being dropped onto microscopic slides. Compared to root-tip chromosomes, leaf chromosomes tend to be longer, or less condensed, and hence more karyotypically differentiated. Metaphase index in young leaf tissues is also very high. Metaphase spread consists of evenly and well-distributed chromosomes and this allows accurate counting. The plant used to demonstrate this method is birch (Betula L.), a group of tree species that has extremely small chromosomes. Root-tip chromosomes of these plants are difficult to obtain, as cutting does not produce roots readily. Seedling chromosomes do not represent the same genomic constitution as their mother trees due to introgressive hybridisation. Furthermore, sample collection in the field is convenient and actively growing leaf buds are available throughout the growing season. FISH experiments with these leaf chromosomes also give good results comparable to those obtained with root-tip chromosomes or even better as mapping on long or extended chromosomes has high resolution in general. Mapping of the 16S–28S ribosomal genes on birch leaf chromosomes has been shown to differentiate between birch species and therefore can accurately confirm their interspecific hybrids.     

An interactive, microcomputer-based karyotype analysis system for phylogenetic cytotaxonomy

A versatile and practical semi-automatic computerized system of karyotype analysis has been developed for phylogenetic cytotaxonomy for under $4,000. The modular software system is designed for use solely with a small 8-bit microcomputer and requires virtually no custom made hardware. The system interacts with the operator and greatly augments the speed and accuracy of cytotaxonomic investigations.     

中孕期胎儿染色体异常高危孕妇羊水细胞胎儿染色体核型及介入性产前诊断指征的大样本分析

目的探讨中孕期胎儿染色体异常(FCA)高危孕妇羊水细胞胎儿染色体核型(FK)及其介入性产前诊断(IPD)指征。方法选择2014—2018年,在四川大学华西第二医院产前诊断中心进行羊膜腔穿刺术羊水细胞FK检测的63581例FCA高危孕妇(孕龄为19~27+6孕周)为研究对象。回顾性分析孕妇不同IPD指征及其胎儿染色体核型异常(FKA)检测结果。本研究遵循的程序符合四川大学华西第二医院伦理委员会所制定的伦理学标准,并通过该伦理委员会批准[审批文号:医学科研2019伦审批第(077)号]。结果①本组63581例中孕期孕妇的FKA检出率为3.13%(1989/63581)。这63581例孕妇的IPD指征分别为高龄(预产期年龄≥35岁)(25648例)、血清学筛查高风险(29009例)、无创产前筛查(NIPT)高风险(333例)、夫妇一方为染色体异常携带者(603例)、超声筛查发现胎儿结构异常及超声软指标异常(2647例)、异常儿生育史(1546例)、于外院进行羊水细胞FK分析结果异常者(7例)、孕妇智力低下及合并智力低下家族史(149例)、孕妇早孕期有害物质接触史(1400例)、其他(2239例),FKA检出率分别为3.26%(836/25648)、2.04%(593/29009)、65.17%(217/333)、34.33%(207/603)、3.51%(93/2647)、1.68%(26/1546)、85.71%(6/7)、4.03%(6/149)、0.14%(2/1400)、0.13%(3/2239)。②351例孕妇的IPD指征为超声筛查发现胎儿结构异常中,IPD指征为胎儿淋巴水囊瘤、皮肤水肿的FKA检出率最高,为26.09%(6/23)。2296例孕妇的IPD指征为胎儿超声软指标异常中,IPD指征为胎儿颈项透明层(NT)值≥2.5 mm的FKA检出率最高,为7.74%(66/853)。结论孕妇高龄、血清学筛查高风险、NIPT高风险、夫妇一方为染色体异常携带者、超声筛查发现胎儿结构异常及超声软指标异常等,均为中孕期孕妇FCA的IPD指征,孕妇IPD指征类型不同,FCA风险不同。羊膜腔穿刺术羊水细胞FK检测,可预测有IPD指征孕妇的妊娠结局,为降低FKA出生率提供参考。     

骨髓增生异常综合征和再生障碍性贫血等细胞遗传学研究

为了探讨骨髓细胞遗传学分析在鉴别诊断骨髓增生异常综合征（ＭＤＳ）和再生障碍性贫血（ＡＡ）等不同血液病中的意义，我们联合应用骨髓细胞Ｒ－带核型分析和姐妹染色单体分化（ＳＣＤ）检测，对３３４例ＭＤＳ、ＡＡ等不同血液病进行分析并随访。结果表明：（１）ＲＡ／ＡＡ、ＲＡ／ＩＴＰ和ＲＡ／ＨＡ等可疑ＲＡ即为不典型ＲＡ或早期ＲＡ；（２）骨髓细胞从ＳＣＤ阳性转为ＳＣＤ阴性是骨髓细胞癌变过程；（３）骨髓细胞ＳＣＤ检测和核型分析具有肯定的诊断和预后价值；（４）ＦＡＢ分类法同细胞遗传学技术相结合可明显地提高ＭＤＳ诊断率或确诊率；（５）ＭＤＳ核型异常检出率６４．４％，与国外（４０％～７０％）相仿。本系列ＭＤＳ常见染色体异常为＋８，２ｑ￣－，一５／５ｑ￣－，一７／７ｑ￣－，７ｐ￣＋，以及一１１，一１４等，也与国外相似。（６）ＭＤＳ发病最初染色体异常看来是染色体数目异常即单体性为主。     

273例曾生育非整倍体患儿父母染色体核型分析

目的：探讨曾生育非整倍体患儿父母染色体核型异常的检出情况。方法：利用G显带技术对273例曾生育非整倍体患儿父母以及116例健康体检者进行染色体核型分析,必要时加做C显带。结果：273例样本中共检出72例染色体变异,其中包括4例染色体结构异常,检出率为1.46%;68例染色体多态变异,检出率为24.91%;剔除高龄女性样本后,多态变异检出率为64/255（25.10%）。116例对照组染色体核型共检出1例染色体结构异常,5例染色体多态变异,多态变异检出率为4.31%,2组多态变异检出率差异有统计学意义（P＜0.05）。结论：曾生育非整倍体患儿父母染色体多态变异具有较高检出率,应引起临床医生的重视。     

1193例慢性粒细胞白血病细胞及分子遗传学分析

目的了解国内慢性粒细胞白血病（CML）不同病期染色体核型及其演变和ber—abl融合基因特点。方法对1193例CML患者的染色体核型及524例CML患者的ber-abl融合基因资料进行回顾性分析。染色体的检测采用R显带技术，融合基因检测采用RT-PCR技术。结果在所有病例中，Ph染色体阳性（Ph^＋）患者占98．07％，Ph^-患者占1．93％。在Ph^＋患者中，95．64％为典型Ph染色体阳性，4．36％为变异型Ph染色体阳性。11．88％的典型Ph^＋患者发生染色体核型演变。急变期、加速期和慢性期染色体核型演变的发生率分别为49．04％、27．78％及7．94％。在所有典型Ph^＋患者中，发生染色体核型演变后最常见的附加染色体异常类型为＋Ph（14．62％），＋8（10．77％）和-21（7．69％）。急变期和加速期最常见的附加染色体异常类型为＋Ph（28．57％），＋8（16．67％）和＋19（7．14％）；慢性期最常见的附加染色体异常为-21（10．26％），＋Ph（8．97％）和＋8（8．97％）。附加染色体异常联合出现类型以＋Ph与＋8的联合最多（3．60％）。在所有524例检测过融合基因的标本中，h3a2（＋）为54．01％，b2a2（＋）为27．67％。结论国内CML患者染色体的核型及演变可能有着自己的特点。     

孕中晚期取脐血制作染色体的临床应用

目的研究染色体病的产前诊断。方法对不同原因产前咨询的278例孕妇于孕中期B超监测下采取脐血,其中68例制作染色体行核型分析。结果68例中7例为异常核型,分别为46,XY,21P+,46,XX,t(1;4)(q44;q25);47,XX,+21及4例46,X,Yq+。结论于孕中晚期采取脐血制作染色体,具有周期短、染色体形态好及成功率高等优点,可获取供临床诊断有价值的结果,对于有遗传病家族史、畸形胎儿分娩史、异常孕产史等的诊断有其特异性。     

骨髓增生异常综合征的细胞遗传学分析及其预后意义

目的:探讨骨髓增生异常综合征(MDS)的细胞遗传学异常及其演变与MDS的亚型和转归的关系。方法:采用骨髓细胞直接法和(或)短期培养法按常规制备染色体,采用R显带技术进行核型分析。结果:8例MDS检出染色体异常核型,占40%,主要异常有5q-,+8,-7,t/del(3)(q21),-18;MDS-RAEB和RAEBT(63.7%)比MDS-RA(11.1%)异常核型检出率高(P<0.05),且多为复杂异常;核型异常者进展为白血病的危险性明显高于核型正常者。结论:MDS的核型分析对其明确诊断,分型和预后评价有重要的参考价值。     

广西地区50975例孕妇无创产前筛查分析

目的 探讨无创产前筛查(NIPS)在胎儿染色体非整倍体异常(CAA)及全基因组拷贝数变异(CNV)筛查中的临床应用价值.方法 选择2018年1月至2019年12月,广西壮族自治区60余家医疗机构采集血液样本后送至本院完成NIPS的50975例单胎孕妇为研究对象.其分娩年龄为13～54岁,高龄孕妇(分娩时年龄≥35岁)为...     

Percutaneous umbilical blood sampling

In the present day, fetal blood is sampled from the umbilical vein via a needle guided by dynamic ultrasound from the maternal abdomen (percutaneous umbilical blood sampling, PUBS). PUBS has become important in the fields of fetal physiology, diagnosis and therapy. Indications for PUBS are fetal karyotyping, prenatal diagnosis of blood disorders and congenital infection, and evaluation of fetal hypoxemia. Although risk of fetal loss following PUBS depends on the indication for the procedure and the experience of the operator, the rate of fetal loss after PUBS is assumed to be around 1%. Recent advances in molecular and cytogenetic techniques have restricted the number of reasons for using PUBS. However, since this technique offers a considerable advantage in enabling access directly to the fetal circulation, PUBS is likely to be used more frequently for fetal therapy than for prenatal diagnosis in the future.