应用抑制性消减杂交技术筛选及鉴定高温致金黄地鼠神经管畸形下调表达基因

目的克隆高温致金黄地鼠神经管畸形下调表达基因，探讨其分子生物学机理。方法应用抑制性消减杂交技术构建高温致畸金黄地鼠胚胎神经管反向消减cDNA文库；联合蓝白斑和菌落PCR方法筛选阳性克隆进行测序和同源性分析；用Northern印迹方法证实这些基因的表达。结果成功构建高温致畸金黄地鼠胚胎神经管反向消减cDNA文库，从中筛选到15个基因，均与GenBank中已知基因有同源性。Northern印迹证实这些基因在高温致畸胚胎神经管中均呈下调表达。结论发现了高温致金黄地鼠神经管畸形过程中的一些重要相关基因并对其功能进行了初步探讨。     

Chromosome translocation (T(2;4)1 Sn)-induced neural tube defects in the mouse embryo

Neural tube closure was studied in embryos obtained from matings of male mice heterozygous for a reciprocal chromosome translocation (T(2;4)1 Sn) with normal female (CFLP) mice. When litters were examined on the 9th to 12th days of gestation, there was a high incidence of resorption, developmental delay and neural tube closure defects in these embryos. SEM observations indicated that the neural tube closure defects ranged in severity from a side-to-side flattening of the midbrain to extensive anomalies in which the entire cephalic neural tube had failed to close. In addition to cephalic defects, a number of embryos exhibited open defects or abnormal subectodermal blebbing in the future lumbosacral region. In spinal regions, even in areas in which the neural tube had previously closed, it often was irregular and folded. These observations are discussed in relation to studies of gene-related defects of neural tube closure.     

神经管缺陷的病因学研究进展

脊柱裂、无脑儿和脑膜脑膨出通常被统称为神经管缺陷(neural tube defects,NTDs),是在神经胚形成过程中由于神经管闭合异常导致的中枢神经系统先天性疾病.其病因极其复杂,目前认为与神经管发育有关的基因异常和诸多环境因素均能导致NTDs,尽管很多学者对NTDs的病因做了大量的研究,但目前对于导致人NTDs的关键病因仍知之甚少.本文就目前研究最多的与神经管缺陷有关的基因和环境因素作一综述.     

Transferrin and HLA: spontaneous abortion, neural tube defects, and natural selection

We report evidence that transferrin C3, a gene present in 9 to 10 per cent of whites, is associated with recurrent spontaneous abortion (P = 0.001) and that maternal transferrin genotype has an effect on the transmission ratio of the common transferrin genes (C1, C2, and C3) from heterozygous fathers to normal offspring (P less than 0.002). The effect of maternal genotype on paternal gene transmission is an unusual example of the operation of selection in the human reproductive process. This effect, together with the separate evidence for association of the transferrin C3 allele with spontaneous abortion, indicates that transferrin is a second marker (in addition to HLA) of genes important in reproduction. On the basis of comparison of the frequencies of transferrin (chromosome 3) and HLA (chromosome 6) mating types in 348 control couples and in 81 couples who had had a child with a neural tube defect, we hypothesize that some combinations of maternal and fetal genes on these two chromosomes may be associated with neural tube defects.     

Association of neural tube defects with omphalocele in chromosomally normal fetuses

Omphalocele is frequently associated with other congenital malformations or a chromosome abnormality. Previously published series of omphalocele have emphasized the association of congenital heart defects or chromosomal abnormalities. We present five cases of omphalocele with concurrent neural tube defect from among the 15 cases of omphalocele evaluated between 1981 and 1985. Fourteen of 15 were detected prenatally. A sixth case is presented in which both a neural tube defect and an omphalocele were suspected on a prenatal ultrasound, but only the latter was found on autopsy. We recommend that a systematic evaluation be performed on every fetus with an omphalocele to include amniotic fluid alpha fetoprotein, acetylcholinesterase levels, chromosome study, and careful ultrasonography looking for evidence of other abnormalities, especially neural tube defects, before counseling the parents.     

同型半胱氨酸代谢相关基因与神经管缺陷的研究进展

神经管缺陷(neural tube defects,NTDs)是由于神经管的发生和分化紊乱而出现的人类出生缺陷中最常见和最严重的一组畸形。目前对其发病原因尚不清楚,一般认为是由环境因素和遗传因素共同作用造成的,目前研究的热点是同型半胱氨酸代谢相关因素与神经管缺陷的关系。本文对同型半胱氨酸代谢过程中某些关键酶和因子及其基因多态性与神经管缺陷的关系进行了综述。     

Neural tube closure and neural tube defects: studies in animal models reveal known knowns and known unknowns

The vertebrate central nervous system is a hollow structure that develops first as a flat sheet of cells and subsequently rolls into a tube during embryogenesis. Failure of this rolling process, called neural tube closure, results in a class of common human birth defects called neural tube defects. The cellular and molecular mechanisms governing neural tube closure have been studied extensively in animal models, but much remains to be elucidated. In this review, I will highlight recent progress in understanding neural tube closure mechanisms and how these studies can inform our search for the genes that underlie human neural tube defects. Supplementary material for this article can be found on the American Journal of Medical Genetics (Part C) website (http://www.mrw.interscience.wiley.com/suppmat/1552-4868/suppmat/2005/135/v135.1.wallingford.html)     

Sex and congenital malformations: an international perspective

The study evaluated the sex distribution of major isolated malformations and common trisomies among a large and geographically varied sample. Eighteen registries from 24 countries contributed cases, which were centrally reviewed and classified in three clinical types as isolated, associated, or syndromic. We selected cases of 26 major defects (n = 108,534); trisomy 21, 18, and 13 (n = 30,114); other syndromes (n = 2,898); and multiple congenital anomalies (n = 24,197), for a total of 165,743 cases. We observed a significant deviation of sex distribution (compared to a sex ratio of 1.06 or male proportion of 51.4%) for 24 of the 29 groups (a male excess in 16, a female excess in 8), and in 8 of such groups these estimates varied significantly across registries. A male excess was noted for two left obstructive cardiac defects (hypoplastic left heart and coarctation of the aorta) and a female excess for all the main types of neural tube defects. A male excess was seen for omphalocele but not gastroschisis. For neural tube defects the female excess tended to be stronger in areas with historically high prevalence for these defects. For 15 of the 26 birth defects the sex distribution differed among isolated, associated, and syndromic cases. Some of these epidemiologic commonalities are consistent with known or putative developmental processes. Further, the geographic variation for some defects may reflect local prevalence rates and risk factors. Finally, the findings underscore the need for clinical classification (e.g., into isolated, multiple, syndromes) in studies of birth defects.     

神经管缺陷与Dishevelled基因表达的关系

神经管缺陷是复杂的多基因疾病，是中枢神经系统最常见的先天畸形。虽然其发病机制尚不清楚，但是研究已证实遗传因素与其发病具有相关性。本文将着重对Dishevelled基因细胞信号通路在神经管发育、神经管缺陷发病机制中的作用及有关Dishevelled基因的研究进展进行阐述。     

Oral and dental development in X chromosome aneuploidy

Though frequently noted, orofacial anomalies in poly X syndromes have been seldom reviewed. In a study of patients with an X chromosome aneuploidy (XXXXX, XXXX, XXXXY, XXXY) the following facial and dental defects were found to be characteristic features of these syndromes: mainly bifid uvula and macroglossia, enamel defects, dental taurodontism and abnormal roots. These observations are discussed in the light of the possible role of X-linked genes.     

孕中期产前筛查11716例分析

目的评价妊娠中期（AFP/β-hCG）唐氏综合征/神经管缺陷产前筛查系统产前筛查唐氏综合征和神经管缺陷的临床应用价值。方法采用酶联免疫分析11716例孕龄为14-20周,年龄为20-45岁妊娠妇女AFP/β-hCG,并结合孕妇年龄、孕周等其它因素,用唐氏综合征产前筛查风险估算和管理软件综合评价孕中期妇女妊娠唐氏综合征和神经管缺陷的风险度。结果检出唐氏综合征高危妊娠650例,筛查阳性率为5.54%,经过羊水染色体核型分析、出生缺陷监测和新生儿外周血染色体核型分析,共筛查出16例唐氏综合征患儿,而在低高危妊娠中发现1例唐氏综合征患儿。检出神经管缺陷高危妊娠60例,筛查阳性率为0.51%,均经过B超检查,共检出20例神经管缺陷胎儿;在11656例神经管缺陷低危妊娠中,未发现神经管缺陷患儿。结论AFP/β-hCG产前筛查扩大了孕妇人群,提高了唐氏综合征和神经管缺陷患儿的检出率,最大可能避免了这些缺陷儿的出生,同时也减少了因唐氏综合征和神经管缺陷导致的围产儿死亡,具有明显的经济效益和社会效益,也是落实优生优育政策非常有效的技术手段。     

Testing for genetic associations in a spina bifida population: analysis of the HOX gene family and human candidate gene regions implicated by mouse models of neural tube defects

Neural tube defects (NTDs) are among the most common severely disabling birth defects in the United States, affecting approximately 1-2 of every 1,000 live births. The etiology of NTDs is multifactorial, involving the combined action of both genetic and environmental factors. HOX genes play a central role in establishing the initial body plan by providing positional information along the anterior-posterior body and limb axis and have been implicated in neural tube closure. There are many mouse models that exhibit both naturally occurring NTDs in various mouse strains as well as NTDs that have been created by "knocking out" various genes. A nonparametric linkage method, the transmission disequilibrium test (TDT), was utilized to test the HOX gene family and human equivalents of genes (when known) or the syntenic region in humans to those in mouse models which could play a role in the formation of NTDs. DNA from 459 spina bifida (SB) affected individuals and their parents was tested for linkage and association utilizing polymorphic markers from within or very close to the HOXA, HOXB, HOXC, and HOXD genes as well as from within the genes/gene regions of eight mouse models that exhibit NTDs. No significant findings were obtained for the tested markers.     

Immunodeficiency as a component of recognizable syndromes

Immunodeficiency occurs in numerous genetic syndromes. While it is the dominant manifestation in primary immunodeficiencies, immune deficits may also be seen in a variety of other recognizable syndromes. Immunodeficiency has been reported in 64 such conditions, adding to the 45 recognized primary immunodeficiencies. These uncommon syndromes with immune defects can present with: (a) growth deficiency (11 syndromes with disproportionate or proportionate short stature), (b) specific organ system dysfunction (18 with gastrointestinal, dermatologic, or neurologic abnormalities), (c) inborn errors of metabolism (13), (d) miscellaneous anomalies (10), or (e) chromosome anomalies (12). In most of the disorders, only some of the affected patients have immune defects. However, in 27 syndromes, immunodeficiency is a constant finding. We briefly review the clinical manifestations of each syndrome and delineate the specific associated immune defects. In most syndromes, the connection between the immune and other defects is unknown. Recognition of these conditions involving both the immune and other organ systems may facilitate accurate diagnosis and management as well as yield information regarding genes critical for the development of the involved systems. © 1996 Wiley-Liss, Inc.     

Neural tube defects and maternal hyperthermia in early pregnancy: Epidemiology in a human embryo population

A causal relationship between neural tube defects and maternal febrile illness in early pregnancy was investigated retrospectively using human embryo data from Japan. The frequency of febrile illness was compared with corresponding data from normal controls, and holoprosencephalic and polydactylous embryos. Within the group of neural tube defects, the prevalence of maternal hyperthermia was significantly higher than in normal control and holoprosencephaly mothers. The association was constant and highly significant specifically for exencephaly, which is an embryonic forerunner of anencephaly. The correlation with myeloschisis (without exencephaly) was not significant. In eight out of the ten cases in which the timing of the fever was known, it occurred during the clinically determined critical period of neural tube closure in human embryos. These results support the hypothesis that maternal hyperthermia in early pregnancy can cause neural tube defects in man, especially anencephaly.     

高迁移率族蛋白B1基因的克隆及其与神经管发育的相关关系

目的:构建神经管cDNA文库,寻找神经管发育相关基因。方法:提取E8.5 d金黄地鼠神经管总RNA;SMART技术构建神经管cDNA噬菌体表达文库;重组噬菌体PCR鉴定。将出现频率很高的重组噬菌斑,经质粒转化、酶切鉴定和DNA序列分析,证实为高迁移率族蛋白B1基因(HMGB1)。将HMGB1 cDNA片段回收、纯化,制备探针;Northern杂交检测不同发育阶段神经管中HMGB1 mRNA的表达变化。结果:构建的HMGB1cDNA片段含有完整的cDNA序列。Northern杂交显示:随胚胎发育,神经管HMGB1 mRNA表达量逐渐增加,E10 d增加最为明显,E12 d仍处于较高水平;而8.5 d高温致畸胚神经管,HMGB1 mRNA表达量较对照组明显减少。结论:HMGB1基因的表达与神经管发育及高温致神经管畸形的发生密切相关。     

The embryology of body wall closure: relevance to gastroschisis and other ventral body wall defects

During the 3rd and 4th weeks post-fertilization (5 and 6 weeks from the last normal menstrual period [LNMP]), the human embryo is transformed from a flat disc-shaped organism into the classic shape of an embryo in the "fetal" position. This change is effected by simultaneously rolling the top layer of the disc, the ectoderm, into the neural tube and the bottom layers of the disc, the endoderm and mesoderm, into the gut tube and body wall, respectively. In this manner, the flat disc is transformed into two tubes, one dorsal to the other, surrounded by supporting structures in the body wall. If closure of the neural tube fails, then neural tube defects (NTDs), such as anencephaly and spina bifida, occur; if closure of the ventral body wall fails, then ventral body wall defects, such as ectopia cordis, gastroschisis, and bladder and cloacal exstrophy, occur. Interestingly, no known closure defects have been described for the gut tube. Note, however, that all of the closure defects that do occur have their origins early in gestation during the third and fourth weeks of development.     

Mutations in the planar cell polarity gene, Fuzzy, are associated with neural tube defects in humans

Neural tube defects (NTDs) are a heterogeneous group of common severe congenital anomalies which affect 1-2 infants per 1000 births. Most genetic and/or environmental factors that contribute to the pathogenesis of human NTDs are unknown. Recently, however, pathogenic mutations of VANGL1 and VANGL2 genes have been associated with some cases of human NTDs. Vangl genes encode proteins of the planar cell polarity (PCP) pathway that regulates cell behavior during early stages of neural tube formation. Homozygous disruption of PCP genes in mice results in a spectrum of NTDs, including defects that affect the entire neural axis (craniorachischisis), cranial NTDs (exencephaly) and spina bifida. In this paper, we report the dynamic expression of another PCP gene, Fuzzy, during neural tube formation in mice. We also identify non-synonymous Fuzzy amino acid substitutions in some patients with NTDs and demonstrate that several of these Fuzzy mutations affect formation of primary cilia and ciliary length or affect directional cell movement. Since Fuzzy knockout mice exhibit both NTDs and defective primary cilia and Fuzzy is expressed in the emerging neural tube, we propose that mutations in Fuzzy may account for a subset of NTDs in humans.