Genetische Risiken der assistierten Reproduktion

Infertility patients have to be counseled about the genetic risks before treatment. Chromosomal anomalies can be found in 5% of subfertile men and in cases of azoospermia the frequency even rises to 15%. Therefore a chromosome analysis should be performed in men with a sperm count <20 million/ml and also in their partners. Klinefelter’s syndrome as well as a Robertsonian translocation can cause male subfertility. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and deletions in the Y chromosome have been described as being more frequent in these cases. Regarding pregnancy and neonatal outcome of children, patients have to be counseled about the increased risk of complications. The abortion rate is increased by 1.3-fold, although this is most likely caused by the subfertility of the couple and other risk factors and not caused by the therapy. Complications during pregnancy, such as preeclampsia, growth retardation, stillbirth and a low birth weight are more common after assisted reproduction. The incidence of congenital anomalies is increased by 1.3-fold after in vitro fertilization (IVF) as well as after intracytoplasmic sperm injection (ICSI) therapy.     

Diagnostic test for Y chromosome microdeletion screening in male infertility

Despite the current lack of understanding the mechanism of deleterious effects of Y chromosome microdeletions and their prognostic influence on male subfertility, the Y chromosome microdeletion test is widely used in the diagnostic evaluation of male subfertility. However, currently used diagnostic schemes have not been sufficiently evaluated for their diagnostic performance. The purpose of this study was to analyze a large database of published Y chromosome microdeletions to develop the optimal screening strategy for male subfertility. Therefore, we created a database from genetic and clinical data published in 52 peer-reviewed studies reporting on 512 cases with Y chromosome microdeletions. We developed a computerized procedure with the goal of minimizing the number of genetic markers included in the diagnostic set while maximizing the detection rate in patients with microdeletions. We estimate that 85.6% of all published Y chromosome microdeletions can be covered by a set of six genetic markers (sY84, sY127, sY152, RBMY1, sY147, sY254-DAZ). Inclusion of additional markers brings relatively little to the sensitivity of the test and is potentially related to the population origin.     

Application of 7-amino-actinomycin D for the fluorescence microscopical analysis of DNA in cells and polytene chromosomes

Summary The cytochemical properties of a guanine-specific synthetic fluorescent analogue of actinomycin D, 7-amino-actinomycin D, have been studied in fixed and living preparations of L cells and polytene chromosomes of salivary glands ofChironomus thummi thummi andDrosophila lummei (Hackman).7-Amino-actinomycin D has been shown to bind to DNA-containing structures, thereby inducing in them a bright red fluorescence. No specific fluorescence has been found in RNA-containing structures treated with this fluorescent probe.The fluorescence pattern of some regions of polytene chromosomes with a known nucleotide composition was analysed. It has been established that 7-amino-actinomycin D induces a very weak fluorescence in GC-poor chromosome regions of theDrosophila lummei toromere structure. Data indicating a nonlinear dependence between the fluorescence intensity of a stained chromosome region and the GC content in its DNA have been obtained. The influence of DNA nucleotide composition in a chromosome region on the fluorescence of 7-amino-actinomycin D is discussed. In combination with quinacrine staining and the Feulgen fluorescence reaction, treatment with 7-amino-actinomycin D provides useful information about the distribution of GC base pairs in the chromosome region under study.     

Physical map of the centromeric region of human chromosome 7: relationship between two distinct alpha satellite arrays.

A long-range physical map of the centromeric region of human chromosome 7 has been constructed in order to define the region containing sequences with potential involvement in centromere function. The map is centered around alpha satellite DNA, a family of tandemly repeated DNA forming arrays of hundreds to thousands of kilobasepairs at the primary constriction of every human chromosome. Two distinct alpha satellite arrays (the loci D7Z1 and D7Z2) have previously been localized to chromosome 7. Detailed one- and two- locus maps of the chromosome 7 centromere have been constructed. Our data indicate that D7Z1 and D7Z2 arrays are not interspersed with each other but are both present on a common Mlu I restriction fragment estimated to be 3500 kb and 5500 kb on two different chromosome 7's investigated. These long-range maps, combined with previous measurements of the D7Z1 and D7Z2 array lengths, are used to construct a consensus map of the centromere of chromosome 7. The analysis used to construct the map provides, by extension, a framework for analysis of the structure of DNA in the centromeric regions of other human and mammalian chromosomes.     

Case-control study of whether subfertility in men is familial.

OBJECTIVE--To test the hypothesis that subfertility in men is familial and to examine the distribution of subfertility within families for consistency with a genetic cause. DESIGN--Case-control study and segregation analysis. SETTING--Two teaching hospitals in Leeds. SUBJECTS--Cases (probands) were men with an abnormal sperm count who attended a subfertility clinic and whose partners had no major factor contravening fertility. Controls were fathers of two or more children recruited through vasectomy clinics or a maternity department. MAIN OUTCOME MEASURES--The incidence of involuntary childlessness among brothers with partners and among sisters and second and third degree male relatives. When possible clinical and laboratory details were obtained from involuntarily childless brothers. RESULTS--Seventeen of the 148 (11.5%) brothers of probands but none of the 169 brothers of controls had sought medical advice for childlessness (P < 0.0005). Four probands had more than one involuntarily childless brother. There were six further brothers whose childlessness was thought to be involuntary bringing the total prevalence of subfertility among brothers of probands to 16%. Segregation analysis was consistent with an autosomal recessive mode of inheritance accounting for 60% of subfertility in men. Seventeen of the 346 (4.9%) uncles of probands and 10 of 420 (2.8%) uncles of controls were reported to be involuntarily childless (P = 0.09), but there was no difference in childlessness among sisters. In three families sperm counts from "affected" brothers confirmed the diagnosis and showed considerable similarities within but not between families. CONCLUSION--Subfertility in men has a familial component, and the observations are consistent with an autosomal recessive mode of inheritance in over half the cases. Several different genes are probably involved.     

A complex chromosomal rearrangement with a translocation 4;10;14 in a fertile male carrier: ascertainment through an offspring with partial trisomy 14q13-->q24.1 and partial monosomy 4q27-->q28 [corrected

Complex chromosomal rearrangements (CCRs) are usually associated with infertility or subfertility in male carriers. If fertility is maintained, there is a high risk of abnormal pregnancy outcome. Few male carriers have been identified by children presenting with mental retardation/congenital malformations (MR/CM) or by spontaneous abortions of the spouses. We report a de novo CCR with five breakpoints involving chromosomes 4, 10 and 14 in a male carrier who was ascertained through a son presenting with MR/CM due to an unbalanced karyotype with partial trisomy 14 and partial monosomy 4. The child has a healthy elder brother. In the family history no abortions were reported. No fertility treatment was necessary. Cytogenetic analysis from the affected son showed a reciprocal translocation t(4;10) with additional chromosomal material inserted between the translocation junctions in the derivative chromosome 10. The father showed the same derivative chromosome 10 but had additionally one aberrant chromosome 14. Further molecular cytogenetic analyses determined the inserted material in the aberrant chromosome 10 as derived from chromosome 14 and revealed a small translocation with material of chromosome 4 inserted into the derivative chromosome 14. Thus the phenotype of the son is supposed to be associated with a partial duplication 14q13-->q24.1 and a partial monosomy 4q27-->q28. Including our case we are aware of eleven CCR cases with fertile male carriers. In eight of these families normal offspring have been reported. We propose that exceptional CCRs in fertile male carriers might form comparatively simple pachytene configurations increasing the chance of healthy offspring.     

Physical mapping of the HOXA1 gene and the hnRPA2B1 gene in a YAC contig from human chromosome 7p14-p15

A cluster of homeobox-containing genes (HOXA) and a heterogeneous nuclear ribonucleoprotein (hnRPA2B1) have both previously been assigned to chromosome 7p15 by in situ hybridization. In this report, we constructed a YAC contig from chromosome 7p14-p15, between markers D7S2496 and D7S1838, and determined the position of the HOXA1 gene and the hnRPA2B1 gene in this YAC contig. Received: 19 November 1996 / Revised: 2 January 1997     

Comparison of genetic and physical maps of group 7 chromosomes from Triticum aestivum L.

We present a high density physical map of homoeologous group 7 chromosomes from Triticum aestivum L. using a series of 54 deletion lines, 6 random amplified polymorphic DNA (RAPD) markers and 91 cDNA or genomic DNA clones from wheat, barley and oat. So far, 51 chromosome segments have been distinguished by molecular markers, and 54 homoeoloci have been allocated among chromosomes 7A, 7B and 7D. The linear order of molecular markers along the chromosomes is almost identical in the A- B- and D-genome of wheat. In addition, there is colinearity between the physical and genetic maps of chromosomes 7A, 7B and 7D from T. aestivum, indicating gene synteny among the Triticeae. However, comparison of the physical map of chromosome 7D from T. aestivum with the genetic map from Triticum tauschii some markers have been shown to be physically allocated with distortion in more distal chromosome regions. The integration of genetic and physical maps could assist in estimating the frequency and distribution of recombination in defined regions along the chromosome. Physical distance did not correlate with genetic distance. A dense map facilitates the detection of multiple rearrangements. We present the first evidence for an interstitial inversion either on chromosome arm 7AS or 7DS of Chinese Spring. Molecularly tagged chromosome regions (MTCRs) provide landmarks for long-range mapping of DNA fragments.     

Development of a set of compensating Triticum aestivum-Dasypyrum villosum Robertsonian translocation lines

Dasypyrum villosum (L.) Candargy, a wild relative of bread wheat ( Triticum aestivum L.), is the source of many agronomically important genes for wheat improvement. Production of compensating Robertsonian translocations (cRobTs), consisting of D. villosum chromosome arms translocated to homoeologous wheat chromosome arms, is one of the initial steps in exploiting this variation. The cRobTs for D. villosum chromosomes 1V, 4V, and 6V have been reported previously. Here we report attempted cRobTs for wheat - D. villosum chromosome combinations 2D/2V, 3D/3V, 5D/5V, and 7D/7V. The cRobTs for all D. villosum chromosomes were recovered except for the 2VS and 5VL arms. As was the case with the 6D/6V combination, no cRobTs involving 2D/2V chromosomes were recovered; instead, cRobT T2BS·2VL involving a nontargeted chromosome was recovered. All cRobTs are fertile, although the level of spike fertility and hundred kernel weight (HKW) varied among the lines. The set of cRobTs involving 12 of the 14 D. villosum chromosomes will be useful in wheat improvement programs. In fact, among the already reported cRobTs, T6AL·6VS carrying the Pm21 gene is deployed in agriculture and many useful genes have been reported on other cRobTs including resistance to stem rust race UG99 on T6AS·6VL.     

Possible genetic heterogeneity in the Saethre-Chotzen syndrome

Saethre-Chotzen syndrome is an autosomal dominant acrocephalosyndactyly syndrome whose gene has been assigned to chromosome 7p. Cytogenetic and linkage analyses have enabled the interval encompassing the disease gene to be delimited to a short region of chromosome 7p15.3–p21.2. Based on the genetic analysis of three unreported families, we confirm the location of the disease gene(s) in the interval defined by loci D7S664 and D7S493 (Z_max = 4.78 at * = 0 at the D7S488 locus) but fail to decide whether one or more disease-causing genes map in this genetic interval. Received: 2 January 1996 / Revised: 21 March 1996     

Detailed comparison between the wheat chromosome group 7 short arms and the rice chromosome arms 6S and 8L with special reference to genes involved in starch biosynthesis

Rice bacterial artificial chromosome (BAC) clones have been identified that contain sequences orthologous to each EST localized to wheat chromosome 7AS deletion stocks by Southern blot hybridization. This information has been used to relate the DNA sequence included in each wheat deletion stock to a complement of rice BACs. A virtual contig was used that covered 90 cM (21 Mb) of DNA sequence (with a gap for the 6S/8L junction). Comparison of the positions of orthologous genes on the rice virtual contig and on wheat chromosome 7AS showed that there was an unexpectedly low level of synteny (31.4%) and a high level of chromosome rearrangements (68.6%). The non-syntenous loci were of two classes: wheat and rice genes found at different locations in the genome (32.6%), and ESTs in wheat not present in rice (36.0%). Four starch synthetic genes, GBSSI, SSI, SSIIa and DBEI, were located at similar positions on wheat chromosome 7AS and the virtual rice contig covering wheat chromosome 7AS. A preliminary comparison between the short arms of chromosome 7A and 7D in wheat showed that both chromosomes had a similar level of sequence synteny with rice. Therefore, there appears to be considerable variation in gene order between wheat chromosome 7S and rice chromosome 6S and 8L.     

Genetic homogeneity of cystic fibrosis.

We studied large Amish/Mennonite/Hutterite kindreds that segregate cystic fibrosis (CF) for linkage between CF and the polymorphic DNA markers pJ3.11 and 7C22 located on chromosome 7. These inbred pedigrees consist of more than 300 members including 30 affected individuals. In these families, linkage between the CF locus and the chromosome 21 marker D21S5 and between CF and the marker at the met oncogene locus on chromosome 7 had been previously indicated. We now report linkage between CF and pJ3.11 (Z = 4.92, theta = 0) and between CF and 7C22 (Z = 3.42, theta = 0). Therefore, CF segregates in these large pedigrees in a manner consistent with data from smaller outbred families with respect to the markers on chromosome 7 closest to CF. These data are consistent with locus homogeneity for the defect causing CF in the populations that have been examined to date.     

X/XY/XYY mosaicism as a cause of subfertility in boars: a single case study

Sex chromosome abnormalities are common in mammals and humans and are often associated with subfertility. In this study a boar with normal sperm parameters was indicated to have reduced prolificacy from figures obtained for return rate, farrowing rate and total number of piglets born. G-banded cytogenetic analysis of peripheral blood identified an abnormal mosaic sex chromosome constitution 39,XYY[74]/38,XY[23]/37,X[3]. Cytogenetic analysis of fibroblasts confirmed this mosaic karyotype with similar percentages of cell lines observed 39,XYY[76]/38,XY[19]/37,X[5]. External genitalia revealed a poorly developed scrotum with the right testicle being smaller than the left. To the best of our knowledge this is the first time that this chromosome constitution has been reported in the pig. It is of particular interest that this karyotype is associated with reduced boar fertility, which could lead to potential economic losses if such a boar were selected for breeding purposes.     

Identification of two sex-specific quantitative trait loci in chromosome 11q for hip bone mineral density in Chinese

BACKGROUND: Chromosome 11q has not only been found to contain mutations responsible for the several Mendelian disorders of the skeleton, but it has also been linked to bone mineral density (BMD) variation in several genome-wide linkage studies. Furthermore, quantitative trait loci (QTL) affecting BMD in inbred mice and baboons have been mapped to a region syntenic to human chromosome 11q. The aim of the present study is to determine whether there is a QTL for BMD variation on chromosome 11q in the Chinese population. METHODS: Nineteen microsatellite markers were genotyped for a 75 cM region on 11q13-25 in 306 Chinese families with 1,459 subjects. BMD (g/cm(2)) was measured by DXA. Linkage analyses were performed using the variance component linkage analysis method implemented in Merlin software. RESULTS: For women, a maximum LOD score of 1.62 was achieved at 90.8 cM on 11q21 near the marker D11S4175 for femoral neck BMD; LOD scores greater than 1.0 were observed on 11q13 for trochanter BMD. For men, a maximum LOD score of 1.57 was achieved at 135.8 cM on 11q24 near the marker D11S4126 for total hip BMD. CONCLUSION: We have not only replicated the previous linkage finding on chromosome 11q but also identified two sex-specific QTL that contribute to BMD variation in Chinese women and men.     

精子端粒长度与特发性男性不育相关

端粒是真核生物染色体末端的多功能特异性DNA-蛋白结构,覆盖在染色体末端,保护基因组的稳定性。端粒在减数分裂过程中起到了十分重要的作用,协助染色体配对、联会、同源重组和分离。精子中的端粒可能在精子的受精能力和胚胎发育中起到重要作用。近年来,端粒与生殖的相关性研究成为一个新的热点,但精子端粒与男性不育间的相关性并不明确。本文采用实时荧光定量PCR方法检测中国特发性男性不育人群(126例)和正常可育男性人群(138例)的精子相对端粒长度,结果发现,特发性男性不育病例的精子平均相对端粒长度(2.894±0.115)低于正常对照组(4.016±0.603),差异具有统计学意义(P=5.097×10^-5);并且精子相对端粒长度与精子密度、精子总数和精子活力都有显著的相关性：精子数量较多和/或精子活力较高,精子相对端粒长度较长。研究结果提示,在中国人群中,精子端粒长度与特发性男性不育具有相关性,精子的端粒长度可能影响精子发生和精子的功能,精子端粒的缩短导致精子数目及活力的降低从而导致男性不育。     

An interchromosomal reciprocal translocation in wheat involving leaf rust resistance gene Lr34.

'Thatcher' backcross lines RL6058 and RL6077 have adult-plant leaf rust resistance and were believed to have Lr34. However, genetic analysis revealed that the genes in the two lines were independent of each other. Previous work demonstrated that Lr34 is located on chromosome 7D. The leaf rust resistance gene in RL6058 must be on chromosome 7DS because no recombinants were observed between it and gene Lr29, known to be on chromosome 7DS. It was also linked with Rc3 (30.25 +/- 2.88%), a gene for purple coleoptile on chromosome 7DS. It was independent of Lr19 and NS1 (nonsuppressor mutant), which are located on 7DL. The leaf rust resistance gene in RL6077 was independent of genes Lr19 and Lr29. The presence of quadrivalents in pollen mother cells of the RL6058/RL6077 hybrid indicates that the Lr34 gene in RL6077 may have been translocated onto another chromosome. Lr34 from RL6058 and RL6077 may have been combined in four F3 lines derived from their intercross.     

A chromosomal walk in the region of polytene bands 7C-D of theDrosophila X chromosome

A chromosomal walk on the X chromosome ofDrosophila in the region of polytene bands 7C1 to 7D5 is described. The region is of interest since three olfactory genes have been found to map here in addition to a haplo-inviable locus. Genomic clones spanning 160 kilobases have been isolated and their complete restriction map is presented. The clones have been aligned on the polytene chromosome bands byin situ hybridisation. In addition the end-points of a deficiency and duplication lying in this region have been mapped approximately, showing that an overlap exists between them.     

Genetics of Differences in Pheromonal Hydrocarbons between Drosophila Melanogaster and D. Simulans

Females of Drosophila melanogaster and its sibling species D. simulans have very different cuticular hydrocarbons, with the former bearing predominantly 7,11-heptacosadiene and the latter 7-tricosene. This difference contributes to reproductive isolation between the species. Genetic analysis shows that this difference maps to only the third chromosome, with the other three chromosomes having no apparent effect. The D. simulans alleles on the left arm of chromosome 3 are largely recessive, allowing us to search for the relevant regions using D. melanogaster deficiencies. At least four nonoverlapping regions of this arm have large effects on the hydrocarbon profile, implying that several genes on this arm are responsible for the species difference. Because the right arm of chromosome 3 also affects the hydrocarbon profile, a minimum of five genes appear to be involved. The large effect of the thrid chromosome on hydrocarbons has also been reported in the hybridization between D. simulans and its closer relative D. sechellia, implying either an evolutionary convergence or the retention in D. sechellia of an ancestral sexual dimorphism.     

Chromosome abnormalities in sperm from infertile men with asthenoteratozoospermia

Research over the past few years has clearly demonstrated that infertile men have an increased frequency of chromosome abnormalities in their sperm. These studies have been further corroborated by an increased frequency of chromosome abnormalities in newborns and fetuses from pregnancies established by intracytoplasmic sperm injection. Most studies have considered men with any type of infertility. However, it is possible that some types of infertility have an increased risk of sperm chromosome abnormalities, whereas others do not. We studied 10 men with a specific type of infertility, asthenozoospermia (poor motility), by multicolor fluorescence in situ hybridization analysis to determine whether they had an increased frequency of disomy for chromosomes 13, 21, XX, YY, and XY, as well as diploidy. The patients ranged in age from 28 to 42 yr (mean 34.1 yr); they were compared with 18 normal control donors whose ages ranged from 23 to 58 yr (mean 35.6 yr). A total of 201 416 sperm were analyzed in the men with asthenozoospermia, with a minimum of 10 000 sperm analyzed per chromosome probe per donor. There was a significant increase in the frequency of disomy in men with asthenozoospermia compared with controls for chromosomes 13 and XX. Thus, this study indicates that infertile men with poorly motile sperm but normal concentration have a significantly increased frequency of sperm chromosome abnormalities.