Fluorescence In Situ Hybridization and Spectral Imaging Analysis of Human Oocytes and First Polar Bodies

Chromosome-specific DNA repeats: rapid identification in silico and validation using fluorescence in situ hybridization

Chromosome enumeration in interphase and metaphase cells using fluorescence in situ hybridization (FISH) is an established procedure for the rapid and accurate cytogenetic analysis of cell nuclei and polar bodies, the unambiguous gender determination, as well as the definition of tumor-specific signatures. Present bottlenecks in the procedure are a limited number of commercial, non-isotopically labeled probes that can be combined in multiplex FISH assays and the relatively high price and effort to develop additional probes. We describe a streamlined approach for rapid probe definition, synthesis and validation, which is based on the analysis of publicly available DNA sequence information, also known as “database mining”. Examples of probe preparation for the human gonosomes and chromosome 16 as a selected autosome outline the probe selection strategy, define a timeline for expedited probe production and compare this novel selection strategy to more conventional probe cloning protocols.

Analysis of clinical data of patients with different outcomes after short-time insemination

The study is to analyse the clinical data of the two groups of patients with different fertilisation outcomes after short-time insemination and probe into short-time insemination indications. A retrospective study including 558 cycles of short-time insemination in our centre during January 2009 to June 2010 which were divided into two groups by the method of fertilisation, 472 cycles by IVF and 86 cycles by Re-ICSI group according to fertilisation conditions to and compare the differences between the two groups in the indexes of average female age, average male age, duration of infertility, forward-moving sperm counts, abnormal sperm rate, proportion of primary infertility, etc. The differences between the two groups have statistical significance in duration of infertility, forward-moving sperm counts, abnormal sperm rate and proportion of primary infertility (5.02 ± 3.12 versus 5.86 ± 3.35; 83.06 ± 78.55 versus 54.02 ± 61.78; 83.56 ± 5.24% versus 86.31 ± 5.26%; 56.87% versus 74.42%; P < 0.05). The discrepancy between the two groups has no statistical significance in average female age and average male age (P > 0.05). Duration of infertility, forward-moving sperm counts, abnormal sperm rate and previous pregnancy history have great significance to predict fertilisation failure, so decisions should be made on the basis of the above indexes when evaluating whether a patient should conduct short-time insemination.

Predicting aneuploidy in human oocytes: key factors which affect the meiotic process

BACKGROUND

To estimate the incidence of aneuploidy in relation to patients' characteristics, the type of hormonal stimulation and their response to induction of multiple follicular growth, 4163 first polar bodies (PB1s) were analyzed.

METHODS

Five hundred and forty four infertile couples underwent 706 assisted conception cycles (640 with poor prognosis indications and 66 controls) in which chromosomal analysis of PB1 for the chromosomes 13, 15, 16, 18, 21 and 22 was performed. Results were evaluated in a multivariate analysis.

RESULTS

The proportion of normal oocytes was directly correlated (P < 0.01) with (i) the number of mature oocytes and (ii) the establishment of a clinical pregnancy; and inversely correlated (P < 0.01) with (i) female age, (ii) causes of female infertility (endometriosis, abortions, ovulatory factor), (iii) poor prognosis indications (female age, number of previous cycles, multiple poor prognosis indications), (iv) number of FSH units per oocyte and (v) number of FSH units per metaphase II oocyte. There was a weak significance of frequency (P < 0.05) between type of abnormality (originated by chromatid predivision, chromosome non-disjunction or combined mechanisms in the same oocyte) and groups of the studied variables, rather than to a specific abnormality or a specific chromosome.

CONCLUSIONS

The type of infertility had a significant effect on errors derived from the first meiotic division, whose incidence was significantly higher in the presence of endometriosis or of an ovulatory factor, and in women that experienced repeated abortions. Each aneuploidy event was found to be dependent not on a specific variable, but on groups of variables. In addition, the tendency of chromosomal abnormalities to occur simultaneously implies that the deriving aneuploidies can be of any type.

Multiple immunoenzyme staining: methods and visualizations for the observation with spectral imaging

Several staining concepts and color combinations exist to perform successful double immunoenzyme staining on human tissue specimens. Most of these concepts are based on differences between both primary antibodies: animal species, mouse Ig isotype or IgG subclasses, conjugates, or concentrations. Traditionally, double immunoenzyme staining has used chromogens selected to provide maximum color contrast when observed with the unaided eye. Unfortunately, visually good color combinations always include at least one diffuse chromogen, because of the paucity of appropriate chromogen colors. This situation is drastically changed with the use of spectral imaging, where multicolor microscopy can be unmixed in individual images based on their spectral characteristics. Spectral unmixing can be performed even up to quadruple immunoenzyme staining. This work contains practical suggestions for immunoenzyme double staining procedures for some frequently encountered primary antibody combinations: rabbit-mouse, goat-mouse, mouse-mouse, and rabbit-rabbit. The suggested protocols are all suitable for a classical red-brown color combination plus blue nuclear counterstain that is composed of peroxidase activity (diaminobenzidine tetrahydrochloride), alkaline phosphatase activity (Liquid Permanent Red), and hematoxylin, respectively. Although the red and brown chromogens do not contrast very well visually, they both show a crisp localization and can be perfectly unmixed by spectral imaging.

Gender effects on the incidence of aneuploidy in mammalian germ cells

Aneuploidy occurs in 0.3% of newborns, 4% of stillbirths, and more than 35% of all human spontaneous abortions. Human gametogenesis is uniquely and gender-specific susceptible to errors in chromosome segregation. Overall, between 1% and 4% of sperm and as many as 20% of human oocytes have been estimated by molecular cytogenetic analysis to be aneuploid. Maternal age remains the paramount aetiological factor associated with human aneuploidy. The majority of extra chromosomes in trisomic offspring appears to be of maternal origin resulting from nondisjunction of homologous chromosomes during the first meiotic division. Differences in the recombination patterns between male and female meiosis may partly account for the striking gender- and chromosome-specific differences in the genesis of human aneuploidy, especially in aged oocytes. Nondisjunction of entire chromosomes during meiosis I as well as premature separation of sister chromatids or homologues prior to meiotic anaphase can contribute to aneuploidy. During meiosis, checkpoints at meiotic prophase and the spindle checkpoint at M-phase can induce meiotic arrest and/or cell death in case of disturbances in pairing/recombination or spindle attachment of chromosomes. It has been suggested that gender differences in aneuploidy may result from more permissive checkpoints in females than males. Furthermore, age-related loss of chromosome cohesion in oocytes as a cause of aneuploidy may be female-specific. Comparative data about the susceptibility of human male and female germ cells to aneuploidy-causing chemicals is lacking. Increases of aneuploidy frequency in sperm have been shown after exposure to therapeutic drugs, occupational agents and lifestyle factors. Conversely, data on oocyte aneuploidy caused by exogenous agents is limited because of the small numbers of oocytes available for analysis combined with potential maternal age effects. The vast majority of animal studies on aneuploidy induction in germ cells represent cause and effect data. Specific studies designed to evaluate possible gender differences in induction of germ cell aneuploidy have not been found. However, the comparison of rodent data available from different laboratories suggests that oocytes are more sensitive than male germ cells when exposed to chemicals that effect the meiotic spindle. Only recently, in vitro experiments, analyses of transgenic animals and knockdown of expression of meiotic genes have started to address the molecular mechanisms underlying chromosome missegregation in mammalian germ cells whereby striking differences between genders could be shown. Such information is needed to clarify the extent and the mechanisms of gender effects, including possible differential susceptibility to environmental agents.