人类遗传学与胚胎学

Direct testing of the outcome of human female meiosis demonstrated that up over a half of oocytes from IVF patients of advanced reproductive age are aneuploid, originating comparably from meiosis I and meiosis II errors, with potential probability of aneuploidy rescue in an almost half of oocytes with sequential first and second meiotic errors. One fifth of abnormalities originating from meiosis I and II are of complex nature, with nonrandom distribution of chrmomatid/chromosome (10:1 ratio), and missing/extra chromotid (chromosome) errors (2:1 ratio). The data also demonstrate the relationship between embryo viability and meiotic origin of chromosomal errors, affecting their clinical impact on preimplantation and post-implantation development

In plants, undifferentiated or totally differentiated cells can be easily in vitro cultured to generate undifferentiated embryogenic cells that can regenerate complete plants. This is the most spectacular expression of totipotency. Embryogenic cells represent a key material in plant biotechnologies as they are used in many processes aiming at asexual reproduction by somatic embryogenesis (SE), genetic transformation, protoplast regeneration and cryopreservation. Nevertheless, tissue culture systems that involve the acquisition of competence for totipotency and extensive cell division remain risky with respect to genome and epigenome instabilities. Particularly, the use of embryogenic cell suspensions has frequently been associated with an increased likelihood of genetic instability and somaclonal variation (SV) in the regenerated plants. SV is a major concern in all in vitro vegetative plant propagation systems because it leads to the loss of genetic fidelity. Since 20 years, embryogenic cell suspension based SE techniques have been applied to coffee for the large-scale dissemination of exceptional Arabica hybrids. Here, we present our production and research experience showing that SE is efficient and reliable for true-to-type propagation. Over 99% of coffee trees regenerated fully conform to the mother plant, both morphologically - they grow, flower and produce normally. Hence strong genetic and epigenetic changes in proliferating embryogenic cells are not a fatality. The results also demonstrated the importance of embryogenic culture age on SV and hence the non-random nature of this phenomenon. The genetic and epigenetic alterations are particularly limited during SE. The main change in most of phenotypic variants was aneuploidy showing that mitotic aberrations play a major role in SV in coffee. These results provide a proof of concept for the use of embryogenic cell suspensions with other plant species: a revolution in the world of plant micropropagation on an industrial scale.

We report here a macroscopic analysis of one fetus conserved in Bouin then in formol having an arhinencephaly, synophthalmia associated with holoprosencephaly. We aimed to relate the various etiologies of observed anomalies in conjunction with the literature review. To perform the study, a fetopathologic examination including autopsy and radiologic analysis were done. Assay of FISH and OncoScan were made. Fetopathologic examination showed severe craniofacial malformations associated with extracranial defects including persistent troncus arteriosus communis, abnormal lung lobulation, extremities deformities and single umbilical artery. FISH and OncoSan had given unsuccessful results, because nucleic acids were highly degraded. The macroscopic examination of the fetus having arhinencephaly and synophthalmia highlights asymptomatology association with holoprosencephaly sequence and visceral defects.

To determine if prolonged time in embryo culture has an effect on the rate, sex ratio, and perinatal outcomes of monozygotic twins (MZT) following either cleavage stage or blastocyst embryo transfer after assisted conception. This is a retrospective study of 2,316 consecutive clinical pregnancies resulting from cleavage stage transfer (CT) and blastocyst transfer (BT). Criteria examined included (i) incidences (ii) sex ratios (iii) gestational age and birth weight; (iv) perinatal outcomes of these pregnancies from cleavage stage and blastocyst transfer procedures. Monozygotic twin pregnancies were identified by (i) presence of a gestational sac containing more than one fetal pole with cardiac activity, (ii) the number of gestational sacs or fetal hearts exceeds the number of embryos transferred and (iii) twin pregnancies following a single embryo transfer. Overall the incidence of twinning was 1.64% (38 out of 2,316 pregnancies). The frequency of twinning was 2.3 × higher following BT (18 out of 649) compared to CT (20 out of 1,667). IVF techniques skewed the sex ratio in favour of males while ICSI significantly favoured females. There was no statistically significant difference between transfer type and gestational age, birth weight and perinatal outcome. All pregnancies resulted in the birth of 86 infants. In our experience, BT more than doubles the chances of conceiving a monozygotic twin pregnancy, however IVF techniques lead to a greater likelihood of male birth(s) if twins are conceived. Appropriate pre-conception counselling should be given to advise the potential risks associated with both types of transfer as well as using alternative methods such as single embryo transfer to reduce the risk of multiple gestations.

The widespread availability of genome sequencing data has yielded different rare variant association methods in population-based or family-based designs. However, it is challenging to know which method is appropriate in practice. Our purpose of this paper is to provide a general review of the literature for rare variant association studies and suggestions on future research directions. This paper discusses methods for recent rare variant association studies in three categories. The first two categories are for population-based designs, with/without considering the direction of the effects of causal rare variants. In the third category, methods for family-based designs are concluded.