Tales of methylomes and centrosomes in the human embryo.

Nothing pleases patients more than the arrival of good news the day after ovum pickup. The Bmorning after^ headliners brought to the attention of couples undergoing infertility treatment have as much to do with receiving the head count of fertilized eggs as it does with the anticipation of just how many will take the journey to producing a live birth. It comes as no surprise then that while the news of fertilization is uplifting, proof of the pudding awaits the outcomes of embryo culture. The opening act staged deep within the embryology laboratory was long thought to hold the secret to success given the ability to recognize male and female pronuclei striving towards syngamy and that tell-tale sign of second polar body extrusion, the true sentinel of the end of meiosis. And beyond the patently visible, it is with confidence that observers of human embryology associate the onset of the earliest cleavage divisions with what must have been the timely execution of those initial cell cycles hand in hand with the duplication of paternal centrosomes introduced by fertilization or ICSI. The wonderful world of morphokinetics has taken to task the temporal cadence of those initial cell divisions with algorithm after algorithm being proffered as a useful standard for embryo selection to improve pregnancy chances. But, the lingering question is whether any of the currently used measures from time-lapse recordings report on the fidelity of egg activation and the earliest cell cycle-based events. This month, a series of papers approach this question from different angles, offering our readership something to think about before investing in time-lapse technology as it presently stands. The first of these studies comes from Neyer and colleagues, who query the impact of paternal factors and sperm quality on several morphokinetic parameters based on the IMSI scoring method (BThe impact of paternal factors on cleavage stage and blastocyst development analyzed by time-lapse imaging—a retrospective observational study^ 10.1007/s10815-015-0558-3). Interestingly, while some of the early morphokinetic parameters examined displayed predictive value for blastocyst development, others were unable do so based on ICSI with sperm bearing structural line abnormalities. Studies of this kind reinforce what has been obvious when male factor is a consideration in developing a treatment plan, and they also raise the issue of launching embryogenesis with defective gametes that precludes neither achieving fertilization nor sustaining development in many cases to the blastocyst stage with t ransfer l ike ly based on an apparent ly pos i t ive morphokinetic profile. For patients demonstrating repeated pregnancy failures with suspected male involvement, looking a bit deeper into the initial steps of fertilization would improve pregnancy chances. Such is the message from the latest paper in JARG from the Mio laboratory in Japan (Kai et al., BDiagnosis of abnormal human fertilization status based on pronuclear origin and/or centrosome number^ 10.1007/s10815-015-0568-1). If you have not already done so, we encourage our readership to follow the work of Mio and colleagues as they have established a reputation for utilizing time-lapse imaging and high-resolution confocal microscopy to reveal the inner workings of the human embryo including their discovery of a fast Capsule Recent studies on pronuclear chromatin remodeling, in conjunction with tracking of centrosomes in human embryos, raise questions regarding the significance of pronuclear number as indicators of blastocyst and implantation potential.