Female fruit flies cannot protect stored sperm from high temperature damage

Recently, it has been demonstrated that heat-induced male sterility is likely to shape population persistence as climate change progresses. However, an under-explored possibility is that females may be able to successfully store and preserve sperm at temperatures that sterilise males, which could ameliorate the impact of male infertility on populations. Here, we test whether females from two fruit fly species can protect stored sperm from a high temperature stress. We find that sperm carried by female Drosophila virilis are almost completely sterilised by high temperatures, whereas sperm carried by female Zaprionus indianus show only slightly reduced fertility. Heat-shocked D. virilis females can recover fertility when allowed to remate, suggesting that the delivered heat-shock is destroying stored sperm and not directly damaging females in this species. The temperatures required to reduce fertility of mated females are substantially lower than the temperatures required to destroy mature sperm in males, suggesting that females are worse than males at protecting mature sperm. This suggests that female sperm storage is unlikely to ameliorate the impacts of high temperature fertility losses in males, and instead exacerbates fertility costs of high temperatures, representing an important determinant of population persistence during climate change.

The Coronavirus Disease 2019 pandemic as a threat to reproductive health and fetal life

Objective: Covid-19 disease has spread rapidly across the world since its first appearance in 2019. At the beginning of the pandemic, Covid-19 disease was thought to affect only the respiratory system, although it has since been realized that it causes numerous transient or permanent problems in various body systems. One of these effects involves the reproductive system. Several studies have investigated the effects of Covid-19 disease on the female and male reproductive systems. Embryological life depends on the fertilization of a healthy mature oocyte, a healthy mature sperm, and the continuation of pregnancy. The purpose of this article is to examine the effects of Covid-19 disease on the male and female reproductive systems and embryological life through a review of the current literature.

P–045 A retrospective study on Hyaluronic acid binding sperm selection in ICSI cycles

Study question Does Hyaluronic acid(HA) binding sperm selection prior ICSI produce better outcome compare to PVP? Summary answer No significant difference in fertilization rate, blastocyst utilization rate, pregnancy rate and miscarriage rate in HA vs PVP group. What is known already HA is natural, non-sulphated glycosaminoglycan secretion that abundantly found in the cervical mucus and the cumulus oophorus complex (COC). In in-vivo, HA binding sites on the sperm plasma membrane indicate sperm maturity, mature sperm reaching HA-coated COC can bind and digest HA and subsequent hyperactivation further facilitate fertilization. In IVF, the use of HA tries to mimic in-vivo to select mature sperm with high DNA integrity prior to ICSI. In HA, movement of mature sperm is ‘slowed’ thus allow the selection of sperm to be used in ICSI. Sperm immaturity is known to associated with aneuploidy incidence in the embryos. Study design, size, duration ICSI cycle using HA (N = 83) was adapted from January to December 2020 while ICSI cycle using PVP (N = 133) was adapted from January 2018 to December 2019. Mean age of patient were 35.64±4.33 vs 34.15±4.75 for HA vs PVP group respectively. Fertilization rate, blastocyst utilization rate, pregnancy rate and miscarriage rate were recorded. This study included all ICSI cycle and both frozen and fresh embryo transfer data. Surgical retrieved sperm was excluded from this study. Participants/materials, setting, methods A 1.5ul of treated spermatozoa suspension was connected with a pipette tip to a 5ul droplet of fresh holding medium (Cook Gamete Buffer). Simultaneously, a 5ul droplet of HA medium (Origio SpermSlow) was connected to the 5ulL droplet of holding medium in a ICSI dish (Sparmed Oosafe) covered with oil (Vitrolife Ovoil). Sperm which were ‘slowed’ in the Sperm slow droplets with normal morphology according to WHO 2010 guideline were selected for ICSI at 400X. Main results and the role of chance The fertilization rate of the HA vs PVP- binding sperm are 68.6% vs 66.2%. As for the blastocyst utilisation rate is 61.6% vs 73.22% for HA vs PVP- binding sperm group. Pregnancy and miscarriage rate for HA vs PVP are 42.3% vs 51.5% and 19.4% vs 26.2% respectively. There was no significant difference in the fertilization rates, blastocysts utilisation rate, pregnancy rate and miscarriage rate between the HA vs PVP- binding sperm groups (P < 0.05). However, a trend of higher pregnancy (51.5% vs 42.3%; P = 0.279) and miscarriage rate were observed in the PVP group (26% vs 19%; P = 0.545) as compared to the HA group, but the difference was not statistically significant. The reason behind this might be the HA assist to select the mature sperm with higher DNA integrity and low frequency of chromosomal aneuploidies which contribute to the lower miscarriage rate in the study. Limitations, reasons for caution This is a retrospective study on HA binding sperm selection vs PVP prior to ICSI. Further research which includes a large number of RCT sample size should be warranted. Wider implications of the findings: The HA- sperm binding selection ICSI might only be beneficial to certain group of patients (high- DNA fragmentation sperm). A larger RCT study may be necessary to establish a relationship between HA-sperm binding selection vs aneuploidy rate via PGT analysis. Trial registration number Not applicable

Mice With Targeted Deletion of ARC Kisspeptin Exhibit Immature Gametogenesis and Impaired Fertility

Hypothalamic kisspeptin is primarily synthesized in two discrete nuclei - the anteroventral periventricular (AVPV) and the arcuate (ARC) nuclei. We have previously developed a selective, conditional ARC kisspeptin knock-out (KO) mouse line, namely the Pdyn-Cre/Kissfl/fl KO mice, that exhibited normal puberty onset in both sexes, but impaired estrous cyclicity and LH pulsatility in Pdyn-Cre/Kissfl/fl KO females. To examine the end-organ effect of the lack of ARC kisspeptin, we examined gametogenesis, gonad morphology, and fertility. Hematoxylin and eosin (H&E) staining of serial-sectioned whole ovaries demonstrated that Pdyn-Cre/Kissfl/fl KO female mice lacked corpora lutea - their ovarian folliculogenesis did not progress beyond antral follicle development, suggesting an ovulatory defect in Pdyn-Cre/Kissfl/fl KO females. 75% of the Pdyn-Cre/Kissfl/fl KO male mice had testes exhibiting a striking decrease in mature sperm in the seminiferous tubules. The remaining 25% showed evidence of mature sperm. Further evidence of a hypogonadal phenotype of the Pdyn-Cre/Kissfl/fl KO mice included the significantly low weight and small size of the ovaries, uteri, and testes when compared to control littermates. In a controlled, continuous mating paradigm with proven WT males, 2-4-month-old Pdyn-Cre/Kissfl/fl KO female mice failed to become pregnant or produce any pups, whereas age-matched WT females exhibited normal pregnancies to term. Thus, Pdyn-Cre/Kissfl/fl KO females have complete infertility. Ongoing studies of male fertility data suggest that Pdyn-Cre/Kissfl/fl KO males are subfertile, in accordance with their variable spermatogenesis phenotype - some KO males sired pups when paired with proven, WT females, whereas other KO males are infertile. Future experiments include assessing the capability of Pdyn-Cre/Kissfl/fl KO mice to respond to chronic, exogenous kisspeptin and GnRH administration to rescue abnormal LH pulsatility and estrous cyclicity in females, as well as the impaired fertility in both sexes.

Intergenerational metabolic priming by sperm piRNAs

Preconception parental environment can reproducibly program offspring phenotype without altering the DNA sequence, yet the mechanisms underpinning this epigenetic inheritance remains elusive. Here, we demonstrate the existence of an intact piRNA-pathway in mature Drosophila sperm and show that pathway modulation alters offspring gene transcription in a sequence-specific manner. We map a dynamic small RNA content in developing sperm and find that the mature sperm carry a highly distinct small RNA cargo. By biochemical pulldown, we identify a small RNA subset bound directly to piwi protein. And, we show that piRNA-pathway controlled sperm small RNAs are linked to target gene repression in offspring. Critically, we find that full piRNA-pathway dosage is necessary for the intergenerational metabolic and transcriptional reprogramming events triggered by high paternal dietary sugar. These data provide a direct link between regulation of endogenous mature sperm small RNAs and transcriptional programming of complementary sequences in offspring. Thus, we identify a novel mediator of paternal intergenerational epigenetic inheritance.

Expression of Mst89B and CG31287 is Needed for Effective Sperm Storage and Egg Fertilization in Drosophila

In Drosophila, male reproductive fitness can be affected by any number of processes, ranging from development of gametes, transfer to and storage of mature sperm within the female sperm storage organs, and utilization of sperm for fertilization. We have previously identified the 89B cytogenetic map position of D. melanogaster as a hub for genes that effect male paternity success when disturbed. Here, we used RNA interference to test 11 genes that are highly expressed in the testes and located within the 89B region for their role in sperm competition and male fecundity when their expression is perturbed. Testes-specific knockdown (KD) of bor and CSN5 resulted in complete sterility, whereas KD of CG31287, Manf and Mst89B, showed a breakdown in sperm competitive success when second to mate (P2 < 0.5) and reduced fecundity in single matings. The low fecundity of Manf KD is explained by a significant reduction in the amount of mature sperm produced. KD of Mst89B and CG31287 does not affect sperm production, sperm transfer into the female bursa or storage within 30 min after mating. Instead, a significant reduction of sperm in female storage is observed 24 h after mating. Egg hatchability 24 h after mating is also drastically reduced for females mated to Mst89B or CG31287 KD males, and this reduction parallels the decrease in fecundity. We show that normal germ-line expression of Mst89B and CG31287 is needed for effective sperm usage and egg fertilization.

A genetic screen in Drosophila reveals an unexpected role for the KIP1 ubiquitination-promoting complex in male fertility

A unifying feature of polycystin-2 channels is their localization to both primary and motile cilia/flagella. In Drosophila melanogaster, the fly polycystin-2 homologue, Amo, is an ER protein early in sperm development but the protein must ultimately cluster at the flagellar tip in mature sperm to be fully functional. Male flies lacking appropriate Amo localization are sterile due to abnormal sperm motility and failure of sperm storage. We performed a forward genetic screen to identify additional proteins that mediate ciliary trafficking of Amo. Here we report that Drosophila homologues of KPC1 and KPC2, which comprise the mammalian KIP1 ubiquitination-promoting complex (KPC), form a conserved unit that is required for the sperm tail tip localization of Amo. Male flies lacking either KPC1 or KPC2 phenocopy amo mutants and are sterile due to a failure of sperm storage. KPC is a heterodimer composed of KPC1, an E3 ligase, and KPC2 (or UBAC1), an adaptor protein. Like their mammalian counterparts Drosophila KPC1 and KPC2 physically interact and they stabilize one another at the protein level. In flies, KPC2 is monoubiquitinated and phosphorylated and this modified form of the protein is located in mature sperm. Neither KPC1 nor KPC2 directly interact with Amo but they are detected in proximity to Amo at the tip of the sperm flagellum. In summary we have identified a new complex that is involved in male fertility in Drosophila melanogaster.