Are zona pellucida genes involved in recurrent oocyte lysis observed during in vitro fertilization?

Identification and in silico Characterization of Deleterious Single Nucleotide Variations in Human ZP2 Gene

ZP2, an important component of the zona matrix, surrounds mammalian oocytes and facilitates fertilization. Recently, some studies have documented the association of mutations in genes encoding the zona matrix with the infertile status of human females. Single nucleotide polymorphisms are the most common type of genetic variations observed in a population and as per the dbSNP database, around 5,152 SNPs are reported to exist in the human ZP2 (hZP2) gene. Although a wide range of computational tools are publicly available, yet no computational studies have been done to date to identify and analyze structural and functional effects of deleterious SNPs on hZP2. In this study, we conducted a comprehensive in silico analysis of all the SNPs found in hZP2. Six different computational tools including SIFT and PolyPhen-2 predicted 18 common nsSNPs as deleterious of which 12 were predicted to most likely affect the structure/functional properties. These were either present in the N-term region crucial for sperm-zona interaction or in the zona domain. 31 additional SNPs in both coding and non-coding regions were also identified. Interestingly, some of these SNPs have been found to be present in infertile females in some recent studies.

Empty Zona Pellucida Only Case: A Critical Review of the Literature

The presence of empty zona pellucida (EZP) in oocytes following oocyte retrieval (OR) during an in vitro fertilization (IVF) cycle presents a major clinical and laboratory challenge in assisted reproduction. It has been attributed to several factors such as the ovarian stimulation protocol employed, the damaging of the follicles during oocyte retrieval (OR) mainly through the high aspiration pressure, during the denudation technique, and the degeneration of oolemma within the zona pellucida (ZP) through apoptosis. The role of ZP is pivotal from the early stages of follicular development up to the preimplantation embryo development and embryo hatching. Polymorphisms or alterations on the genes that encode ZP proteins may contribute to EZP. We present a critical review of the published literature hitherto on EZP and available options when encountered with the phenomenon of EZP. Concerning the former, we found that there is rare data on this phenomenon that merits documentation. The latter includes technical, genetic, and pathophysiological perspectives, along with specific treatment options. In conclusion, we identify the lack of a definitive management proposal for couples presenting with this phenomenon, we underline the need for an algorithm, and indicate the questions raised that point towards our goal for a strategy when addressing a previous finding of EZP.

A comparison of the clinical effects of thinning and drilling on laser-assisted hatching

To systematically investigate the effects of two methods used for laser-assisted hatching (LAH) on clinical outcomes after day 4 (D4) on frozen-embryo-transfer (FET) cycles. Data from 11471 infertile patients who underwent FET cycles between January 2014 and October 2018 was retrospectively analyzed. The 1410 patients who met the inclusion criteria were further categorized into two groups based on the hatching procedure used: the thinning laser-assisted hatching group (T-LAH, 716 patients), and the drilling laser-assisted hatching group (D-LAH, 694 patients). The baseline characteristics of the patients were consistent between the two groups. However, the rates of implantation and clinical pregnancy were significantly higher in the T-LAH group compared to the D-LAH group (32.73% vs. 29.09%, P < 0.01, and 50.98% vs. 43.95%, P < 0.01). The proportion of live birth was also higher in the T-LAH group, but the difference was insignificant (39.11% vs. 36.89%, P > 0.05). Moreover, there were no significant differences in rates of miscarriages, multiple pregnancies, ectopic pregnancies, preterm births, and congenital disabilities between the two groups. Nonetheless, significantly higher rates of implantation and pregnancy were reported in the T-LAH group compared to the D-LAH group among patients aged <35 years, patients with at least one previously failed cycle, and patients with an endometrial thickness of 8-10 mm. T-LAH is superior to D-LAH in improving clinical implantation and pregnancy outcomes in D4 FET, particularly in patients aged <35 years with at least one previously failed cycle or an endometrial thickness of 8-10 mm. The findings of this study provide theoretical support for clinical individualized diagnosis and treatment of patients with infertility.

Novel mutation in the ZP1 gene and clinical implications

PURPOSE

Empty follicle syndrome (EFS) is a complex reproductive disorder characterized by the repeated failure to aspirate oocytes from mature ovarian follicles during in vitro fertilization (IVF). In addition to some cases caused by iatrogenic problems and known genetic factors, there are still many unexplained aspects of EFS. Here, we aimed to assess the clinical and genetic characteristics of two EFS patients.

METHODS

We have characterized two primary infertility patients with EFS in a nonconsanguineous family from China. Both the patients presented similar clinical phenotypes, that is a few granulosa cells but no oocytes could be retrieved during repeated cycles with normal follicular development, E2 levels, and bioavailable hCG plasma levels. Abnormal oocytes were obtained once or twice between multiple IVF cycles. We performed Sanger sequencing of the LHCGR and ZP1~ZP4 genes in the patients, and further bioinformatics analysis was performed to identify pathogenic elements in the genes.

RESULTS

A novel mutation, c.181C>T (p.Arg61Cys), and a known mutation, c.1169_1176delTTTTCCCA (p.Ile390Thrfs*16), in the ZP1 gene were both identified in patient 2, but no mutations were identified in patient 1. The novel mutation inherited from her mother was absent in the control cohort and the ExAc database. The arginine residue is conserved at this position, and its replacement by cysteine was predicted to be deleterious. In another allele, a paternal frameshift mutation was predicted to introduce premature stop codons, resulting in the deletion of 234 amino acids from the C-terminus of the ZP1 protein.

CONCLUSIONS

Our findings presented compound heterozygous mutations in ZP1 associated with EFS and abnormal oocytes and provided further new evidence for the genetic basis of EFS and support for the genetic diagnosis of infertile individuals.