The Recurrent Mutation in PATL2 Inhibits Its Degradation Thus Causing Female Infertility Characterized by Oocyte Maturation Defect Through Regulation of the Mos-MAPK Pathway

Identification novel mutations and phenotypic spectrum expanding in PATL2 in infertile women with IVF/ICSI failure

AIM

Abnormalities in oocyte maturation, fertilization, and early embryonic development are major causes of primary infertility in women who are undergoing IVF/ICSI attempts. Although many genetic factors responsible for these abnormal phenotypes have been identified, there are more additional pathogenic genes and variants yet to be discovered. Previous studies confirmed that bi-allelic PATL2 deficiency is an important factor for female infertility. In this study, 935 infertile patients with IVF/ICSI failure were selected for whole-exome sequencing, and 18 probands carrying PATL2 variants with a recessive inheritance pattern were identified.

METHODS

We estimated that the prevalence contributed by PATL2 was 1.93% (18/935) in our study cohort.

RESULTS

15 novel variants were found in those families, including c.1093C > T, c.1609dupA, c.1204C > T, c.643dupG, c.877-2A > G, c.1228C > G, c.925G > A, c.958G > A, c.4A > G, c.1258T > C, c.1337G > A, c.1264dupA, c.88G > T, c.1065-2A > G, and c.1271T > C. The amino acids altered by the corresponding variants were highly conserved in mammals, and in silico analysis and 3D molecular modeling suggested that the PATL2 mutants impaired the physiologic function of the resulting proteins. Diverse clinical phenotypes, including oocyte maturation defect, fertilization failure, and early embryonic arrest might result from different variants of PATL2.

CONCLUSIONS

These results expand the spectrum of PATL2 variants and provide an important reference for genetic counseling for female infertility, and they increase our understanding of the mechanisms of oocyte maturation arrest caused by PATL2 deficiency.

Live birth derived from a markedly large polar body oocyte: a rare case report

Oocytes with excessively large first polar bodies (PB1) often occur in assisted reproductive procedures. Many times these oocytes are discarded without insemination and, as a result, the application of this portion of oocytes has scarcely been reported to date. Few studies have examined large PB1 oocytes in infertile women and have virtually entirely studied genetic variations for large PB1 oocyte abnormalities. Here, we describe an unusual case of a live birth from a remarkably large PB1 oocyte in a frozen embryo transfer (FET) cycle. This is the first instance of a successful live birth resulting from a PB1 oocyte with an extremely large polar body measuring 80 μM × 40 μM in size. The large PB1 oocyte was performed by an early rescue intracytoplasmic sperm injection (r-ICSI) and was formed into a blastocyst on day 5. Following FET, a healthy boy baby weighing 3100 g was finally delivered by caesarean section at 37 weeks and 5 days after conception. Additionally, there were no complications throughout the antenatal period or the perinatal phase of this following full-term delivery. In this study, it is revealed for the first time that a huge PB1 oocyte can be fertilized, resulting in the growth of a blastocyst, a subsequent pregnancy, and a live birth. This new information prompts us to reconsider the use of large PB1 oocytes. More insightful talks should be given attention to prevent the waste of embryos because not all oocytes with aberrant morphology are unavailable.

Diagnosis of acute myeloid leukaemia on microarray gene expression data using categorical gradient boosted trees

We define an iterative method for dimensionality reduction using categorical gradient boosted trees and Shapley values and created four machine learning models which potentially could be used as diagnostic tests for acute myeloid leukaemia (AML). For the final Catboost model we use a dataset of 2177 individuals using as features 16 probe sets and the age in order to classify if someone has AML or is healthy. The dataset is multicentric and consists of data from 27 organizations, 25 cities, 15 countries and 4 continents. The performance of our last model is specificity: 0.9909, sensitivity: 0.9985, F1-score: 0.9976 and its ROC-AUC: 0.9962 using ten fold cross validation. On an inference dataset the perormance is: specificity: 0.9909, sensitivity: 0.9969, F1-score: 0.9969 and its ROC-AUC: 0.9939. To the best of our knowledge the performance of our model is the best one in the literature, as regards the diagnosis of AML using similar or not data. Moreover, there has not been any bibliographic reference which associates AML or any other type of cancer with the 16 probe sets we used as features in our final model.

C-X-C motif chemokine ligand 12 improves the developmental potential of bovine oocytes by activating SH2 domain-containing tyrosine phosphatase 2 during maturation†

In vitro maturation of mammalian oocytes is an important means in assisted reproductive technology. Most bovine immature oocytes complete nuclear maturation, but less than half develop to the blastocyst stage after fertilization. Thus, inefficient in vitro production is mainly caused by a suboptimal in vitro culture process, in which oocyte quality appears to be the limiting factor. In our study, a potential maternal regulator, C-X-C motif chemokine ligand 12, was identified by analyzing transcriptome data. C-X-C motif chemokine ligand 12 supplementation promoted the developmental potential of oocytes by improving protein synthesis and reorganizing cortical granules and mitochondria during in vitro maturation, which eventually increased blastocyst formation efficiency and cell number after parthenogenesis, fertilization, and cloning. All these promoting effects by C-X-C motif chemokine ligand 12 were achieved by activating SH2 domain-containing tyrosine phosphatase 2, thereby promoting the mitogen-activated protein kinase signaling pathway. These findings provide an in vitro maturation system that closely resembles the maternal environment to provide high-quality oocytes for in vitro production.

High carrier frequency of pathogenic PATL2 gene mutations predicted in population: a bioinformatics-based approach

Topoisomerase II homologue 2 (PATL2) has been confirmed to be a key gene that contributes to oocyte maturation. However, the allele distribution and carrier frequency of these mutations remain uncharacterized. So a bioinformatics subcategory analysis of PATL2 mutations from outcome data and Single Nucleotide Polymorphism (SNP) databases was conducted. Altogether, the causative PATL2 mutation number detected in patients with oocyte maturation defects in the clinical studies and pathogenic PATL2 mutation sites predicted by software based on the database was approximately 53. The estimated carrier frequency of pathogenic mutation sites was at least 1.14‰ based on the gnomAD and ExAC database, which was approximately 1/877. The highest frequency of mutations detected in the independent patients was c.223-14_223-2del13. The carrier frequency of this mutation in the population was 0.25‰, which may be a potential threat to fertility. Estimated allele and carrier frequency are relatively higher than those predicted previously based on clinical ascertainment. A review of PATL2 mutation lineage identified in 34 patients showed that 53.81%, 9.22% and 14.72% of the oocytes with PATL2 mutations were arrested at the germinal vesicle (GV) stage, metaphase I (MI) stage and first polar body stage, respectively. Oocytes that could develop to the first polar body stage were extremely rare to fertilise, and their ultimate fate was early embryonic arrest. Phenotypic variability is related to the function of the regions and degree of loss of function of PATL2 protein. A 3D protein structure changes predicted by online tools, AlphaFold, showed aberrations at the mutation sites, which may explain partially the function loss. When the mutated and wild-type proteins are not in the same amino acid category, the protein structure will be considerably unstable. The integration of additional mutation sites with phenotypes is helpful in drawing a complete picture of the disease. Bioinformatics analysis of PATL2 mutations will help reveal molecular epidemiological characteristics and provide an important reference for new mutation assessment, genetic counselling and drug research.

Bi-allelic pathogenic variants in PABPC1L cause oocyte maturation arrest and female infertility

Oocyte maturation arrest is one of the important causes of female infertility, but the genetic factors remain largely unknown. PABPC1L, a predominant poly(A)-binding protein in Xenopus, mouse, and human oocytes and early embryos prior to zygotic genome activation, plays a key role in translational activation of maternal mRNAs. Here, we identified compound heterozygous and homozygous variants in PABPC1L that are responsible for female infertility mainly characterized by oocyte maturation arrest in five individuals. In vitro studies demonstrated that these variants resulted in truncated proteins, reduced protein abundance, altered cytoplasmic localization, and reduced mRNA translational activation by affecting the binding of PABPC1L to mRNA. In vivo, three strains of Pabpc1l knock-in (KI) female mice were infertile. RNA-sequencing analysis showed abnormal activation of the Mos-MAPK pathway in the zygotes of KI mice. Finally, we activated this pathway in mouse zygotes by injecting human MOS mRNA, and this mimicked the phenotype of KI mice. Our findings reveal the important roles of PABPC1L in human oocyte maturation and add a genetic potential candidate gene to be screened for causes of infertility.

The infertile individual analysis based on whole-exome sequencing in chinese multi-ethnic groups

BACKGROUND

Infertility is a common and rapidly growing health issue around the world. The genetic analysis based on the infertile population is crucial for intervention and treatment.

OBJECTIVE

To find candidate gene locus led to azoospermia in Chinese multi-ethnic groups and provide theoretical guidance for the diagnosis of genetic diseases to progressively aggravated infertility patients and sterile offspring with ART.

METHODS

The study based on whole-exome sequencing (WES) was presented for genetic characteristic analysis of multi-ethnics and identification of variants related to infertility in Xinjiang area of China.

RESULTS

The frequency of pathogenic variants showed significant ethnic differences among four main ethnics in Xinjiang. The population structure analysis confirmed that the Hui was close to the Han population, the Kazak was close to the Uygur population, and there are three ancestry components in the four ethnics. In addition, ten candidate variants potentially regulated azoospermia were detected, and KNTC1 (rs7968222: G > T) was chosen to validate the association. Through the analysis in the valid group, the frequency of rs7968222 (G > T) has a significant difference in the azoospermia population (11.76%, 8/68) and normospermia population (4.63%, 35/756) (P < 0.001). Interestingly, the proportion of people with abnormal follicle-stimulating hormone (FSH) level in the group carrying rs7968222 (G > T) was significantly higher than non-carriers (P < 0.05). Therefore, rs7968222 may regulate spermatogenesis through affecting hormone level.

CONCLUSION

Our study establishes the genetics analysis of Northwest China and finds a candidate gene locus KNTC1 (rs7968222: G > T), which is one of the genetic susceptibility factors for male azoospermia.

Inactivation of Exosc10 in the oocyte impairs oocyte development and maturation, leading to a depletion of the ovarian reserve in mice

EXOSC10 is a catalytic subunit of the nuclear RNA exosome, and possesses a 3'-5' exoribonuclease activity. The enzyme processes and degrades different classes of RNAs. To delineate the role of EXOSC10 during oocyte growth, specific Exosc10 inactivation was performed in oocytes from the primordial follicle stage onward using the Gdf9-iCre; Exosc10 ^f/- mouse model (Exosc10 ^cKO(Gdf9)). Exosc10 ^cKO(Gdf9) female mice are infertile. The onset of puberty and the estrus cycle in mutants are initially normal and ovaries contain all follicle classes. By the age of eight weeks, vaginal smears reveal irregular estrus cycles and mutant ovaries are completely depleted of follicles. Mutant oocytes retrieved from the oviduct are degenerated, and occasionally show an enlarged polar body, which may reflect a defective first meiotic division. Under fertilization conditions, the mutant oocytes do not enter into an embryonic development process. Furthermore, we conducted a comparative proteome analysis of wild type and Exosc10 knockout mouse ovaries, and identified EXOSC10-dependent proteins involved in many biological processes, such as meiotic cell cycle progression and oocyte maturation. Our results unambiguously demonstrate an essential role for EXOSC10 in oogenesis and may serve as a model for primary ovarian insufficiency in humans. Data are available via ProteomeXchange with identifier PXD039417.

MOS mutation causes female infertility with large polar body oocytes

The Moloney sarcoma oncogene (MOS) encodes a protein serine/threonine kinase and MOS is expressed at high levels in oocytes undergoing meiotic maturation. The MOS/MAPK pathway is normally required for the maintenance of microtubules and chromatin in a metaphasic state during the meiotic divisions. To determine the pathogenic genes in a female infertile patient due to large polar body oocytes, whole-exome sequencing was performed on the patient and available family members. We identified a novel homozygous missense mutation c.591T > G in MOS. Bioinformatics analysis showed that the mutation is harmful. These findings suggest that MOS mutation results in oocytes with a large polar body and poor embryonic development in patients. The MOS variant may regulate oocyte asymmetric division by MAPK/WAVE2/Arp2/3/actin signaling pathway. This will help to understand the comprehensive role of MOS in early human reproductive process and provide genetic markers for future genetic counseling for more individualized treatments.

Prediction of Weight Loss in Filipino Americans to Decrease Risk for Type 2 Diabetes: Using Multi-Dimensional Data (Preprint)

BACKGROUND

Type 2 diabetes (T2D) has an immense disease burden, affecting millions of people worldwide and costing billions of dollars in treatment. As T2D is a multifactorial disease with both genetic and nongenetic influences, accurate risk assessments for patients are difficult to perform. Machine learning has served as a useful tool in T2D risk prediction, as it can analyze and detect patterns in large and complex data sets like that of RNA sequencing. However, before machine learning can be implemented, feature selection is a necessary step to reduce the dimensionality in high-dimensional data and optimize modeling results. Different combinations of feature selection methods and machine learning models have been used in studies reporting disease predictions and classifications with high accuracy.

OBJECTIVE

The purpose of this study was to assess the use of feature selection and classification approaches that integrate different data types to predict weight loss for the prevention of T2D.

METHODS

The data of 56 participants (ie, demographic and clinical factors, dietary scores, step counts, and transcriptomics) were obtained from a previously completed randomized clinical trial adaptation of the Diabetes Prevention Program study. Feature selection methods were used to select for subsets of transcripts to be used in the selected classification approaches: support vector machine, logistic regression, decision trees, random forest, and extremely randomized decision trees (extra-trees). Data types were included in different classification approaches in an additive manner to assess model performance for the prediction of weight loss.

RESULTS

Average waist and hip circumference were found to be different between those who exhibited weight loss and those who did not exhibit weight loss (P=.02 and P=.04, respectively). The incorporation of dietary and step count data did not improve modeling performance compared to classifiers that included only demographic and clinical data. Optimal subsets of transcripts identified through feature selection yielded higher prediction accuracy than when all available transcripts were included. After comparison of different feature selection methods and classifiers, DESeq2 as a feature selection method and an extra-trees classifier with and without ensemble learning provided the most optimal results, as defined by differences in training and testing accuracy, cross-validated area under the curve, and other factors. We identified 5 genes in two or more of the feature selection subsets (ie, CDP-diacylglycerol-inositol 3-phosphatidyltransferase [CDIPT], mannose receptor C type 2 [MRC2], PAT1 homolog 2 [PATL2], regulatory factor X-associated ankyrin containing protein [RFXANK], and small ubiquitin like modifier 3 [SUMO3]).

CONCLUSIONS

Our results suggest that the inclusion of transcriptomic data in classification approaches for prediction has the potential to improve weight loss prediction models. Identification of which individuals are likely to respond to interventions for weight loss may help to prevent incident T2D. Out of the 5 genes identified as optimal predictors, 3 (ie, CDIPT, MRC2, and SUMO3) have been previously shown to be associated with T2D or obesity.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02278939; https://clinicaltrials.gov/ct2/show/NCT02278939.

The translation regulator Zar1l controls timing of meiosis in Xenopus oocytes

Oocyte maturation and early embryo development occur in vertebrates in the near absence of transcription. Thus, sexual reproduction of vertebrates critically depends on the timely translation of mRNAs already stockpiled in the oocyte. Yet how translational activation of specific mRNAs is temporally coordinated is still incompletely understood. Here, we elucidate the function of Zar1l, a yet uncharacterized member of the Zar RNA-binding protein family, in Xenopus oocytes. Employing TRIM-Away, we demonstrate that loss of Zar1l accelerates hormone-induced meiotic resumption of Xenopus oocytes due to premature accumulation of the M-phase-promoting kinase cMos. We show that Zar1l is a constituent of a large ribonucleoparticle containing the translation repressor 4E-T and the central polyadenylation regulator CPEB1, and that it binds directly to the cMos mRNA. Partial, hormone-induced degradation of Zar1l liberates 4E-T from CPEB1, which weakens translational repression of mRNAs encoding cMos and likely additional M-phase-promoting factors. Thus, our study provides fundamental insights into the mechanisms that ensure temporally regulated translation of key cell cycle regulators during oocyte maturation, which is essential for sexual reproductivity.

Genetics of Oocyte Maturation Defects and Early Embryo Development Arrest

Various pathogenic factors can lead to oogenesis failure and seriously affect both female reproductive health and fertility. Genetic factors play an important role in folliculogenesis and oocyte maturation but still need to be clarified. Oocyte maturation is a well-organized complex process, regulated by a large number of genes. Pathogenic variants in these genes as well as aneuploidy, defects in mitochondrial genome, and other genetic and epigenetic factors can result in unexplained infertility, early pregnancy loss, and recurrent failures of IVF/ICSI programs due to poor ovarian response to stimulation, oocyte maturation arrest, poor gamete quality, fertilization failure, or early embryonic developmental arrest. In this paper, we review the main genes, as well as provide a description of the defects in the mitochondrial genome, associated with female infertility.

Identification and characterization of a novel homozygous splice site variant of PATL2 causing female infertility due to oocyte germinal vesicle arrest

Background: This study aims to describe clinical and diagnostic phenotype and identify pathogenic variants of a female with unknown causes of infertility.

Methods: Clinical assessment was performed for the phenotype diagnosis. Whole-exome sequencing (WES) and the followed cDNA-PCR sequencing were applied to identify the pathogenic variant and investigate the potentially aberrant mRNA splicing event. The pathogenicity of the variant was analysed using multiple in silico prediction tools, including the 3D protein remodelling. Quantitative RT-PCR (qRT-PCR) was performed to measure PATL2 mRNA expression in the peripheral blood leukocytes of the proband and controls.

Results: The proband was diagnosed with the female infertility due to oocyte germinal vesicle (GV) arrest. A novel homozygous splice site variant of PATL2 (NM_001145112.2, c.871-1G&gt;A), inherited from her asymptomatic heterozygous parents, was detected by WES. Sequencing of cDNA amplification products demonstrated that this variant resulted in the exon 10 skipping and in-frame loss of 54 nucleotides in the PATL2 transcript. Quantitative RT-PCR suggested that the mutant transcript escape the mRNA degradation.

Conclusion: We identified a novel pathogenic homozygous splice site of PATL2 (c.871-1G&gt;A) underlying the oocyte GV arrest phenotype and elucidated its molecular mechanism. This study expands the variant spectrum of PATL2 and benefits our understanding of its genotype-phenotype correlations.

Gene mutations impede oocyte maturation, fertilization, and early embryonic development

Reproductive diseases are a long-standing problem and have become more common in the world. Currently, 15% of the world's population suffers from infertility, and half of them are women. Maturation of oocytes, successful fertilization, and high-quality embryos are prerequisites for pregnancy. With the development of assisted reproductive technology and advanced genetic assays, we have found that infertility in many young female patients is caused by mutations in various developmental regulators. These pathogenic factors may result in impediment of oocyte maturation, failure of fertilization or early embryonic development arrest. In this review, we categorize these clinically-identified, mutated genetic factors by their molecular characteristics: nuclear factors (PALT2, TRIP13, WEE2, TBPL2, REC114, MEI1 and CDC20), cytoplasmic factors (TLE6, PADI6, NLRP2/5, FBXO43, MOS and BTG4), a factor unique to primates (TUBB8), cell membrane factor (PANX1), and zona pellucida factors (ZP1-3). We compared discrepancies observed in phenotypes between human and mouse models to provide clues for clinical diagnosis and treatment of related reproductive diseases.

Biallelic variants in MOS cause large polar body in oocyte and human female infertility

STUDY QUESTION

What is the genetic basis of female infertility involving abnormal oocyte morphology with the production of a large first polar body (PB1)?

SUMMARY ANSWER

The homozygous missense variant (c.791C>G) and compound missense variants (c.596A>T and c.875C>T) in MOS proto-oncogene, serine/threonine kinase (MOS) (Online Mendelian Inheritance in Man (OMIM) reference: 190060; NM_005372.1) are responsible for abnormal oocyte morphology with the production of a large PB1 to cause infertility in women.

WHAT IS KNOWN ALREADY

MOS, an oocyte-specific gene, encodes a serine/threonine-protein kinase that directly phosphorylates mitogen-activated protein kinase (MAPK) kinase (MEK) to activate MAPK (also called extracellular-signal-regulated kinase (ERK)) signal cascade in the oocyte. Female mice lacking Mos remained viable, but infertile because of oocyte symmetric division, spontaneous parthenogenetic activation and early embryonic arrest. Recently, two independent studies demonstrated that female infertility with early embryonic arrest and fragmentation can be caused by biallelic mutations in MOS. However, so far, MOS variants have not been associated with the phenotype of large PB1 extrusion in human oocytes to contribute to female infertility.

STUDY DESIGN, SIZE, DURATION

Two independent infertile families characterized by the presence of large PB1 in oocytes were recruited between December 2020 and February 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Genomic DNA was extracted from the peripheral blood samples of the subjects for whole-exome sequencing. Pedigree analysis was validated by Sanger sequencing. Then, the pathogenic effects of the MOS variants on MOS protein properties and ERK1/2 activation were determined in HEK293 cells and mouse oocytes.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified three rare missense variants in MOS, including a homozygous missense variant (c.791C>G) from Patient 1 in Family 1 and two compound missense variants (c.596A>T and c.875C>T) from twin sisters in Family 2. The MOS variants followed a recessive inheritance pattern in infertile patients. All three patients displayed a high percentage of large PB1 extrusion in the oocytes. The three MOS variants could not activate MEK1/2 and ERK1/2 in oocytes and HEK293 cells. In addition, when compared with wild-type MOS, the MOS variants decreased the MOS protein level and attenuated the binding capacity with MEK1. Microinjection of wild-type human MOS complementary RNAs (cRNAs) reversed the symmetric division of oocytes after siMos treatment. In contrast, the three MOS variants demonstrated no rescuing ability.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Owing to the scarcity of human oocyte samples and the associated ethical restrictions, we could not perform the rescue attempt for the study patients.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings expand the genetic and phenotypic spectrum of MOS variants in causing female infertility. Our study findings facilitate the early genetic diagnosis of abnormal oocyte morphology characterized as large PB1 that eventually causes infertility in women.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Natural Science Foundation of China (82071640 and 82001633), Natural Science Foundation of Zhejiang Province (LD22C060001), the Key Projects Jointly Constructed by the Ministry and the Province of Zhejiang Medical and Health Science and Technology Project (WKJ-ZJ-2005), China Postdoctoral Science Foundation (2020M682575 and 2021T140198), the Changsha Municipal Natural Science Foundation (kq2007022) and Hunan Provincial Grant for Innovative Province Construction (2019SK4012). None of the authors declare any competing interests.

TRIAL REGISTRATION NUMBER

N/A.