Novel axonemal protein ZMYND12 interacts with TTC29 and DNAH1, and is required for male fertility and flagellum function

Male infertility is common and complex, presenting a wide range of heterogeneous phenotypes. Although about 50% of cases are estimated to have a genetic component, the underlying cause often remains undetermined. Here, from whole-exome sequencing on samples from 168 infertile men with asthenoteratozoospermia due to severe sperm flagellum, we identified homozygous ZMYND12 variants in four unrelated patients. In sperm cells from these individuals, immunofluorescence revealed altered localization of DNAH1, DNALI1, WDR66, and TTC29. Axonemal localization of ZMYND12 ortholog TbTAX-1 was confirmed using the Trypanosoma brucei model. RNAi knock-down of TbTAX-1 dramatically affected flagellar motility, with a phenotype similar to the sperm from men bearing homozygous ZMYND12 variants. Co-immunoprecipitation and ultrastructure expansion microscopy in T. brucei revealed TbTAX-1 to form a complex with TTC29. Comparative proteomics with samples from Trypanosoma and Ttc29 KO mice identified a third member of this complex: DNAH1. The data presented revealed that ZMYND12 is part of the same axonemal complex as TTC29 and DNAH1, which is critical for flagellum function and assembly in humans, and Trypanosoma. ZMYND12 is thus a new asthenoteratozoospermia-associated gene, bi-allelic variants of which cause severe flagellum malformations and primary male infertility.

First successful pregnancy outcome after twelve abortions in a Tunisian-woman with the rare p phenotype

INTRODUCTION

Anti-PP1P k alloantibody, is produced in the serum of individuals with the rare p phenotype. It is associated with severe haemolytic transfusion reactions, recurrent spontaneous early abortions as well as haemolytic disease of the foetus and newborn. Anti-PP1P k alloimmunization in pregnancy differ from others in their physiopathology. It seems that the placenta would be the main target of anti-PP1P k antibody.

CASE REPORT

This report concerns a 35 year old female, with a history of a high incidence (12) of early and recurrent miscarriages. She was found to have the extremely rare p phenotype and anti-PP1P k antibody in her serum. Her 13th pregnancy was successfully managed by plasmapheresis. No substitution fluid was added. Oral hydration was recommended before and after the apheresis sessions. 12 plasmapheresis cycles were performed before a healthy term female infant weighing 3kg600g, was delivered by caesarean section at 38 weeks of gestation.

CONCLUSION

Plasmapheresis seems to be the treatment of choice in the management of anti-PP1P k fetomaternal incompatibilities. However in this case, we opted for an original and less expensive protocol. We did resort, neither to substitution fluid nor to intravenous immunoglobulin.

Tunisian Recommendations for resumption of Reproductive Medicine activity in the Covid-19 pandemic

The activity of the Reproductive Medicine poses a dilemma in this pandemic Covid-19. In fact, this is a theoretically non-emergency activity except for fertility preservation with oncological reasons. The majority of fertility societies in the world such as the American Society for Reproductive Medicine (ASRM) and the European Society of Human Reproduction and Embryology (ESHRE) recommended stopping the inclusion of new patients and continuing only the In Vitro Fertilization (IVF) cycles that have already been initiated by promoting Freeze-all as much as possible. Initilaly, the "Société Tunisienne de Gynécologie Obstétrique" (STGO) issued national recommendations that echo the international recommendations. These recommendations were followed by the majority of IVF center in Tunisia. However, a number of new data are prompting us to update these recommendations.

Mutations in TTC29, Encoding an Evolutionarily Conserved Axonemal Protein, Result in Asthenozoospermia and Male Infertility

In humans, structural or functional defects of the sperm flagellum induce asthenozoospermia, which accounts for the main sperm defect encountered in infertile men. Herein we focused on morphological abnormalities of the sperm flagellum (MMAF), a phenotype also termed "short tails," which constitutes one of the most severe sperm morphological defects resulting in asthenozoospermia. In previous work based on whole-exome sequencing of a cohort of 167 MMAF-affected individuals, we identified bi-allelic loss-of-function mutations in more than 30% of the tested subjects. In this study, we further analyzed this cohort and identified five individuals with homozygous truncating variants in TTC29, a gene preferentially and highly expressed in the testis, and encoding a tetratricopeptide repeat-containing protein related to the intraflagellar transport (IFT). One individual carried a frameshift variant, another one carried a homozygous stop-gain variant, and three carried the same splicing variant affecting a consensus donor site. The deleterious effect of this last variant was confirmed on the corresponding transcript and protein product. In addition, we produced and analyzed TTC29 loss-of-function models in the flagellated protist T. brucei and in M. musculus. Both models confirmed the importance of TTC29 for flagellar beating. We showed that in T. brucei the TPR structural motifs, highly conserved between the studied orthologs, are critical for TTC29 axonemal localization and flagellar beating. Overall our work demonstrates that TTC29 is a conserved axonemal protein required for flagellar structure and beating and that TTC29 mutations are a cause of male sterility due to MMAF.

Step-by-step loupes-mTESE in non-obstructive azoospermic men, a retrospective study

Background

Men with non-obstructive azoospermia (NOA) may have sperm in their testes and a procedure of sperm retrieval and assisted reproduction is required in them to allow fertility. Standard procedures such as fine needle aspiration (FNA) and conventional testicular sperm extraction (cTESE) harvest random samples with a sperm retrieval rate (SRR) of 45%. Microdissection testicular sperm extraction (mTESE) is nowadays considered to be the most accurate technique to retrieve sperm in men with NOA. This procedure can identify dilated tubules that are more likely to contain viable sperm with a SRR of 60%.

Results

In our center, testicular biopsy was conducted in a standard fashion in 321 patients with NOA until March 2003. From then to December 2017, due to the lack of an operating microscope, we used 6 fold magnifying loupes to perform a step-by-step macro- mTESE in 1050 patients. Sperm was found in the first testis in 61% of the cases, leading to stop the procedure with less testicular damage. We increased our SRR from 43 to 51.8% in an acceptable operating time of 75mn for both sides.

Conclusions

In institutions where surgeons cannot afford an operating microscope, this modified mTESE technique using × 6 magnifying loupes is reliable, especially in patients with low testicular volumes and high FSH, in whom dilated tubules can be easily identified from the surrounding tissue.

PATL2 is a key actor of oocyte maturation whose invalidation causes infertility in women and mice

The genetic causes of oocyte meiotic deficiency (OMD), a form of primary infertility characterised by the production of immature oocytes, remain largely unexplored. Using whole exome sequencing, we found that 26% of a cohort of 23 subjects with OMD harboured the same homozygous nonsense pathogenic mutation in PATL2, a gene encoding a putative RNA‐binding protein. Using Patl2 knockout mice, we confirmed that PATL2 deficiency disturbs oocyte maturation, since oocytes and zygotes exhibit morphological and developmental defects, respectively. PATL2's amphibian orthologue is involved in the regulation of oocyte mRNA as a partner of CPEB. However, Patl2's expression profile throughout oocyte development in mice, alongside colocalisation experiments with Cpeb1, Msy2 and Ddx6 (three oocyte RNA regulators) suggest an original role for Patl2 in mammals. Accordingly, transcriptomic analysis of oocytes from WT and Patl2^−/− animals demonstrated that in the absence of Patl2, expression levels of a select number of highly relevant genes involved in oocyte maturation and early embryonic development are deregulated. In conclusion, PATL2 is a novel actor of mammalian oocyte maturation whose invalidation causes OMD in humans.

Bi-allelic Mutations in ARMC2 Lead to Severe Astheno-Teratozoospermia Due to Sperm Flagellum Malformations in Humans and Mice

Male infertility is a major health concern. Among its different causes, multiple morphological abnormalities of the flagella (MMAF) induces asthenozoospermia and is one of the most severe forms of qualitative sperm defects. Sperm of affected men display short, coiled, absent, and/or irregular flagella. To date, six genes (DNAH1, CFAP43, CFAP44, CFAP69, FSIP2, and WDR66) have been found to be recurrently associated with MMAF, but more than half of the cases analyzed remain unresolved, suggesting that many yet-uncharacterized gene defects account for this phenotype. Here, whole-exome sequencing (WES) was performed on 168 infertile men who had a typical MMAF phenotype. Five unrelated affected individuals carried a homozygous deleterious mutation in ARMC2, a gene not previously linked to the MMAF phenotype. Using the CRISPR-Cas9 technique, we generated homozygous Armc2 mutant mice, which also presented an MMAF phenotype, thus confirming the involvement of ARMC2 in human MMAF. Immunostaining experiments in AMRC2-mutated individuals and mutant mice evidenced the absence of the axonemal central pair complex (CPC) proteins SPAG6 and SPEF2, whereas the other tested axonemal and peri-axonemal components were present, suggesting that ARMC2 is involved in CPC assembly and/or stability. Overall, we showed that bi-allelic mutations in ARMC2 cause male infertility in humans and mice by inducing a typical MMAF phenotype, indicating that this gene is necessary for sperm flagellum structure and assembly.

Patients with multiple morphological abnormalities of the sperm flagella due to DNAH1 mutations have a good prognosis following intracytoplasmic sperm injection

STUDY QUESTION

Does DNAH1 status influence intracytoplasmic sperm injection (ICSI) outcomes for patients with multiple morphological abnormalities of the sperm flagella (MMAF)?

SUMMARY ANSWER

Despite a highly abnormal morphology, sperm from MMAF patients with DNAH1 mutations have a low aneuploidy rate and good nuclear quality, leading to good embryonic development following ICSI and a high pregnancy rate.

WHAT IS KNOWN ALREADY

Teratozoospermia represents a heterogeneous group including a wide range of phenotypes. Among all these qualitative defects, a flagellar phenotype called MMAF is characterized by a mosaic of morphological abnormalities of the flagellum, including coiled, bent, irregular, short or/and absent flagella, mainly due to the absence of the axonemal central pair microtubules. We previously demonstrated that homozygous mutations in the DNAH1 gene, encoding an inner arm heavy chain dynein, are frequently found in patients with MMAF (28% of the patients from the initial cohort). Numerous studies have reported an increased rate of aneuploidy and a poor sperm nuclear quality related to sperm flagellar abnormalities, which could impede ICSI outcome. Moreover, success rates after ICSI may be influenced by the type of ultrastructural flagellar defects and/or by the gene defects carried by the patients.

STUDY DESIGN, SIZE, DURATION

This retrospective cohort study included 6 infertile males with MMAF due to deleterious homozygous DNAH1 mutations and their respective spouses, who underwent 9 ISCI cycles, with 16 embryos being transferred. ICSI results were compared with two control populations of 13 MMAF men without DNAH1 mutations and an aged-matched control group of 1431 non-MMAF couples. All ICSI attempts took place between 2000 and 2012.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Clinical and biological data were collected from patients treated for infertility at the CPSR les Jasmins in Tunis (Tunisia). We compared the ICSI outcomes obtained with couples including DNAH1 mutated and nonmutated patients and non-MMAF couples. For the analysis of the chromosomal status, fluorescence in situ hybridization (FISH) analyses were performed on sperm cells from 3 DNAH1-mutated patients and from 29 fertile control subjects. Sperm chromatin condensation and DNA fragmentation were evaluated using aniline blue staining and TUNEL assays, respectively, on sperm cells from 3 DNAH1-mutated men and 6 fertile controls.

MAIN RESULTS AND THE ROLE OF CHANCE

There was a significantly increased proportion of disomy XY and 18 in sperm from DNAH1 mutated patients compared with fertile controls (1.52 versus 0.28%, P = 0.0001 and 0.64 versus 0.09%, P = 0.0001). However, there were no statistically significant differences among sperm from the two groups in their frequencies of either 13, 21, XX or YY disomy or diploidy. Measures of DNA compaction and fragmentation demonstrated a good nuclear sperm quality among DNAH1 mutated men. The overall fertilization, pregnancy and delivery rates of couples including DNAH1 mutated men were of 70.8, 50.0 and 37.5%, respectively. There were no statistically significant differences in any of these parameters compared with the two control groups (P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

A limitation of this study is the small number of DNAH1-mutated patients available and the low number of genes identified in MMAF. Further genetic studies are warranted to identify other MMAF-inducing genes to better characterize the genetic etiology of the MMAF phenotype and to improve the management of patients diagnosed with flagellar defects.

WIDER IMPLICATIONS OF THE FINDINGS

MMAF patients with DNAH1 mutations have low aneuploidy rates and good nuclear sperm quality, explaining the high pregnancy rate obtained with these patients. Good ICSI results were obtained for both MMAF groups (DNAH1 mutated and nonmutated), suggesting that patients presenting with asthenozoospermia due to flagellar defects have a good ICSI prognosis irrespective of their genotype. The majority of MMAF cases currently remain idiopathic with no genetic cause yet identified. In depth genetic analysis of these patients using next generation sequencing should reveal new causal genes. Subsequent genotype phenotype analyses could improve advice and care provided to MMAF patients.

STUDY FUNDING/COMPETING INTERESTS

None of the authors have any competing interest. This work is part of the project 'Identification and Characterization of Genes Involved in Infertility (ICG2I)', funded by the program GENOPAT 2009 from the French Research Agency (ANR) and the MAS-Flagella project, financed by the French ANR and the Direction Générale de l'Offre de Soins (DGOS).

Homozygous mutation of PLCZ1 leads to defective human oocyte activation and infertility that is not rescued by the WW-binding protein PAWP

In mammals, sperm-oocyte fusion initiates Ca(2+) oscillations leading to a series of events called oocyte activation, which is the first stage of embryo development. Ca(2+) signaling is elicited by the delivery of an oocyte-activating factor by the sperm. A sperm-specific phospholipase C (PLCZ1) has emerged as the likely candidate to induce oocyte activation. Recently, PAWP, a sperm-born tryptophan domain-binding protein coded by WBP2NL, was proposed to serve the same purpose. Here, we studied two infertile brothers exhibiting normal sperm morphology but complete fertilization failure after intracytoplasmic sperm injection. Whole exomic sequencing evidenced a missense homozygous mutation in PLCZ1, c.1465A>T; p.Ile489Phe, converting Ile 489 into Phe. We showed the mutation is deleterious, leading to the absence of the protein in sperm, mislocalization of the protein when injected in mouse GV and MII oocytes, highly abnormal Ca(2+) transients and early embryonic arrest. Altogether these alterations are consistent with our patients' sperm inability to induce oocyte activation and initiate embryo development. In contrast, no deleterious variants were identified in WBP2NL and PAWP presented normal expression and localization. Overall we demonstrate in humans, the absence of PLCZ1 alone is sufficient to prevent oocyte activation irrespective of the presence of PAWP. Additionally, it is the first mutation located in the C2 domain of PLCZ1, a domain involved in targeting proteins to cell membranes. This opens the door to structure-function studies to identify the conserved amino acids of the C2 domain that regulate the targeting of PLCZ1 and its selectivity for its lipid substrate(s).

A new AURKC mutation causing macrozoospermia: implications for human spermatogenesis and clinical diagnosis

The presence of close to 100% large-headed multi-tailed spermatozoa in the ejaculate has been described as a rare phenotype of male infertility with a very poor prognosis. We demonstrated previously that most cases were caused by a homozygous mutation (c.144delC) in the Aurora Kinase C gene (AURKC) leading to the absence or the production of a non-functional protein. AURKC deficiency in these patients blocked meiosis and resulted in the production of tetraploid spermatozoa unsuitable for fertilization. We describe here the study of two brothers presenting with large-headed spermatozoa. Molecular analysis of the AURKC gene was carried out in two brothers presenting with a typical large-headed spermatozoa phenotype. Both affected brothers were heterozygous for the c.144delC mutation. After complete sequencing of the gene a new heterozygous variant, c.436-2A>G, was identified in both patients. This mutation is located in the acceptor consensus splice site of exon 5. AURKC transcripts were extracted from one of the patient's leukocytes and reverse transcription polymerase chain reaction could be realized showing the presence of a truncated transcript indicating that c.436-2A>G leads to the skipping of exon 5. These results indicate that AURKC molecular analysis of patients with large-headed spermatozoa should not be stopped in the absence of a homozygous recurrent mutation on exon 3 but complete sequence analysis should be performed. This diagnosis is important as the identification of AURKC mutations in patients indicates that all spermatozoa will be chromosomally abnormal and that ICSI should not be attempted.

A recurrent deletion of DPY19L2 causes infertility in man by blocking sperm head elongation and acrosome formation

An increasing number of couples require medical assistance to achieve a pregnancy, and more than 2% of the births in Western countries now result from assisted reproductive technologies. To identify genetic variants responsible for male infertility, we performed a whole-genome SNP scan on patients presenting with total globozoospermia, a primary infertility phenotype characterized by the presence of 100% round acrosomeless spermatozoa in the ejaculate. This strategy allowed us to identify in most patients (15/20) a 200 kb homozygous deletion encompassing only DPY19L2, which is highly expressed in the testis. Although there was no known function for DPY19L2 in humans, previous work indicated that its ortholog in C. elegans is involved in cell polarity. In man, the DPY19L2 region has been described as a copy-number variant (CNV) found to be duplicated and heterozygously deleted in healthy individuals. We show here that the breakpoints of the deletions are located on a highly homologous 28 kb low copy repeat (LCR) sequence present on each side of DPY19L2, indicating that the identified deletions were probably produced by nonallelic homologous recombination (NAHR) between these two regions. We demonstrate that patients with globozoospermia have a homozygous deletion of DPY19L2, thus indicating that DPY19L2 is necessary in men for sperm head elongation and acrosome formation. A molecular diagnosis can now be proposed to affected men; the presence of the deletion confirms the diagnosis of globozoospermia and assigns a poor prognosis for the success of in vitro fertilization.