MNS1 variant associated with situs inversus and male infertility

Localisation and function of key axonemal microtubule inner proteins and dynein docking complex members reveal extensive diversity among vertebrate motile cilia

Vertebrate motile cilia are classified as (9+2) or (9+0), based on the presence or absence of the central pair apparatus, respectively. Cryogenic electron microscopy analyses of (9+2) cilia have uncovered an elaborate axonemal protein composition. The extent to which these features are conserved in (9+0) cilia remains unclear. CFAP53, a key axonemal filamentous microtubule inner protein (fMIP) and a centriolar satellites component, is essential for motility of (9+0), but not (9+2) cilia. Here, we show that in (9+2) cilia, CFAP53 functions redundantly with a paralogous fMIP, MNS1. MNS1 localises to ciliary axonemes, and combined loss of both proteins in zebrafish and mice caused severe outer dynein arm loss from (9+2) cilia, significantly affecting their motility. Using immunoprecipitation, we demonstrate that, whereas MNS1 can associate with itself and CFAP53, CFAP53 is unable to self-associate. We also show that additional axonemal dynein-interacting proteins, two outer dynein arm docking (ODAD) complex members, show differential localisation between types of motile cilia. Together, our findings clarify how paralogous fMIPs, CFAP53 and MNS1, function in regulating (9+2) versus (9+0) cilia motility, and further emphasise extensive structural diversity among these organelles.

Biallelic Variants in MNS1 Are Associated with Laterality Defects and Respiratory Involvement

Defects in motile cilia, termed motile ciliopathies, result in clinical manifestations affecting the respiratory and reproductive system, as well as laterality defects and hydrocephalus. We previously defined biallelic MNS1 variants causing situs inversus and male infertility, mirroring the findings in Mns1-/- mice. Here, we present clinical and genomic findings in five newly identified individuals from four unrelated families affected by MNS1-related disorder. Ciliopathy panel testing and whole exome sequencing identified one previously reported and two novel MNS1 variants extending the genotypic spectrum of disease. A broad spectrum of laterality defects including situs inversus totalis and heterotaxia was confirmed. Interestingly, a single affected six-year-old girl homozygous for an MNS1 nonsense variant presented with a history of neonatal respiratory distress syndrome, recurrent respiratory tract infections, chronic rhinitis, and wet cough. Accordingly, immunofluorescence analysis showed the absence of MNS1 from the respiratory epithelial cells of this individual. Two other individuals with hypomorphic variants showed laterality defects and mild respiratory phenotype. This study represents the first observation of heterotaxia and respiratory disease in individuals with biallelic MNS1 variants, an important extension of the phenotype associated with MNS1-related motile ciliopathy disorder.

Novel SPEF2 variants cause male infertility and likely primary ciliary dyskinesia

PURPOSE

This study aimed to identify the genetic causes of male infertility and primary ciliary dyskinesia (PCD)/PCD-like phenotypes in three unrelated Han Chinese families.

METHODS

We conducted whole-exome sequencing of three patients with male infertility and PCD/PCD-like phenotypes from three unrelated Chinese families. Ultrastructural and immunostaining analyses of patient spermatozoa and respiratory cilia and in vitro analyses were performed to analyze the effects of SPEF2 variants. Intracytoplasmic sperm injection (ICSI) was administered to three affected patients.

RESULTS

We identified four novel SPEF2 variants, including one novel homozygous splicing site variant [NC_000005.10(NM_024867.4): c.4447 + 1G > A] of the SPEF2 gene in family 1, novel compound heterozygous nonsense variants [NC_000005.10(NM_024867.4): c.1339C > T (p.R447*) and NC_000005.10(NM_024867.4): c.1645G > T (p.E549*)] in family 2, and one novel homozygous missense variant [NC_000005.10(NM_024867.4): c.2524G > A (p.D842N)] in family 3. All the patients presented with male infertility and PCD/likely PCD. All variants were present at very low levels in public databases, predicted to be deleterious in silico prediction tools, and were further confirmed deleterious by in vitro analyses. Ultrastructural analyses of the spermatozoa of the patients revealed the absence of the central pair complex in the sperm flagella. Immunostaining of the spermatozoa and respiratory cilia of the patients validated the pathogenicity of the SPEF2 variants. All patients carrying SPEF2 variants underwent one ICSI cycle and delivered healthy infants.

CONCLUSION

Our study reported four novel pathogenic variants of SPEF2 in three male patients with infertility and PCD/PCD-like phenotypes, which not only extend the spectrum of SPEF2 mutations but also provide information for genetic counseling and treatment of such conditions.

Genomics of post-bottleneck recovery in the northern elephant seal

Populations and species are threatened by human pressure, but their fate is variable. Some depleted populations, such as that of the northern elephant seal (Mirounga angustirostris), recover rapidly even when the surviving population was small. The northern elephant seal was hunted extensively and taken by collectors between the early 1800s and 1892, suffering an extreme population bottleneck as a consequence. Recovery was rapid and now there are over 200,000 individuals. We sequenced 260 modern and 8 historical northern elephant seal nuclear genomes to assess the impact of the population bottleneck on individual northern elephant seals and to better understand their recovery. Here we show that inbreeding, an increase in the frequency of alleles compromised by lost function, and allele frequency distortion, reduced the fitness of breeding males and females, as well as the performance of adult females on foraging migrations. We provide a detailed investigation of the impact of a severe bottleneck on fitness at the genomic level and report on the role of specific gene systems.

Heart failure-related genes associated with oxidative stress and the immune landscape in lung cancer

Background

Lung cancer is a common comorbidity of heart failure (HF). The early identification of the risk factors for lung cancer in patients with HF is crucial to early diagnosis and prognosis. Furthermore, oxidative stress and immune responses are the two critical biological processes shared by HF and lung cancer. Therefore, our study aimed to select the core genes in HF and then investigate the potential mechanisms underlying HF and lung cancer, including oxidative stress and immune responses through the selected genes.

Methods

Differentially expressed genes (DEGs) were analyzed for HF using datasets extracted from the Gene Expression Omnibus database. Functional enrichment analysis was subsequently performed. Next, weighted gene co-expression network analysis was performed to select the core gene modules. Support vector machine models, the random forest method, and the least absolute shrinkage and selection operator (LASSO) algorithm were applied to construct a multigene signature. The diagnostic values of the signature genes were measured using receiver operating characteristic curves. Functional analysis of the signature genes and immune landscape was performed using single-sample gene set enrichment analysis. Finally, the oxidative stress-related genes in these signature genes were identified and validated in vitro in lung cancer cell lines.

Results

The DEGs in the GSE57338 dataset were screened, and this dataset was then clustered into six modules using weighted gene co-expression network analysis; MEblue was significantly associated with HF (cor = -0.72, p < 0.001). Signature genes including extracellular matrix protein 2 (ECM2), methyltransferase-like 7B (METTL7B), meiosis-specific nuclear structural 1 (MNS1), and secreted frizzled-related protein 4 (SFRP4) were selected using support vector machine models, the LASSO algorithm, and the random forest method. The respective areas under the curve of the receiver operating characteristic curves of ECM2, METTL7B, MNS1, and SFRP4 were 0.939, 0.854, 0.941, and 0.926, respectively. Single-sample gene set enrichment analysis revealed significant differences in the immune landscape of the patients with HF and healthy subjects. Functional analysis also suggested that these signature genes may be involved in oxidative stress. In particular, METTL7B was highly expressed in lung cancer cell lines. Meanwhile, the correlation between METTL7B and oxidative stress was further verified using flow cytometry.

Conclusion

We identified that ECM2, METTL7B, MNS1, and SFRP4 exhibit remarkable diagnostic performance in patients with HF. Of note, METTL7B may be involved in the co-occurrence of HF and lung cancer by affecting the oxidative stress immune responses.

BBOF1 is required for sperm motility and male fertility by stabilizing the flagellar axoneme in mice

The sperm flagellum is a specialized type of motile cilium composed of a typical "9 + 2" axonemal structure with peri-axonemal structures, such as outer dense fibers (ODFs). This flagellar arrangement is crucial for sperm movement and fertilization. However, the association of axonemal integrity with ODFs remains poorly understood. Here, we demonstrate that mouse BBOF1 could interact with both MNS1, an axonemal component, and ODF2, an ODF protein, and is required for sperm flagellar axoneme maintenance and male fertility. BBOF1 is expressed exclusively in male germ cells from the pachytene stage onwards and is detected in sperm axoneme fraction. Spermatozoa derived from Bbof1-knockout mice exhibit a normal morphology, however, reduced motility due to the absence of certain microtubule doublets, resulting in the failure to fertilize mature oocytes. Furthermore, BBOF1 is found to interact with ODF2 and MNS1 and is also required for their stability. Our findings in mice suggest that Bbof1 could also be essential for human sperm motility and male fertility, thus is a novel potential candidate gene for asthenozoospermia diagnosis.

Biallelic DAW1 variants cause a motile ciliopathy characterized by laterality defects and subtle ciliary beating abnormalities

PURPOSE

The clinical spectrum of motile ciliopathies includes laterality defects, hydrocephalus, and infertility as well as primary ciliary dyskinesia when impaired mucociliary clearance results in otosinopulmonary disease. Importantly, approximately 30% of patients with primary ciliary dyskinesia lack a genetic diagnosis.

METHODS

Clinical, genomic, biochemical, and functional studies were performed alongside in vivo modeling of DAW1 variants.

RESULTS

In this study, we identified biallelic DAW1 variants associated with laterality defects and respiratory symptoms compatible with motile cilia dysfunction. In early mouse embryos, we showed that Daw1 expression is limited to distal, motile ciliated cells of the node, consistent with a role in left-right patterning. daw1 mutant zebrafish exhibited reduced cilia motility and left-right patterning defects, including cardiac looping abnormalities. Importantly, these defects were rescued by wild-type, but not mutant daw1, gene expression. In addition, pathogenic DAW1 missense variants displayed reduced protein stability, whereas DAW1 loss-of-function was associated with distal type 2 outer dynein arm assembly defects involving axonemal respiratory cilia proteins, explaining the reduced cilia-induced fluid flow in particle tracking velocimetry experiments.

CONCLUSION

Our data define biallelic DAW1 variants as a cause of human motile ciliopathy and determine that the disease mechanism involves motile cilia dysfunction, explaining the ciliary beating defects observed in affected individuals.

The Plasmodium falciparum CCCH Zinc Finger Protein ZNF4 Plays an Important Role in Gametocyte Exflagellation through the Regulation of Male Enriched Transcripts

CCCH zinc finger proteins (ZFPs) function mainly as RNA-binding proteins (RBPs) and play a central role in the mRNA metabolism. Over twenty seven CCCH-ZFPs are encoded in the genome of the human malaria parasite Plasmodium falciparum, the causative agent of malaria tropica. However, little is known about their functions. In this study, we characterize one member of the PfCCCH-ZFP named ZNF4. We show that ZNF4 is highly expressed in mature gametocytes, where it predominantly localizes to the cytoplasm. Targeted gene disruption of ZNF4 showed no significant effect in asexual blood stage replication and gametocyte development while male gametocyte exflagellation was significantly impaired, leading to reduced malaria transmission in the mosquito. Comparative transcriptomics between wildtype (WT) and the ZNF4-deficient line (ZNF4-KO) demonstrated the deregulation of about 473 genes (274 upregulated and 199 downregulated) in mature gametocytes. Most of the downregulated genes show peak expression in mature gametocyte with male enriched genes associated to the axonemal dynein complex formation, and cell projection organization is highly affected, pointing to the phenotype in male gametocyte exflagellation. Upregulated genes are associated to ATP synthesis. Our combined data therefore indicate that ZNF4 is a CCCH zinc finger protein which plays an important role in male gametocyte exflagellation through the regulation of male gametocyte-enriched genes.

Heterotaxy syndrome: Prenatal diagnosis, concomitant malformations and outcomes

OBJECTIVE

The aim of this study is to define cardiac and extracardiac malformations in fetuses with heterotaxy syndrome and to determine perinatal and childhood prognosis.

METHODS

In this retrospective study, fetuses diagnosed with heterotaxy syndrome on antenatal ultrasonography in a tertiary center between January 2014 and January 2021 were analyzed. Fetuses with heterotaxy syndrome were grouped as right atrial isomerism (RAI) and left atrial isomerism (LAI).

RESULTS

A total of 62 fetuses, 32 (51.6%) with RAI and 30 (48.4%) with LAI, were included in the study. Extracardiac anomaly was detected in 25% of fetuses with RAI and 44% of fetuses with LAI (p = 0.13). Patients with univentricular repair had a higher childhood mortality than patients with biventricular repair (p = 0.031). The presence of conotruncal anomaly was an independent factor affecting mortality (HR = 5.09, CI 95% 1.09-23.71, p = 0.039).

CONCLUSION

Hydrops fetalis, univentricular physiology and conotruncal anomalies are associated with poor outcomes in heterotaxy syndrome. The severity of the cardiac malformation is the main determinant of the outcomes. The presence of extracardiac malformations is associated with increased morbidity and mortality.

De novo identification of mammalian ciliary motility proteins using cryo-EM

Dynein-decorated doublet microtubules (DMTs) are critical components of the oscillatory molecular machine of cilia, the axoneme, and have luminal surfaces patterned periodically by microtubule inner proteins (MIPs). Here we present an atomic model of the 48-nm repeat of a mammalian DMT, derived from a cryoelectron microscopy (cryo-EM) map of the complex isolated from bovine respiratory cilia. The structure uncovers principles of doublet microtubule organization and features specific to vertebrate cilia, including previously unknown MIPs, a luminal bundle of tektin filaments, and a pentameric dynein-docking complex. We identify a mechanism for bridging 48- to 24-nm periodicity across the microtubule wall and show that loss of the proteins involved causes defective ciliary motility and laterality abnormalities in zebrafish and mice. Our structure identifies candidate genes for diagnosis of ciliopathies and provides a framework to understand their functions in driving ciliary motility.

Telomere Length and Male Fertility

Over the past decade, telomeres have attracted increasing attention due to the role they play in human fertility. However, conflicting results have been reported on the possible association between sperm telomere length (STL) and leukocyte telomere length (LTL) and the quality of the sperm parameters. The aim of this study was to run a comprehensive study to investigate the role of STL and LTL in male spermatogenesis and infertility. Moreover, the association between the sperm parameters and 11 candidate single nucleotide polymorphisms (SNPs), identified in the literature for their association with telomere length (TL), was investigated. We observed no associations between sperm parameters and STL nor LTL. For the individual SNPs, we observed five statistically significant associations with sperm parameters: considering a p < 0.05. Namely, ACYP2˗rs11125529 and decreased sperm motility (p = 0.03); PXK˗rs6772228 with a lower sperm count (p = 0.02); NAF1˗rs7675998 with increased probability of having abnormal acrosomes (p = 0.03) and abnormal flagellum (p = 0.04); ZNF208˗rs8105767 and reduction of sperms with normal heads (p = 0.009). This study suggests a moderate involvement of telomere length in male fertility; however, in our analyses four SNPs were weakly associated with sperm variables, suggesting the SNPs to be pleiotropic and involved in other regulatory mechanisms independent of telomere homeostasis, but involved in the spermatogenic process.

Genetic testing for men with infertility: techniques and indications

Genetic testing is an integral component in the workup of male infertility as genetic conditions may be responsible for up to 15% of all cases. Currently, three genetic tests are commonly performed and recommended by major urologic associations: karyotype analysis (KA), Y-chromosome microdeletion testing, and CFTR mutation testing. Despite widespread adoption of these tests, an etiology for infertility remains elusive in up to 80% of cases. Recent work has identified intriguing new targets for genetic testing which may soon see clinical relevance. This review will discuss the indications and techniques for currently offered genetic tests and briefly explore ongoing research directions within this field.

A novel homozygous frameshift mutation in MNS1 associated with severe oligoasthenoteratozoospermia in humans

Oligoasthenoteratozoospermia (OAT) refers to the combination of various sperm abnormalities, including a decreased sperm count, reduced motility, and abnormal sperm morphology. Only a few genetic causes have been shown to be associated with OAT. Herein, we identified a novel homozygous frameshift mutation in meiosis-specific nuclear structural 1 (MNS1; NM_018365: c.603_604insG: p.Lys202Glufs*6) by whole-exome sequencing in an OAT proband from a consanguineous Chinese family. Subsequent variant screening identified four additional heterozygous MNS1 variants in 6/219 infertile individuals with oligoasthenospermia, but no MNS1 variants were observed among 223 fertile controls. Immunostaining analysis showed MNS1 to be normally located in the whole-sperm flagella, but was absent in the proband's sperm. Expression analysis by Western blot also confirmed that MNS1 was absent in the proband's sperm. Abnormal flagellum morphology and ultrastructural disturbances in outer doublet microtubules were observed in the proband's sperm. A total of three intracytoplasmic sperm injection cycles were carried out for the proband's wife, but they all failed to lead to a successful pregnancy. Overall, this is the first study to report a loss-of-function mutation in MNS1 causing OAT in a Han Chinese patient.

Haploid male germ cells-the Grand Central Station of protein transport

BACKGROUND

The precise movement of proteins and vesicles is an essential ability for all eukaryotic cells. Nowhere is this more evident than during the remarkable transformation that occurs in spermiogenesis-the transformation of haploid round spermatids into sperm. These transformations are critically dependent upon both the microtubule and the actin cytoskeleton, and defects in these processes are thought to underpin a significant percentage of human male infertility.

OBJECTIVE AND RATIONALE

This review is aimed at summarising and synthesising the current state of knowledge around protein/vesicle transport during haploid male germ cell development and identifying knowledge gaps and challenges for future research. To achieve this, we summarise the key discoveries related to protein transport using the mouse as a model system. Where relevant, we anchored these insights to knowledge in the field of human spermiogenesis and the causality of human male infertility.

SEARCH METHODS

Relevant studies published in English were identified using PubMed using a range of search terms related to the core focus of the review-protein/vesicle transport, intra-flagellar transport, intra-manchette transport, Golgi, acrosome, manchette, axoneme, outer dense fibres and fibrous sheath. Searches were not restricted to a particular time frame or species although the emphasis within the review is on mammalian spermiogenesis.

OUTCOMES

Spermiogenesis is the final phase of sperm development. It results in the transformation of a round cell into a highly polarised sperm with the capacity for fertility. It is critically dependent on the cytoskeleton and its ability to transport protein complexes and vesicles over long distances and often between distinct cytoplasmic compartments. The development of the acrosome covering the sperm head, the sperm tail within the ciliary lobe, the manchette and its role in sperm head shaping and protein transport into the tail, and the assembly of mitochondria into the mid-piece of sperm, may all be viewed as a series of overlapping and interconnected train tracks. Defects in this redistribution network lead to male infertility characterised by abnormal sperm morphology (teratozoospermia) and/or abnormal sperm motility (asthenozoospermia) and are likely to be causal of, or contribute to, a significant percentage of human male infertility.

WIDER IMPLICATIONS

A greater understanding of the mechanisms of protein transport in spermiogenesis offers the potential to precisely diagnose cases of male infertility and to forecast implications for children conceived using gametes containing these mutations. The manipulation of these processes will offer opportunities for male-based contraceptive development. Further, as increasingly evidenced in the literature, we believe that the continuous and spatiotemporally restrained nature of spermiogenesis provides an outstanding model system to identify, and de-code, cytoskeletal elements and transport mechanisms of relevance to multiple tissues.

The association of rs11457523 in HSP90AA1 with idiopathic male infertility in the Chinese population

The association of single nucleotide polymorphisms (SNPs) in heat shock protein 90 (HSP90) genes with idiopathic male infertility remains unclear. In this study, the five selected SNPs in HSP90AA1 namely rs10133307, rs10873531, rs11547523, rs11621560 and rs7145597 were genotyped in 116 idiopathic infertile males and 185 ethnically matched fertile males using the Sequenom MassARRAY assay. The role of these SNPs in male infertility was then studied using multiple genetic models. We observed that genotype distribution (p = .028) and allelic frequency (p = .032) of rs11547523 were significantly different between the infertile and fertile groups. In particular, A genotype of rs11547523 was associated with an increased risk of infertility in the allele (OR = 2.508, p = .048), dominant (OR = 2.733, p = .030) and additive models (OR = 0.366, p = .031). However, there were no significant differences in semen parameters including seminal volume (p = .452), sperm concentration (p = .727), total sperm number (p = .588), motility (p = .282) and morphology (p = .975) between A and A/G genotypes of rs11547523. These results indicate that rs11547523 in HSP90AA1 may be associated with idiopathic male infertility in the Chinese population. The outcome of this study contributes to the development of the diagnosis of male infertility.

Cep55 promotes cytokinesis of neural progenitors but is dispensable for most mammalian cell divisions

In mammalian cell lines, the endosomal sorting complex required for transport (ESCRT)-III mediates abscission, the process that physically separates daughter cells and completes cell division. Cep55 protein is regarded as the master regulator of abscission, because it recruits ESCRT-III to the midbody (MB), the site of abscission. However, the importance of this mechanism in a mammalian organism has never been tested. Here we show that Cep55 is dispensable for mouse embryonic development and adult tissue homeostasis. Cep55-knockout offspring show microcephaly and primary neural progenitors require Cep55 and ESCRT for survival and abscission. However, Cep55 is dispensable for cell division in embryonic or adult tissues. In vitro, division of primary fibroblasts occurs without Cep55 and ESCRT-III at the midbody and is not affected by ESCRT depletion. Our work defines Cep55 as an abscission regulator only in specific tissue contexts and necessitates the re-evaluation of an alternative ESCRT-independent cell division mechanism.

Rare Human Diseases: Model Organisms in Deciphering the Molecular Basis of Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is a recessive heterogeneous disorder of motile cilia, affecting one per 15,000-30,000 individuals; however, the frequency of this disorder is likely underestimated. Even though more than 40 genes are currently associated with PCD, in the case of approximately 30% of patients, the genetic cause of the manifested PCD symptoms remains unknown. Because motile cilia are highly evolutionarily conserved organelles at both the proteomic and ultrastructural levels, analyses in the unicellular and multicellular model organisms can help not only to identify new proteins essential for cilia motility (and thus identify new putative PCD-causative genes), but also to elucidate the function of the proteins encoded by known PCD-causative genes. Consequently, studies involving model organisms can help us to understand the molecular mechanism(s) behind the phenotypic changes observed in the motile cilia of PCD affected patients. Here, we summarize the current state of the art in the genetics and biology of PCD and emphasize the impact of the studies conducted using model organisms on existing knowledge.