Valérie Mitchell

Loss-of-Function Mutations in LRRC6, a Gene Essential for Proper Axonemal Assembly of Inner and Outer Dynein Arms, Cause Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is a group of autosomal-recessive disorders resulting from cilia and sperm-flagella defects, which lead to respiratory infections and male infertility. Most implicated genes encode structural proteins that participate in the composition of axonemal components, such as dynein arms (DAs), that are essential for ciliary and flagellar movements; they explain the pathology in fewer than half of the affected individuals. We undertook this study to further understand the pathogenesis of PCD due to the absence of both DAs. We identified, via homozygosity mapping, an early frameshift in LRRC6, a gene that encodes a leucine-rich-repeat (LRR)-containing protein. Subsequent analyses of this gene mainly expressed in testis and respiratory cells identified biallelic mutations in several independent individuals. The situs inversus observed in two of them supports a key role for LRRC6 in embryonic nodal cilia. Study of native LRRC6 in airway epithelial cells revealed that it localizes to the cytoplasm and within cilia, whereas it is absent from cells with loss-of-function mutations, in which DA protein markers are also missing. These results are consistent with the transmission-electron-microscopy data showing the absence of both DAs in cilia or flagella from individuals with LRRC6 mutations. In spite of structural and functional similarities between LRRC6 and DNAAF1, another LRR-containing protein involved in the same PCD phenotype, the two proteins are not redundant. The evolutionarily conserved LRRC6, therefore, emerges as an additional player in DA assembly, a process that is essential for proper axoneme building and that appears to be much more complex than was previously thought.

A predictive score for testicular sperm extraction quality and surgical ICSI outcome in non-obstructive azoospermia: a retrospective study

BACKGROUNDnIn non-obstructive azoospermia (NOA), testicular sperm extraction (TESE) is successful in ≈ 50% of cases. A parameter for predicting TESE quality and pregnancy rates after ICSI of testicular spermatozoa is still lacking.nnnMETHODSnWe retrospectively evaluated the total testicular volume (TTV), hormone levels and TESE quality in 280 patients with NOA. After successful TESE, the characteristics of the ICSI cycles and the take-home baby rates were evaluated.nnnRESULTSnTESE was successful in 149 patients (53.2%). In a multivariate logistic regression analysis, only TTV, FSH and inhibin B were correlated with the TESE outcome. A score including these three parameters was the best predictor of successful TESE (positive likelihood ratio: +3.01). When the score was <18.5, TESE was successful in 77.4% of cases and sperm rich (i.e. yielding >100 spermatozoa) in 91.1% of cases; 42.8% of couples took a baby home. The take-home baby rate did not depend on whether the score was <18.5 or between 18.5 and 3700. If the score was >3700, TESE was successful in 37.8% of cases and sperm rich in 14.3% of cases; only one couple took a baby home (a rate of 7.7 versus 42.8% when the score was <18.5; P< 0.001). Owing to low sperm retrieval on the day of oocyte retrieval, fewer oocytes were injected when the score was >3700 than when <3700.nnnCONCLUSIONSnThanks to better knowledge of TESE quality, the present score could help to improve care and pre-ICSI counseling for patients with NOA.

Identification of a new recurrent Aurora kinase C mutation in both European and African men with macrozoospermia

STUDY QUESTIONnCan we identify new sequence variants in the aurora kinase C gene (AURKC) of patients with macrozoospermia and establish a genotype-phenotype correlation?nnnSUMMARY ANSWERnWe identified a new non-sense mutation, p.Y248*, that represents 13% of all mutant alleles. There was no difference in the phenotype of individuals carrying this new mutation versus the initially described and main mutation c.144delC.nnnWHAT IS KNOWN ALREADYnThe absence of a functional AURKC gene causes primary infertility in men by blocking the first meiotic division and leading to the production of tetraploid large-headed spermatozoa. We previously demonstrated that most affected men were of North African origin and carried a homozygous truncating mutation (c.144delC).nnnSTUDY DESIGN, SIZE, DURATIONnThis is a retrospective study carried out on patients consulting for infertility and described as having >5% large-headed spermatozoa. A total of 87 patients are presented here, 43 patients were published previously and 44 are new patients recruited between January 2008 and December 2011.nnnPARTICIPANTS/MATERIALS, SETTING, METHODSnAll patients consulted for primary infertility in fertility clinics in France (n = 44), Tunisia (n = 30), Morocco (n = 9) or Algeria (n = 4). Sperm analysis was carried out in the recruiting fertility clinics and all molecular analyses were performed at Grenoble teaching hospital. DNA was extracted from blood or saliva and the seven AURKC exons were sequenced. RT-PCR was carried out on transcripts extracted from leukocytes from one patient homozygous for p.Y248*. Microsatellite analysis was performed on all p.Y248* patients to evaluate the age of this new mutation.nnnMAIN RESULTS AND THE ROLE OF CHANCEnWe identified a new non-sense mutation, p.Y248*, in 10 unrelated individuals of European (n = 4) and North African origin (n = 6). We show that this new variant represents 13% of all mutant alleles and that the initially described c.144delC variant accounts for almost all of the remaining mutated alleles (85.5%). No mutated transcripts could be detected by RT-PCR suggesting a specific degradation of the mutant transcripts by non-sense mediated mRNA decay. A rare variant located in the 3 untranslated region was found to strictly co-segregate with p.Y248*, demonstrating a founding effect. Microsatellite analysis confirmed this linkage and allowed us to estimate a mutational age of between 925 and 1325 years, predating the c.144delC variant predicted by the same method to have arisen 250-650 years ago. Patients with no identified AURKC mutation (n = 15) have significantly improved parameters in terms of vitality and concentration of normal spermatozoa, and a decreased rate of spermatozoa with a large head and multiple flagella (P < 0.001).nnnLIMITATIONS, REASONS FOR CAUTIONnDespite adherence to the World Health Organization guidelines, large variations in most characteristic sperm parameters were observed, even for patients with the same homozygous mutation. We believe that is mainly related to inter-laboratory variability in sperm parameter scoring. This prevented us from establishing clear-cut values to indicate a need for molecular analysis of patients with macrozoospermia.nnnWIDER IMPLICATIONS OF THE FINDINGSnThis study confirms yet again the importance of AURKC mutations in the aetiology of macrozoospermia. Although a large majority of patients are of North African origin, we have now identified European patients carrying a new non-sense mutation indicating that a diagnosis of absence of a functional AURKC gene should not be ruled out for non-Magrebian individuals. Indirect evidence indicates that AURKC might be playing a role in the meiotic spindle assembly checkpoint (SAC) during meiosis. We postulate that heterozygous men might have a more relaxed SAC leading to a more abundant sperm production and a reproductive advantage. This could be the reason for the rapid accumulation of the two AURKC mutations we observe in North African individuals.nnnSTUDY FUNDING/COMPETING INTEREST(S)nNone 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 programme GENOPAT 2009 from the French Research Agency (ANR).

Truncating Mutations in the Adhesion G Protein-Coupled Receptor G2 Gene ADGRG2 Cause an X-Linked Congenital Bilateral Absence of Vas Deferens

In 80% of infertile men with obstructive azoospermia caused by a congenital bilateral absence of the vas deferens (CBAVD), mutations are identified in the cystic fibrosis transmembrane conductance regulator gene (CFTR). For the remaining 20%, the origin of the CBAVD is unknown. A large cohort of azoospermic men with CBAVD was retrospectively reassessed with more stringent selection criteria based on consistent clinical data, complete description of semen and reproductive excurrent ducts, extensive CFTR testing, and kidney ultrasound examination. To maximize the phenotypic prioritization, men with CBAVD and with unilateral renal agenesis were considered ineligible for the present study. We performed whole-exome sequencing on 12 CFTR-negative men with CBAVD and targeted sequencing on 14 additional individuals. We identified three protein-truncating hemizygous mutations, c.1545dupT (p.Glu516Ter), c.2845delT (p.Cys949AlafsTer81), and c.2002_2006delinsAGA (p.Leu668ArgfsTer21), in ADGRG2, encoding the epididymal- and efferent-ducts-specific adhesion G protein-coupled receptor G2, in four subjects, including two related individuals with X-linked transmission of their infertility. Previous studies have demonstrated that Adgrg2-knockout male mice develop obstructive infertility. Our study confirms the crucial role of ADGRG2 in human male fertility and brings new insight into congenital obstructive azoospermia pathogenesis. In men with CBAVD who are CFTR-negative, ADGRG2 testing could allow for appropriate genetic counseling with regard to the X-linked transmission of the molecular defect.

Mutations in CFAP43 and CFAP44 cause male infertility and flagellum defects in Trypanosoma and human

Spermatogenesis defects concern millions of men worldwide, yet the vast majority remains undiagnosed. Here we report men with primary infertility due to multiple morphological abnormalities of the sperm flagella with severe disorganization of the sperm axoneme, a microtubule-based structure highly conserved throughout evolution. Whole-exome sequencing was performed on 78 patients allowing the identification of 22 men with bi-allelicxa0mutations in DNAH1 (nu2009=u20096), CFAP43 (nu2009=u200910), and CFAP44 (nu2009=u20096). CRISPR/Cas9 created homozygous CFAP43/44 male mice that were infertile and presented severe flagellar defects confirming the human genetic results. Immunoelectron and stimulated-emission-depletion microscopy performed on CFAP43 and CFAP44 orthologs in Trypanosoma brucei evidenced that both proteins are located between the doublet microtubules 5 and 6 and the paraflagellar rod. Overall, we demonstrate that CFAP43 and CFAP44 have a similar structure with a unique axonemal localization and are necessary to produce functional flagella in species ranging from Trypanosoma to human.Asthenozoospermia is a major cause of male infertility, and multiple morphological abnormalities of the flagella (MMAF) is a particularly severe form. Here, using whole-exome sequencing of 78 MMAF patients, the authors identify mutations in two WDR proteins, CFAP43 and CFAP44, and confirm that these proteins are required for flagellogenesis in mouse and Trypanosoma brucei.

Congenital bilateral absence of the vas deferens: the impact of spermatogenesis quality on intracytoplasmic sperm injection outcomes in 108 men.

In azoospermic men with congenital bilateral absence of the vas deferens (CBAVD), it is not known whether the outcomes of intracytoplasmic sperm injection (ICSI) depend on the quality of testicular spermatogenesis (as determined histopathologically). We retrospectively studied the impact of spermatogenesis quality on ICSI outcomes in 108 azoospermic men with CBAVD consulting in a university hospitals department of andrology and reproductive biology. As part of an ICSI program, sperm samples were obtained from the epididymis [by microsurgical epididymal sperm aspiration (MESA); n = 47] or the testis [by testicular sperm extraction (TESE); n = 14] or both (MESA + TESE, n = 47). In the TESE group (i.e., TESE‐only and MESA + TESE), spermatogenesis was normal in 21 of the 108 men (19.4%) and hypospermatogenesis occurred in 33 (30.5%). The fertilization rate was significantly lower in the hypospermatogenic group than in the normospermatogenesis group (65.6 and 72.9%, respectively; p = 0.02); this was also true for the embryo cleavage rate (88.6 and 92.1%, respectively; p = 0.007), and the proportion of embryos with fewer than 30% of enucleate fragments (79.5 and 86.9%, respectively; p = 0.02). Our study results showed that impaired spermatogenesis had a negative impact on certain early‐stage biological outcomes of ICSI. In CBAVD, male factors are likely to exert a harmful effect on the early stages of embryo development.

Light microscopy morphological characteristics of the sperm flagellum may be related to axonemal abnormalities

Although electron microscopy provides a detailed analysis of ultrastructural abnormalities, this technique is not available in all laboratories. We sought to determine whether certain characteristics of the flagellum as assessed by light microscopy were related to axonemal abnormalities. Forty‐one patients with an absence of outer dynein arms (type I), a lack of a central complex (type III) and an absence of peripheral doublets (type IV) were studied. Sperm morphology was scored according to Davids modified classification. Flagella with an irregular thickness were classified as being of normal length, short or broken. There were correlations between missing outer dynein arms and abnormal, short or coiled flagellum. Type III patients showed the highest flagellar defects (a short (P = 0.0027) or an absent flagellum (P = 0.011)). Just over 68% of the irregular flagella were short in Type III patients, whereas this value was only 34.5% in type I and 26.4% in type IV (P = 0.002). There was a negative correlation between misassembly and spermatozoa of irregular flagella (r = −0.79; P = 0.019). It is concluded that light microscopy analysis of flagellum abnormalities may help provide a correct diagnosis, identify sperm abnormalities with fertility potentials and outcomes in assisted reproduction technologies and assess the genetic risk.

Transition protein 1 mRNA expression is not related to pregnancy rate in azoospermic men undergoing TESE–ICSI

Our laboratory has previously reported significantly low levels of protamine (PRM) gene expression in infertile men. This drop was correlated with a low pregnancy rate, suggesting that PRMs may be useful as predictive factors for the outcome of testicular sperm extraction and intracytoplasmic sperm injection (TESE‐ICSI) in azoospermic men. Transition nuclear proteins (TPs) are expressed earlier in spermatogenesis than protamines and are required for normal sperm development. In the present study, we examined the expression of the transition nuclear protein 1 gene (TNP1) in azoospermia and its relationship with TESE‐ICSI outcomes. The cellular expression of TNP1 mRNA in spermatids was quantified by in situ hybridisation on paraffin sections of testis biopsies from 21 men with obstructive azoospermia and 23 men with non‐obstructive azoospermia. Cases of non‐obstructive and obstructive azoospermia did not differ significantly in terms of TNP1 expression. Furthermore, TNP1 mRNA expression was similar in non‐pregnant and pregnant couples. Hence, the pregnancy rate was not related to TNP1 mRNA expression levels in azoospermia. Our results emphasise the value of TNP1 as a reliable predictive marker for the presence of spermatids/spermatozoa in the testis biopsies used for TESE but also indicate that expression of the TNP1 gene (believed to be a major player in spermiogenesis and required for production of normal sperm) may not be a predictive factor for successful post‐ICSI embryonic development.

Extreme spermatogenesis failure: andrological phenotype and intracytoplasmic sperm injection outcomes

Patients with very low sperm count through direct sperm examination can exhibit extreme oligozoospermia or cryptozoospermia (after centrifugation). The management of these patients is a real challenge for both clinicians and biologists. In this retrospective and comparative cohort study, we compared the andrological phenotype of patients with extreme alterations of spermatogenesis and assessed whether the origin of spermatozoa (testicular or ejaculate) had any influence on intracytoplasmic sperm injection (ICSI) outcomes. A total of 161 ICSI cycles were performed using ejaculated spermatozoa from 75 patients with extreme oligozoospermia (EOS) or cryptozoospermia (CS) and 150 ICSI cycles using extracted testicular spermatozoa from 74 patients with non‐obstructive azoospermia (NOA). Physical, hormonal, ultrasound assessments, and ICSI outcomes were performed in each group. Cryptorchidism was significantly more frequent in the NOA group (60.8% vs. 22.6%, p = 0.001). FSH levels were significantly higher [18.9 IU/L (5.9–27.0) vs. 15.3 IU/L (9.0–46.5), p = 0.001] and the majority of inhibin B levels measured were found mostly undetectable in the NOA group as compared to EOS/CS group (31.1% vs. 10.7%, p = 0.0004). Moreover, we found no significant differences in the respect to the fertilization rates (48.9% and 43.3%, p = 0.43), implantation rates (17.4% and 15.9%, p = 0.77), and percentage of top quality embryo (22.4% and 20.4%, p = 0.73) between the two groups. The clinical pregnancy rates per embryo transferred were comparable in both groups (28.3% and 27.4%, p = 0.89). In this study, we showed for the first time a different andrological phenotype between EOS/CS and NOA groups. Indeed, cryptorchidism was significantly more frequent with more severe endocrine parameters found in the NOA group. These results reflect a more profound alteration in spermatogenesis in NOA patients. However, there was no difference in ICSI outcomes between NOA and EOS/CS groups.

New insights into the morphological and hormonal characteristics of spermatogenic arrest

The reported sperm retrieval rate (SRR) in patients with nonobstructive azoospermia (NOA) due to spermatogenic arrest (SA) is highly variable in the literature. This discrepancy could be explained by the heterogeneity of testicular tissues. Surprisingly, even though inhibin B levels reflect directly Sertoli cell function; no studies have evaluated this parameter in SA. We aimed to clarify the morphological and biological profile in 158 men with SA. From the total population, patients whose seminiferous tubules diameter was below 165 µm have higher SRR (46.9% vs. 27.4%, p < 0.05), lower inhibin levels and a higher frequency of nonuniform SA (71.9% vs. 38.7%, p < 0.001). On multivariate analysis, patients with late SA and a history of cryptorchidism were positively associated with successful sperm extraction. Patients with successful SRR and uniform SA exhibited inhibin levels twofold lower than those with failed TESE (45 pg/ml vs. 95 pg/ml, p < 0.05), whereas FSH levels were similar in the two groups. In this study, we showed for the first time that the mean diameter of the seminiferous tubules may be of value in the diagnosis of SA. Our results suggest that inhibin levels could be useful in the management of NOA with SA, along with FSH levels and testicular volume.