Pathogenic gene variants in CCDC39, CCDC40, RSPH1, RSPH9, HYDIN, and SPEF2 cause defects of sperm flagella composition and male infertility.

Primary Ciliary Dyskinesia (PCD) is a rare genetic disorder affecting the function of motile cilia in several organ systems. In PCD, male infertility is caused by defective sperm flagella composition or deficient motile cilia function in the efferent ducts of the male reproductive system. Different PCD-associated genes encoding axonemal components involved in the regulation of ciliary and flagellar beating are also reported to cause infertility due to multiple morphological abnormalities of the sperm flagella (MMAF). Here, we performed genetic testing by next generation sequencing techniques, PCD diagnostics including immunofluorescence-, transmission electron-, and high-speed video microscopy on sperm flagella and andrological work up including semen analyses. We identified ten infertile male individuals with pathogenic variants in CCDC39 (one) and CCDC40 (two) encoding ruler proteins, RSPH1 (two) and RSPH9 (one) encoding radial spoke head proteins, and HYDIN (two) and SPEF2 (two) encoding CP-associated proteins, respectively. We demonstrate for the first time that pathogenic variants in RSPH1 and RSPH9 cause male infertility due to sperm cell dysmotility and abnormal flagellar RSPH1 and RSPH9 composition. We also provide novel evidence for MMAF in HYDIN- and RSPH1-mutant individuals. We show absence or severe reduction of CCDC39 and SPEF2 in sperm flagella of CCDC39- and CCDC40-mutant individuals and HYDIN- and SPEF2-mutant individuals, respectively. Thereby, we reveal interactions between CCDC39 and CCDC40 as well as HYDIN and SPEF2 in sperm flagella. Our findings demonstrate that immunofluorescence microscopy in sperm cells is a valuable tool to identify flagellar defects related to the axonemal ruler, radial spoke head and the central pair apparatus, thus aiding the diagnosis of male infertility. This is of particular importance to classify the pathogenicity of genetic defects, especially in cases of missense variants of unknown significance, or to interpret HYDIN variants that are confounded by the presence of the almost identical pseudogene HYDIN2.

Bi-allelic variants in DNA mismatch repair proteins MutS Homolog MSH4 and MSH5 cause infertility in both sexes.

STUDY QUESTION: Do bi-allelic variants in the genes encoding the MSH4/MSH5 heterodimer cause male infertility? SUMMARY ANSWER: We detected biallelic, (likely) pathogenic variants in MSH5 (4 men) and MSH4 (3 men) in six azoospermic men, demonstrating that genetic variants in these genes are a relevant cause of male infertility. WHAT IS KNOWN ALREADY: MSH4 and MSH5 form a heterodimer, which is required for prophase of meiosis I. One variant in MSH5 and two variants in MSH4 have been described as causal for premature ovarian insufficiency (POI) in a total of five women, resulting in infertility. Recently, pathogenic variants in MSH4 have been reported in infertile men. So far, no pathogenic variants in MSH5 had been described in males. STUDY DESIGN, SIZE, DURATION: We utilized exome data from 1305 men included in the Male Reproductive Genomics (MERGE) study, including 90 males with meiotic arrest (MeiA). Independently, exome sequencing was performed in a man with MeiA from a large consanguineous family. PARTICIPANTS/MATERIALS, SETTING, METHODS: Assuming an autosomal-recessive mode of inheritance, we screened the exome data for rare, biallelic coding variants in MSH4 and MSH5. If possible, segregation analysis in the patients' families was performed. The functional consequences of identified loss-of-function (LoF) variants in MSH5 were studied using heterologous expression of the MSH5 protein in HEK293T cells. The point of arrest during meiosis was determined by γH2AX staining. MAIN RESULTS AND THE ROLE OF CHANCE: We report for the first time (likely) pathogenic, homozygous variants in MSH5 causing infertility in 2 out of 90 men with MeiA and overall in 4 out of 902 azoospermic men. Additionally, we detected biallelic variants in MSH4 in two men with MeiA and in the sister of one proband with POI. γH2AX staining revealed an arrest in early prophase of meiosis I in individuals with pathogenic MSH4 or MSH5 variants. Heterologous in vitro expression of the detected LoF variants in MSH5 showed that the variant p.(Ala620GlnTer9) resulted in MSH5 protein truncation and the variant p.(Ser26GlnfsTer42) resulted in a complete loss of MSH5. LARGE SCALE DATA: All variants have been submitted to ClinVar (SCV001468891-SCV001468896 and SCV001591030) and can also be accessed in the Male Fertility Gene Atlas (MFGA). LIMITATIONS, REASONS FOR CAUTION: By selecting for variants in MSH4 and MSH5, we were able to determine the cause of infertility in six men and one woman, leaving most of the examined individuals without a causal diagnosis. WIDER IMPLICATIONS OF THE FINDINGS: Our findings have diagnostic value by increasing the number of genes associated with non-obstructive azoospermia with high clinical validity. The analysis of such genes has prognostic consequences for assessing whether men with azoospermia would benefit from a testicular biopsy. We also provide further evidence that MeiA in men and POI in women share the same genetic causes. STUDY FUNDING/COMPETING INTEREST(S): This study was carried out within the frame of the German Research Foundation sponsored Clinical Research Unit 'Male Germ Cells: from Genes to Function' (DFG, CRU326), and supported by institutional funding of the Research Institute Amsterdam Reproduction and Development and funds from the LucaBella Foundation. The authors declare no conflict of interest.

Age and markers of Leydig cell function, but not of Sertoli cell function predict the success of sperm retrieval in adolescents and adults with Klinefelter's syndrome.

Microsurgical testicular sperm extraction (mTESE), combined with intracytoplasmic sperm injection (ICSI) represents a chance for azoospermic men with Klinefelter's syndrome (KS) to father children. The objective of this study was to identify predictive factors for the success of mTESE from adolescents and adults with KS. The clinical data of 50 late pubertal adolescents (13-19 years) and 85 adult patients (20-61 years) with non-mosaic KS, who underwent mTESE, were analysed with respect to factors, potentially predictive of active spermatogenesis; specifically a history of cryptorchidism, age, testicular volumes, serum levels of LH, FSH, testosterone (T) and estradiol at the time of surgery. Inhibin B, AMH and INSL3 were additionally analysed in the adolescents. A younger age and a near-compensated Leydig cell function were associated with higher success of sperm retrieval via mTESE: In adolescents ≥15-19 years, spermatozoa were retrieved in 45%, compared to 31% in adults; in adolescents aged 13-14 years, spermatozoa were collected in only 10%. Adolescents with an LH ≤17.5 U/L, along with a T level ≥7.5 nmol/L had the best success rate (54%), which fell to 44% with higher LH, whereas those with low T (<7.5 nmol/L), irrespective of LH had no sperm retrieval. In adults with T levels above and LH below these thresholds, the success rate was 51%, falling to 19%, if LH was higher. When T was lower than threshold, the rate was 17%. No association between testicular volumes, serum levels of FSH, Inhibin B, AMH, estradiol and mTESE success was found. A history of cryptorchidism was associated with lower retrieval rates. A window of opportunity for an approximate 50% chance to retrieve spermatozoa via mTESE exists for young, late pubertal KS patients between age 15 and young adulthood, when Leydig cell function is at its best. In these cases, referral to a centre of expertise should be considered.

Optimizing TESE-ICSI by laser-assisted selection of immotile spermatozoa and polarization microscopy for selection of oocytes.

For most azoospermic men testicular sperm extraction (TESE) is the only treatment, however it presents challenges for the ART laboratory, as the retrieval of motile spermatozoa is difficult. In the absence of sperm movement no unequivocal distinction can be made between either dead or immotile, but vital spermatozoa. However, a single laser shot directed to the tip of the tail allows recognition of viability because the flagellum coils at the area of impact. To rank the quality and the maturity of oocytes, polarization microscopy can be used. The zona score and the visualization of the meiotic spindle correlate with implantation and pregnancy rates. We compared 65 TESE-ICSI cycles of the years 2007 and 2008 (Group 1, G1) with 58 TESE-ICSI cycles of the years 2009 and 2010 (Group 2, G2). Testicular spermatozoa were injected according to motility and morphology into selected oocytes. In G1 both, oocyte and spermatozoa were rated using light microscopy only, whereas in G2 the laser was used for sperm selection and the oocytes were rated by light and polarization microscopy. In G2 we enhanced our fertilization rate (FR) significantly in comparison to G1 (G1 42.1% vs. G2 52.7%, p < 0.001). The fertilization rate with immotile, but vital spermatozoa improved significantly when applying laser-based selection (p = 0.006). The laser selection of immotile spermatozoa and the use of polarization microscopy can enhance the FR of TESE-ICSI. No negative effect of the laser was seen on birth rates. The FR with immotile, but vital spermatozoa clearly benefits from laser selection and is a non-hazardous and safe method for the selection of viable but immotile sperm. To our knowledge this is the first report using new technology creating novel endpoints for the analysis of spermatozoa and oocytes in TESE-ICSI.