P–568 Homozygous Pathogenic Variants in ACTL9 Cause Fertilization Failure and Male Infertility in Human and Mouse

Abstract Study question What are the other male factors that cause total fertilization failure (TFF) excepting for variants in PLCZ1? Summary answer Homozygous variants in ACTL9 (actin like 9) cause abnormal localization of PLCζ in a loosened perinuclear theca (PT) structure and leads to TFF. What is known already In previous studies, investigators have reported that the female factors in TFF after intracytoplasmic sperm injection (ICSI) include pathogenic variants in WEE2, TLE6, and TUBB8, whereas for male factors, pathogenic variants in PLCZ1 were reported to be the primary cause of TFF, which account for approximately 30% of couples with male factors in TFF excluding globozoospermia. Most recently, it was reported that pathogenic variants in ACTL7A led to reduced expression and abnormal localization of PLCζ, thereby identifying this genetic variant as a potential cause of TFF. Study design, size, duration Fifty-four infertile couples with TFF or poor fertilization (fertilization rate of < 20%) at the Reproductive and Genetic Hospital of CITIC-Xiangya during January 2014 to June 2020 were recruited into this study. Participants/materials, setting, methods Male factors were identified in (MOAT). WES analysis was used to analyze the genetic factors of individuals with male factors. Sperm morphological study was conducted by H&E staining and TEM. Immunostaining of PLCζ was used to analyze the status of sperm-borne activation factor. A knock-in mouse model was generated by CRISPER-Cas9 technology. Sperm from homozygous Actl9 variant mice were analyzed by TEM and ICSI. ICSI with AOA was performed in couples with ACTL9 variants. Main results and the role of chance A total of 54 couples with TFF or poor fertilization were screened, with 21 couples determined to have a male infertility factor by MOAT. Whole-exome sequencing of these 21 male individuals identified three homozygous pathogenic variants in ACTL9 in three individuals. ACTL9 variations led to abnormal ultrastructure of the PT, with PLCζ absent in the head and present in the neck of the mutant sperm, which contributed to failed normal calcium oscillations in oocytes and subsequent TFF. The key roles of ACTL9 in the PT structure and TFF after ICSI were further confirmed in Actl9-mutated mouse model. Furthermore, assisted oocyte activation by calcium ionophore exposure successfully overcame TFF and achieved live births in a couple with an ACTL9 variant. Limitations, reasons for caution The mechanism of how ACTL9 regulate PLCζ remains unknown. Wider implications of the findings: It provided a genetic marker and a therapeutic option for individuals who have undergone ICSI without successful fertilization. Trial registration number not applioable

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Diagnosis and Treatment of Male Infertility-Related Fertilization Failure

Journal of Clinical Medicine ◽

10.3390/jcm9123899 ◽

2020 ◽

Vol 9 (12) ◽

pp. 3899

Author(s):

Arantxa Cardona Barberán ◽

Annekatrien Boel ◽

Frauke Vanden Meerschaut ◽

Dominic Stoop ◽

Björn Heindryckx

Keyword(s):

Male Infertility ◽

Current Knowledge ◽

Oocyte Activation ◽

Fertilization Failure ◽

Sperm Abnormalities ◽

Normal Sperm ◽

Activation Mechanisms ◽

Sperm Factor ◽

Male Factors ◽

Assisted Oocyte Activation

Infertility affects approximately 15% of reproductive-aged couples worldwide, of which up to 30% of the cases are caused by male factors alone. The origin of male infertility is mostly attributed to sperm abnormalities, of which many are caused by genetic defects. The development of intracytoplasmic sperm injection (ICSI) has helped to circumvent most male infertility conditions. However, there is still a challenging group of infertile males whose sperm, although having normal sperm parameters, are unable to activate the oocyte, even after ICSI treatment. While ICSI generally allows fertilization rates of 70 to 80%, total fertilization failure (FF) still occurs in 1 to 3% of ICSI cycles. Phospholipase C zeta (PLCζ) has been demonstrated to be a critical sperm oocyte activating factor (SOAF) and the absence, reduced, or altered forms of PLCζ have been shown to cause male infertility-related FF. The purpose of this review is to (i) summarize the current knowledge on PLCζ as the critical sperm factor for successful fertilization, as well as to discuss the existence of alternative sperm-induced oocyte activation mechanisms, (ii) describe the diagnostic tests available to determine the cause of FF, and (iii) summarize the beneficial effect of assisted oocyte activation (AOA) to overcome FF.

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Novel mutations in PLCZ1 cause male infertility due to fertilization failure or poor fertilization

Human Reproduction ◽

10.1093/humrep/dez282 ◽

2020 ◽

Vol 35 (2) ◽

pp. 472-481 ◽

Cited By ~ 3

Author(s):

Zheng Yan ◽

Yong Fan ◽

Fei Wang ◽

Zhiguang Yan ◽

Menghui Li ◽

...

Keyword(s):

Male Infertility ◽

Conflicts Of Interest ◽

Missense Mutations ◽

Oocyte Activation ◽

Fertilization Failure ◽

Novel Mutations ◽

Primary Infertility ◽

Human Fertilization ◽

Poor Fertilization

Abstract STUDY QUESTION Do sperm-specific phospholipase C zeta (PLCZ1) mutations account for male infertility due to fertilization failure? SUMMARY ANSWER Six novel mutations and one reported mutation in PLCZ1 were identified in five of 14 independent families characterized by fertilization failure or poor fertilization, suggesting that these mutations may be responsible for fertilization failure in men exhibiting primary infertility. WHAT IS KNOWN ALREADY PLCZ1 is essential for the induction of intracellular calcium (Ca2+) oscillations and the initiation of oocyte activation during mammalian fertilization. However, genetic evidence linking PLCZ1 mutations with male infertility remains limited. STUDY DESIGN, SIZE, DURATION Fourteen unrelated primary infertility patients were recruited into this study from January 2016 to December 2018; the patients exhibited total fertilization failure or poor fertilization, as evidenced by ICSI and sperm-related oocyte activation deficiencies identified in mouse oocyte activation assays. PARTICIPANTS/MATERIALS, SETTING, METHODS Genomic DNA samples were extracted from the peripheral blood of patients. The whole exons of PLCZ1 were sequenced by Sanger sequencing. The PLCZ1 sequences were aligned by CodonCode software to identify rare variants. The ExAC database was used to search for the frequency of corresponding mutations. The pathogenicity of identified variants and their possible effects on the protein were assessed in silico. PLCZ1 protein levels in semen samples were evaluated by western blotting. Oocyte activation ability was assessed by the injection of wild-type and mutant PLCZ1 cRNAs into human mature metaphase II (MII) oocytes in vitro. MAIN RESULTS AND THE ROLE OF CHANCE We identified six novel mutations and one reported mutation in PLCZ1 among five affected individuals. In addition to four novel missense mutations, two new types of genetic variants were identified, including one in-frame deletion and one splicing mutation. Western blot analysis revealed that PLCZ1 protein expression was not observed in the semen samples from the five affected patients. Microinjection with the PLCZ1 cRNA variants was performed, and a significant decrease in the percentage of pronuclei was observed for four novel missense mutations and one novel in-frame deletion mutation, suggesting that these mutations have a deleterious influence on protein function. By artificial oocyte activation treatment, the fertilization failure phenotypes of four affected patients were successfully rescued and three healthy babies were delivered. LARGE SCALE DATA N/A LIMITATIONS, REASONS FOR CAUTION We screened only the whole exons of PLCZ1. Additional possible mutations in the non-coding region of PLCZ1 should be further studied. WIDER IMPLICATIONS OF THE FINDINGS Our study not only further confirms the important role of PLCZ1 in human fertilization but also expands the mutational spectrum of PLCZ1 associated with male infertility, which provides a basis for assessing genetic variation in PLCZ1 as a potential diagnostic marker for infertile men suffering from fertilization failure. STUDY FUNDING/COMPETING INTEREST(S) This research was supported by the National Natural Foundation of China (81 571 486 and 81 771 649). All authors have no conflicts of interest to declare.

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