Actl7a deficiency in mice leads to male infertility and fertilization failure.

Mutations in the Actl7a gene have been reported to lead to male infertility; however, the detailed mechanism of this phenomenon remains unknown. In this study, we constructed Actl7a gene knockout (KO) mice and found that Actl7a deficiency led to malformed formation of sperm acrosomes, male infertility, fertilization failure during in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), and reduced sperm-zona pellucida (ZP) binding ability. Moreover, we found that the localization of the zona pellucida binding protein (ZPBP) was altered in the sperm of Actl7a homozygous KO male mice, which may affect the sperm-zona pellucida binding ability. ACTL7A and ZPBP could form complex, which may be involved in acrosomal formation. Further studies found that localization and expression of the PLCZ1 protein were abnormal in misshapen sperm, leading to reduced calcium oscillations in oocytes. Herein, we provide more detailed mechanisms underlining Actl7a deficiency and male infertility.

Zhou X ，Liu Z ，Jia W ，Hou M ，Zhang X ... -  《-》

ACROSIN deficiency causes total fertilization failure in humans by preventing the sperm from penetrating the zona pellucida.

Does a homozygous nonsense mutation in ACR lead to total fertilization failure (TFF) resulting in male infertility in humans? A novel homozygous nonsense mutation of ACR (c.167G>A, p.Trp56X) was identified in two infertile brothers and shown to cause human TFF. ACROSIN, encoded by ACR, is a major acrosomal enzyme expressed only in the acrosome of the sperm head. Inhibition of acrosin prevents sperm penetration of the zona pellucida (ZP) in several species, including humans. Acr-knockout in hamsters causes male infertility with completely blocked fertilization. Of note, there are no reports of ACR mutations associated with TFF in humans. Whole-exome sequencing (WES) was used for the identification of pathogenic genes for male factor TFF in eight involved couples. Data from eight infertile couples who had experienced TFF during their IVF or ICSI attempts were collected. Functional assays were used to verify the pathogenicity of the potential genetic factors identified by WES. Subzonal insemination (SUZI) and IVF assays were performed to determine the exact pathogenesis of TFF caused by deficiencies in ACROSIN. A novel homozygous nonsense mutation in ACR, c.167G>A, p.Trp56X, was identified in two additional primary infertile brothers whose parents were first cousins. This rare mutation caused ACROSIN deficiency and acrosomal ultrastructural defects in the affected sperm. Spermatozoa lacking ACROSIN were unable to penetrate the ZP, rather than hampering sperm binding, disrupting gamete fusion, or preventing oocyte activation. These findings were supported by the fertilization success of SUZI and ICSI attempts, as well as the normal expression of ACTL7A and PLCζ in the mutant sperm, suggesting that ICSI without remedial assisted oocyte activation is an optimal treatment for ARCOSIN-deficient TFF. The absence of another independent pedigree to support our argument is a limitation of this study. The findings expand our understanding of the genes involved in human TFF, providing information for appropriate genetic counseling and fertility guidance for these patients. This study was supported by the National Natural Science Foundation of China (grant no. 82201803, 81901541, 82271639, and 32000584), University Synergy Innovation Program of Anhui Province (GXXT-2019-044), and the Nonprofit Central Research Institute Fund of the Chinese Academy of Medical Sciences (grant no. 2019PT310002). The authors declare no conflicts of interest. N/A.

Hua R ，Xue R ，Liu Y ，Li Y ，Sha X ，Li K ，Gao Y ，Shen Q ，Lv M ，Xu Y ，Zhang Z ，He X ，Cao Y ，Wu H ... -  《-》

Novel variants in ACTL7A and PLCZ1 are associated with male infertility and total fertilization failure.

Total fertilization failure (TFF), which refers to fertilization failure in all mature oocytes, accounting for 5%-10% of in vitro fertilization (IVF) cycles and 1%-3% of intracytoplasmic sperm injection (ICSI) cycles in human. In this study, we recruited three unrelated primary infertile men with repeated cycles of TFF and performed whole-exome sequencing to identify the potential pathogenic variants. We identified homozygous or compound-heterozygous variants of paternal-effect genes ACTL7A and PLCZ1 that followed a Mendelian recessive inheritance pattern. Novel homozygous nonsense variant in ACTL7A [c.C146G: p.S49*] was identified in case 1, who came from a consanguineous family. Ultrastructural observation of ACTL7A-mutated spermatozoa by transmission electron microscopy (TEM) indicated that apparent increased thickness of perinuclear matrix and the acrosome was detached from the nuclear envelop. Besides, two novel compound-heterozygous variants in PLCZ1 were identified in case 2 [c.1174+3A>C:p.?; c.A1274G:p.N425S] and case 3 [c.136-1G>C:p.?; c.G1358A:p.G453D]. Mutated spermatozoa from case 2 with reduced expression of PLCZ1 showed apparent acrosome detachment by TEM analysis. And ICSI with assisted oocyte activation (ICSI-AOA) treatment can partly rescue the TFF. Taken together, our findings revealed that novel biallelic variants in the paternal-effect genes ACTL7A and PLCZ1 were associated with human TFF, which expanding the spectrum of genetic causes and facilitating the genetic diagnosis of male infertility with TFF.

Zhao S ，Cui Y ，Guo S ，Liu B ，Bian Y ，Zhao S ，Chen Z ，Zhao H ... -  《-》

A novel homozygous mutation in ACTL7A leads to male infertility.

Male infertility, a global public health problem, exhibits complex pathogenic causes and genetic factors deserve further discovery and study. We identified a novel homozygous missense mutation c.224A > C (p.D75A) in ACTL7A gene in two infertile brothers with teratozoospermia by whole-exome sequencing (WES). In vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) showed fertilization failure of the two affected couples. The three-dimensional (3D) models showed that a small section of α-helix transformed into random coil in the mutant ACTL7A protein and mutant amino acid lacked a hydrogen bond with Ser170 amino acid. Immunofluorescence revealed that ACTL7A protein was degraded in sperms of patients. Transmission electron microscopy (TEM) analysis of sperms from the infertile patients showed that the irregular perinuclear theca (PT) and acrosomal ultrastructural defects. Furthermore, ACTL7A mutation caused abnormal localization and reduced the expression of PLCZ1 in sperms of the patients, which may be the key reasons for the fertilization failure after ICSI. Our findings expand the spectrum of ACTL7A mutations and provide novel theoretical basis for genetic counseling.

Zhou X ，Xi Q ，Jia W ，Li Z ，Liu Z ，Luo G ，Xing C ，Zhang D ，Hou M ，Liu H ，Yang X ，Luo Y ，Peng X ，Wang G ，Zou T ，Zhu L ，Jin L ，Zhang X ... -  《-》

Deletion of ACTRT1 is associated with male infertility as sperm acrosomal ultrastructural defects and fertilization failure in human.

Could actin-related protein T1 (ACTRT1) deficiency be a potential pathogenic factor of human male infertility? A 110-kb microdeletion of the X chromosome, only including the ACTRT1 gene, was identified as responsible for infertility in two Chinese males with sperm showing acrosomal ultrastructural defects and fertilization failure. The actin-related proteins (e.g. ACTRT1, ACTRT2, ACTL7A, and ACTL9) interact with each other to form a multimeric complex in the subacrosomal region of spermatids, which is crucial for the acrosome-nucleus junction. Actrt1-knockout (KO) mice are severely subfertile owing to malformed sperm heads with detached acrosomes and partial fertilization failure. There are currently no reports on the association between ACTRT1 deletion and male infertility in humans. We recruited a cohort of 120 infertile males with sperm head deformations at a large tertiary hospital from August 2019 to August 2023. Genomic DNA extracted from the affected individuals underwent whole exome sequencing (WES), and in silico analyses were performed to identify genetic variants. Morphological analysis, functional assays, and ART were performed in 2022 and 2023. The ACTRT1 deficiency was identified by WES and confirmed by whole genome sequencing, PCR, and quantitative PCR. Genomic DNA of all family members was collected to define the hereditary mode. Papanicolaou staining and electronic microscopy were performed to reveal sperm morphological changes. Western blotting and immunostaining were performed to explore the pathological mechanism of ACTRT1 deficiency. ICSI combined with artificial oocyte activation (AOA) was applied for one proband. We identified a whole-gene deletion variant of ACTRT1 in two infertile males, which was inherited from their mothers, respectively. The probands exhibited sperm head deformations owing to acrosomal detachment, which is consistent with our previous observations on Actrt1-KO mice. Decreased expression and ectopic distribution of ACTL7A and phospholipase C zeta were observed in sperm samples from the probands. ICSI combined with AOA effectively solved the fertilization problem in Actrt1-KO mice and in one of the two probands. Additional cases are needed to further confirm the genetic contribution of ACTRT1 variants to male infertility. Our results reveal a gene-disease relation between the ACTRT1 deletion described here and human male infertility owing to acrosomal detachment and fertilization failure. This report also describes a good reproductive outcome of ART with ICSI-AOA for a proband. This work was supported by the Chongqing medical scientific research project (Joint project of Chongqing Health Commission and Science and Technology Bureau, 2023MSXM008 and 2023MSXM054). There are no competing interests to declare. N/A.

Zhang Q ，Jin H ，Long S ，Tang X ，Li J ，Liu W ，Han W ，Liao H ，Fu T ，Huang G ，Chen S ，Lin T ... -  《-》