Loss of perinuclear theca ACTRT1 causes acrosome detachment and severe male subfertility in mice

Abstract

The perinuclear theca (PT) is a cytoskeletal element encapsulating the sperm nucleus; however, physiological roles of PT in sperm are largely uncertain. Here, we revealed that ACTRT1, ACTRT2, ACTL7A, and ACTL9 proteins interact to form a multimeric complex and localize to the subacrosomal region of spermatids. Furthermore, we engineered Actrt1-knockout (KO) mice to define the functions of ACTRT1. Despite the normal sperm count and motility, Actrt1-KO males were severely subfertile due to a deficiency in fertilization. Loss of ACTRT1 caused a high incidence of malformed heads and detachment of acrosomes from sperm nuclei, which were caused by the loosened acroplaxome structure during spermiogenesis. Furthermore, Actrt1-KO sperm showed reduced ACTL7A and PLCζ protein content as a potential cause of fertilization defects. Moreover, we revealed that ACTRT1 anchors developing acrosomes to the nucleus, likely by interacting with the inner acrosomal membrane protein SPACA1 and the nuclear envelope proteins PARP11 and SPATA46. Loss of ACTRT1 weakened the interaction between ACTL7A and SPACA1. Our study and recent findings of ACTL7A/ACTL9-deficient sperm together reveal that the sperm PT-specific ARP complex mediates the acrosome-nucleus connection.

Testis-specific actin-like 7A (ACTL7A) is an indispensable protein for subacrosomal-associated F-actin formation, acrosomal anchoring, and male fertility

“…7A and Supplementary Fig. S7 ) despite ACTRT2 being present in the acroplaxome and implicated to be a structural component ( Zhang et al , 2022a , b ). This observation could be due to an inability to coprecipitate these proteins in the soluble fraction but may also indicate a necessity to interact in a larger complex of acroplaxome protein components.…”

“…Most recently, the depicted phenotype of peeling acrosomes has been described in humans where coding point mutations in the actin-like 7A ( ACTL7A ) ( Xin et al , 2020 ) and ACTL7C (aka ACTL9 ) ( Dai et al , 2021 ) genes have been identified as pathogenic variants of significance in cases of complete human male infertility. Additionally, separate murine studies have described the same occurrence of acrosomal instability when knocking out protein kinase Hipk4 ( Crapster et al , 2020 ), actin-related testis 1 ( Actrt1 ) ( Zhang et al , 2022b ), actin-binding protein profilin 3 ( Pfn3 ) ( Umer et al , 2021 ), actin-like 7B ( Actl7b ) ( Clement et al , 2023 ), and Actl7a ( Zhou et al , 2022 ). Given the overlapping phenotype of these mutant mouse lines, the implication is that these proteins are essential for male fertility through their shared function in acroplaxome formation, regulation, stability, and conservation in mammals including humans.…”

Identification of CFAP52 as a novel diagnostic target of male infertility with defects of sperm head-tail connection and flagella development

“…With the development of whole-exome sequencing (WES) technology, DNAH1 , CFAP43 , CFAP44 , CFAP69 , CFAP251 , ARMC2 , TTC21A , TTC29 , CFAP58 , CFAP91 , DNAH8 , CFAP47 , DNAH10 , DNAH17 , and WDR63 ( Ben et al, 2014 ; Coutton et al, 2019 ; Dong et al, 2018 ; He et al, 2020 ; Kherraf et al, 2018 ; Liu et al, 2019 ; Liu et al, 2020 ; Liu et al, 2021 ; Lu et al, 2021 ; Martinez et al, 2020 ; Tang et al, 2017 ; Tu et al, 2021 ; Wang et al, 2019 ; Zhang et al, 2020 ) have been suggested as MMAF-associated genes. Our groups have reported mutations in CFAP65 , QRICH2 , CEP78 , CEP128 , CFAP70 , and AKAP3 in Chinese patients with MMAF ( Jin et al, 2023 ; Shen et al, 2019 ; Zhang et al, 2019 ; Zhang et al, 2022a ; Zhang et al, 2022b ; Yang et al, 2020 ). However, the etiology of MMAF remains incompletely understood.…”

“…The detailed procedure of co-IP and Western blotting was described in our previous studies (Jin et al, 2023;Zhang et al, 2022a;Zhang et al, 2022b).…”

A recessive ACTL7A founder variant leads to male infertility due to acrosome detachment in Pakistani Pashtuns

“…Actin‐related proteins (Arps) are a group of proteins with amino acid sequence and basal structure similarities to conventional actins 2,3 . Recent studies reported critical roles of Arps in acrosomal biogenesis and male fertility 4–7 . Noticeably, disruption of Arp protein ACTL7A could lead to acrosomal ultrastructural abnormalities and in vitro fertilization failure, but some of the affected patients displayed normozoospermia with no obvious defects observed in routine semen analyses 4,5 .…”