P-027 Absence of perinuclear theca ACTRT1 protein induces sperm head deformation and primary male infertility in humans
Authors: Zhang Q , Jin H , Long S , Tang X , Liu W , Han W , Huang G , Chen S , Lin T 
Published: June 2023

Abstract

Study question
Given that Actrt1 knockout induces teratospermia, fertilization failure and severe male infertility in mice, will ACTRT1 deficiency affect sperm morphology and male fertility in humans?

Summary answer
The ∼110 kb microdeletion of X chromosome only including ACTRT1 gene was identified inducing sperm head deformation and fertilization failure in an infertile Chinese man.

What is known already
The actin-related proteins, ACTRT1, ACTRT2, ACTL7A, and ACTL9, interact to form a multimeric complex in the sperm subacrosomal region and is vital for the attachment of acrosome to nucleus. The disruption of ACTL7A or ACTL9 have been identified to cause acrosomal detachment, total fertilization failure and male infertility in humans and mice. Actrt1-knockout mice are severely subfertile also because of malformed sperm heads with detached acrosomes and a partial deficiency in fertilization. Loss/reduced expression and/or abnormal localization of PLCζ, a well-known sperm-borne activating factor, are identified in ACTL7A/ACTL9 mutant patients as well as Actrt1-, Actl7a-, and Actl9-deficient mice.

Study design, size, duration
We recruited a cohort of 85 infertile men with teratospermia which is characterized by deformed sperm heads in the center for reproductive medicine from August 2019 to June 2022. Genomic DNA (gDNA) of patients was extracted from peripheral blood, then whole-exome sequencing and in silico analyses were performed to identify gene mutations. Morphological analysis, functional assays, and assisted reproductive therapy were performed in 2022.

Participants/materials, setting, methods
The ACTRT1 deficiency was identified by whole-exome sequencing and confirmed by whole-genome sequencing, PCR and qPCR. Family members’ gDNA was collected to define the hereditary mode. Papanicolaou-staining, scanning and transmission electronic microscopy were performed to reveal sperm morphologies. Western blot and immunostaining of spermatozoa were conducted to explore the pathological mechanism of the ACTRT1 deficiency. Intracytoplasmic sperm injection (ICSI) combined with artificial oocyte activation (AOA) was applied for the assisted reproductive therapy of ACTRT1-deletion patient.

Main results and the role of chance
We identified a whole-gene deletion mutation of ACTRT1 on Chromosome X in an infertile male with teratospermia, which was inherited from his mother. Papanicolaou-staining, scanning electronic microscopy, and transmission electronic microscopy showed the sperm head deformation owing to acrosome detachment, which mimicked the previously reported phenotype of Actrt1-knockout mice. The results of western blot and immunostaining suggested that ACTRT1 deficiency induced a down-regulated expression of ACTL7A and PLCζ proteins, but not ACTRT2, in human sperm samples. The detached acrosomes induced fertilization failure in assisted reproductive therapy of both Actrt1-knockout mice and the ACTRT1-deletion patient, which could be effectively rescued by ICSI combined with AOA.

Limitations, reasons for caution
Additional cases are needed to confirm the genetic contribution of ACTRT1 mutations to male infertility with teratospermia and fertilization failure. In addition, the proband with ACTRT1 deletion was with severe oligozoospermia and mild asthenozoospermia. The effect of ACTRT1 mutations on sperm count and motility still need more investigation.

Wider implications of the findings
Our results reveal a gene–disease relationship between ACTRT1 deficiency and human male infertility owing to teratospermia and fertilization failure. This report also describe a good fertility outcome of assisted reproductive therapy with ICSI and AOA for the ACTRT1-deficient patient.

Trial registration number
not applicable