This study aimed to identify genetic causes responsible for multiple morphological abnormalities of the sperm flagella (MMAF) in the Han Chinese population. Three primary infertile males with completely immobile sperm and MMAF were enrolled. Whole-exome sequencing and Sanger sequencing were performed to identify disease-causing genes. Subsequently, morphological and ultrastructural analyses of sperm flagella were investigated. The probable impact of genetic variants on protein function was analyzed by online bioinformatic tools and immunofluorescence assay. Three patients with dynein axonemal heavy chain 1 (DNAH1) gene compound heterozygous variations were identified. DNAH1 c.7435C>T, p.R2479X and c.10757T>C, p.F3586S were identified in the patient from Family 1, c.11726_11727delCT, p.P3909fs and c.12154delC, p.L4052fs were found in the patient from Family 2, and c.10627-3C>G and c.11726_11727delCT, p.P3909fs existed in the patient from Family 3. Four of these variations have not been reported, and all the mutations showed pathogenicity by functional effect predictions. The absence of the center pair and disorganization of the fibrous sheath were present in sperm flagella at the ultrastructural level. Moreover, the expression of DNAH1 was absent in spermatozoa from the participants, validating the pathogenicity of the variants. All three couples have undergone intracytoplasmic sperm injection (ICSI), and two couples of them became pregnant after the treatment. In conclusion, the newly identified DNAH1 mutations can expand the mutational and phenotypic spectrum of MMAF genes and provide a theoretical basis for genetic diagnosis in MMAF patients. It is recommended to conduct genetic screening in male infertility patients with MMAF and provide rational genetic counseling, and ICSI might be an optimal strategy to help with fertilization and conception for patients with DNAH1 mutations.

Keywords: DNAH1; intracytoplasmic sperm injection; male infertility; MMAF; mutation

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