HGNC Approved Gene Symbol: CFAP61
Cytogenetic location: 20p11.23 Genomic coordinates (GRCh38): 20:20,052,532-20,360,698 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 20p11.23 | Spermatogenic failure 84 | 620409 | Autosomal recessive | 3 |
CFAP61 is a testis-specific protein essential for sperm flagella formation and male fertility (Huang et al., 2020).
Huang et al. (2020) stated that mouse Cfap61 contains 1,230 amino acids and includes 8 alpha helices in its C-terminal region. RT-PCR analysis of mouse tissues detected Cfap61 expression specifically in testis. Cfap61 expression started 25 days after birth and continued thereafter in adult mice.
By Western blot analysis of ciliated/flagellated organs, including brain and lung, Liu et al. (2021) observed that CFAP61 is expressed mainly in the testis. In addition, no expression of Cfap61 was detected in the respiratory tract cilia of wildtype mice, and there was no significant difference in the length or in the beating of respiratory tract cilia between Cfap61 -/- and Cfap61 +/+ mice. The authors suggested that CFAP61 plays an essential role in the formation of the mammalian sperm flagellum, but is not necessary for respiratory cilia.
Gross (2023) mapped the CFAP61 gene to chromosome 20p11.23 based on an alignment of the CFAP61 sequence (GenBank BC028708) with the genomic sequence (GRCh38).
Huang et al. (2020) stated that the Cfap61 gene maps to mouse chromosome 2.
In a cohort of 101 men with infertility due to multiple morphologic abnormalities of the sperm flagella (MMAF), who were negative for mutation in known MMAF-associated genes, Liu et al. (2021) reanalyzed exome data and identified 1 man (patient PaCFAP61) who was homozygous for a splice site mutation in the CFAP61 gene (620381.0001); see SPGF84 (620409). Familial segregation was not reported; the variant was present in the gnomAD database at low minor allele frequency. Minigene assay revealed that the mutation causes skipping of exon 2 resulting in a frameshift shortly after exon 1.
By whole-exome sequencing (WES) in 3 unrelated Pakistani families with infertility due to MMAF, Ma et al. (2022) identified homozygosity for mutations in the CFAP61 gene: a 2-bp deletion (620381.0002) in 1 family, and the same nonsense mutation (R283X; 620381.0003) in 2 families. Sanger sequencing confirmed the mutations and their segregation with disease in each family. The 2-bp deletion was not found in the gnomAD database, whereas the nonsense variant was present at very low minor allele frequency.
By WES in 325 Chinese men with infertility due to oligoasthenoteratozoospermia, Hu et al. (2023) identified 2 unrelated men (F1 and F2) with compound heterozygous mutations in the CFAP61 gene (620381.0004-620381.0007). Segregation analysis was performed in family 1 and demonstrated heterozygosity for 1 of the variants in each parent. None of the mutations were found in 392 fertile Chinese men; all were present at very low minor allele frequency or not found in public variant databases.
Huang et al. (2020) found that Cfap61 -/- mice were born at the expected mendelian ratio and had normal testis size and weight, body weight, and testis mass to body mass ratio. However, Cfap61 -/- males were infertile due to multiple morphologic abnormalities of flagella (MMAF). Mutant sperm exhibited reduced number and motility as well as impaired flagellar development, with abnormal flagellar morphology including short, coiled, irregular, or absent flagella. Cfap61 localized to sperm flagella in both mouse and human, and further analysis showed that Cfap61 was required for spermatid elongation, shaping of sperm head, and development of sperm flagella.
Using the CRISPER/Cas9 system, Liu et al. (2021) generated Cfap61 -/- mice and observed that mutant males were completely infertile. Cfap61 -/- sperm lacked flagella of normal length in the lumen of the seminiferous tubules. Epididymal sections showed fewer sperm in the cauda and caput regions compared to wildtype mice, and quantification confirmed that the number of sperm collected from the epididymal cauda was significantly lower for knockout mice than wildtype mice. Acrosome morphology of Cfap61 -/- sperm appeared normal, but the formation of the tail was clearly disordered. Almost all mutant sperm exhibited short, bent, curled, thick, or missing flagella, and mutant sperm were immobile. Immunofluorescence analysis showed disordered microtubules that could not form a normal axonemal structure. Transmission electron microscopy revealed that mutant microtubules and outer dense fibers were separated from the axoneme. Evaluation of radial spoke assembly during spermiogenesis showed that Cfap61 -/- axonemes from early round spermatids appeared normal, but their structure became disordered in elongating spermatids and spermatozoa. In addition, intraflagellar transport proteins were retained in the flagellum of the elongating spermatid. However, no abnormal axoneme assembly was observed in the cilia of respiratory tract cells.
Using CRISPER/Cas9 technology, Hu et al. (2023) generated Cfap61 -/- mice. Although mutant females were fertile, mutant males fathered no offspring during a 3-month mating period. Compared to wildtype males, the mutant males showed slightly reduced daily sperm production and markedly reduced epididymal sperm counts and sperm motility. The sperm flagella of mutant mice exhibited multiple morphologic abnormalities, including coiled, short, irregular-caliber, and absent flagella. Immunofluorescence assays revealed that Cfap61 localized to the sperm axoneme in wildtype mice, whereas Cfap61 staining was almost absent from sperm flagella of Cfap61 -/- mice. TEM analysis of mutant sperm revealed that components of the sperm flagellum were disordered within the cytoplasm. Flagellar cross-sections showed hypertrophy and hyperplasia of mitochondria, and disarrangement and hyperplasia of outer dense fibers. In addition, there were central pair structural defects, and various periaxonemal microtubule components were distorted. TUNEL staining showed that apoptotic cells were more abundant in the testes of the mutant mice than wildtype mice, suggesting that increased apoptosis might be one of the reasons for the decreased sperm counts observed in the mutants.
In a man (patient PaCFAP61) with infertility due to multiple morphologic abnormalities of the sperm flagella (SPGF84; 620409), Liu et al. (2021) identified homozygosity for a splice site mutation (c.143+5G-A, NM_015585.4) in intron 1 of the CFAP61 gene. Familial segregation was not reported; the variant was present in the gnomAD database at low minor allele frequency (1.59 x 10(-5)). Minigene assay revealed that the mutation causes skipping of exon 2 resulting in a frameshift shortly after exon 1. RT-PCR and Sanger sequencing showed skipping of exon 2 with retention of intron 2, and Western blot in transfected HEK293T cells confirmed the expression of aberrant CFAP61.
In 4 brothers from a Pakistani family (family 1) with infertility due to multiple morphologic abnormalities of the sperm flagella (SPGF84; 620409), Ma et al. (2022) identified homozygosity for a 2-bp deletion (c.451_452del, NM_015585.4) in exon 6 of the CFAP1 gene, causing a frameshift predicted to result in a premature termination codon (Ile151AsnfsTer13). The mutation segregated with disease in the family and was not found in the gnomAD database. Immunofluorescence staining of a patient semen smear showed absence of CFAP61, as well as absence of another component of the calmodulin- and spoke-associated complex, CFAP251 (618146). The authors concluded that CFAP61 is essential for localization of CFAP251 in sperm flagella.
In 7 affected individuals from 2 Pakistani families (families 2 and 3) with infertility due to multiple morphologic abnormalities of the sperm flagella (SPGF84; 620409), Ma et al. (2022) identified homozygosity for a c.847C-T transition (c.847C-T, NM_015585.4) in exon 8 of the CFAP61, resulting in an arg283-to-ter (R283X) substitution. The mutation segregated with disease in the families and was not found in the gnomAD database. Immunofluorescence staining of a patient semen smear showed absence of CFAP61, as well as absence of another component of the calmodulin- and spoke-associated complex, CFAP251 (618146). The authors concluded that CFAP61 is essential for localization of CFAP251 in sperm flagella.
In a Chinese man (F1) with infertility due to oligoasthenoteratozoospermia (SPGF84; 620409), Hu et al. (2023) identified compound heterozygosity for a c.1654C-T transition (c.1654C-T, NM_015585.4) in exon 16 of the CFAP61 gene, resulting in an arg552-to-cys (R552C) substitution, and a c.2911G-A transition in exon 23, resulting in an asp971-to-asn (D971N; 620381.0005) substitution, both at highly conserved residues. The proband's parents were each heterozygous for 1 of the mutations, neither of which was found in 392 fertile Chinese men, although both were present at very low minor allele frequency in public variant databases. Immunofluorescence analysis showed that CFAP61 staining was nearly absent in patient sperm flagella.
For discussion of the c.2911G-A transition (c.2911G-A, NM_015585.4) in exon 23 of the CFAP gene, resulting in an asp971-to-asn (D971N) substitution, that was found in compound heterozygous state in a Chinese man (F1) with infertility due to oligoasthenoteratozoospermia (SPGF84; 620409) by Hu et al. (2023), see 620381.0004.
In a Chinese man (F2) with infertility due to oligoasthenoteratozoospermia (SPGF84; 620409), Hu et al. (2023) identified compound heterozygosity for a splice site mutation (c.144-2A-G, NM_015585.4) in intron 2 of the CFAP61 gene, and a c.1666G-A transition in exon 16, resulting in a gly556-to-arg (G556R; 620381.0007) substitution at a highly conserved residue. In vitro mRNA functional characterization showed that the splice site variant causes a 7-bp deletion (c.144_150delAGAAAAG) resulting in a premature termination codon (Glu49ProfsTer50). Familial segregation was not reported. Neither mutation was found in 392 fertile Chinese men; the splice site mutation was not found in public variant databases, although the missense mutation was present at very low minor allele frequency.
For discussion of the c.1666G-A transition (c.1666G-A, NM_015585.4) in exon 16 of the CFAP61 gene, resulting in a gly556-to-arg (G556R) substitution, that was found in compound heterozygous state in a Chinese man (F2) with infertility due to oligoasthenoteratozoospermia (SPGF84; 620409) by Hu et al. (2023), see 620381.0006.
Gross, M. B. Personal Communication. Baltimore, Md. 4/20/2023.
Hu, T., Meng, L., Tan, C., Luo, C., He, W.-B., Tu, C., Zhang, H., Du, J., Nie, H., Lu, G.-X., Lin, G., Tan, Y.-Q. Biallelic CFAP61 variants cause male infertility in humans and mice with severe oligoasthenoteratozoospermia. J. Med. Genet. 60: 144-153, 2023. [PubMed: 35387802] [Full Text: https://doi.org/10.1136/jmedgenet-2021-108249]
Huang, T., Yin, Y., Liu, C., Li, M., Yu, X., Wang, X., Zhang, H., Muhammad, T., Gao, F., Li, W., Chen, Z. J., Liu, H., Ma, J. Absence of murine CFAP61 causes male infertility due to multiple morphological abnormalities of the flagella. Sci. Bull. (Beijing) 65: 854-864, 2020. [PubMed: 36659204] [Full Text: https://doi.org/10.1016/j.scib.2020.01.023]
Liu, S., Zhang, J., Kherraf, Z. E., Sun, S., Zhang, X., Cazin, C., Coutton, C., Zouari, R., Zhao, S., Hu, F., Fourati Ben Mustapha, S., Arnoult, C., Ray, P. F., Liu, M. CFAP61 is required for sperm flagellum formation and male fertility in human and mouse. Development 148: dev199805, 2021. [PubMed: 34792097] [Full Text: https://doi.org/10.1242/dev.199805]
Ma, A., Zeb, A., Ali, I., Zhao, D., Khan, A., Zhang, B., Zhou, J., Khan, R., Zhang, H., Zhang, Y., Khan, I., Shah, W., Ali, H., Javed, A. R., Ma, H., Shi, Q. Biallelic variants in CFAP61 cause multiple morphological abnormalities of the flagella and male infertility. Front. Cell Dev. Biol. 9: 803818, 2022. [PubMed: 35174165] [Full Text: https://doi.org/10.3389/fcell.2021.803818]