CFAP47 is a novel causative gene implicated in X-linked polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a well-described condition in which ~80% of cases have a genetic explanation, while the genetic basis of sporadic cystic kidney disease in adults remains unclear in ~30% of cases. This study aimed to identify novel genes associated with polycystic kidney disease (PKD) in patients with sporadic cystic kidney disease in which a clear genetic change was not identified in established genes. A next-generation sequencing panel analyzed known genes related to renal cysts in 118 sporadic cases, followed by whole-genome sequencing on 47 unrelated individuals without identified candidate variants. Three male patients were found to have rare missense variants in the X-linked gene Cilia And Flagella Associated Protein 47 (CFAP47). CFAP47 was expressed in primary cilia of human renal tubules, and knockout mice exhibited vacuolation of tubular cells and tubular dilation, providing evidence that CFAP47 is a causative gene involved in cyst formation. This discovery of CFAP47 as a newly identified gene associated with PKD, displaying X-linked inheritance, emphasizes the need for further cases to understand the role of CFAP47 in PKD.

A novel mutation in CFAP47 causes male infertility due to multiple morphological abnormalities of the sperm flagella

Introduction

A previous study suggested that loss of CFAP47 function is involved in multiple morphological abnormalities of the sperm flagella (MMAF) in humans and mice. However, the comprehensive role of CFAP47 in spermatogenesis is largely unknown.

Methods

Whole-exome sequencing (WES) was conducted to identify pathogenic variant in two patients with MMAF. The functional effect of the identified mutations was investigated by immunofluorescence staining and western blotting. Intracytoplasmic sperm injection (ICSI) was used to assist fertilization for the patient with MMAF.

Results

In this study, we identified a novel missense mutation (c.1414G>A; p.V472M) in CFAP47 in two unrelated patients with oligoasthenoteratozoospermia. Intriguingly, in addition to the MMAF phenotype very analogous to the previous report, the two patients notably presented abnormal morphology of sperm heads, the sperm mitochondrial sheath was obviously disorganized, and the sperm annulus were almost defective. Further functional experiments confirmed that the expression of CFAP47 was markedly reduced in the spermatozoa of the patients. Mechanism analysis suggested that CFAP47 might regulate the expression of CFAP65, CFAP69 and SEPTIN4 through their physical interactions and thus modulating sperm morphogenesis.

Conclusion

we revealed a novel mutation in CFAP47 and further expanded the phenotype and mutation spectrum of CFAP47, as well as the potential mechanism of CFAP47 manipulating spermatogenesis, finally providing important guidance for genetic counseling and targeted treatment for CFAP47 mutation-related male infertility.

WDR87 interacts with CFAP47 protein in the middle piece of spermatozoa flagella to participate in sperm tail assembly

Spermatogenesis is a complex process that includes spermatogonia self-renewal, spermatocyte meiosis and spermatozoa assembly. Recent studies have revealed that WD40-repeat domain-containing (WDR) proteins play important roles in spermatocyte division, spermatozoa flagella assembly and head shaping. In this study, we investigated the expression pattern of WDR87 and found that it was highly expressed in the testis of both humans and mice. Immunofluorescence staining revealed that mouse WDR87 was distributed in the perinuclear cytoplasm of primary spermatocytes, secondary spermatocytes and round spermatids. In the spermiogenesis stage, with extension of the nucleus, WDR87 migrated to the manchette and finally localized to the middle piece of the spermatozoa tail. Furthermore, we identified a cilia- and flagella-associated protein, CFAP47, which interacted with WDR87 in the flagellar midpiece of the spermatozoa, suggesting that WDR87 may be associated with multiple morphological abnormalities of the flagella (MMAF). Subsequently, we screened gene mutations in seven MMAF individuals and found two novel mutations in CFAP47 (c.706G>A, Val236Met; c.1337C>T, Thr446Met) in one case. Immunoblotting and immunofluorescence revealed that CFAP47 was dramatically reduced in spermatozoa from the CFAP47-mutated man. Meanwhile, the expression of WDR87 was also significantly decreased, and weak signals were detected adjacent to the spermatozoa nuclei, indicating that CFAP47 was necessary for WDR87 transportation during spermatozoa flagella biogenesis. These data indicate that WDR87 is located in the middle piece of the sperm tail and interacts with CFAP47 to form a complex which is involved in spermatozoa tail assembly.

Deleterious variants in X-linked CFAP47 induce asthenoteratozoospermia and primary male infertility

Asthenoteratozoospermia characterized by multiple morphological abnormalities of the flagella (MMAF) has been identified as a sub-type of male infertility. Recent progress has identified several MMAF-associated genes with an autosomal recessive inheritance in human affected individuals, but the etiology in approximately 40% of affected individuals remains unknown. Here, we conducted whole-exome sequencing (WES) and identified hemizygous missense variants in the X-linked CFAP47 in three unrelated Chinese individuals with MMAF. These three CFAP47 variants were absent in human control population genome databases and were predicted to be deleterious by multiple bioinformatic tools. CFAP47 encodes a cilia- and flagella-associated protein that is highly expressed in testis. Immunoblotting and immunofluorescence assays revealed obviously reduced levels of CFAP47 in spermatozoa from all three men harboring deleterious missense variants of CFAP47. Furthermore, WES data from an additional cohort of severe asthenoteratozoospermic men originating from Australia permitted the identification of a hemizygous Xp21.1 deletion removing the entire CFAP47 gene. All men harboring hemizygous CFAP47 variants displayed typical MMAF phenotypes. We also generated a Cfap47-mutated mouse model, the adult males of which were sterile and presented with reduced sperm motility and abnormal flagellar morphology and movement. However, fertility could be rescued by the use of intra-cytoplasmic sperm injections (ICSIs). Altogether, our experimental observations in humans and mice demonstrate that hemizygous mutations in CFAP47 can induce X-linked MMAF and asthenoteratozoospermia, for which good ICSI prognosis is suggested. These findings will provide important guidance for genetic counseling and assisted reproduction treatments.