Low Level of Cystic Fibrosis Transmembrane Conductance Regulator Is Associated with Human Sperm Autophagy and Vitality

Low sperm motility is one of the main causes of male infertility. Cystic fibrosis transmembrane conductance regulator (CFTR, an anion channel protein) is related to the progressive motility of sperm. CFTR disruptor CFTRinh-172 or forskolin (FSK) in this study were used to treat human sperm separately, and the rates of sperm autophagy and progressive motility, mitochondrial membrane potential (MMP) and ATP concentration, and the expression levels of related factors were detected to explore their relationship. It was showed that sperms treated with CFTRinh-172 or FSK reduced the levels of cAMP, CFTR and PKA, but increased sperm autophagy rate, expression levels of AMPK and LC3B. However, reactive oxygen species content had no significant difference. It was indicated that low level of CFTR performed with cAMP and its downstream effectors such as PKA and AMPK to regulate mitochondrial structure and function, leading to increased autophagy rate and reduced vitality of sperm.

Tetramethylpyrazine stimulates cystic fibrosis transmembrane conductance regulator-mediated anion secretion in distal colon of rodents

AIM： To investigate the effect of tetramethylpyrazine （TMP）, an active compound from Ligustium Wollichii Franchat, on electrolyte transport across the distal colon of rodents and the mechanism involved.METHODS： The short-circuit current （Isc） technique in conjunction with pharmacological agents and specific inhibitors were used in analyzing the electrolyte transport across the distal colon of rodents. The underlying cellular signaling mechanism was investigated by radioimmunoassay analysis （RIA） and a special mouse model of cystic fibrosis.RESULTS： IMP stimulated a conoentration-dependent rise in ISCl, which was dependent on both Cl^- and HCO3^-, and inhibited by apical application of diphenylamine-2,2＇-dicarboxylic acid （DPC） and glibenclamide, but resistant to 4,4＇-diisothiocyanatostilbene-2,2＇-disulfonic acid disodium salt hydrate （DIDS）. Removal of Na^＋ from basolateral solution almost completely abolished the Isc response to TMP, but it was insensitive to apical Na^＋ replacement or apical Na^＋ channel blocker, amiloride. Pretreatment of colonic mucosa with BAPTA-AM, a membrane-permeable selective Ca2＋ chelator, did not significantly alter the TMP-induced Iso No additive effect of forskolin and 3-isobutyl-l-methylxanthine （[BMX） was observed on the TMP-induced Isc, but it was significantly reduced by a protein kinase A inhibitor, H89.RIA results showed that TMP （1 mmol/L） elicited a significant increase in cellular cAMP production, which was similar to that elicited by the adenylate cyclase activator, forskolin （10μmol/L）. The TMP-elicited Isc as well as forskolin- or IBMX-induced Isc were abolished in mice with homozygous mutation of the cystic fibrosis transmembrane conductance regulator （CFTR） presenting defective CFTR functions and secretions.CONCLUSION： TMP may stimulate cAMP-dependent and CFTR-mediated Cl^- and HCO3^- secretion. This may have implications in the future development of alternative treatment for constipation.

Emerging role of cystic fibrosis transmembrane conductance regulator- an epithelial chloride channel in gastrointestinal cancers

Cystic fibrosis transmembrane conductance regulator(CFTR), a glycoprotein with 1480 amino acids, has been well established as a chloride channel mainly expressed in the epithelial cells of various tissues and organs such as lungs, sweat glands, gastrointestinal system, and reproductive organs. Although defective CFTR leads to cystic fibrosis, a common genetic disorder in the Caucasian population, there is accumulating evidence that suggests a novel role of CFTR in various cancers, especially in gastroenterological cancers, such as pancreatic cancer and colon cancer. In this review, we summarize the emerging findings that link CFTR with various cancers, with focus on the association between CFTR defects and gastrointestinal cancers as well as the underlying mechanisms. Further study of CFTR in cancer biology may help pave a new way for the diagnosis and treatment of gastrointestinal cancers.

Cystic fibrosis transmembrane conductance regulator prevents ischemia/reperfusion induced intestinal apoptosis via inhibiting PI3K/AKT/NF-κB pathway

BACKGROUND Intestinal ischemia/reperfusion(I/R)injury is a fatal syndrome that occurs under many clinical scenarios.The apoptosis of intestinal cells caused by ischemia can cause cell damage and provoke systemic dysfunction during reperfusion.However,the mechanism of I/R-induced apoptosis remains unclear.Cystic fibrosis transmembrane conductance regulator(CFTR)is a cAMP-activated chloride channel.Few researchers have paid attention to its role in intestinal I/R injury,or the relationship between CFTR and intestinal apoptosis induced by hypoxia/reoxygenation(H/R).AIM To investigate the effects of CFTR on I/R-induced intestinal apoptosis and its underlying molecular mechanisms.METHODS An intestinal I/R injury model was established in mice with superior mesenteric artery occlusion, and Caco2 cells were subjected to H/R for the simulation of I/R in vivo.RESULTSThe results suggested that CFTR overexpression significantly increased the Caco2 cell viability anddecreased cell apoptosis induced by the H/R. Interestingly, we found that the translocation of p65,an NF-κB member, from the cytoplasm to the nucleus after H/R treatment can be reversed by theoverexpression of CFTR, the NF-κB P65 would return from the nucleus to the cytoplasm asdetermined by immunostaining. We also discovered that CFTR inhibited cell apoptosis in theH/R-treated cells, and this effect was significantly curbed by the NF-κB activator BA, AKTinhibitor GSK690693 and the PI3K inhibitor LY294002. Moreover, we demonstrated that CFTRoverexpression could reverse the decreased PI3K/AKT expression induced by the I/R treatment invivo or H/R treatment in vitro.CONCLUSIONThe results of the present study indicate that the overexpression of CFTR protects Caco2 cells fromH/R-induced apoptosis;furthermore, it also inhibits H/R-induced apoptosis through thePI3K/AKT/NF-κB signaling pathway in H/R-treated Caco2 cells and intestinal tissues.

Expression of Cystic Fibrosis Transmembrane Conductance Regulator in Rat Ovary

The protein expression of cystic fibrosis transmembrane conductance regulator （CFTR）, a cAMP-activated Cl- channel, in ovarian stimulated premature female rat ovary during a cycle of follicle development and corpus luteum formation was investigated. Animals were injected with 10 U pregnant Mare＇s serum gonadotropin （PMSG） and subsequently 10 U hCG 48 h later. Time-dependent immunohistochemistry and Western blotting experiments were performed before and 24, 48, 72 h after hCG treatment. The immunohistochemistry revealed that administration of PMSG stimulated the CFTR expression in thecal cell layer and granulosa cell layer of mature follicles 48 h post injection, coincident with the PMSG-induced peak in follicular estradiol. However, the expression of CFTR in the granulose lutein cell layer and thecal lutein cell layer was time-dependently reduced following hCG injection, in accordance with the gradually increased progestogen level during luteum corpus formation. Western blotting analysis demonstrated that rat ovarian tissue expressed the special CFTR band at 170 kD. It is concluded that cAMP-dependent Cl- channels are involved in regulation of follicle development and luteum formation.

Cystic fibrosis associated liver disease in children

Cystic fibrosis(CF)is an autosomal recessive disorder caused by mutations in the CF transmembrane conductance regulator gene.CF liver disease develops in 5%-10%of patients with CF and is the third leading cause of death among patients with CF after pulmonary disease or lung transplant complications.We review the pathogenesis,clinical presentations,complications,diagnostic evaluation,effect of medical therapies especially CF transmembrane conductance regulator modulators and liver transplantation in CF associated liver disease.

Lumacaftor/ivacaftor therapy is associated with reduced hepatic steatosis in cystic fibrosis patients

BACKGROUND Hepatic steatosis is a common form of cystic fibrosis associated liver disease(CFLD)seen in an estimated 15%-60%of patients with cystic fibrosis(CF).The pathophysiology and health implications of hepatic steatosis in cystic fibrosis remain largely unknown.In the general population,hepatic steatosis is strongly associated with insulin resistance and type 2 diabetes.Cystic fibrosis related diabetes(CFRD)impacts 40%-50%of CF adults and is characterized by both insulin insufficiency and insulin resistance.We hypothesized that patients with CFRD would have higher levels of hepatic steatosis than cystic fibrosis patients without diabetes.AIM To determine whether CFRD is associated with hepatic steatosis and to explore the impact of lumacaftor/ivacaftor therapy on hepatic steatosis in CF.METHODS Thirty patients with CF were recruited from a tertiary care medical center for this cross-sectional study.Only pancreatic insufficient patients with CFRD or normal glucose tolerance(NGT)were included.Patients with established CFLD,end stage lung disease,or persistently elevated liver enzymes were excluded.Mean magnetic resonance imaging(MRI)proton density fat fraction(PDFF)was obtained for all participants.Clinical characteristics[age,sex,body mass index,percent predicted forced expiratory volume at 1 s(FEV1),lumacaftor/ivacaftor use]and blood chemistries were assessed for possible association with hepatic steatosis.Hepatic steatosis was defined as a mean MRI PDFF>5%.Patients were grouped by diabetes status(CFRD,NGT)and cystic fibrosis transmembrane conductance regulator(CFTR)modulator use(lumacaftor/ivacaftor,no lumacaftor/ivacaftor)to determine between group differences.Continuous variables were analyzed with a Wilcoxon rank sum test and discrete variables with a Chi square test or Fisher’s exact test.RESULTS Twenty subjects were included in the final analysis.The median age was 22.3 years(11.3-39.0)and median FEV1 was 77%(33%-105%).Twelve subjects had CFRD and 8 had NGT.Nine subjects were receiving lumacaftor/ivacaftor.The median PDFF was 3.0%(0.0%-21.0%).Six subjects(30%)had hepatic steatosis defined as PDFF>5%.Hepatic fat fraction was significantly lower in patients receiving lumacaftor/ivacaftor(median,range)(2.0%,0.0%-6.4%)than in patients not receiving lumacaftor/ivacaftor(4.1%,2.7-21.0%),P=0.002.Though patients with CFRD had lower PDFF(2.2%,0.0%-14.5%)than patients with NGT(4.9%,2.4-21.0%)this did not reach statistical significance,P=0.06.No other clinical characteristic was strongly associated with hepatic steatosis.CONCLUSION Use of the CFTR modulator lumacaftor/ivacaftor was associated with significantly lower hepatic steatosis.No association between CFRD and hepatic steatosis was found in this cohort.

Cystic fibrosis-related diabetes:The unmet need

Cystic fibrosis(CF)is a common autosomal recessive disease.Life expectancy of patients with CF continues to improve mainly driven by the evolving therapies for CF-related organ dysfunction.The prevalence of CF-related diabetes(CFRD)increases exponentially as patients’age.Clinical care guidelines for CFRD from 2010,recommend insulin as the mainstay of treatment.Many patients with CFRD may not require exogenous insulin due to the heterogeneity of this clinical entity.Maintenance of euglycemia by enhancing endogenous insulin production,secretion and degradation with novel pharmacological therapies like glucagonlike peptide-1 agonist is an option that remains to be fully explored.As such,the scope of this article will focus on our perspective of glucagon-like peptide-1 receptor agonist in the context of CFRD.Other potential options such as sodiumglucose cotransporter-2 and dipeptidyl peptidase 4 inhibitors and their impact on this patient population is limited and further studies are required.

Comprehensive semen examination in patients with pancreatic-sufficient and pancreatic-insufficient cystic fibrosis

We examined a cohort of 93 cystic fibrosis(CF)male patients who were pancreatic-sufficient(PS-CF;n=40)or pancreatic-insufficient(PI-CF;n=53).Complex semen examination was performed,including standard semen analysis,quantitative karyological analysis(QKA)of immature germ cells(IGCs),transmission electronic microscopy(TEM),biochemical analysis,and sperm DNA fragmentation by terminal deoxynucleotidyl transferase-mediated dUTP nickend labeling(TUNEL)assay.Azoospermia was diagnosed in 83(89.2%)patients.The other 10(10.8%)patients were found to be nonazoospermic and showed various spermatological diagnoses(asthenozoospermia,n=2;asthenoteratozoospermia,n=3;oligoasthenozoospermia,n=1;oligoasthenoteratozoospermia,n=3;and normozoospermia,n=1)with no specific morphological abnormalities.Oligospermia was detected in 89.2%azoospermic and 30.0%nonazoospermic patients.Low seminal pH(<7.0)was found in 74(89.2%)of 83 azoospermic patients.Moderate leukocytospermia(2.0×10^(6)-2.2×10^(6)ml^(-1))was revealed in 2.4%azoospermic and 40.0%nonazoospermic semen samples.The signs of partial meiotic arrest at prophase I were found in 4 of 6 nonazoospermic patients examined by QKA of IGCs.The content of fructose and citrate was low in oligospermic and normal in nonoligospermic semen samples.An increased percentage(>30%)of spermatozoa with noncondensed(“immature”)chromatin was revealed in 2 of 6 nonazoospermic semen samples analyzed by TEM.

The susceptibility of T5-TG12 of theCFTR gene in chronic bronchitis occurrence in a Chinese population in Jiangsu province,China

Mutations in the cystic fibrosis transmembrane conductance regulator （CFTR） gene have been implicated in the onset of cystic fibrosis and other clinical respiratory disorders. In the present study, we investigated the role of CFTR variations, poly-T, TG-repeats, and M470V in susceptibility to bronchial asthma and chronic bronchitis in a Chinese population in Jiangsu province, China. A total of 72 bronchial asthma patients, 68 chronic bronchitis pa- tients, and 117 healthy subjects were included in this study. The Tn-TGm haplotype was sequenced and the CFTR variant M470V was detected using restriction fragment length polymorphism （RFLP）. We found that the fre- quency of TS-TG12-V470 in chronic bronchitis patients was 0.07%, which was notably higher than that in healthy subjects （0.01%） and bronchial asthma patients （0.04%）. Thus, the presence of the TS-TG12 haplotype of the CFTR gene is likely to play a role in the development and progression of respiratory conditions, such as chronic bronchitis.

Identification of the second CFTR mutation in patients with congenital bilateral absence of vas deferens undergoing ART protocols

Congenital bilateral absence of vas deferens （CBAVD） is a manifestation of the mildest form of cystic fibrosis （CF） and is characterized by obstructive azoospermia in otherwise healthy patients. Owing to the availability of assisted reproductive technology, CBAVD patients can father children. These fathers are at risk of transmitting a mutated allele of the CF transmembrane conductance regulator （CFTR） gene, responsible for CF, to their offspring. The identification of mutations in both CFTR alleles in CBAVD patients is a crucial requirement for calculating the risk of producing a child with full-blown CF if the female partner is a healthy CF carrier. However, in the majority of CBAVD patients, conventional mutation screening is not able to detect mutations in both CFTR alleles, and this difficulty hampers the execution of correct genetic counselling. To obtain information about the most represented CFTR mutations in CBAVD patients, we analysed 23 CBAVD patients, 15 of whom had a single CFTR mutation after screening for 36 mutations and the 5T allele. The search for the second CFTR mutation in these cases was performed by using a triplex approach： （i） first, a reverse dot-blot analysis was performed to detect mutations with regional impact; （ii） next, multiple ligation-dependent probe amplification assays were conducted to search for large rearrangements; and （iii） finally, denaturing high-performance liquid chromatography was used to search for point mutations in the entire coding region. Using these approaches, the second CFTR mutation was detected in six patients, which increased the final detection rate to 60.8%.

Interference with the formation of the epididymal microenvironment——a new strategy for male contraception?

The cystic fibrosis transmembrane conductance regulator (CFIR) or the small conductance cAMP-activated chlo-ride channel encoded by the CFTR gene has been shown to play an important role in the formation of the epididymalfluid microenvironment. Recent work in our laboratory has shown that this protein is also expressed by developing germcells indicating a role of this protein in spermatogenesis. In view of the fact that the CFTR gene has a far reaching andwidespread effect on human reproduction, understanding the role of CFTR in the male reproductive tissues and its inter-vention by pharmacological agents can open a new avenue of research into the development of novel male contracep-tives. (Asian J Androl 2000; 2: 39 - 45 )

Synthesis and Characterization of A Small Molecule CFTR Chloride Channel Inhibitor

A thiazolidinone CFTR inhibitor(CFTR_ inh-172 ) was synthesized by a three-step procedure with trifluromethylaniline as the starting material. The synthesized CFTR inhibitor was characterized structurally by means of 1H NMR and functionally in a CFTR-expressing cell line FRT/hCFTR/EYFP-H148Q by both fluorescent and electrophysiological methods. A large amount(100 g) of high-quality small molecule thiazolidinone CFTR chloride channel inhibitor,CFTR_ inh-172 ,can be produced with this simple three-step synthetic procedure. The structure of the final product 2-thioxo-3-(3-trifluromethylphenyl)-5-[4-carboxyphenyl- methylene]-4-thiazolidinone was confirmed by 1H NMR. The overall yield was 58% with a purity over 99% as analyzed by HPLC. The synthesized CFTR_ inh-172 specifically inhibited CFTR chloride channel function in a cell-based fluorescence assay( K _d≈1.5 μmol/L) and in a Ussing chamber-based short-circuit current assay( K _d≈0.2 μmol/L),indicating better quality than that of the commercial combinatorial compound. The synthesized inhibitor is nontoxic to cultured cells at a high concentration and to mouse at a high dose. The synthetic procedure developed here can be used to produce a large amount of the high-quality CFTR_ inh-172 suitable for antidiarrheal studies and for creation of cystic fibrosis models in large animals. The procedure can be used to synthesize radiolabled CFTR_ inh-172 for in vivo pharmacokinetics studies.

Activation of CFTR-mediated Cl^- Transport by Capsaicinoids in Cell Culture Model

Previous studies reported that capsaicin potentiates AF508 mutant cystic fibrosis transmembrane conductance regulator（CFTR） channel gating defect by transfected cell-based assays. It has been postulated that orally ingested capsaicin may conceptually be used to develop a therapeutic strategy to treat gastrointestinal disorders in CF patients. We tried to reproduce and extend those pre-clinical data of previous studies. Cell-based fluorescence func- tional measurements in Fischer thyroid epithelial cells（FRT） expressing CFTR showed no effect of capsaicin on potentiating AF508-CFTR, while genistein showed a strongly positive activity. Studies show that capsaicin and dihy- drocapsaicin activated cAMP-prestimulated wild-type CFTR in a dose-dependent manner with a maximal response of 70% of that activated by genistein, thus gave an apparent EC50 of （40.4±6.8）μmol/L and （150.2±7.4） μtmol/L respectively. Preliminary study shows that the binding sites for capsaicin and dihydrocapsaicin may be probably partially overlapped with that for genistein because the maximal activation of wild-type CFTR with genistein is partially blocked by caosaicin and dihydrocapsaicin.

Ginkgolide C Stimulates CFTR-mediate Anion Conductance in Distal Colon:Implication for Therapy of Gastrointestinal Diseases

The effects and the mechanisms of natural compounds ginkgolides on CFTR-mediate anion transport were investigated. The CFTR-mediate iodide influx rates were studied via a cell-based fluorescence assay done for FRT cells stably transfected by CFTR; transepithelial short-circuit current recordings of FRT cells and rat distal colon mucosa were respectively obtained. Cellular cAMP concentrations were measured via a radioimmunoassay analysis kit. Ginkgolide C dose-dependently increases CFTR-mediate anion transport, whereas ginkgolide A and B show no effect. The activation is sensitive to CFTR specific activator CFTRinh-172. Ginkgolide C stimulated amiloride and indomethacin pre-treated Cl currents in rat distal colon mucosa. Studies on FRT cells also manifest that ginkgolide C had additive effect with FSK/IBMX mixture and didn＇t elevate intracellular cAMP concentration, which implies it works through a direct binding mechanism. In conclusion, Ginkgolide C directly stimulates CFTR-mediate anion transport. Ginkgolide C may be a promising drug for the prevention and treatment of CFTR-related diseases such as idiopathic chronic pancreatitis（ICP）, habitual constipation, and kcratoconjunctivitis sicca（KCS）.

Identification of Herbal Compound Imperatorin with Adverse Effects on ANO1 and CFTR Chloride Channels

Calcium-activated chloride channels（CaCCs） are the crucial regulators of transepithelial fluid secretion, smooth muscle contraction and sensory transduction. Recently, compelling evidence has indicated that TMEM16A（ANO1 or anoctamin-1） is a bona fide calcium-acvtivated chloride channel. A few small molecule CaCCs regulators are available for functional and therapeutic studies. We screened 126 natural compounds from Chinese herbs. Screening was performed with an iodide influx assay in Fischer rat thyroid epithelial cells to coexpress ANO1 and an iodide-sensitive fluorescent indicator（EYFP-H148Q/I152L）. Imperatorin, a coumarin compound, was identified to inhibit ANO1-mediated chloride transport activated by multiple calcium-elevating agonists. The inhibitory effect is dose-dependent with IC50～14.63 μmol/L. Interestingly, imperatorin activated CFTR chloride channel with EC50～35.52 μmol/L. The adverse effects of imperatorin on CaCC and CFTR chloride channels will make it useful in pharmacological dissection of chloride transport in airway and intestinal epithelium. Further studies are required to evaluate the therapeutic effects of imperatorin on hypertension, asthma and certain tumors.

Activation of G551D-CFTR by Bicyclooctane Compounds Is cAMP-dependent and Exhibits Low Sensitivity to Thiazolidinone CFTR Inhibitor CFTRinh-172

The G551D-CFTR mutation causing cystic fibrosis(CF) results from a missense mutation at codon 551(G551D) in the gene encoding of the cystic fibrosis transmembrane conductance regulator(CFTR). The G551D mutation in CFTR results in a reduced functional channel but G551D-CFTR is appropriately inserted in the apical membrane. In previous studies we discovered a class of high-affinity bicyclooctane(BCO) G551D-CFTR activators(G551D_ BCOs) with K_d down to 1 μmol/L. In this study, we analyzed the pharmacological activation of G551D-CFTR by the G551D_ BCOs by means of short circuit current analysis and cell-based fluorescence quenching assay. The G551D_ BCOs-induced G551D-CFTR activation is cAMP-dependent and is less sensitive to thiazolidinone CFTR inhibitor CFTRinh-172. These data suggest that (1) the phosphorylation of G551D-CFTR by protein kinase A is required for the activation by G551D_ BCOs; (2) G551D_ BCOs and CFTRinh-172 may act at the same site on the G551D-CFTR molecule.

Direct Activation of CFTR Chloride Channel by Natural Compound Theophylline

Theophylline has been widely used in the＇treatment of airway disease but molecular mechanism has not been clearly elucidated. Previous studies have manifested that theophylline increases intracellular cAMP concentra- tion. Because cystic fibrosis transmembrane conductance regulator（CFTR） is a cAMP-dependent Cl- channel that plays key roles in fluid secretion in vivo, we postulated that theophylline activates CFTR channel gating. We found （1） theophylline stimulated CFTR-mediated anion transport in a concentration-dependent manner, and CFTR specific blocker completely reversed the effect; （2） theophylline had no effect on △F508 or G551D mutant CFTR chloride channel activity; （3） theophylline had additive effect with forskolin（FSK） and 3-isobutyl-xanthin（IBMX）, thus a direct binding activation mechanism was suggested. In conclusion, the results may provide a clue to elucidating the molecular mechanism of theophylline activities and theophylline may present a novel lead drug in treating CFTR-related disease.

Identification of CFTR Gene Mutations in Chinese Patients with Congenital Obstructive Azoospermia

ve To analyze the frequency and hot spot of CFTR gene mutations in Chinese patients with congenital obstructive azoospermia

Identification of risk genes in Chinese nonobstructive azoospermia patients based on whole-exome sequencing

Nonobstructive azoospermia(NOA)is a severe condition in infertile men,and increasing numbers of causative genes have been identified during the last few decades.Although certain causative genes can explain the presence of NOA in some patients,a proportion of NOA patients remain to be addressed.This study aimed to investigate potential high-risk genes associated with spermatogenesis in idiopathic NOA patients by whole-exome sequencing.Whole-exome sequencing was performed in 46 male patients diagnosed with NOA.First,screening was performed for 119 genes known to be related to male infertility.Next,further screening was performed to determine potential high-risk causative genes for NOA by comparisons with 68 healthy male controls.Finally,risk genes with high/specific expression in the testes were selected and their expression fluctuations during spermatogenesis were graphed.The frequency of cystic fibrosis transmembrane conductance regulator(CFTR)gene pathogenic variant carriers was higher in the NOA patients compared with the healthy controls.Potential risk genes that may be causes of NOA were identified,including seven genes that were highly/specifically expressed in the testes.Four risk genes previously reported to be involved in spermatogenesis(MutS homolog 5[MSH5],cilia-and flagella-associated protein 54[CFAP54],MAP7 domain containing 3[MAP7D3],and coiled-coil domain containing 33[CCDC33])and three novel risk genes(coiled-coil domain containing 168[CCDC168],chromosome 16 open reading frame 96[C16orf96],and serine protease 48[PRSS48])were identified to be highly or specifically expressed in the testes and significantly different in the 46 NOA patients compared with 68 healthy controls.This study on clinical NOA patients provides further evidence for the four previously reported risk genes.The present findings pave the way for further functional investigations and provide candidate risk genes for genetic diagnosis of NOA.