Study On Y Chromosome Microdeletions And Pedigree Analysis In Patients With Idiopathic Azospermia And Oligozoospermia

BackgroundAccording to World Health Organization assessment, there was average one inseven couples suffering from the reproductive barrier. In China, approximately10–15%of the reproductive-aged population is infertile. Male-specific factors havebeen implicated in approximately half of these cases. Related studies havedemonstrated that the sperm quality declined remarkably in half a century. Thespermatogenic failure has already become the most common cause for male infertility,from which about30%are genetic abnormalities, including abnormal Chromosomal,Y chromosome microdeletions and related gene mutations.In1976, Tiepolo speculated that the long arm of human Y chromosome existedgenes which control spermatogenesis, and named it azoospermia factor (AZF) region.Then it has been subdivided into3regions: AZFa region, AZFb region and AZFcregion, among which, AZFc microdeletions are now believed to be the most prevalentgenetic lesions that cause male infertility. The patients with AZFc deletions show avariable clinical and histological phenotype from azoospermia to severeoligozoospermia. Deletions of the entire AZFa region invariably result in sertoli cellonly syndrome (SCOS) and azoospermia. Deletions of the AZFb region results inspermatogenetic arrest. At present, for the choose of STSs, most laboratories are focuson the only six STSs that are recommended by the the European Academy ofAndrology (EAA) and European Molecular Genetics Quality Network (EMQN). Onthe sperm concentration, the current study was focused on azoospermia and severeoligozoospermia, it was rare for the study of less severe oligozoospermia (0<spermconcentration<1×106/ml) and moderate oligozoospermia (5×106/ml<spermconcentration<15×106/ml). The pedigrees study of Y chromosome microdeletionmainly focuses on through the assisted reproductive technology. However, to thenatural transmission the reported is rare. At the same time, because the diverse of thestudy population and geography, the variation of the inclusion criteria and testmethods, the incidence of Y chromosome microdeletion is different in disparatecountries and regions. Our study which focused on the above questions, was aim to confirm the frequency, types, modes of Y chromosome microdeletion under differentsperm concentrations in the northeast China, to investigate the deletion resource of itthrough natutally conceived and at the same time increase the screening sites todetermine the location of breakpoint and deletion mode. Finally, provide importanttheoretical and experimental basis for genetic counseling of patients with maleinfertility in the northeast china.MethodsWe evaluated1601idiopathic infertile men including1184azoospermia aged29±5years and417oligozoospermia aged29±5years, who attended the infertileclinic in the clinical hospitals of Jilin University between2008and2013. Everypatient was adopted by questionnaire survey and regular physical examination.Peripheral blood samples of the subjects were taken to examine genetic characteristicusing karyotype analysis and PCR technology, Electrochemiluminescenceimmunoassay was used to analyze reproductive hormone levels. For the deletionpatients, the pedigree study was implemented.Results1. One hundred and thirty-nine of1601patients showed Y chromosomemicrodeletions, the deletion rate was8.68%, the highest deletion rate was in0～1×106/ml group（20.83%）, Followed by azoospermia group (8.87%),1～5×106/mlgroup (8.51%) and5～15×106/ml group (1.11%). AZFc microdeletions were the mostfrequent deletion type.2. In patients with different type of Y chromosome microdeletions, thereproductive hormones show high level of FSH and LH, low level of T. Especially inpatients with AZFc and AZFb+c deletions.3. A total of26pedigrees were studied, the pedigrees of AZFa, AZFb andAZFb+c deletion were de-nove mutation ones, of which the fathers had no deletionbut their sons showed deletions in the AZF region. For the17AZFc deletion families,4cases were vertical transmission, the transmission rate was23.53%(4/17), thede-nove mutation rate was76.47%（13/17）. There was no significant differencebewteen the vertical transmission and the de-nove mutation ones.4. Through the breakpoint sequence alignment analysis, we discovered six AZFcdeletion pattern, among these the mode B was the frequency one showed absence ofsY1191, sY1291, sY152, sY254, sY255and presence of sY1161, sY1197, sY157, sY1201. The proximal and distal deletion breakpoint was located in b2and b4amplicon, respectively. It was in accordance with the homologous recombinationmechanism. In additional, we detected some special cases involving innon-homologous recombination mechanisms.5. Found2partial AZFb+c deletion patients with oligozoospermia, the proximalbreakpoint was located at amplification u1; the distal breakpoint was located in P1and P2, respectively. the deletion pattern were classified as IR4/diatalP2、IR4/diatalP1.Conclusions1. In patients with idiopathic infertility in the northeast of China, the frequencydeletion was in less severe oligozoospermia (0<sperm concentration<1×106/ml) group.the AZFc deletion was the most frequency type and the pattern of absence of sY152、sY254、sY255was the most common in the conventional detection.2. If the idiopathic infertility patients show a higher level of FSH, LH and lowerlevel of T, they need to detect Y chromosome microdeltions.3. The patients with complete AZFc deletion can naturally conceived, and theiroffsprings were vertical transmission the deletions of the fathers; the partial AZFcdeletions are associated with an increased risk of complete deletion in AZFc region.4. It is necessary to add new screening sites located in the proximal and distal ofeach AZF region, and it is helpful to evaluate the degree of spermatogenetic obstaclesand clinical treatment.