Analysis Of Meiotic Recombination In Human And Chinese Muntjac

Spermotogenesis is a complex and regulated progress in mammals. During meiosis I, meiotic pairing and recombination play a crucial role in holding homologous chromosomes together and guaranteeing their accurate segregation into daughter cells. Abnormalities in the frequency and location of crossovers are associated with non-disjunction of homologous chromosomes and the production of aneuploid gametes. In the study, in order to investigate the mechanisms of meiotic recombination and the possible roles of RNAs in spermatogenesis, we done the work including three parts:1. The muntjacs (Muntiacus, Cervidae) have been extensively studied in terms of chromosomal and karyotypic evolution. However, little is known about their meiotic chromosomes particularly the recombination patterns of homologous chromosomes. Spermatocyte preparations were obtained from Chinese muntjac (Muntiacus reevesi) by a drying down spreading technique and immunostained to show synaptonemal complexes (SCs), recombination foci and kinetochores with antibodies against the SC protein SCP3, mismatch repair protein MLH1and kintochores, respectively. The mean number of MLH1foci on autosome SCs per cell was29.8, ranging from25-34.39.4%of XY bivalents lacked MLH1foci compared to less than0.5%of autosomes. The average number of MLH1foci per pachytene cell in M. reevesi was29.8. The distribution of MLH1foci differed from other mammals. On SCs with one focus, the distribution was more even in M. reevesi than in other mammals; for SCs that have two or more MLH1foci, usually there was a larger peak in the sub-centromere region than other regions on SC in M. reevesi. Additionally, there was a lower level of interference between foci in M. reevesithan in mouse or human. These observations may suggest that the regulation of homologous recombination in M. reevesiis slightly different from other mammals and will improve our understanding of the regulation of meiotic recombination, with respect to recombination frequency and position.2. Although the relationship between meiotic recombination frequency and synaptonemal complex (SC) length has been of interest for a long time, how recombination frequency is related to SC length has not been carefully explored. To address this question, we have measured the meiotic recombination frequency as represented by MLH1foci in889pachytene spermatocytes and measured the length of19,558autosomal SCs from10human males. A complex relationship between the number of MLH1foci and total autosomal SC length per cell was observed. A positive correlation with significant correlation coefficients between the two variables was found in eight of the ten donors examined, with three donors showing weak correlation, and five showing moderate correlation. Two donors who did not show any correlation between the two variables were identified for the first time. Moreover, most cells with similar total autosomal SC length showed very different number s of MLH1foci both between individuals and even within an individual, and vice versa. Our data provide the first evidence for a complex relation-ship between the recombination frequency and total length of autosomal SCs per cell in human males.3. MicroRNAs (miRNAs) are a class of small endogenous RNAs that play a regulatory role in cells by negatively affecting gene expression at transcriptional and post-transcriptional levels. There have been extensive studies aiming to discover miRNAs and to analyze their functions in cells from a variety of species. However, there are no published studies of miRNA profiles in human testis using next generation sequencing (NGS) technology. In this study, we employed Solexa sequencing technology to profile miRNAs in normal human testis. We detected770known and5novel human miRNAs, and20121piRNAs, indicating that the human testis has a complex population of small RNAs. The expression of miRNAs detected by NGS was validated by qRT-PCR of15known and5novel miRNAs. We have predicted potential target genes of the abundant known miRNAs and novel miRNAs and subjected them to GO and pathway analysis, revealing the involvement of miRNAs in many important biological functions including meiosis and p53-related pathways that are implicated in the regulation of spermatogenesis.