Comparative Transcriptomic Study On Sexual Differences In The Chinese Horseshoe Bat(Rhinolophus Sinicus)

Differences between males and females,such as morphology,behavior and physiology,are quite common in sexual organisms.Most sexual differences can be achieved by differential expression of shared genes between males and females.Males and females also show variations in behavior and physiology due to seasonal changes.These variations can also result from differential gene expression.Apart from differential gene expression,gene alternative splicing also plays an important role in sexual differences and seasonal changes.However,little is known about the relative role of differential gene expression and alternative splicing in sexual differences,and the effect of seasonal changes on differential gene expression and alternative splicing between sexes.In this study,comparative transcriptomics were conducted in Rhinolophus sinicus to investigate differential gene expression and alternative splicing between the sexes and the effects of seasonal changes on them.For this aim,we sampled female and male individuals in April and October respectively(April: 4 females and 4 males;October:3 females and 4 males).For each individual,we collected brain,cochlea and liver.By performing differential expression analysis and alternative splicing analysis based on transcriptomic data(RNA-seq)of 45 samples,I draw three main conclusions below.Firstly,consistent with previous results in birds and other mammals,differential gene expression and alternative splicing might play an important role in sexual differences in Rhinolophus sinicus.Secondly,seasonal contrast of sexual differences was observed in gene expression and alternative splicing.More differentially expressed genes(DEGs)and differentially spliced genes(DSGs)between sexes were identified in April than in October(411DEGs and 4,605 DSGs in April,while 24 DEGs and 2,158 DSGs in October).Functional enrichment analysis also revealed that DEGs and DSGs identified in different seasons were enriched into different functional categories or signal pathways.For example,DEGs identified in April were mostly involved in mitochondrial oxidative phosphorylation process,while most DEGs identified in October were associated with immune response.Although there were some DSGs overlapped between April and October,some DSGs with specific functions still were found in each season.For example,DSGs identified in April were enriched on Gene Ontology(GO)terms related to cognition and learning,while some GO terms related to female mating behavior were enriched on DSGs identified in October.Thirdly,differential gene expression and alternative splicing may play different roles in regulatory networks of sexual differences.In each tissue,we found far more DSGs than DEGs and less observed overlap than expected between DSGs and DEGs.In addition,genomic distribution patterns of DEGs and DSGs are also different(DEGs are enriched in X chromosome but DSGs are enriched in autosomes),although these enrchemnt results are not significant.In summary,this study provides some insights into the genetic basis of sexual differences and the impacts of seasonal changes on sexual differences.However,this work also has some limitations.In the future,we need to verify the conclusions of this study by increasing the sample size,including gonadal tissues,collecting samples at more time points,and using single-cell RNA-sequencing.