From the Bovine Y Chromosome to Male Fertility

The mammalian Y chromosome is unique by its presence only in males, its involvement in sex determination and male fertility, its poor conservation in gene content among mammalian lineages and its accumulation of Y-specific repeat sequences during evolution. In this presentation, I will use the bovine Y as an example to demonstrate how to get from genotype to phenotype, i.e. from the Y chromosome to male fertility. I will present four sets of data: (I) Gene content of male-specific region (MSY) in the bovine Y. A total of 28 protein-coding genes/families are present, 12 of which are single copy genes and remaining 16 are multicopy gene families. These gene families have a total of ~1270 genes, made the MSY gene density the highest in the bovine genome. (II) Copy number variation (CNV) of Y-linked genes in Holstein bulls. We found that CNVs of PRAMEY, HSFY, and ZNF280BY are associated with testicular size and semen quality. (III) Transcriptome of the bovine Y during testis development.  RNA-seq data from the bovine testis tissue at the age of 20 days, 8 months, and 2 years old revealed that 95% of the Y genes/ncRNAs are expressed predominantly in testis and may involve in spermatogenesis and male fertility.  A weighted gene co-expression network has been built. The integration of the co-expression network and the known interaction profiles resulted in a dynamic network that was used to identify functional modules/motifs in spermatogenesis based on gene ontology (GO). (IV) Role of PRAMEY in spermiogenesis. The PRAMEY protein has been confirmed to play a role in acrosome formation and fertilization.