Comparative genomics approach to identify candidate genetic loci for male fertility.

The article presents multi-species, genome-wide, comparative approach to review male fertility-associated loci to contribute to the development of new genetic markers that could be of interest for functional studies and have the potential to be implemented in farm animal breeding programmes. We reviewed 835 male fertility-associated candidate loci from seven species and presented them as bovine orthologues where possible. The candidate loci were identified exploiting seven different research approaches: (i) data from animal models: mouse transgenics and knock-outs (569 genes) and random chemical mutagenesis of mouse genome (31); (ii) animal QTL (69); (iii) genes differentially expressed between fertile and subfertile phenotype in humans and mouse (95); (iv) DNA sequence variations that show specific allele-phenotype interactions (43 in human and 13 in farm animals); (v) germ line-specific small non-coding RNAs (47); (vi) testes expressed genes controlling complex differentiation process of mammalian spermatogenesis (6); and (vii) epigenetically regulated genes (4). According to the number of different research approaches reporting effects of individual genes, we selected 33 most promising candidate genes, which were further in silico analysed for expression levels in testes, genetic variability and top biological functions in functional networks. The aim of this study was to review systematically male fertility-associated candidate loci using integrated information from different study approaches and species, which will further facilitate development of novel genetic markers for selection towards improved fertility in domestic animals.