A list of authors and their affiliations appears at the end of the paperWe present a draft genome sequence of the platypus, Ornithorhynchus anatinus. This monotreme exhibits a fascinating combination of reptilian and mammalian characters. For example, platypuses have a coat of fur adapted to an aquatic lifestyle; platypus females lactate, yet lay eggs; and males are equipped with venom similar to that of reptiles. Analysis of the first monotreme genome aligned these features with genetic innovations. We find that reptile and platypus venom proteins have been co-opted independently from the same gene families; milk protein genes are conserved despite platypuses laying eggs; and immune gene family expansions are directly related to platypus biology. Expansions of protein, non-protein-coding RNA and microRNA families, as well as repeat elements, are identified. Sequencing of this genome now provides a valuable resource for deep mammalian comparative analyses, as well as for monotreme biology and conservation.

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Eutherian spermatozoa are dependent on the environment of the proximal epididymis to complete their maturation; however, no specific epididymal factors that mediate this process have so far been identified. Here, we show that targeted disruption of the novel gene Rnase10 encoding a secreted proximal epididymal protein in the mouse results in a binding defect in spermatozoa and their inability to pass through the uterotubal junction in the female. The failure to gain the site of fertilization in the knockout spermatozoa is associated with a gradual loss of ADAM3 and ADAM6 proteins during epididymal transit. In the distal epididymis, these spermatozoa appear to lack calcium-dependent associations with the immobilizing glutinous extracellular material and are released as single, vigorously motile cells that display no tendency for head-to-head agglutination and lack affinity to the oviductal epithelium. In sperm-egg binding assay, they are unable to establish a tenacious association with the zona pellucida, yet they are capable of fertilization. Furthermore, these sperm show accelerated capacitation resulting in an overall in vitro fertilizing ability superior to that of wild-type sperm. We conclude that the physiological role of sperm adhesiveness is in the mechanism of restricted sperm entry into the oviduct rather than in sperm-egg interaction.—Krutskikh, A., Poliandri, A., Cabrera-Sharp, V., Dacheux, J. L., Poutanen, M., Huhtaniemi, I. Epididymal protein Rnase10 is required for post-testicular sperm maturation and male fertility.

Convincingly demonstrated by immunocytological methods in females of several mammalian species, relaxin has not yet been localized in the male. Immunocytologically, a related antigen was identified in adult normal boar testes using and anti- [NIH P-relaxin/HSA] antiserum free of anti HSA Abs. A strong reaction was observed in interstitial cells, a weaker but very clear one in Sertoli cells. NIH P-relaxin and HC1-acetone extracts of either corpora lutea from pregnant sows or boar testes inhibited the immunofluorescence of the reactive structures in the boar testes as well as in ovaries of pregnant sows. Ethanol-acetone precipitates from boar rete testis or caudal epididymal fluids inhibited the reaction of interstitial and Sertoli cells, but this inhibition in the sow was limited only to degenerative ovarian structures, probably due to an insufficient level of inhibiting antigen in these two seminal fluids, in contrast with the very high concentration of relaxin in luteal cells of pregnant sows. Specific immunofluorescence was observed neither in ectopic testes of adult monocryptorchid boars (contrary to scrotal testes in these same animals) nor in testes of prepuberal pigs. The specificity and meaning of these results are discussed.