A novel MSMB-related microprotein in the postovulatory egg coats of marsupials

<p>Abstract</p> <p>Background</p> <p>Early marsupial conceptuses differ markedly from those of eutherian mammals, especially during cleavage and early blastocyst stages of development. Additionally, in marsupials the zona pellucida is surrounded by two acellular layers, the mucoid coat and shell, which are formed from secretions from the reproductive tract.</p> <p>Results</p> <p>We report the identification of a novel postovulatory coat component in marsupials, which we call uterinesecreted microprotein (USM). USM belongs to a family of disulfide-rich microproteins of unconfirmed function that is found throughout deuterostomes and in some protostomes, and includes β-microseminoprotein (MSMB) and prostate-associated microseminoprotein (MSMP). We describe the evolution of this family in detail, including USM-related sequences in other vertebrates. The orthologue of <it>USM </it>in the tammar wallaby, <it>USM1</it>, is expressed by the endometrium with a dynamic temporal profile, possibly under the control of progesterone.</p> <p>Conclusions</p> <p>USM appears to have evolved in a mammalian ancestor specifically as a component of the postovulatory coats. By analogy with the known properties of MSMB, it may have roles in regulating sperm motility/survival or in the immune system. However, its C-terminal domain is greatly truncated compared with MSMB, suggesting a divergent function.</p

Platypus and echidna genomes reveal mammalian biology and evolution

Egg-laying mammals (monotremes) are the only extant mammalian outgroup to therians (marsupial and eutherian animals) and provide key insights into mammalian evolution1,2. Here we generate and analyse reference genomes of the platypus (Ornithorhynchus anatinus) and echidna (Tachyglossus aculeatus), which represent the only two extant monotreme lineages. The nearly complete platypus genome assembly has anchored almost the entire genome onto chromosomes, markedly improving the genome continuity and gene annotation. Together with our echidna sequence, the genomes of the two species allow us to detect the ancestral and lineage-specific genomic changes that shape both monotreme and mammalian evolution. We provide evidence that the monotreme sex chromosome complex originated from an ancestral chromosome ring configuration. The formation of such a unique chromosome complex may have been facilitated by the unusually extensive interactions between the multi-X and multi-Y chromosomes that are shared by the autosomal homologues in humans. Further comparative genomic analyses unravel marked differences between monotremes and therians in haptoglobin genes, lactation genes and chemosensory receptor genes for smell and taste that underlie the ecological adaptation of monotremes.We thank members of BGI-Shenzhen, China National GeneBank and VGP, and P. Baybayan, R. Hall and J. Howard for help carrying out the sequencing of the platypus and echidna genomes, M. Asahara for discussion, and D. Charlesworth for comments. Work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB31020000), the National Key R&D Program of China (MOST) grant 2018YFC1406901, International Partnership Program of Chinese Academy of Sciences (152453KYSB20170002), Carlsberg foundation (CF16-0663) and Villum Foundation (25900) to G.Z. Q.Z. is supported by the National Natural Science Foundation of China (31722050, 31671319 and 32061130208), Natural Science Foundation of Zhejiang Province (LD19C190001), European Research Council Starting Grant (grant agreement 677696) and start-up funds from Zhejiang University.T.H. was financed by JSPS KAKENHI grant numbers 16K18630 and 19K16241 and the Sasakawa Scientific Research Grant from the Japan Science Society. The echidna RNA-sequencing analysis was supported by H.K.’s grant from the European Research Council (615253, OntoTransEvol). This work was supported by Guangdong Provincial Academician Workstation of BGI Synthetic Genomics No. 2017B090904014 (H.Y.), Robert and Rosabel Osborne Endowment, Howard Hughes Medical Institute (E.D.J.), Rockefeller University start-up funds (E.D.J.), Intramural Research Program of the National Human Genome Research Institute, National Institutes of Health (A.R. and A.M.P.), Korea Health Technology R&D Project through the Korea Health Industry Development Institute HI17C2098 (A.R.). This work used the computational resources of BGI-Shenzhen and the NIH HPC Biowulf cluster (https://hpc.nih.gov). Animal icons are from https://www.flaticon.com/ (made by Freepik) and http://phylopic.org/

Transcriptomic analysis supports similar functional roles for the two thymuses of the tammar wallaby

Background: The thymus plays a critical role in the development and maturation of T-cells. Humans have a single thoracic thymus and presence of a second thymus is considered an anomaly. However, many vertebrates have multiple thymuses. The tammar wallaby has two thymuses: a thoracic thymus (typically found in all mammals) and a dominant cervical thymus. Researchers have known about the presence of the two wallaby thymuses since the 1800s, but no genome-wide research has been carried out into possible functional differences between the two thymic tissues. Here, we used pyrosequencing to compare the transcriptomes of a cervical and thoracic thymus from a single 178 day old tammar wallaby.Results: We show that both the tammar thoracic and the cervical thymuses displayed gene expression profiles consistent with roles in T-cell development. Both thymuses expressed genes that mediate distinct phases of T-cells differentiation, including the initial commitment of blood stem cells to the T-lineage, the generation of T-cell receptor diversity and development of thymic epithelial cells. Crucial immune genes, such as chemokines were also present. Comparable patterns of expression of non-coding RNAs were seen. 67 genes differentially expressed between the two thymuses were detected, and the possible significance of these results are discussed.Conclusion: This is the first study comparing the transcriptomes of two thymuses from a single individual. Our finding supports that both thymuses are functionally equivalent and drive T-cell development. These results are an important first step in the understanding of the genetic processes that govern marsupial immunity, and also allow us to begin to trace the evolution of the mammalian immune system

Transient role of the middle ear as a lower jaw support across mammals

Mammals articulate their jaws using a novel joint between the dentary and squamosal bones. In eutherian mammals, this joint forms in the embryo, supporting feeding and vocalisation from birth. In contrast, marsupials and monotremes exhibit extreme altriciality and are born before the bones of the novel mammalian jaw joint form. These mammals need to rely on other mechanisms to allow them to feed. Here we show that this vital function is carried out by the earlier developing, cartilaginous incus of the middle ear, abutting the cranial base to form a cranio-mandibular articulation. The nature of this articulation varies between monotremes and marsupials, with juvenile monotremes retaining a double articulation, similar to that of the fossil mammaliaform , while marsupials use a versican-rich matrix to stabilise the jaw against the cranial base. These findings provide novel insight into the evolution of mammals and the changing relationship between the jaw and ear

Genetic Sex Test for the Short-Beaked Echidna (\u3cem\u3eTachyglossus aculeatus\u3c/em\u3e)

Monotremes (echidnas and platypus) possess five X and four or five Y sex chromosomes, respectively, that evolved independently from the sex chromosomes found in therian mammals. While the platypus has obvious venomous spurs in the male, the short-beaked echidna (Tachyglossus aculeatus) lacks easily identifiable sexually dimorphic characteristics, making it difficult to sex adults out of the breeding season and almost impossible to sex juveniles or embryonic material. Here, we used restriction-site associated DNA sequencing (RADseq) to identify novel sex-specific markers in the short-beaked echidna. We identified and validated a subset of male-specific markers that can be used as a non-invasive genetic sex test for the short-beaked echidna. We also assessed how laboratory conditions, including DNA extraction protocol and number of PCR cycles, can influence the outcome of genetic sex tests. The combined use of these markers will provide a valuable toolkit for researchers, conservationists, and zoo-keepers to reliably and non-invasively determine sex in the short-beaked echidna