AZFa Y Gene, DDX3Y, Evolved Novel Testis Transcript Variants in Primates with Proximal 3´UTR Polyadenylation for Germ Cell Specific Translation

Translational control is a major level of gene expression regulation in the male germ line. DDX3Y located in the AZFa region of the human Y chromosome encodes a conserved RNA helicase important for translational control at the G1-S phase of the cell cycle. In human, DDX3Y protein is expressed only in premeiotic male germ cells. In primates, DDX3Y evolved a second promoter producing novel testis-specific transcripts. Here, we show primate species-specific use of alternative polyadenylation (APA) sites for the testis-specific DDX3Y transcript variants. They have evolved first in the 3´UTRs of primate DDX3Y transcripts. A distal APA site is used for polyadenylation of DDX3Y testis transcripts in Callithrix jacchus; two proximal APAs in Macaca mulatta, in Pan trogloydates and in human. This shift corresponds with a significant increase of DDX3Y protein expression in the macaque testis and kidney tissue. In chimpanzee and human, shift to predominant use of the most proximal APA site is associated with translation of these DDX3Y transcripts in only premeiotic male germ cells. We therefore assume evolution of a positive selection process for functional DDX3Y testis transcripts in these primates to promote increase of their stability and balancing translation efficiency especially in the male germ line.

Spermatogonial Dio3 as a Potential Germ Line Sensor for Thyroid Hormone-Driven Epigenetic Inheritance

Summary Sentence: Thyroid hormone-clearing type 3 deiodinase is located in spermatogonia, where it may serve as a critical modulator of the thyroid hormone exposure of the male germ line and its epigenetic information, with implications for neurodevelopmental and endocrine disorders in subsequent generations.

HAG1 and SWI3A/B control of male germ line development in P. patens suggests conservation of epigenetic reproductive control across land plants

Key message Bryophytes as models to study the male germ line: loss-of-function mutants of epigenetic regulators HAG1 and SWI3a/b demonstrate conserved function in sexual reproduction. Abstract With the water-to-land transition, land plants evolved a peculiar haplodiplontic life cycle in which both the haploid gametophyte and the diploid sporophyte are multicellular. The switch between these phases was coined alternation of generations. Several key regulators that control the bauplan of either generation are already known. Analyses of such regulators in flowering plants are difficult due to the highly reduced gametophytic generation, and the fact that loss of function of such genes often is embryo lethal in homozygous plants. Here we set out to determine gene function and conservation via studies in bryophytes. Bryophytes are sister to vascular plants and hence allow evolutionary inferences. Moreover, embryo lethal mutants can be grown and vegetatively propagated due to the dominance of the bryophyte gametophytic generation. We determined candidates by selecting single copy orthologs that are involved in transcriptional control, and of which flowering plant mutants show defects during sexual reproduction, with a focus on the under-studied male germ line. We selected two orthologs, SWI3a/b and HAG1, and analyzed loss-of-function mutants in the moss P. patens. In both mutants, due to lack of fertile spermatozoids, fertilization and hence the switch to the diploid generation do not occur. Pphag1 additionally shows arrested male and impaired female gametangia development. We analyzed HAG1 in the dioecious liverwort M. polymorpha and found that in Mphag1 the development of gametangiophores is impaired. Taken together, we find that involvement of both regulators in sexual reproduction is conserved since the earliest divergence of land plants.

Cytogenotoxicity Assessment of Aqueous Extracts of Rauvolfia vomitoria (Apocynaceae) on the Male Germ Line Cells of the Pest Grasshopper Zonocerus variegatus (Orthoptera: Pyrgomorphidae)

Cytogenotoxic effects of aqueous extracts of Rauvolfia vomitoria Afzel (Apocynaceae) stem bark were assessed on male germ line cells of the grasshopper Zonocerus variegatus. Concentrations of 0, 10, 15 and 20 µg/ml of infused and macerated aqueous extracts of R. vomitoria were prepared and administered through injection to the grasshoppers. Grasshoppers were dissected after 72 hours of incubation and the different parameters were then evaluated. Results revealed significant (p < 0.05) reduction of the length and the width of testis follicles with increasing concentrations of the two aqueous plant extracts. Meiosis analysis revealed a significant (p < 0.05) increase in meiotic abnormalities with increasing concentrations of the two aqueous plant extracts. Infused and macerated aqueous extracts of R. vomitoria at different concentrations did not modify the karyotype of Z. variegatus. Cyclophosphamide (CP) induced chromosomes aberrations and significantly (p < 0.05) reduced the mean chromosomes complement number which ranged from 2n= 19.00 ± 0.00 (controlled individuals) to 2n= 17.60 ± 1.82 (CP treated individuals). These observations indicate that infused and macerated aqueous extracts of R. vomitoria stem bark could induced cytogenotoxicity on the germ line cells of the grasshopper Z. variegatus. These results also confirm the utilization of CP as positive control in chromosomes aberration assays on grasshoppers.

Tissue specific requirement of Drosophila Rcd4 for centriole duplication and ciliogenesis

Rcd4 is a poorly characterized Drosophila centriole component whose mammalian counterpart, PPP1R35, is suggested to function in centriole elongation and conversion to centrosomes. Here, we show that rcd4 mutants exhibit fewer centrioles, aberrant mitoses, and reduced basal bodies in sensory organs. Rcd4 interacts with the C-terminal part of Ana3, which loads onto the procentriole during interphase, ahead of Rcd4 and before mitosis. Accordingly, depletion of Ana3 prevents Rcd4 recruitment but not vice versa. We find that neither Ana3 nor Rcd4 participates directly in the mitotic conversion of centrioles to centrosomes, but both are required to load Ana1, which is essential for such conversion. Whereas ana3 mutants are male sterile, reflecting a requirement for Ana3 for centriole development in the male germ line, rcd4 mutants are fertile and have male germ line centrioles of normal length. Thus, Rcd4 is essential in somatic cells but is not absolutely required in spermatogenesis, indicating tissue-specific roles in centriole and basal body formation.

Thyroid hormone action in the developing testis: intergenerational epigenetics

Male fertility involves the successful transmission of the genetic code to the next generation. It requires appropriately timed cellular processes during testis development, adequate support of spermatogenesis by hormonal cues from the reproductive axis and cellular cross-talk between germ and somatic cells. In addition to being the vessel of the father’s genome, increasing evidence shows that the mature sperm carries valuable epigenetic information – the epigenome – that, after fecundation, influences the development of the next generation, affecting biological traits and disease susceptibility. The epigenome of the germ line is susceptible to environmental factors, including exogenous chemicals and diet, but it is also affected by endogenous molecules and pathophysiological conditions. Factors affecting testis development and the epigenetic information of the germ line are critical for fertility and of relevance to the non-genetic but heritable component in the etiology of complex conditions. Thyroid hormones are one of those factors and their action, when untimely, produces profound effects on the developing testis, affecting spermatogenesis, steroidogenesis, testis size, reproductive hormones and fertility. Altered thyroid hormone states can also change the epigenetic information of the male germ line, with phenotypic consequences for future generations. In the context of past literature concerning the consequences of altered thyroid hormone action for testis development, here we review recent findings about the pathophysiological roles of the principal determinants of testicular thyroid hormone action. We also discuss limited work on the effects of thyroid hormone on the male germ line epigenome and the implications for the intergenerational transmission of phenotypes via epigenetic mechanisms.

Form from Function, Order from Chaos in Male Germline Chromatin

Spermatogenesis requires radical restructuring of germline chromatin at multiple stages, involving co-ordinated waves of DNA methylation and demethylation, histone modification, replacement and removal occurring before, during and after meiosis. This Special Issue has drawn together papers addressing many aspects of chromatin organization and dynamics in the male germ line, in humans and in model organisms. Two major themes emerge from these studies: the first is the functional significance of nuclear organisation in the developing germline; the second is the interplay between sperm chromatin structure and susceptibility to DNA damage and mutation. The consequences of these aspects for fertility, both in humans and other animals, is a major health and social welfare issue and this is reflected in these nine exciting manuscripts.

Detailed profiles of histone modification in male germ line cells of the young and aged mice

Human epidemiological studies have shown paternal aging as one of the risks for neurodevelopmental disorders such as autism in offspring. A recent study has suggested that factors other than de novo mutations due to aging can influence biology of offspring. Here we are focusing on epigenetic alterations in sperm that can influence offspring developmental programs. In this study, we qualitatively and semi-quantitatively evaluated histone modification patterns in male germ line cells throughout spermatogenesis based on immunostaining of testes taken from young (3 months) and aged (12 months) old mice. Although localization patterns were not obviously changed between young and aged testes, some histone modification showed differences in their intensity. Among histone modifications that repress gene expression, H3K9me3 was decreased in the male germ line cells in the aged testis, while H3K27me2/3 was increased. The intensity of H3K27ac, an active mark, was relatively low in the aged testis. Interestingly, H3K27ac was detected in putative sex chromosomes of round spermatids, while other chromosomes were occupied by a repressive mark H3K27me3. Among other histone modifications that activate gene expression, H3K4me2 was drastically decreased in the male germ line cells in the aged testis. H3K79me3 was contrastingly increased and accumulated on the sex chromosomes at M-phase spermatocytes. Therefore, aging induced alterations in the amount of histone modifications, of which patterns were different in individual histone modifications. Moreover, histone modification seems to be differentially regulated by aging on the sex chromosomes and on others. These findings would help elucidate epigenetic mechanisms underlying influence of paternal aging on offspring's development.