Boule and the Evolutionary Origin of Metazoan Gametogenesis: A Grandpa's Tale

The evolution of sex remains a hotly debated topic in evolutionary biology. In particular, studying the origins of the molecular mechanisms underlying sexual reproduction and gametogenesis (its fundamental component) in multicellular eukaryotes has been difficult due to the rapid divergence of many reproductive proteins, pleiotropy, and by the fact that only a very small number of reproductive proteins specifically involved in reproduction are conserved across lineages. Consequently, during the last decade, many efforts have been put into answering the following question: did gametogenesis evolve independently in different animal lineages or does it share a common evolutionary origin in a single ancestral prototype? Among the various approaches carried out in order to solve this question, the characterization of the evolution of the DAZ gene family holds much promise because these genes encode reproductive proteins that are conserved across a wide range of animal phyla. Within this family, BOULE is of special interest because it represents the most ancestral member of this gene family (the “grandfather” of DAZ). Furthermore, BOULE has attracted most of the attention since it represents an ancient male gametogenic factor with an essential reproductive-exclusive requirement in urbilaterians, constituting a core component of the reproductive prototype. Within this context, the aim of the present work is to provide an up-to-date insight into the studies that lead to the characterization of the DAZ family members and the implications in helping decipher the evolutionary origin of gametogenesis in metazoan animals

Barcelona conference on epigenetics and cancer: 50 years of histone acetylation

The Barcelona Conference on Epigenetics and Cancer (BCEC) was held in Barcelona, Spain, on October 1 and 2 , 2014. The meeting was co-organized by the Cancer Epigenetics and Biology Program (PEBC-IDIBELL) and B·Debate, an initiative of Biocat, with the support of 'la Caixa' Foundation. The scientific committee was comprised of leading scientists in the field of epigenetics: Dr. Manel Esteller, director of PEBC-IDIBELL, Dr. Alejandro Vaquero and Dr. Esteban Ballestar, from PEBC-IDIBELL, Juan Ausió from the University of Victoria (Canada), and Marcus Buschbeck, from the Institute of Predictive and Personalized Medicine of Cancer (IMPPC), as BCEC series coordinator. This meeting was the second edition of the BCEC series, which was launched by 5 leading Barcelonan institutes to bring together leading investigators in the fields of epigenetics and chromatin research. The topics discussed during the meeting included the current challenges, opportunities, and perspectives surrounding the study of histone modifications (focusing in acetylation), chromatin structure and gene expression, and the involvement of histone acetylation in physiology and diseases, such as cancer or neurological diseases

Magnesium-dependent Association and Folding of Oligonucleosomes Reconstituted with Ubiquitinated H2A

The MgCl2-induced folding of defined 12-mer nucleosomal arrays, in which ubiquitinated histone H2A (uH2A) replaced H2A, was analyzed by quantitative agarose gel electrophoresis and analytical centrifugation. Both types of analysis showed that uH2A arrays attained a degree of compaction similar to that of control arrays in 2 mM MgCl2. These results indicate that attachment of ubiquitin to H2A has little effect on the ability of nucleosomal arrays to form higher order folded structures in the ionic conditions tested. In contrast, uH2A arrays were found to oligomerize at lower MgCl2 concentrations than control nucleosomal arrays, suggesting that histone ubiquitination may play a role in nucleosomal fiber association

Polyploidy in a Natural Population of Mussel, Mytilus Trossulus

[Abstract] We have analyzed natural polyploidy in a population of “Mytilus trossulus” from Vancouver Island (British Columbia, Canada) by means of cytogenetic techniques. Results obtained are the first reporting on this type of numerical chromosome aberrations in mussels.Natural Sciences and Engineering Research Council of Canada (NSERC); OGP0046399Xunta de Galicia; 10303B93Xunta de Galicia; 10306B9

Karyotypes and Ag-NORs of the mussels “Mytilus californianus” and “M. trossulus” from the Pacific Canadian coast

[Abstract]: The karyotypes and the nucleolus organizer regions (NORs) of “M. californianus” and “M. trossulus” from the Pacific coast are reported here for the first time. The karyotypes show seven metacentric and seven submetacentric chromosome pairs. In “M. californianus”, nucleolar organizer regions appear located in terminal position on the short arm of one metacentric chromosome pair and of one submetacentric. A third Ag-NOR is located near to the telomere region on the short arm of one submetacentric. In “M. trossulus”, Ag- NORs appear terminally located on the short arms of two metacentric chromosome pairs and on the short and long arms of one submetacentric. The comparison of the karyotypes and Ag-NORs among the species of mussels from the Pacific and European coasts shows remarkable differences.Natural Sciences and Engineering Research Council of Canada (NSERC); OGP 0046399Xunta de Galicia; 10303B93Xunta de Galicia; 10306B9

Interaction of nucleoplasmin with core histones

Nucleoplasmin is one of the most abundant proteins in Xenopus laevis oocytes, and it has been involved in the chromatin remodeling that takes place immediately after fertilization. This molecule has been shown to be responsible for the removal of the sperm-specific proteins and deposition of somatic histones onto the male pronuclear chromatin. To better understand the latter process, we have used sedimentation velocity, sedimentation equilibrium, and sucrose gradient fractionation analysis to show that the pentameric form of nucleoplasmin binds to a histone octamer equivalent consisting of equal amounts of the four core histones, H2A, H2B, H3, and H4, without any noticeable preference for any of these proteins. Removal of the histone N-terminal 'tail' domains or the major C-terminal polyglutamic tracts of nucleoplasmin did not alter these binding properties. These results indicate that interactions other than those electrostatic in nature (likely hydrophobic) also play a critical role in the formation of the complex between the negatively charged nucleoplasmin and positively charged histones. Although the association of histones with nucleoplasmin may involve some ionic interactions, the interaction process is not electrostatically driven

Transició de proteïnes nuclears i condensació de la cromatina espermiogènica : proposta d'un model ancestral de l'espermiogènesi nuclear

Revisem la correlació entre tres processos que es donen en l'espermiogènesi: a) el recanvi de proteïnes nuclears, b) el patró de condensació de la cromatina i c) l'acetilació de les histones. L'estudi s'aplica a quatre espècies que presenten transicions de proteïnes nuclears de complexitat creixent: Sparus aurata, que reté les histones en els nuclis espermàtics madurs, Dicentrarchus labrax i Monodonta turbinata, en les quals les histones són substituïdes per una proteïna molt més bàsica, i Sepia officinalis, en la qual les histones són desplaçades per una proteïna precursora que es transforma en protamina en les últimes fases de l'espermiogènesi. Els resultats indiquen que en la primera fase de l'espermiogènesi de les quatre espècies, es dóna un procés idèntic, en el qual: a) la cromatina perd l'organització de tipus somàtic i queda estructurada en grànuls de 20 nm de diàmetre i b) les histones experimenten una acetilació moderada. A partir de l'estructura granular de 20 nm, cada tipus d'espermiogènesi segueix camins diferents. En les espermàtides de S. aurata les histones es desacetilen i la cromatina es condensa definitivament. En canvi, en les altres espermiogènesis es produeixen transicions estructurals més complexes que són analitzades en el text.We study the correlation between: i) nuclear protein exchange in spermiogenic nuclei, ii) the chromatin condensation pattern, and iii) the acetylation of histones. The study is applied to four species which demonstrate an increasing complexity in nuclear protein transitions. In Sparus aurata histones remain in sperm nuclei. In Dicentrarchus labrax and Monodonta turbinata the histones are substituted by a much more basic molecules. In spermiogenesis of Sepia officinalis histones are replaced by a precursor protamine, which is transformed into the protamine in the last phases of spermiogenesis. The results indicate that in the first phase of spermiogenesis of all four species an identical process is involved, in which: i) the chromatin looses typical somatic structure and ends up organized into granules measuring 20 nm in diameter, and ii) the histones undergo a moderate acetylation

DNA content, karyotypes, and chromosomal location of 18S-5.8S-28S ribosomal loci in some species of bivalve molluscs from the Pacific Canadian coast

[Abstract]: The DNA content of 10 species of bivalve molluscs from British Columbia coast was determined by image analysis, and the karyotypes of the horse clam “Tressus capax”, the bent-nose macoma “Macoma nasuta”, and the nuttall's mahogany clam “Nuttallia nuttallii” are described here for the first time. We also have analyzed the location of rDNA loci using a 28S-5.8S-18S probe in four of these species: “Mytilus californianus”, “M. trossulus”, “Macoma nasuta” and “N. nuttallii”. Results obtained report new data about cytogenetic characteristics of bivalve molluscs.Xunta de Galicia; 10303B93Xunta de Galicia; 10306B95Natural Sciences and Engineering Research Council of Canada (NSERC); OGP 004639

Spermiogenesis and biflagellate spermatozzoon of the teleost fish Lampanyctus crocodilus (Myctophiformes, Myctophidae): ultrastructure and characterization of its sperm basic nuclear proteins

We undertook an ultrastructural study of the spermiogenesis of the lanternfish Lampanyctus crocodilus (Myctophiformes, Myctophidae) with special emphasis on the condensation of chromatin and the biochemical characterisation of its sperm nuclear basic proteins (SNBPs). The round head of the early spermatid of L. crocodilus develops into a curved conical-shaped head in the spermatozoon. Two flagella, present even in the spermatid, are inserted laterally at the convex side of the sperm head. Both flagella possess an axoneme with a 9 + 0 instead of the typical 9 + 2 axonemal structure. Mitochondria undergo a characteristic redistribution during spermiogenesis. A reduced number of them are present lying away from the centrioles at both ends of the concave side of the sperm head. During the chromatin condensation stages in spermiogenesis, fibrogranular structures with granules of 25 ± 5 and 50 ± 5 nm can be observed in the early spermatid and develop into larger granules of about 150 ± 50 nm in the middle spermatid. The latter granules coalesce during the transition to the advanced spermatid and spermatozoon giving rise to highly condensed chromatin in the sperm cell. Protamines are the main SNBPs associated with this chromatin; however, they are unusually large and correspond to the largest protamines described in fish to date. Small stoichiometric amounts of histones and other basic proteins coexist with these protamines in the spermatozoon