Matters of the heart

What does it take to make a heart? Even in the fruit fly, in which matters of the heart don’t extend to either pop music or pulp fiction, making a heart requires big decisions and processes of surprising complexity

Assembly of the Inner Perivitelline Layer, a Homo log of the Mammalian Zona Pellucida: An Immunohistochemical and Ultrastructural Study

The avian inner perivitelline layer (IPVL), a homologous structure to the mammalian zona pellucida, is deposited between the granulosa cells and the oocyte cell membrane during folliculogenesis. The glycoprotein meshwork of the IPVL forms a 3-dimensional matrix and possesses important functions in the fertilization process: it contributes to the binding of avian spermatozoa to the oocyte and induces acrosomal exocytosis. In contrast to the zona pellucida of mammals, the IPVL does not prevent the physiological polyspermy found in birds. Previous studies have shown that in the Japanese quail (Cotumix japonica) at least 5 glycoproteins are constituents of the IPVL (ZP1, ZP2, ZP3, ZP4, and ZPD). In this study, we investigated the spatiotennporal assembly pattern of the IPVL during folliculogenesis using immunohistochemical and ultrastructural methods. The obtained results clearly show that these glycoproteins are incorporated into the IPVL at distinct points during follicular development, supporting the hypothesis that ZP2 and ZP4 form a type of prematrix into which ZP1, ZP3, and ZPD are integrated at a later stage of development. Copyright (C) 2011 S. Karger AG, Base

Tombola, a tesmin/TSO1 family protein, regulates transcriptional activation in the Drosophila male germline and physically interacts with Always early

During male gametogenesis a developmentally regulated and cell type specific transcriptional programme is activated in primary spermatocytes to prepare for differentiation of sperm. The Drosophila aly-class meiotic arrest loci (aly, comr, achi/vis and topi) are essential for activation of transcription of many differentiation-specific genes, and several genes important for meiotic cell cycle progression, thus linking meiotic divisions to cellular differentiation during spermatogenesis. Protein interaction studies suggests that the aly-class gene products form a chromatin-associated complex in primary spermatocytes. We identify, clone and characterise a new aly-class meiotic arrest gene, tombola (tomb), which encodes a testis-specific CXC domain protein that interacts with Aly. The tomb mutant phenotype is more like aly and comr than like achi/vis or topi in terms of target gene profile and chromosome morphology. tomb encodes a chromatin-associated protein required for localisation of Aly and Comr, but not Topi, to chromatin Reciprocally, aly and comr, but not topi or achi/vis, are required to maintain the normal localisation of Tomb. tomb and aly may be components of a complex paralogous to the Drosophila dREAM/MybMuv-B and C. elegans DRM transcriptional regulatory complexes

Evolution and spermatogenesis

Sexual reproduction depends on the production of haploid gametes, and their fusion to form diploid zygotes. Here, we discuss sperm production and function in a molecular and functional evolutionary context, drawing predominantly from studies in model organisms (mice, Drosophila, Caenorhabditis elegans). We consider the mechanisms involved in establishing and maintaining a germline stem cell population in testes, as well as the factors that regulate their contribution to the pool of differentiating cells. These processes involve considerable interaction between the germline and the soma, and we focus on regulatory signalling events in a variety of organisms. The male germline has a unique transcriptional profile, including expression of many testis-specific genes. The evolutionary pressures associated with gene duplication and acquisition of testis function are discussed in the context of genome organization and transcriptional regulation. Post-meiotic differentiation of spermatids involves very dramatic changes in cell shape and acquisition of highly specialized features. We discuss the variety of sperm motility mechanisms and how various reproductive strategies are associated with the diversity of sperm forms found in animals

Mechanisms of JAK/STAT pathway negative regulation by the short coreceptor Eye Transformer/Latran

Transmembrane receptors interact with extracellular ligands to transduce intracellular signaling cascades, modulate target gene expression, and regulate processes such as proliferation, apoptosis, differentiation, and homeostasis. As a consequence, aberrant signaling events often underlie human disease. Whereas the vertebrate JAK/STAT signaling cascade is transduced via multiple receptor combinations, the Drosophila pathway has only one fulllength signaling receptor, Domeless (Dome), and a single negatively acting receptor, Eye Transformer/Latran (Et/Lat). Here we investigate the molecular mechanisms underlying Et/Lat activity. We demonstrate that Et/Lat negatively regulates the JAK/STAT pathway activity and can bind to Dome, thus reducing Dome:Dome homodimerization by creating signaling-incompetent Dome:Et/Lat heterodimers. Surprisingly, we find that Et/Lat is able to bind to both JAK and STAT92E but, despite the presence of putative cytokine-binding motifs, does not detectably interact with pathway ligands. We find that Et/Lat is trafficked through the endocytic machinery for lysosomal degradation but at a much slower rate than Dome, a difference that may enhance its ability to sequester Dome into signaling-incompetent complexes. Our data offer new insights into the molecular mechanism and regulation of Et/Lat in Drosophila that may inform our understanding of how short receptors function in other organisms