Dynamics of notch pathway expression during mouse testis post-natal development and along the spermatogenic cycle

Articles in International JournalsThe transcription and expression patterns of Notch pathway components (Notch 1–3, Delta1 and 4, Jagged1) and effectors (Hes1, Hes2, Hes5 and Nrarp) were evaluated (through RT-PCR and IHC) in the mouse testis at key moments of post-natal development, and along the adult spermatogenic cycle. Notch pathway components and effectors are transcribed in the testis and expressed in germ, Sertoli and Leydig cells, and each Notch component shows a specific cell-type and timewindow expression pattern. This expression at key testis developmental events prompt for a role of Notch signaling in prepubertal spermatogonia quiescence, onset of spermatogenesis, and regulation of the spermatogenic cycle

Sedimentary recycling in arc magmas: geochemical and U–Pb–Hf–O constraints on the Mesoproterozoic Suldal Arc, SW Norway

The Hardangervidda-Rogaland Block within southwest Norway is host to ~1.52 to 1.48 Ga continental building and variable reworking during the ~1.1 to 0.9 Ga Sveconorwegian orogeny. Due to the lack of geochronological and geochemical data, the timing and tectonic setting of early Mesoproterozoic magmatism has long been ambiguous. This paper presents zircon U–Pb–Hf–O isotope data combined with whole-rock geochemistry to address the age and petrogenesis of basement units within the Suldal region, located in the centre of the Hardangervidda-Rogaland Block. The basement comprises variably deformed grey gneisses and granitoids that petrologically and geochemically resemble mature volcanic arc lithologies. U–Pb ages confirm that magmatism occurred from ~1,521 to 1,485 Ma, and conspicuously lack any xenocrystic inheritance of distinctly older crust. Hafnium isotope data range from εHf(initial) +1 to +11, suggesting a rather juvenile magmatic source, but with possible involvement of late Palaeoproterozoic crust. Oxygen isotope data range from mantle-like (δ18O ~5 ‰) to elevated (~10 ‰) suggesting involvement of low-temperature altered material (e.g., supracrustal rocks) in the magma source. The Hf–O isotope array is compatible with mixing between mantle-derived material with young low-temperature altered material (oceanic crust/sediments) and older low-temperature altered material (continent-derived sediments). This, combined with a lack of xenoliths and xenocrysts, exposed older crust, AFC trends and S-type geochemistry, all point to mixing within a deep-crustal magma-generation zone. A proposed model comprises accretion of altered oceanic crust and the overlying sediments to a pre-existing continental margin, underthrusting to the magma-generation zone and remobilisation during arc magmatism. The geodynamic setting for this arc magmatism is comparable with that seen in the Phanerozoic (e.g., the Sierra Nevada and Coast Range batholiths), with compositions in the Suldal Sector reaching those of average upper continental crust. As within these younger examples, factors that drive magmatism towards the composition of the average continental crust include the addition of sedimentary material to magma source regions, and delamination of cumulate material. Underthrusting of sedimentary materials and their subsequent involvement in arc magmatism is perhaps a more widespread mechanism involved in continental growth than is currently recognised. Finally, the Suldal Arc magmatism represents a significant juvenile crustal addition to SW Fennoscandia

Genetically haploid spermatids are phenotypically diploid

Because chromosomal homologues segregate from one another during meiosis, spermatids are genetically different. Post-meiotic gene expression could lead to gametic differences, some of which might lead to preferential transmission of certain alleles over others. In both insects and mammals, however, all the cells derived from a single spermatogonial cell develop within a common syncytium formed as a result of incomplete cytokinesis at each of the mitotic and meiotic cell divisions. It has been proposed that the intercellular bridges connecting the cells, which are about 1 micron in diameter, permit the sharing of cytoplasmic constituents, thus ensuring the synchronous development of a clone of cells and gametic equivalence between haploid spermatids. By analysing the product of a transgene which is expressed exclusively in post-meiotic germ cells in hemizygous transgenic mice, we have shown that genetically distinct spermatids share the product of the transgene and hence can be phenotypically equivalent