A rapidly evolved domain, the SCML2 DNA-binding repeats, contributes to chromatin binding of mouse SCML2†.

Genes involved in sexual reproduction diverge rapidly as a result of reproductive fitness. Here, we identify a novel protein domain in the germline-specific Polycomb protein SCML2 that is required for the establishment of unique gene expression programs after the mitosis-to-meiosis transition in spermatogenesis. We term this novel domain, which is comprised of rapidly evolved, DNA-binding repeat units of 28 amino acids, the SCML2 DNA-binding (SDB) repeats. These repeats are acquired in a specific subgroup of the rodent lineage, having been subjected to positive selection in the course of evolution. Mouse SCML2 has two DNA-binding domains: one is the SDB repeats and the other is an RNA-binding region, which is conserved in human SCML2. For the recruitment of SCML2 to target loci, the SDB repeats cooperate with the other functional domains of SCML2 to bind chromatin. The cooperative action of these domains enables SCML2 to sense DNA hypomethylation in an in vivo chromatin environment, thereby enabling SCML2 to bind to hypomethylated chromatin. We propose that the rapid evolution of SCML2 is due to reproductive adaptation, which has promoted species-specific gene expression programs in spermatogenesis.

Clinical outcomes after IVF or ICSI using human blastocysts derived from oocytes containing aggregates of smooth endoplasmic reticulum.

In this study the clinical and neo-natal outcomes after transfer of blastocysts derived from oocytes containing aggregates of smooth endoplasmic reticulum (SER) were compared between IVF and intracytoplasmic sperm injection (ICSI) cycles. Clinical and neo-natal outcomes of blastocysts in cycles with at least one SER metaphase II oocyte (SER + MII; SER + cycles) did not significantly differ between the two insemination methods. When SER + MII were cultured to day 5/6, fertilization, embryo cleavage and blastocyst rates were not significantly different between IVF and ICSI cycles. In vitrified-warmed blastocyst transfer cycles, the clinical pregnancy rates from SER + MII in IVF and ICSI did not significantly differ. In this study, 52 blastocysts (27 IVF and 25 ICSI) derived from SER + MII were transferred, yielding 15 newborns (5 IVF and 10 ICSI) and no malformations. Moreover, 300 blastocysts (175 IVF and 125 ICSI) derived from SER-MII were transferred, yielding 55 newborns (24 IVF and 31 ICSI cycles). Thus, blastocysts derived from SER + cycles exhibited an acceptable ongoing pregnancy rate after IVF (n = 125) or ICSI (n = 117) cycles. In conclusion, blastocysts from SER + MII in both IVF and ICSI cycles yield adequate ongoing pregnancy rates with neo-natal outcomes that do not differ from SER-MII.

DNA polymerase α interacts with PrSet7 and mediates H4K20 monomethylation in Drosophila.

In human cells, appropriate monomethylation of histone H4 lysine 20 by PrSet7 (also known as SET8 and SETD7) is important for the correct transcription of specific genes and timely progression through the cell cycle. Over-methylation appears to be prevented through the interaction of PrSet7 with proliferating cell nuclear antigen (PCNA), which targets PrSet7 for destruction through the pathway mediated by CRL4(C) (dt2) (the cullin ring finger ligase-4 complex containing Cdt2). However, the factors involved in positive regulation of PrSet7 histone methylation remain undefined. Here, we present biochemical and genetic evidence for a previously undocumented interaction between Drosophila PrSet7 (dPrSet7) and DNA polymerase α in Drosophila. Depletion of the polymerase reduces H4K20 monomethylation suggesting that it is required for dPrSet7 histone methylation activity. We also show that the interaction between PCNA and PrSet7 is conserved in Drosophila, but is only detectable in chromatin fractions. Consistent with this, S2 cells show a significant loss of chromatin-bound dPrSet7 protein as S phase progresses. Based on these data we suggest that interaction with the DNA polymerase represents an important route for stimulation of PrSet7 histone methylase activity that is mediated by allowing loading of dPrSet7 onto chromatin or its subsequent activation.

Drosophila Syntrophins are involved in locomotion and regulation of synaptic morphology.

Syntrophin components of the dystrophin glycoprotein complex (DGC) feature multiple protein interaction domains that may act in molecular scaffolding, recruiting signaling proteins to membranes and the DGC. Drosophila Syntrophin-1 (Syn1) and Syntrophin-2 (Syn2) are counterparts of human alpha1/beta1/beta2-syntrophins and gamma1/gamma2-syntrophins, respectively. alpha1/beta1/beta2-syntrophins are well documented, while little is known about gamma1/gamma2-syntrophins. Here, we performed immunohistochemical analyses with a specific antibody to Syn2 and demonstrated predominant expression in the larval and adult central nervous system. To investigate the in vivo functions of Syn2, we have generated Drosophila Syn2 deficiency mutants. Although the Syn2 mutants exhibit no overt phenotype, the combination of Syn1 knockdown and Syn2(37) mutation dramatically shortened life span, synergistically reduced locomotion ability and synergistically enhanced overgrowth of neuromuscular junctions in N-ethylmaleimide sensitive factor 2 mutants. From these data we conclude that Syn1 and Syn2 are required for locomotion and are involved in regulation of synaptic morphology. In addition, the two syntrophins can at least partially compensate for each other's functions.

Syntrophin-2 is required for eye development in Drosophila.

Syntrophins are components of the dystrophin glycoprotein complex (DGC), which is encoded by causative genes of muscular dystrophies. The DGC is thought to play roles not only in linking the actin cytoskeleton to the extracellular matrix, providing stability to the cell membrane, but also in signal transduction. Because of their binding to a variety of different molecules, it has been suggested that syntrophins are adaptor proteins recruiting signaling proteins to membranes and the DGC. However, critical roles in vivo remain elusive. Drosophila Syntrophin-2 (Syn2) is an orthologue of human gamma 1/gamma 2-syntrophins. Western immunoblot analysis here showed Syn2 to be expressed throughout development, with especially high levels in the adult head. Morphological aberrations were observed in Syn2 knockdown adult flies, with lack of retinal elongation and malformation of rhabdomeres. Furthermore, Syn2 knockdown flies exhibited excessive apoptosis in third instar larvae and alterations in the actin localization in the pupal retinae. Genetic crosses with a collection of Drosophila deficiency stocks allowed us to identify seven genomic regions, deletions of which caused enhancement of the rough eye phenotype induced by Syn2 knockdown. This information should facilitate identification of Syn2 regulators in Drosophila and clarification of roles of Syn2 in eye development.

A novel Drosophila Girdin-like protein is involved in Akt pathway control of cell size.

The Akt signaling pathway is well known to regulate cell proliferation and growth. Girdin, a novel substrate of Akt, plays a crucial role in organization of the actin cytoskeleton and cell motility under the control of Akt. We here identified a novel Girdin-like protein in Drosophila (dGirdin), which has two isoforms, dGirdin PA and dGirdin PB. dGirdin shows high homology with human Girdin in the N-terminal and coiled-coil domains, while diverging at the C-terminal domain. On establishment of transgenic fly lines, featuring knockdown or overexpression of dGirdin in vivo, overexpression in the wing disc cells induced ectopic apoptosis, implying a role in directing apoptosis. Knockdown of dGirdin in the Drosophila wing imaginal disc cells resulted in reduction of cell size. Furthermore, this was enhanced by half reduction of the Akt gene dose, suggesting that Akt positively regulates dGirdin. In the wing disc, cells in which dGirdin was knocked down exhibited disruption of actin filaments. From these in vivo analyses, we conclude that dGirdin is required for actin organization and regulation of appropriate cell size under control of the Akt signaling pathway.

dGirdin a new player of Akt /PKB signaling in Drosophila Melanogaster.

A novel substrate of Akt/PKB designated as Girdin (griders of actin filaments) has been identified in mammals and characterized as an actin-binding protein. A Girdin-like protein has been identified in Drosophila, which has two isoforms, dGirdin PA and dGirdin PB. Knockdown of dGirdin in the Drosophila wing imaginal disc cells resulted in reduction of cell size and this was enhanced by half reduction of the Akt gene dose. Furthermore the dGirdin-knockdown wing disc cells exhibited severe disruption of actin filaments. From these in vivo analyses, we conclude that dGirdin is required for actin organization and regulation of appropriate cell size under control of the Akt signaling pathway. Human Girdin plays important roles in cancer progression and angiogenesis. Therefore Girdin and its interacting proteins could be potential pharmaceutical targets for cancer therapies and tumor angiogenesis. Possible use of the Drosophila Girdin model in understanding the mechanisms of cancer progression and in developing preventive and therapeutic strategies will be discussed.