Abstract: The autosomal Sry-related gene, Sox9, encodes a transcription factor, which performs an important role in testis differentiation in mammals. In several reptiles, Sox9 is differentially expressed in gonads, showing a significant upregulation during the thermo-sensitive period (TSP) at the male-promoting temperature, consistent with the idea that SOX9 plays a central role in the male pathway. However, in spite of numerous studies, it remains unclear how SOX9 functions during this event. In the present work, we developed an RNAi-based method for silencing Sox9 in an in vitro gonad culture system for the sea turtle, Lepidochelys olivacea. Gonads were dissected as soon as the embryos entered the TSP and were maintained in organ culture. Transfection of siRNA resulted in the decrease of both Sox9 mRNA and protein. Furthermore, we found coordinated expression patterns for Sox9 and the anti-Müllerian hormone gene, Amh, suggesting that SOX9 could directly or indirectly regulate Amh expression, as it occurs in mammals. These results demonstrate an in vitro method to knockdown endogenous genes in gonads from a sea turtle, which represents a novel approach to investigate the roles of important genes involved in sex determination or differentiation pathways in species with temperature-dependent sex determination.

Abstract: The pathogenesis of Myotonic Dystrophy type 1 (DM1) is linked to unstable CTG repeats in the DMPK gene which induce the mis-splicing to fetal/neonatal isoforms of many transcripts, including those involved in cellular Ca²⁺ homeostasis. Here we monitored the splicing of three genes encoding for Ca²⁺ transporters and channels (RyR1, SERCA1 and CACN1S) during maturation of primary DM1 muscle cells in parallel with the functionality of the Excitation-Contraction (EC) coupling machinery. At 15 days of differentiation, fetal isoforms of SERCA1 and CACN1S mRNA were significantly higher in DM1 myotubes compared to controls. Parallel functional studies showed that the cytosolic Ca²⁺ response to depolarization in DM1 myotubes did not increase during the progression of differentiation, in contrast to control myotubes. While we observed no differences in the size of intracellular Ca²⁺ stores, DM1 myotubes showed significantly reduced RyR1 protein levels, uncoupling between the segregated ER/SR Ca²⁺ store and the voltage-induced Ca²⁺ release machinery, parallel with induction of endoplasmic reticulum (ER) stress markers. In conclusion, our data suggest that perturbed Ca²⁺ homeostasis, via activation of ER stress, contributes to muscle degeneration in DM1 muscle cells likely representing a premature senescence phenotype.

Abstract: The Scribble protein complex genes, consisting of lethal giant larvae (Lgl), discs large (Dlg) and scribble (Scrib) genes, are components of an evolutionarily conserved genetic pathway that links the cell polarity in cells of humans and Drosophila. The tissue expression and developmental changes of the Scribble protein complex genes were documented using qRT-RCR method. The Lgl and Scrib genes could be detected in all the experimental tissues, including fat body, midgut, testis/ovary, wingdisc, trachea, malpighian tubule, hemolymph, prothoracic gland and silk gland. The Dlg gene, mainly expressed only in testis/ovary, could not be detected in prothoracic gland and hemolymph. In fat body, there were two higher expression stages of the three genes. The highest peak of the expression of the Lgl and Scrib genes in wingdisc lay at the 1st day of the 5th instar, but the Dlg gene was at 3rd day of 5th instar. The above results indicate that Scribble complex genes are involved in the process of molting and development of the wingdisc in the silkworm. This will be useful in the future for the elucidation of the detailed biological function of the three genes Scrib, Dlg and Lgl in B. mori.

Abstract: During the last few years microRNAs (miRNAs) have emerged as key mediators of post-transcriptional and epigenetic regulation of gene expression. MiRNAs targets, identified through gene expression profiling and studies in animal models, depict a scenario where miRNAs are fine-tuning metabolic pathways and genetic networks in both plants and animals. MiRNAs have shown to be differentially expressed in brain areas and alterations of miRNAs homeostasis have been recently correlated to pathological conditions of the nervous system, such as cancer and neurodegeneration. Here, we review and discuss the most recent insights into the involvement of miRNAs in the neurodegenerative mechanisms and their correlation with significant neurodegenerative disorders.

Abstract: Short Interspersed Nuclear Elements (SINEs) are non-autonomous retrotransposons that comprise a large fraction of the human genome. SINEs are demethylated in human disease, but whether SINEs become transcriptionally induced and how the resulting transcripts may affect the expression of protein coding genes is unknown. Here, we show that downregulation of the mRNA of the tumor suppressor gene BRCA1 is associated with increased transcription of SINEs and production of sense and antisense SINE small RNAs. We find that BRCA1 mRNA is post-transcriptionally down-regulated in a Dicer and Drosha dependent manner and that expression of a SINE inverted repeat with sequence identity to a BRCA1 intron is sufficient for downregulation of BRCA1 mRNA. These observations suggest that transcriptional activation of SINEs could contribute to a novel mechanism of RNA mediated post-transcriptional silencing of human genes.

Abstract: Synthesis of chromosomal DNA is initiated from multiple origins of replication in higher eukaryotes; however, little is known about these origins’ structures. We isolated the origin-derived nascent DNAs from a human repair-deficient cell line by blocking the replication forks near the origins using two different origin-trapping methods (i.e., UV- or chemical crosslinker-treatment and cell synchronization in early S phase using DNA replication inhibitors). Single-stranded DNAs (of 0.5–3 kb) that accumulated after such treatments were labeled with bromodeoxyuridine (BrdU). BrdU-labeled DNA was immunopurified after fractionation by alkaline sucrose density gradient centrifugation and cloned by complementary-strand synthesis and PCR amplification. Competitive PCR revealed an increased abundance of DNA derived from known replication origins (c-myc and lamin B2 genes) in the nascent DNA fractions from the UV-treated or crosslinked cells. Nucleotide sequences of 85 and 208 kb were obtained from the two libraries (I and II) prepared from the UV-treated log-phase cells and early S phase arrested cells, respectively. The libraries differed from each other in their G+C composition and replication-related motif contents, suggesting that differences existed between the origin fragments isolated by the two different origin-trapping methods. The replication activities for seven out of 12 putative origin loci from the early-S phase cells were shown by competitive PCR. We mapped 117 (library I) and 172 (library II) putative origin loci to the human genome; approximately 60% and 50% of these loci were assigned to the G-band and intragenic regions, respectively. Analyses of the flanking sequences of the mapped loci suggested that the putative origin loci tended to associate with genes (including conserved sites) and DNase I hypersensitive sites; however, poor correlations were found between such loci and the CpG islands, transcription start sites, and K27-acetylated histone H3 peaks.