A cytological revisit on parthenogenetic Artemia and the deficiency of a meiosis-specific recombinase DMC1 in the possible transition from bisexuality to parthenogenesis.

Although parthenogenesis is widespread in nature and known to have close relationships with bisexuality, the transitional mechanism is poorly understood. Artemia is an ideal model to address this issue because bisexuality and "contagious" obligate parthenogenesis independently exist in its congeneric members. In the present study, we first performed chromosome spreading and immunofluorescence to compare meiotic processes of Artemia adopting two distinct reproductive ways. The results showed that, unlike conventional meiosis in bisexual Artemia, meiosis II in parthenogenic Artemia is entirely absent and anaphase I is followed by a single mitosis-like equational division. Interspecific comparative transcriptomics showed that two central molecules in homologous recombination (HR), Dmc1 and Rad51, exhibited significantly higher expression in bisexual versus parthenogenetic Artemia. qRT-PCR indicated that the expression of both genes peaked at the early oogenesis and gradually decreased afterward. Knocking-down by RNAi of Dmc1 in unfertilized females of bisexual Artemia resulted in a severe deficiency of homologous chromosome pairing and produced univalents at the middle oogenesis stage, which was similar to that of parthenogenic Artemia, while in contrast, silencing Rad51 led to no significant chromosome morphological change. Our results indicated that Dmc1 is vital for HR in bisexual Artemia, and the deficiency of Dmc1 may be correlated with or even possibly one of core factors in the transition from bisexuality to parthenogenesis.

Downregulation of a CT10 regulator of kinase (Crk) promotes the formation of diapause embryos in the brine shrimp Artemia.

To survive under harsh environments, embryonic development of Artemia was arrested at the gastrula stage and released as the diapause embryo. Cell cycle and metabolism were highly suppressed in this state of quiescence. However, cellular mechanisms underlying diapause remain largely unclear. In this study, we found that the expression level of a CT10 regulator of kinase-encoding gene (Ar-Crk) in diapause embryos was significantly lower than non-diapause embryos at the early embryogenetic stage of Artemia. Knockdown of Ar-Crk by RNA interference induced formation of diapause embryos, while the control group produced nauplii. Western blot analysis and metabolic assays revealed that the diapause embryos produced by Ar-Crk-knocked-down Artemia had similar characteristics of diapause markers, arrested cell cycle, and suppressed metabolism with those diapause embryos produced by natural oviparous Artemia. Transcriptomic analysis of Artemia embryos revealed knockdown of Ar-Crk induced downregulation of the aurora kinase A (AURKA) signaling pathway, as well as energetic and biomolecular metabolisms. Taken together, we proposed that Ar-Crk is a crucial factor in determining the process of diapause in Artemia. Our results provide insight into the functions of Crk in fundamental regulations such as cellular quiescence.

Identification and characterization of the Doublesex gene and its mRNA isoforms in the brine shrimp Artemia franciscana.

Doublesex (DSX) proteins are members of the Doublesex/mab-3-related (DMRT) protein family and play crucial roles in sex determination and differentiation among the animal kingdom. In the present study, we identified two Doublesex (Dsx)-like mRNA isoforms in the brine shrimp Artemia franciscana (Kellogg 1906), which are generated by the combination of alternative promoters, alternative splicing and alternative polyadenylation. The two transcripts exhibited sex-biased enrichment, which we termed AfrDsxM and AfrDsxF. They share a common region which encodes an identical N-terminal DNA-binding (DM) domain. RT-qPCR analyses showed that AfrDsxM is dominantly expressed in male Artemia while AfrDsxF is specifically expressed in females. Expression levels of both isoforms increased along with the developmental stages of their respective sexes. RNA interference with dsRNA showed that the knockdown of AfrDsxM in male larvae led to the appearance of female traits including an ovary-like structure in the original male reproductive system and an elevated expression of vitellogenin. However, silencing of AfrDsxF induced no clear phenotypic change in female Artemia. These results indicated that the male AfrDSXM may act as inhibiting regulator upon the default female developmental mode in Artemia. Furthermore, electrophoretic mobility shift assay analyses revealed that the unique DM domain of AfrDSXs can specifically bind to promoter segments of potential downstream target genes like AfrVtg. These data show that AfrDSXs play crucial roles in regulating sexual development in Artemia, and further provide insight into the evolution of sex determination/differentiation in sexual organisms.

A Case of Complete Remission from Advanced Gastric Adenocarcinoma with Synchronous Liver Metastasis in Response to EOX Chemotherapy.

Gastric cancer is a malignant tumor with a high degree of malignancy. Multiple liver metastases from gastric cancer (LMGCs) are common. However, the treatment of LMGCs is very difficult. It is rare to achieve complete remission (CR) and long-term survival after treatment. We present the case of a patient with gastric adenocarcinoma and multiple liver metastases who showed CR for more than 33 months after perioperative EOX (epirubicin, oxaliplatin, and capecitabine) combination chemotherapy with radical distal gastrectomy and resection of liver metastases. The patient is still in follow-up without tumor recurrence. These findings suggest that LMGC does not necessarily mean a poor prognosis; preoperative chemotherapy combined with surgery may be a good treatment option for LMGC in selected patients. Further studies are needed to support this treatment approach.

catena-Poly[[[tetra-aqua-iron(II)]-µ-5,5'-diazenediylditetra-zolido] dihydrate].

In the title compound, {[Fe(C(2)N(10))(H(2)O)(4)]·2H(2)O}(n), the coordin-ation geometry around the Fe(II) atom, which lies on a center of inversion, is distorted octa-hedral, with bonds to four O atoms and two N atoms. The azotetra-zolate ligand displays a bridging coordination mode, forming an infinite zigzag chain. Inter-molecular O-H⋯O and O-H⋯N hydrogen bonding and offset face-to-face π-π stacking inter-actions [centroid-centroid distance = 3.4738 (13) Å] lead to a three-dimensional network.

Tetra-aqua-bis-(1,10-phenanthroline-κN,N')strontium 5,5'-diazene-diyl-ditetra-zolide.

The title complex, [Sr(C(12)H(8)N(2))(2)(H(2)O)(4)](C(2)N(10)), contains an [Sr(phen)(2)(H(2)O)(4)](2+) cation (phen is 1,10-phenanthroline) and a 5,5'-diazenediylditetra-zolide anion (site symmetry 2). The Sr(2+) cation (site symmetry 2) is coordinated by four N atoms from two chelating phen and four water mol-ecules. In the crystal structure, the water mol-ecules and the N atoms in the tetra-zolide rings form an extensive range of O-H⋯N hydrogen bonds which link the complex into a two-dimensional structure. An adjacent layer further yields a three-dimensional supramolecular network by offset face-to-face π-π stacking inter-actions of the phen ligands [with centroid-centroid distances of 3.915 (2) and 4.012 (2) Å]. The two bridging N atoms of the anion are equally disordered about the twofold rotation axis.