ZRSR1 co-operates with ZRSR2 in regulating splicing of U12-type introns in murine hematopoietic cells.

Recurrent loss-of-function mutations of spliceosome gene, ZRSR2, occur in myelodysplastic syndromes (MDS). Mutation/loss of ZRSR2 in human myeloid cells primarily causes impaired splicing of the U12-type introns. In order to further investigate the role of this splice factor in RNA splicing and hematopoietic development, we generated mice lacking ZRSR2. Unexpectedly, Zrsr2-deficient mice developed normal hematopoiesis with no abnormalities in myeloid differentiation evident in either young or ≥1-year old knockout mice. Repopulation ability of Zrsr2-deficient hematopoietic stem cells was also unaffected in both competitive and non-competitive reconstitution assays. Myeloid progenitors lacking ZRSR2 exhibited mis-splicing of U12-type introns, however, this phenotype was moderate compared to the ZRSR2-deficient human cells. Our investigations revealed that a closely related homolog, Zrsr1, expressed in the murine hematopoietic cells, but not in human cells contributes to splicing of U12-type introns. Depletion of Zrsr1 in Zrsr2 KO myeloid cells exacerbated retention of the U12-type introns, thus highlighting a collective role of ZRSR1 and ZRSR2 in murine U12-spliceosome. We also demonstrate that aberrant retention of U12-type introns of MAPK9 and MAPK14 leads to their reduced protein expression. Overall, our findings highlight that both ZRSR1 and ZRSR2 are functional components of the murine U12-spliceosome, and depletion of both proteins is required to accurately model ZRSR2-mutant MDS in mice.

A small scale expression screen identifies tissue specific markers in the Dugesia japonica strain Pek-1.

Freshwater planaria has tremendous capacity to reform the missing part of the body and therefore is considered as one of the most important model organism for regeneration study. At present, Schmidtea mediterranea and Dugesia japonica are the two major species utilized for laboratory manipulations. Dugesia japonica flatworms are widely distributed in the Far East including Cherry Valley region in the north-west area of Beijing, China. We reported here the establishment of an asexual Dugesia japonica strain Pek-1, as a suitable system for regeneration study. Using morphological, karyotypical as well as phylogenetic analyses, we confirmed that these flatworms indeed belonged to Dugesia japonica. We went on to show that the commonly used in situ probes and immunohistochemistry reagents and protocols were applicable to the Pek-1 strain. Using this strain, we carried out small scale analysis on EST, RNAi and gene expression. We identified 193 unique EST sequences and 65 of them had not been reported in planarian. By RNAi analysis, we showed that 48 genes, when down-regulated individually, had no effect on regeneration. Furthermore, we identified 3 groups of tissue specific expressing genes that were useful for cell lineage analysis. We concluded that the Dugesia japonica Pek-1 strain could be another suitable animal model to regeneration research.

A new species of haploporid (Digenea) from the South China Sea.

Megasolena dongzhaiensis n. sp. was collected from the intestine of Scatophagus argus (Linnaeus) (Perciformes: Scatophagidae) from the Dongzhai Bay (110 degrees 32'-37'E, 19 degrees 51'-20 degrees 1'N), Hainan Province, China. It resembles Megasolena acanthuri Machida and Uchida, 1991 in having larger body size, but it differs from the latter species in having an oral sucker that is larger, instead of smaller, than the acetabulum (sucker length ratio 1:0.456-0.494, and width ratio 1:0.61-0.65 in M. dongzhaiensis n. sp., as opposed to 1:1.3-1.7 in M. acanthuri). Moreover, the cuticle is spinose rather than aspinose; there is a band of circular muscle in the pharynx, and its eggs are smaller instead of larger (0.062-0.068 x 0.036-0.039 in M. dongzhaiensis n. sp., compared with 0.087-0.103 x 0.058-0.072 in M. acanthuri). Finally, the intestinal bifurcation is anterior, instead of dorsal, to the acetabulum. It resembles other species of Megasolena Linton, 1910 in having oral sucker larger than the acetabulum, and in having a circular muscle band in the oral sucker and pharynx, but it differs in having a larger body and smaller eggs. This is the first record of a Megasolena species from ray-finned fishes as well as in China.

Saccocoelium megasacculum n. sp., a new haploporid trematode from Liza carinatus in the Taiwan strait.

Saccocoelium megasacculum n. sp. (Digenea: Haploporidae) was collected from the intestine of the mugilid fish. Liza carinatus (Cuvier and Valenciennes), in the Taiwan Strait. It is the first record of Saccocoelium in China. The parasite most closely resembles Saccocoelium obesum Looss, 1902 and Saccocoelium tensum Looss, 1902 in general morphology and body size, but it is easily distinguished from them in having a larger hermaphroditic sac in relation to body size; larger eggs; smaller pharynx, testis, ovary, and vitellaria; and a uterine seminal receptacle instead of a true seminal receptacle.