Identification and expression analysis of Dazl homologue in Cynops cyanurus.

The Dazl (deleted in azoospermia-like) gene encodes an RNA-binding protein containing an RNA recognition motif (RRM) and a DAZ motif. Dazl is essential for gametogenesis in vertebrates. In this study, we report the cloning of Dazl cDNA from Cynops cyanurus. Ccdazl mRNA showed a germline-specific expression pattern as expected. Ccdazl expression gradually decreased during oogenesis, suggesting that it may be involved in oocyte development. Phylogenetic analysis revealed that the Ccdazl protein shares conserved motifs/domains with Dazl proteins from other species. Cloning of Ccdazl provides a new tool to carry out comparative studies of germ cell development in amphibians.

Whole-animal genome-wide RNAi screen identifies networks regulating male germline stem cells in Drosophila.

Stem cells are regulated both intrinsically and externally, including by signals from the local environment and distant organs. To identify genes and pathways that regulate stem-cell fates in the whole organism, we perform a genome-wide transgenic RNAi screen through ubiquitous gene knockdowns, focusing on regulators of adult Drosophila testis germline stem cells (GSCs). Here we identify 530 genes that regulate GSC maintenance and differentiation. Of these, we further knock down 113 selected genes using cell-type-specific Gal4s and find that more than half were external regulators, that is, from the local microenvironment or more distal sources. Some genes, for example, versatile (vers), encoding a heterochromatin protein, regulates GSC fates differentially in different cell types and through multiple pathways. We also find that mitosis/cytokinesis proteins are especially important for male GSC maintenance. Our findings provide valuable insights and resources for studying stem cell regulation at the organismal level.

The C. elegans COE transcription factor UNC-3 activates lineage-specific apoptosis and affects neurite growth in the RID lineage.

Mechanisms that regulate apoptosis in a temporal and lineage-specific manner remain poorly understood. The COE (Collier/Olf/EBF) transcription factors have been implicated in the development of many cell types, including neurons. Here, we show that the sole Caenorhabditis elegans COE protein, UNC-3, together with a histone acetyltransferase, CBP-1/P300, specifies lineage-specific apoptosis and certain aspects of neurite trajectory. During embryogenesis, the RID progenitor cell gives rise to the RID neuron and RID sister cell; the latter undergoes apoptosis shortly after cell division upon expression of the pro-apoptotic gene egl-1. We observe UNC-3 expression in the RID progenitor, and the absence of UNC-3 results in the failure of the RID lineage to express a Pegl-1::GFP reporter and in the survival of the RID sister cell. Lastly, UNC-3 interacts with CBP-1, and cbp-1 mutants exhibit a similar RID phenotype to unc-3. Thus, in addition to playing a role in neuronal terminal differentiation, UNC-3 is a cell lineage-specific regulator of apoptosis.

TRIM-9 functions in the UNC-6/UNC-40 pathway to regulate ventral guidance.

TRIpartite Motif (TRIM) family proteins are ring finger domain-containing, multi-domain proteins implicated in many biological processes. Members of the TRIM-9/C-I subfamily of TRIM proteins, including TRIM-9, MID1 and MID2, have neuronal functions and are associated with neurological diseases. To explore whether the functions of C-I TRIM proteins are conserved in invertebrates, we analyzed Caenorhabditis elegans and Drosophila trim-9 mutants. C. elegans trim-9 mutants exhibit defects in the ventral guidance of hermaphrodite specific neuron (HSN) and the touch neuron AVM. Further genetic analyses indicate that TRIM-9 participates in the UNC-6-UNC-40 attraction pathway. Asymmetric distribution of UNC-40 during HSN development is normal in trim-9 mutants. However, the asymmetric localization of MIG-10, a downstream effector of UNC-40, is abolished in trim-9 mutants. These results suggest that TRIM-9 functions upstream of MIG-10 in the UNC-40 pathway. Moreover, we showed that TRIM-9 exhibits E3 ubiquitin ligase activity in vitro and this activity is important for TRIM-9 function in vivo. Additionally, we found that Drosophila trim-9 is required for the midline attraction of a group of sensory neuron axons. Over-expression of the Netrin/UNC-6 receptor Frazzled suppresses the guidance defects in trim-9 mutants. Our study reveals an evolutionarily conserved function of TRIM-9 in the UNC-40/Frazzled-mediated UNC-6/Netrin attraction pathway.

[African origin of Chinese domestic donkeys].

Analysis of the 367 mtDNA D-loop sequences (of which 241 sequences were collected from literature) of 399 bp in 13 Chinese domestic donkey breeds revealed 96 different haplotypes with 57 polymorphic sites. The haplotype diversity and the nucleotide diversity were 0.767-0.967 and 0.014-0.032, respectively, indicating abundant genetic diversity in Chinese domestic donkeys. The Neighbor-joining tree of Chinese domestic donkey sequences was constructed with 3 Nubian wild ass sequences, 3 Somali wild ass sequences and 6 Asian wild ass sequences. Our results suggest that the maternal ancestor of Chinese domestic donkeys is highly likely to be Somali and Nubian of African wild ass instead of Asian wild ass.

[Study on mitochondrial DNA D-loop polymorphism in Chinese donkeys].

The mitochondrial DNA (mtDNA) D-loop sequences with 399 bp in 26 individuals from 5 donkey breeds in China were analyzed. Aligned by Clustal W software,the results showed that 23 polymorphic nucleotide sites and only transition with the percentage of 5.76% in 399 bp were observed. In reference to mtDNA D-loop sequences of European domestic donkey as a control, the average percentage of mtDNA D-loop nucleotide variation in 5 Chinese donkey breeds was 1.80%. The average percentages of D-loop nucleotide variation from Liangzhou donkey (LZ), Yunnan donkey (YN), Guanzhong donkey (GZ), Xinjiang donkey (XJ) and Jiami donkey (JM) were 0. 35%, 1.25%, 2.30%, 2.91% and 2.20% respectively. The average sequence divergence estimated from D-loop sequences varied from 0.25% - 5.01% within breeds and 4.51% - 5.51% among breeds, respectively, demonstrating that there existed rather abundant mitochondrial genetic diversity in Chinese donkeys. Comparisons of the 26 sequences revealed 11 mitochondrial haplotypes; the percentage of haplotype was 42.31%. This phenomenon demonstrated that the mitochondrial genetic diversity in Chinese donkey breeds is being reduced. It is urgent to protect the genetic resources of Chinese donkey. The molecular phylogenetic tree of mtDNA D-loop sequences in 5 Chinese donkey breeds,6 sequences of Asian wild ass (Equus asinus kiang, Equus asinus kulan, Equus asinus hemionus;) and 4 sequences of European domestic donkeys from GenBank was constructed by Neighbor-Joining method. It was the first time proved in molecular level that the origin of Chinese donkey breeds was from African wild ass (Equus africanus africanus and Equus africanus somaliensis), not from Asian wild ass as bescribed in the paper.