WT  Lab

  Laboratory of Developmental Disorders and Toxicology

Research Interest

Disease Mechanism

Our group uses in  vivo and in vitro model to understand the developmental disease. One of our focuses is the craniofacial malformation. Development of the proper facial structure is a complex process that requires tight regulation on various signaling molecules. Gene mutation is known to cause cleft lip and/or palate (CL/ CLP). By understanding the pathogenesis of  the disease, potential gene therapy and small molecule will be identified for treatment. 

The use of glutathione to reduce oxidative stress status and its potential for modifying the extracellular matrix organization in cleft lip.  Cleft lip (CL) is a common congenital anomaly that can be syndromic or non-syndromic.  One of the characterizations in this facial malformation is the increased of reactive oxygen species (ROS). Our group hypothesizes that the antioxidant glutathione (GSH) could help to attenuate the oxidative stress in this disease. By bioinformatics analysis and RNA-sequencing of the CL in vitro model, we suggested that GSH could modulate two major families (matrix metalloproteinase and integrins), which are related to extracellular matrix modification and composition for facial development in CL. We uncovered the possible pharmacological mechanism of GSH for treating CL. (Li et al. 2021)


Pathogenesis of POLR1C-dependent Type 3 Treacher Collins Syndrome revealed by a zebrafish model.  Treacher Collins syndrome (TCS) is an autosomal-dominant craniofacial developmental syndrome that occurs in 1 out of every 50,000 live births, is characterized by craniofacial malformation. Mutations in TCOF1, POLR1C, or POLR1D have been identified in affected individuals.  Our group identified that polr1c is highly expressed in the facial region, and dysfunction of this gene by knockdown or knock-out resulted in mis-expression of neural crest cells during early development that leads to TCS phenotype. Next generation sequencing and bioinformatics analysis of the polr1c mutant further demonstrated the up-regulated p53 pathway and predicted skeletal disorders. Our group further partially rescued the TCS facial phenotype in the background of p53 mutants, which supported the hypothesis that POLR1C-dependent type 3 TCS is associated with the p53 pathway. (Lau et al. 2016; Tse. 2016)
Restoration of polr1c in Early Embryogenesis Rescues the Type 3 Treacher Collins Syndrome Facial Malformation Phenotype in Zebrafish.  Facial development depends on the neural crest cells, in which polr1c plays a role in regulating their expression. Our group has successfully  identified the functional time window of polr1c in TCS by the use of photo-morpholino to restore the polr1c expression at different time points. We suggested that the restoration of polr1c at 8 hours after fertilization could rescue the TCS facial malformation phenotype by correcting the neural crest cell expression, reducing the cell death, and normalizing the p53 mRNA expression level in the rescued morphants. However, such recovery could not be reproduced if the polr1c is restored after 30 hours after fertilization. (Kwong et al. 2017)

Deubiquitinase

Deconjugation of ubiquitin and/or ubiquitin-like modified protein substrates is essential to modulate protein-protein interactions and, thus, signaling processes in cells. Although deubiquitinase (DUBs) play a key role in this process, however, their function and regulation remain insufficiently understood. Our group performed the first genome-wide DUBs loss-of-function analysis in zebrafish, and we are now undergoing different experiments on selected DUBs to unfold their regulatory mechanisms and specific developmental functions. Most importantly, DUBs relate to various diseases, and it is now known that DUBs contribute critical roles in human cancers (Lai et al. 2020). By understanding the biochemistry of DUBs and performing the high-throughput small molecules screening in zebrafish, our group, ultimately, aims to provide potential treatments for DUBs related diseases.

Roles of DUBs in epithelial–mesenchymal transition (EMT) in cancer metastasis. Epithelial cells are held together by numerous proteins, including tight junctions, adherens junctions, and desmosomes. These cells express molecules that are associated with the epithelial state, such as E-cadherin in epithelial state, and N-cadherin in mesenchymal state. Induction of EMT induces different EMT-inducing transcription factors (EMT-TFs) such as SNAIL, SLUG, and TWIST. These factors can then inhibit the epithelial state-related genes, such as E-cadherin, and activate the mesenchymal state related genes, such as N-cadherin. Various DUBs have been shown to interact with different EMT regulators. EMT is a reversible process, and mesenchymal cells can revert to the epithelial state by undergoing mesenchymal–epithelial transition (MET). (Lai et al. 2020)

Osmoregulation

The capability of animal cells to maintain a constant cell volume is a prerequisite for cellular life. When eukaryotic cells are exposed to extracellular hypertonicity or hypotonicity (osmotic stress), they undergo rapid regulatory processes, which include restoration of the cell volume, change in the cytoskeletal architecture, and redistribution of small organic osmolytes, to maintain their cellular homeostatic status. The mechanism is particularly important in gill epithelia in fishes. Our group applies multiple omics technologies to understand the molecular issues in fish osmoregulation. 

Changes in residential gut microbiota during progressive hypotonic stress in marine medaka. Using Oryzias melastigma as a model organism to perform progressive hypotonic transfer experiments, we evaluated three conditions: seawater control (SW), SW to 50% sea water transfer (SFW), and SW to SFW to freshwater transfer (FW). Our results showed that the SFW and FW transfer groups contained higher operational taxonomic unit microbiota diversities. The dominant bacteria in all conditions constituted the phylum Proteobacteria, with the majority in the SW and SFW transfer gut comprising Vibrio at the genus level, whereas this population was replaced by Pseudomonas in the FW transfer gut. Furthermore, our data revealed that the FW transfer gut microbiota exhibited a reduced renin–angiotensin system, which is important in SW acclimation. In addition, induced detoxification and immune mechanisms were found in the FW transfer gut microbiota. The shift of the bacteria community in different osmolality environments indicated possible roles of bacteria in facilitating host acclimation.  (Lai et al. 2020)

Specific osmoregulatory adaptive responses in gill mitochondria-rich cells (MRCs) and pavement cells (PVCs) of the Japanese eel . The study identified more than 12,000 transcripts in the gill cells via the transcriptomics analysis. Remarkable differential expressed genes (DEGs) were identified in PVCs (970 transcripts) instead of MRCs (400 transcripts) in gills of fish adapted to FW or SW. Since PVCs cover more than 90 % of the gill epithelial surface, the greater change in gene expression patterns in PVCs in response to external osmolality is anticipated. In the integrity pathway analysis, 19 common biological functions were identified in PVCs and MRCs. In the enriched signaling pathways analysis, most pathways differed between PVCs and MRCs; 14 enriched pathways were identified in PVCs and 12 in MRCs. The results suggest that the osmoregulatory responses in PVCs and MRCs are cell-type specific, which supports the complementary functions of the cells in osmoregulation. (Lai et al. 2015)

Purposed model of medaka Ostf1b in modulating different effectors upon hypertonic stress. Hypertonic stress activates JNK pathway. Induction of  Ostf1b has been found in medaka gill within 6 h after hypertonic stress. Ostf1b stimulates the phosphorylation of JNK via GCK protein. Our data suggests that Ostf1b might act as a positive regulator in the hypertonic-induced JNK pathway, which the JNK phosphorylation could maintain the Ostf1b stability to sustain the activation process. In addition, knockdown or ectopic over-expression of Ostf1b alerted the transcriptional levels of different ion transporters and water channels. To summarize, Ostf1b could trigger the hypertonic response of different effectors and thus help to maintain the cell homeostasis during osmotic stress.(Tse et al. 2011)

Developmental Toxicology

Our group applies developmental biology to environmental toxicology studies. Effects of toxicants on embryogenesis can be easily being tested in zebrafish embryos. Furthermore, integrated omics approach was used to monitor the genome wide effects of the toxicants.

Triclosan (TCS) exposure impairs lipid metabolism in zebrafish embryos. Triclosan  is an active antimicrobial ingredient used in many household products, such as skin creams and toothpaste. It is produced in high volumes, and humans are directly exposed to it and dispose it on a daily basis. TCS has been found to contaminate water worldwide. We applied zebrafish model to understand the potential developmental and metabolic abnormalities caused by TCS exposure. (Ho et al. 2016)

Developmental toxicity of the common UV filter, benophenone-2, in zebrafish embryos. Benozophenone (BP) type UV filters are extensively used in the personal care products to provide protection against the harmful effects of UV radiation. Humans used these personal care products directly on skin and the chemicals will be washed away to the water system. Our group applies zebrafish model to unfold the possible developmental toxicology of this chemical. Results showed 40 μM or above BP2 exposure in zebrafish embryos for 5 days resulted in lipid accumulation in the yolk sac and facial malformation via affecting the lipid processing and the expression of cranial neural crest cells respectively. (Fong et al. 2016)