Biomedical subjects

Bonny Tsoi

Publications and source records attributed to Bonny Tsoi.

5 recordsLinked to original sources

PubMed2005

IFITM/Mil/fragilis family proteins IFITM1 and IFITM3 play distinct roles in mouse primordial germ cell homing and repulsion.

The family of interferon-induced transmembrane protein (Ifitm/mil/fragilis) genes encodes cell surface proteins that may modulate cell adhesion and influence cell differentiation. Mouse Ifitm1 and -3, which are expressed in primordial germ cells (PGCs), are implicated to have roles in germ cell development, but the specific functions have been unclear. Our results show that Ifitm1 activity is required for PGC transit from the mesoderm into the endoderm, and that it appears to act via a repulsive mechanism, such that PGCs avoid Ifitm1-expressing tissues. In contrast, Ifitm3, which is expressed in migratory PGCs, is sufficient to confer autonomous PGC-like homing properties to somatic cells. These guidance activities are mediated by the N-terminal extracellular domain of the specific IFITM, which cannot be substituted by that of another family member. Complex homo- and/or heterotypic intercellular interactions among various IFITMs in PGCs and neighboring cells may underpin coordinated germ cell guidance in mice.

Animals↗

PubMed2005

A conserved noncoding intronic transcript at the mouse Dnm3 locus.

A 6-kb antisense transcript (Dnm3os) contained within an intron of the mouse Dnm3 gene has been identified in a screen for genes that may be regulated by the basic helix-loop-helix transcription factor Twist during mouse development. The antisense transcript is highly conserved between vertebrate species, but does not appear to encode a protein. We show that expression of the Dnm3 and Dnm3os transcripts overlaps during embryogenesis and in adult tissues, except that Dnm3 is most highly expressed in adult brain and testis and expressed at lower levels in embryos, whereas the antisense transcript is most strongly expressed in embryos and gravid uterus. Both Dnm3 and Dnm3os are downregulated in branchial arch tissue of Twist-null embryos. The conservation and restricted expression pattern of this noncoding transcript suggest that it may perform an important function during embryonic development and further suggest a connection between the regulation of Dnm3 and this novel intronic, antisense transcript.

Animals↗

PubMed2004

A specific requirement for PDGF-C in palate formation and PDGFR-alpha signaling.

PDGF-C is a member of the platelet-derived growth factor (PDGF) family, which signals through PDGF receptor (PDGFR) alphaalpha and alphabeta dimers. Here we show that Pdgfc(-/-) mice die in the perinatal period owing to feeding and respiratory difficulties associated with a complete cleft of the secondary palate. This phenotype was less severe than that of Pdgfra(-/-) embryos. Pdgfc(-/-) Pdgfa(-/-) embryos developed a cleft face, subepidermal blistering, deficiency of renal cortex mesenchyme, spina bifida and skeletal and vascular defects. Complete loss of function of both ligands, therefore, phenocopied the loss of PDGFR-alpha function, suggesting that both PDGF-A and PDGF-C signal through PDGFR-alpha to regulate the development of craniofacial structures, the neural tube and mesodermal organs. Our results also show that PDGF-C signaling is a new pathway in palatogenesis, different from, and independent of, those previously implicated.

Abnormalities, Multiple↗

PubMed2004

Twist is required for patterning the cranial nerves and maintaining the viability of mesodermal cells.

Twist encodes a basic helix-loop-helix transcription factor that is required for normal craniofacial morphogenesis in the mouse. Loss of Twist activity in the cranial mesenchyme leads to aberrant migratory behaviour of the neural crest cells, whereas Twist-deficient neural crest cells are located in an inappropriate location in the first branchial arch and display defective osteogenic and odontogenic differentiation (Soo et al. [2002] Dev. Biol. 247:251-270). Results of the present study further show that loss of Twist impacts on the patterning of the cranial ganglia and nerves but not that of the peripheral ganglia and nerves in the trunk region of the body axis. Analyses of the expression of molecular markers of early differentiation of the paraxial mesoderm and the histogenetic potency of somites of Twist(-/-) embryos reveal that Twist-deficient somites can differentiate into muscles, cartilage, and bones, albeit less prolifically. Twist function, therefore, is not essential for mesoderm differentiation. The poor growth of the Twist-deficient somites after transplantation to the ectopic site may be attributed to reduced proliferative capacity and extensive apoptosis of the paraxial mesoderm, suggesting that Twist is required for maintaining cell proliferation and viability in the mesodermal progenitors.

Animals↗

PubMed2004

Restricted expression of ETn-related sequences during post-implantation mouse development.

In a screen for potential targets of regulation by TWIST in mouse embryos we isolated a fragment with homology to type II early transposon (ETn) and type D endogenous provirus (MusD) elements. Whole-mount in situ hybridization to E7.5-E13.5 mouse embryos reveals a tissue- and stage-specific expression pattern that contrasts with the previously reported lack of expression of ETn elements in mouse embryos beyond late gastrulation. Transcripts were detected in the epiblast at E7.5 and in the neural tube from E8.5 to E10.5. Later expression is predominantly confined to the mesodermal tissues of craniofacial structures, limb buds and somites. The tissue specificity of expression suggests tight regulation of the activity of this early transposon element during embryogenesis.

Animals↗