Parker B Antin
Publications
PMID: 22995917;PMCID: PMC3493895;Abstract:
FGF signaling plays a pivotal role in regulating cell movements and lineage induction during gastrulation. Here we identify 44 microRNAs that are expressed in the primitive streak region of gastrula stage chicken embryos. We show that the primary effect of FGF signaling on microRNA abundance is to negatively regulate the levels of miR-let-7b, -9, -19b, -107, -130b, and -218. LIN28B inhibits microRNA processing and is positively regulated by FGF signaling. Gain- and loss-of-function experiments show that LIN28B negatively regulates the expression of miR-19b, -130b, and let-7b, whereas negative modulation of miR-9, -107, and -218 appears to be independent of LIN28B function. PredictedmRNAtargets of the FGF-regulated microRNAs are over-represented in serine/threonine and tyrosine kinase receptors, including ACVR1, ACVR2B, PDGFRA, TGFBR1, and TGFBR3. Luciferase assays show that these and other candidates are targeted by FGF-regulated microRNAs. PDGFRA,a receptor whose activity is required for cell migration through the primitive streak, is a target of miR-130b and -218 in vivo. These results identify a novel mechanism by which FGF signaling regulates gene expression by negatively modulating microRNA abundance through both LIN28B-dependent and LIN28B-independent pathways. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.
PMID: 12242713;Abstract:
Cardiac troponin T (cTNT) is a component of the troponin complex, which confers calcium sensitivity to contraction in skeletal and cardiac muscle. Although it is thought that most components of the contractile myofibril are expressed exclusively in differentiated muscle cells, we observed that mRNAs coding for cTNT were detectable in explanted late gastrula mesoderm at least 12 hr before cardiac myocyte differentiation. We therefore conducted a detailed analysis of cTNT gene expression in the early chick embryo. Whole-mount in situ hybridization studies showed that by Hamburger and Hamilton stage 5, cTNT mRNAs are detectable in lateral mesoderm and, by stage 6, are observed throughout the lateral embryonic and extraembryonic mesoderm in a distribution that is much broader than the recognized heart field. As myocardial cell differentiation commences, cTNT transcripts become progressively localized to the forming heart and, by stage 14, are completely restricted to heart muscle cells. Western blot analyses demonstrated that cTNT protein expression is under translational control, as cTNT protein is not detectable until stage 9, concomitant with myocardial cell differentiation. Removal of endoderm at stage 5 had no effect on cTNT mRNA levels, and the bone morphogenetic protein (BMP) inhibitor noggin failed to block cTNT expression, even in the heart-forming region and in cases where heart formation was inhibited. Implantation of noggin-expressing CHO cells at the anterior midline of stage 7 embryos resulted in cardia bifida. These findings demonstrate the precocious, BMP-independent expression of a gene coding for a myofibrillar protein and suggest that an additional regulatory pathway exists for activation of some cardiogenic genes. © 2002 Wiley-Liss, Inc.
Abstract:
The chicken coloboma mutation exhibits features similar to human congenital developmental malformations such as ocular coloboma, cleft-palate, dwarfism, and polydactyly. The coloboma-associated region and encoded genes were investigated using advanced genomic, genetic, and gene expression technologies. Initially, the mutation was linked to a 990 kb region encoding 11 genes; the application of the genetic and genomic tools led to a reduction of the linked region to 176 kb and the elimination of 7 genes. Furthermore, bioinformatics analyses of capture array-next generation sequence data identified genetic elements including SNPs, insertions, deletions, gaps, chromosomal rearrangements, and miRNA binding sites within the introgressed causative region relative to the reference genome sequence. Coloboma-specific variants within exons, UTRs, and splice sites were studied for their contribution to the mutant phenotype. Our compiled results suggest three genes for future studies. The three candidate genes, SLC30A5 (a zinc transporter), CENPH (a centromere protein), and CDK7 (a cyclin-dependent kinase), are differentially expressed (compared to normal embryos) at stages and in tissues affected by the coloboma mutation. Of these genes, two (SLC30A5 and CENPH) are considered high-priority candidate based upon studies in other vertebrate model systems. © 2013 Robb et al.