Biology subjects

Waxman, J. S.

Publications and source records attributed to Waxman, J. S..

4 recordsLinked to original sources

bioRxiv2024

A Foxf1-Wnt-Nr2f1 cascade promotes atrial cardiomyocyte differentiation in zebrafish

Nr2f transcription factors (TFs) are conserved regulators of vertebrate atrial cardiomyocyte (AC) differentiation. However, little is known about the mechanisms directing Nr2f expression in ACs. Here, we identified a conserved enhancer 3 to the nr2f1a locus, which we call 3reg1-nr2f1a (3reg1), that can promote Nr2f1a expression in ACs. Sequence analysis of the enhancer identified putative Lef/Tcf and Foxf TF binding sites. Mutation of the Lef/Tcf sites within the 3reg1 reporter, knockdown of Tcf7l1a, and manipulation of canonical Wnt signaling support that Tcf7l1a is derepressed via Wnt signaling to activate the transgenic enhancer and promote AC differentiation. Similarly, mutation of the Foxf binding sites in the 3reg1 reporter, coupled with gain- and loss-of-function analysis supported that Foxf1 promotes expression of the enhancer and AC differentiation. Functionally, we find that Wnt signaling acts downstream of Foxf1 to promote expression of the 3reg1 reporter within ACs and, importantly, both Foxf1 and Wnt signaling require Nr2f1a to promote a surplus of differentiated ACs. CRISPR-mediated deletion of the endogenous 3reg1 abrogates the ability of Foxf1 and Wnt signaling to produce surplus ACs in zebrafish embryos. Together, our data support that downstream members of a conserved regulatory network involving Wnt signaling and Foxf1 function on a nr2f1a enhancer to promote AC differentiation in the zebrafish heart. Author SummaryVertebrate hearts are comprised of atrial chambers, which receive blood, and ventricular chambers which expel blood, whose functions need to be coordinated for proper blood circulation. During development, different genetic programs direct the development of these chambers within the vertebrate heart. Members of a family of genes called Nr2fs are conserved regulators of atrial chamber development in vertebrates, with mutations in Nr2f2 of humans being associated with congenital heart defects affecting the atrium. Here, we examine how the gene nr2f1a, which is required for normal atrial chamber development in the model zebrafish, is regulated. Using tools, including transgenic reporter lines and genetic mutants, we identify that factors previously shown to regulate atrial chamber development in mammals have conserved roles regulating a genetic element that promotes nr2f1a expression within developing atrial cells. Since there is a lack of understanding regarding regulation of Nr2f genes during vertebrate atrial cell development, our work provides insights into the conservation of genetic networks that promote heart development in vertebrates and if perturbed could underlie congenital heart defects.

developmental biology↗

bioRxiv2021

Elevated Hoxb5b expands vagal neural crest pool and blocks enteric neuronal development in zebrafish

Neural crest cells (NCCs) are a migratory, transient, and multipotent stem cell population essential to vertebrate embryonic development, contributing to numerous cell lineages in the adult organism. While great strides have been made in elucidating molecular and cellular events that drive NCC specification, comprehensive knowledge of the genetic factors that orchestrate NCC developmental programs is still far from complete. We discovered that elevated Hoxb5b levels promoted an expansion of zebrafish NCCs, which persisted throughout multiple stages of development. Correspondingly, elevated Hoxb5b also specifically expanded expression domains of the vagal NCC markers foxd3 and phox2bb. Increases in NCCs were most apparent after pulsed ectopic Hoxb5b expression at early developmental stages, rather than later during differentiation stages, as determined using a novel transgenic zebrafish line. The increase in vagal NCCs early in development led to supernumerary Phox2b+ enteric neural progenitors, while leaving many other NCC-derived tissues without an overt phenotype. Surprisingly, these NCC-derived enteric progenitors failed to expand properly into sufficient quantities of enterically fated neurons and stalled in the gut tissue. These results suggest that while Hoxb5b participates in vagal NCC development as a driver of progenitor expansion, the supernumerary, ectopically localized NCC fail to initiate expansion programs in timely fashion in the gut. All together, these data point to a model in which Hoxb5b regulates NCCs both in a tissue specific and temporally restricted manner.

developmental biology↗

bioRxiv2021

Origin and evolutionary landscape of Nr2f transcription factors across Metazoa

BackgroundNuclear Receptor Subfamily 2 Group F (Nr2f) orphan nuclear hormone transcription factors (TFs) are fundamental regulators of many developmental processes in invertebrates and vertebrates. Despite the importance of these TFs throughout metazoan development, previous work has not clearly outlined their evolutionary history. ResultsWe integrated molecular phylogeny with comparisons of intron/exon structure, domain architecture, and syntenic conservation to define critical evolutionary events that distinguish the Nr2f gene family in Metazoa. Our data indicate that a single ancestral pre-metazoan Nr2f gene, we have termed Nr2f1/2/5/6, predated six main Bilateria subfamilies, which include a single Nr2f1/2/5 homolog that is present throughout protostomes and invertebrate deuterostomes, Nr2f1/2 homologs in agnathans, and Nr2f1, Nr2f2, Nr2f5, Nr2f6 orthologs that are found in gnathostomes. The three Nr2f1/2 members in agnathans are due to independent expansions not found in gnathostomes, while the vertebrate Nr2f1, Nr2f2, Nr2f5 members arose from whole-genome duplications (WGDs). However, Nr2f6 members are the most divergent subfamily, likely originating from an ancient duplication, and are only retained by gnathostomes. Interestingly, Nr2f5 TFs have been independently lost in both cartilaginous fish and amniotes, such as humans. Furthermore, our analysis shows there are differential expansions and losses of Nr2f genes in teleosts following their additional rounds of WGDs. ConclusionOverall, our evolutionary genomic analysis of Nr2f proteins helps to reveal the origins and previously unrecognized relationships of this ancient transcription factor family, which may allow for greater insights into the conservation of Nr2f functions that shape Metazoan body plans.

evolutionary biology↗

bioRxiv2018

Enhancing acute kidney injury regeneration by promoting cellular dedifferentiation in zebrafish

Acute kidney injury (AKI) is a serious disorder for which there is no approved pharmaceutical treatment. Following injury, native nephrons display limited regenerative capabilities, relying on the dedifferentiation and proliferation of renal tubular epithelial cells (RTECs) that survive the insult. Previously, we identified 4-(phenylthio)butanoic acid (PTBA), a histone deacetylase inhibitor (HDI) that enhances renal recovery and showed that PTBA treatment increased RTEC proliferation and reduced renal fibrosis. Here, we investigated the regenerative mechanisms of PTBA in zebrafish models of larval renal injury and adult cardiac injury. With respect to renal injury, we showed that delivery of PTBA using an esterified prodrug (UPHD25) increases the reactivation of the renal progenitor gene Pax2a, enhances dedifferentiation of RTECs, reduces Kidney injury molecule-1 expression, and lowers the number of infiltrating macrophages. Further, we find that the effects of PTBA on RTEC proliferation depend upon retinoic acid signaling and demonstrate the therapeutic properties of PTBA are not restricted to the kidney but also increase cardiomyocyte proliferation and decrease fibrosis following cardiac injury in adult zebrafish. These studies provide key mechanistic insights into how PTBA enhances tissue repair in models of acute injury and lay the groundwork for translating this novel HDI into the clinic.\n\nSUMMARY STATEMENTMortality associated with acute kidney injury (AKI) is in part due to limited treatments available to ameliorate kidney injury. We identified a compound that enhances AKI recovery by promoting cellular dedifferentiation.

pharmacology and toxicology↗