Biology subjects

Dickinson, A. J. G.

Publications and source records attributed to Dickinson, A. J. G..

6 recordsLinked to original sources

bioRxiv2026

The XenCart Protocol: A Method for Alcian Blue Labeling and Quantitative Analysis of Craniofacial Cartilage in Xenopus

Craniofacial birth defects, such as cleft lip and palate, are among the most common congenital anomalies and often arise from disruptions in early facial patterning. Many of these defects are linked to environmental teratogens, yet such exposures cannot be directly tested in humans, making animal models essential for evaluating developmental risks. Xenopus laevis offers a powerful solution: its tadpoles develop externally, share deeply conserved craniofacial patterning mechanisms with humans, and provide an accessible platform for uncovering how environmental exposures reshape facial structures during development. Here, we present the XenCart Protocol, a reproducible workflow for Alcian Blue staining and quantitative morphometric analysis of Xenopus craniofacial cartilage. This method provides clear visualization of individual cartilage elements and can be readily applied to investigate genetic or environmental perturbations. The Xenopus craniofacial skeleton contains distinct cartilaginous structures that perform key biomechanical functions and share strong homology with regions of the human craniofacial skeleton. These similarities allow direct comparison of developmental outcomes across vertebrates. As part of a CURE-based undergraduate course, the XenCart Protocol was used to measure jaw cartilage dimensions in tadpoles exposed to an emerging teratogen, e-liquids used in vaping. E-liquid exposure caused consistent reductions across major craniofacial cartilages, including shorter Meckels cartilage, narrowed infrarostral width, decreased basihyobranchial and ceratohyal dimensions, and reduced suprarostral angles, reflecting an overall shift toward a smaller, more compact craniofacial morphology. These patterns suggest potential disruption of neural crest cell migration or signaling pathways for craniofacial cartilage development, mechanisms that, if similarly affected in humans, could contribute to midfacial narrowing, jaw underdevelopment, or increased vulnerability to conditions such as orofacial clefts. The ability to detect robust, structure-specific differences highlights the sensitivity of the protocol and its strong alignment with student-led research. These findings also pinpoint the precise regions of the jaw most affected by e-liquid exposure, providing a foundation for uncovering the developmental mechanisms driving these craniofacial changes. In summary, the XenCart Protocol provides a standardized, scalable method for quantifying craniofacial cartilage development and offers a powerful platform for both mechanistic research and undergraduate training in developmental biology and toxicology.

developmental biology↗

bioRxiv2026

LZTS2 Emerges as a Regulator of Craniofacial Development and Modulator of DYRK1A

BackgroundPrecise control of DYRK1A dosage is essential for embryonic development, including craniofacial morphogenesis. While LZTS2 is among the most consistently identified DYRK1A-interacting proteins, its roles in embryonic development remain incompletely understood, and its potential contribution to craniofacial development has not been examined. Xenopus laevis was used to test the role of LZTS2 in craniofacial development and its functional relationship with DYRK1A. ResultsLzts2 and Dyrk1a showed overlapping expression during craniofacial development, with both proteins present in developing facial tissues. Knockdown of Lzts2 disrupted craniofacial morphogenesis and reduced expression of the neural crest-associated genes sox9 and pax3. These phenotypes closely resembled those caused by decreasing Dyrk1a function. Sub-phenotypic reductions of Lzts2 and Dyrk1a synergized to produce craniofacial defects, while partial reduction of Lzts2 attenuated aspects of the phenotype caused by Dyrk1a overexpression. Comparative analysis of human phenotypes associated with copy number gains of LZTS2 and DYRK1A revealed striking overlap, consistent with a potential functional interaction between these genes in humans. ConclusionsThese findings identify Lzts2 as a previously unrecognized regulator of craniofacial development and support a functional interaction with Dyrk1a during embryogenesis. Modulating LZTS2 or related regulatory partners may provide a strategy to selectively tune DYRK1A-dependent developmental pathways

developmental biology↗

bioRxiv2024

Role of histone variants H2BC1 and H2AZ.2 in H2AK119ub nucleosome organization and Polycomb gene silencing

Ubiquitination of histone H2A at lysine 119 residue (H2AK119ub) plays critical roles in a wide range of physiological processes, including Polycomb gene silencing 1,2, replication 3-5, DNA damage repair 6-10, X inactivation 11,12, and heterochromatin organization 13,14. However, the underlying mechanism and structural basis of H2AK119ub remains largely elusive. In this study, we report that H2AK119ub nucleosomes have a unique composition, containing histone variants H2BC1 and H2AZ.2, and importantly, this composition is required for H2AK119ub and Polycomb gene silencing. Using the UAB domain of RSF1, we purified H2AK119ub nucleosomes to a sufficient amount and purity. Mass spectrometry analyses revealed that H2AK119ub nucleosomes contain the histone variants H2BC1 and H2AZ.2. A cryo-EM study resolved the structure of native H2AK119ub nucleosomes to a 2.6A resolution, confirming H2BC1 in one subgroup of H2AK119ub nucleosomes. Tandem GST-UAB pulldown, Flag-H2AZ.2, and HA-H2BC1 immunoprecipitation revealed that H2AK119ub nucleosomes could be separated into distinct subgroups, suggesting their composition heterogeneity and potential dynamic organization. Knockout or knockdown of H2BC1 or H2AZ.2 reduced cellular H2AK119ub levels, establishing H2BC1 and H2AZ.2 as critical determinants of H2AK119ub. Furthermore, genomic binding profiles of H2BC1 and H2AZ.2 overlapped significantly with H2AK119ub binding, with the most significant overlapping in the gene body and intergenic regions. Finally, assays in developing embryos reveal an interaction of H2AZ.2, H2BC1, and RING1A in vivo. Thus, this study revealed, for the first time, that the H2AK119ub nucleosome has a unique composition, and this composition is required for H2AK119ub and Polycomb gene silencing.

molecular biology↗

bioRxiv2024

Dyrk1a is required for craniofacial development in Xenopus laevis.

Loss of function mutations in the dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) gene are associated with craniofacial malformations in humans. Here we characterized the effects of deficient DYRK1A in craniofacial development using a developmental model, Xenopus laevis. Dyrk1a mRNA and protein was expressed throughout the developing head and was enriched in the branchial arches which contribute to the face and jaw. Consistently, reduced Dyrk1a function, using dyrk1a morpholinos and pharmacological inhibitors, resulted in orofacial malformations including hypotelorism, altered mouth shape, slanted eyes, and narrower face accompanied by smaller jaw cartilage and muscle. Inhibition of Dyrk1a function resulted in misexpression of key craniofacial regulators including transcription factors and members of the retinoic acid signaling pathway. Two such regulators, sox9 and pax3 are required for neural crest development and their decreased expression corresponds with smaller neural crest domains within the branchial arches. Finally, we determined that the smaller size of the faces, jaw elements and neural crest domains in embryos deficient in Dyrk1a could be explained by increased cell death and decreased proliferation. This study is the first to provide insight into why craniofacial birth defects might arise in humans with DYRK1A mutations.

developmental biology↗

bioRxiv2019

Loss of Nance-Horan Syndrome b (nhsb) prevents expansion growth of retinal progenitor cells by selective up-regulation of Δ113p53

The regulation of cell cycle progression and differentiation in retinal progenitor cells is a fundamental feature controlling organ size of the eye in vertebrates. Nance-Horan Syndrome (NHS) is a rare X-linked disorder caused by mutations in the NHS gene. Dysmorphic features of NHS include severe congenital cataracts, micropthalmia, facial dysmorphisms, and visual impairment. In this study we report an evolutionarily conserved role for NHS in vertebrate retinogenesis. Loss of function of nhs leads to small eye size in both zebrafish and Xenopus tropicalis, marked by reduced proliferation but not cell death. Transcriptome analysis of nhs morphant zebrafish eyes revealed a marked upregulation in{Delta} 113p53, an isoform of p53, concomitant with a selective upregulation of p53 responsive genes that inhibit cell cycle progression but not apoptosis. Our data supports a model where Nhs is a negative regulator of{Delta} 113p53 expression and exerts its function through regulation of the p53 pathway to promote expansive growth of retinal progenitor cells prior to differentiation.

developmental biology↗

bioRxiv2018

Desmoplakin is required for epidermal integrity and morphogenesis in the Xenopus laevis embryo

Desmoplakin (Dsp) is a unique and critical desmosomal protein, however, it is unclear whether this protein and desmosomes themselves are required for epidermal morphogenesis. Using morpholinos or Crispr/Cas9 mutagenesis we decreased the function of Dsp in frog embryos to better understand its role during epidermal development. Dsp morphant and mutant embryos had developmental defects that mimicked what has been reported in mammals. Such defects included epidermal fragility which correlated with reduction in cortical keratin and junctional e-cadherin in the developing epidermis. Dsp protein sequence and expression are also highly similar with mammals and suggest shared function across vertebrates. Most importantly, we also uncovered a novel function for Dsp in the morphogenesis of the epidermis in X. laevis. Specifically, Dsp is required during the process of radial intercalation where basally located cells move into the outer epidermal layer. Once inserted these newly intercalated cells expand their apical surface and then they differentiate into specific epidermal cell types. Decreased levels of Dsp resulted in the failure of the radially intercalating cells to expand their apical surface, thereby reducing the number of differentiated multiciliated and secretory cells. Dsp is also required in the development of other ectodermally derived structures such as the mouth, eye and fin that utilize intercalating-like cell movements. We have developed a novel system, in the frog, to demonstrate for the first time that desmosomes not only protect against mechanical stress but are also critical for epidermal morphogenesis.\n\nSummary StatementCritical desmosomal protein, desmoplakin, is required for proper distribution and levels of cytoskeletal elements and e-cadherin. Thus embryos with decreased desmoplakin have defects in epidermal integrity and morphogenesis.

developmental biology↗